Global warming

The release of carbon dioxide into the atmosphere by the burning of fossil fuels is significantly altering the carbon cycle by adding to the amount of carbon in the atmosphere and in the more rapidly interacting portions of the biosphere and oceans. In order better to assess these changes, the basis for calculating global CO2 emissions is reviewed and new annual values are computed for the period 1800 through 1969. The world average fractions of carbon in coal and lignite, estimated from calorific data, are found to be lower than previously assumed. When account is taken of handling losses and partial diversion to produce petrochemicals, road asphalt, and other non-fuels, the calculated CO2 emissions are further reduced by several percent even after allowing that most unburned materials eventually oxidize to CO2 in the environment. On the other hand, the production of CO2 by kilning of limestone adds 1 to 2% to the annual totals. The cumulative increase in carbon in the short term carbon cycle, owing to man's industrial and domestic activities up to 1970, is estimated to be 1.12 + 0.14 × 1017 g (4.1 ± 0.5 × 1017 g CO2), or about 18% of the amount of CO2 in the atmosphere during the late nineteenth century.DOI: 10.1111/j.2153-3490.1973.tb01604.x

@article{doi103402tellusav25i29652,
    author = "Keeling, Charles D.",
    title = "Industrial production of carbon dioxide from fossil fuels and limestone",
    year = "1973",
    journal = "Tellus A Dynamic Meteorology and Oceanography",
    abstract = "The release of carbon dioxide into the atmosphere by the burning of fossil fuels is significantly altering the carbon cycle by adding to the amount of carbon in the atmosphere and in the more rapidly interacting portions of the biosphere and oceans. In order better to assess these changes, the basis for calculating global CO2 emissions is reviewed and new annual values are computed for the period 1800 through 1969. The world average fractions of carbon in coal and lignite, estimated from calorific data, are found to be lower than previously assumed. When account is taken of handling losses and partial diversion to produce petrochemicals, road asphalt, and other non-fuels, the calculated CO2 emissions are further reduced by several percent even after allowing that most unburned materials eventually oxidize to CO2 in the environment. On the other hand, the production of CO2 by kilning of limestone adds 1 to 2\% to the annual totals. The cumulative increase in carbon in the short term carbon cycle, owing to man's industrial and domestic activities up to 1970, is estimated to be 1.12 + 0.14 × 1017 g (4.1 ± 0.5 × 1017 g CO2), or about 18\% of the amount of CO2 in the atmosphere during the late nineteenth century.DOI: 10.1111/j.2153-3490.1973.tb01604.x",
    url = "https://doi.org/10.3402/tellusa.v25i2.9652",
    doi = "10.3402/tellusa.v25i2.9652",
    openalex = "W4246011515"
}

Phenomena related to the natural carbon cycle as the 14C distribution between atmosphere and ocean and the atmospheric response to the input of fossil fuel CO 2 and of 14 C produced in nuclear weapon tests have been quantitatively discussed by other authors using box models. However the exchange coefficients derived from the natural 14 C distribution do not agree with those valid to describe the short-term phenomena. A model consisting of a well mixed atmospheric box coupled to a long-term biosphere, of an ocean surface box and a diffusive deep ocean is discussed. The dynamic parameters were derived from the preindustrial 14 C distribution in atmosphere and ocean. A consistent description of phenomena with completely different characteristic times is possible, because in the box diffusion model the flux from mixed layer to deep sea increases for decreasing time constants of the perturbations. This is in contrary to box models where it is essentially independent of the time constants if they are smaller than a few hundred years. Due to this fact our model is valid for predictions of the atmospheric CO 2 response to the various possible future CO 2 input time functions.

@article{doi103402tellusav27i29900,
    author = "Oeschger, H. and Siegenthaler, U. and Schotterer, U. and Gugelmann, A.",
    title = "A box diffusion model to study the carbon dioxide exchange in nature",
    year = "1975",
    journal = "Tellus A Dynamic Meteorology and Oceanography",
    abstract = "Phenomena related to the natural carbon cycle as the 14C distribution between atmosphere and ocean and the atmospheric response to the input of fossil fuel CO 2 and of 14 C produced in nuclear weapon tests have been quantitatively discussed by other authors using box models. However the exchange coefficients derived from the natural 14 C distribution do not agree with those valid to describe the short-term phenomena. A model consisting of a well mixed atmospheric box coupled to a long-term biosphere, of an ocean surface box and a diffusive deep ocean is discussed. The dynamic parameters were derived from the preindustrial 14 C distribution in atmosphere and ocean. A consistent description of phenomena with completely different characteristic times is possible, because in the box diffusion model the flux from mixed layer to deep sea increases for decreasing time constants of the perturbations. This is in contrary to box models where it is essentially independent of the time constants if they are smaller than a few hundred years. Due to this fact our model is valid for predictions of the atmospheric CO 2 response to the various possible future CO 2 input time functions.",
    url = "https://doi.org/10.3402/tellusa.v27i2.9900",
    doi = "10.3402/tellusa.v27i2.9900",
    openalex = "W2087582584",
    references = "doi101002qj49706427503, doi10100797814684198636, doi101029jc074i023p05491, doi101029jz065i009p02903, doi101029jz068i013p03899, doi101111j215334901957tb01848x, doi101126science1223166415a, doi103402tellusav12i29366, doi103402tellusav25i29652, doi103402tellusav9i19075"
}

@book{crossref1977the,
    title = "The Fate of Fossil Fuel CO2 in the Oceans",
    year = "1977",
    url = "https://doi.org/10.1007/978-1-4899-5016-1",
    doi = "10.1007/978-1-4899-5016-1",
    openalex = "W655165904"
}

Current knowledge of the world carbon budget is reviewed with special emphasis on the question of whether the biota is a source or a sink for CO/sub 2/. The analysis shows through convergent lines of evidence that the biota is not a sink and may be a source of CO/sub 2/ as large or larger than the fossil fuel source. The issue is important because of the potential that changes in the CO/sub 2/ content of air have for changing climate worldwide. Various analyses suggest that human activities in the near future could release large additional amounts of CO/sub 2/ into the atmosphere with results that are substantially unpredictable.

@article{doi101126science1994325141,
    author = "Woodwell, George M. and Whittaker, R. H. and Reiners, William A. and Likens, Gene E. and Delwiche, C. C. and Botkin, Daniel B.",
    title = "The Biota and the World Carbon Budget",
    year = "1978",
    journal = "Science",
    abstract = "Current knowledge of the world carbon budget is reviewed with special emphasis on the question of whether the biota is a source or a sink for CO/sub 2/. The analysis shows through convergent lines of evidence that the biota is not a sink and may be a source of CO/sub 2/ as large or larger than the fossil fuel source. The issue is important because of the potential that changes in the CO/sub 2/ content of air have for changing climate worldwide. Various analyses suggest that human activities in the near future could release large additional amounts of CO/sub 2/ into the atmosphere with results that are substantially unpredictable.",
    url = "https://doi.org/10.1126/science.199.4325.141",
    doi = "10.1126/science.199.4325.141",
    openalex = "W2025836562",
    references = "doi101007978940098514835, doi101029jz070i024p06053, doi101093icb8119, doi1010970001069419611100000024, doi101111j215334901976tb00701x, doi101126science1223166415a, doi101126science1223166415b, doi101146annureves08110177000411, doi103402tellusav27i29900, openalexw3022078416"
}

The fate of fossil fuel carbon dioxide released into the atmosphere depends on the exchange rates of carbon between the atmosphere and three major carbon reservoirs, namely, the oceans, shallow-water sediments, and the terrestrial biosphere. Various assumptions and models used to estimate the global carbon budget for the last 20 years are reviewed and evaluated. Several versions of recent atmosphere-ocean models appear to give reliable and mutually consistent estimates for carbon dioxide uptake by the oceans. On the other hand, there is no compelling evidence which establishes that the terrestrial biomass has decreased at a rate comparable to that of fossil fuel combustion over the last two decades, as has been recently claimed.

@article{broecker1979fate,
    author = "Broecker, W. S. and Takahashi, T. and Simpson, H. J. and Peng, T. -H.",
    title = "Fate of Fossil Fuel Carbon Dioxide and the Global Carbon Budget",
    year = "1979",
    journal = "Science",
    abstract = "The fate of fossil fuel carbon dioxide released into the atmosphere depends on the exchange rates of carbon between the atmosphere and three major carbon reservoirs, namely, the oceans, shallow-water sediments, and the terrestrial biosphere. Various assumptions and models used to estimate the global carbon budget for the last 20 years are reviewed and evaluated. Several versions of recent atmosphere-ocean models appear to give reliable and mutually consistent estimates for carbon dioxide uptake by the oceans. On the other hand, there is no compelling evidence which establishes that the terrestrial biomass has decreased at a rate comparable to that of fossil fuel combustion over the last two decades, as has been recently claimed.",
    url = "https://doi.org/10.1126/science.206.4417.409",
    doi = "10.1126/science.206.4417.409",
    number = "4417",
    openalex = "W2095051466",
    pages = "409-418",
    volume = "206",
    references = "crossref1977the, doi1010079783642809132, doi1010160304420374900152, doi101126science1223166415a, doi101126science1223166415b, doi101126science1994325141, doi101146annureves08110177000411, doi103402tellusav26i129733, doi103402tellusav27i29900, doi104319lo19731860897"
}

@misc{broecker1979fate1,
    author = "Broecker, W. S. and Takahashi, T. and Simpson, J. and Peng, T. H",
    title = "Fate of fossil fuel carbon dioxide and the global carbon budget",
    year = "1979",
    howpublished = "Science, v. 206, p. 409-418",
    note = "talkorigins\_source = {true}; raw\_reference = {Broecker, W. S., Takahashi, T., Simpson, J., and Peng, T. H., 1979, Fate of fossil fuel carbon dioxide and the global carbon budget: Science, v. 206, p. 409-418.}"
}

Changes in land use over the past two centuries have caused a significant release of CO 2 to the atmosphere from the terrestrial biota and soils. An analysis of this release is based on amounts of organic carbon within an ecosystem following changes such as harvest of forests; it is also based on rates of changes, such as conversion of forest to agriculture, deduced from agricultural and forestry statistics. A model is used to calculate the net amount of carbon stored or released each year by the biota and soils of 69 regional ecosystems. Some of the changes, such as afforestation, the growth of harvested forests, and buildup of soil organic matter, result in a storage of carbon; others, such as harvest of forests and increase in pasture and agricultural areas, result in a loss of carbon to the atmosphere. According to this analysis, there has been a net release of carbon from terrestrial ecosystems worldwide since at least 1860. Until °1960, the annual release was greater than release of carbon from fossil fuels. The total net release of carbon from terrestrial ecosystems since 1860 is estimated to have been 180 x 10 1 5 g (a range of estimates is 135—228 x 10 1 5 g). The estimated net release of carbon in 1980 was 1.8—4.7 x 10 1 5 g; for the 22 yr since 1958 the release of C was 38—76 x 10 1 5 g. The ranges reflect the differences among various estimates of forest biomass, soil carbon, and agricultural clearing. Improvements in the data on the clearing of tropical forests alone would reduce the range of estimates for 1980 by almost 60%. Estimates of the other major terms in the global carbon budget, the atmospheric increase in CO 2, the fossil fuel release of CO 2, and the oceanic uptake of CO 2, are all subject to uncertainties. The combined errors in these estimates are large enough that the global carbon budget appears balanced if the low estimate for the biotic release of carbon given above is used (1.8 x 10 1 5 g released in 1980) with the higher estimates of oceanic uptake. If higher estimates for biotic release are used, then the carbon budget does not balance, and the estimates of oceanic uptake or of other factors require revision.

@article{doi1023071942531,
    author = "Houghton, R. A. and Hobbie, John E. and Melillo, Jerry M. and Moore, Berrien and Peterson, B. J. and Shaver, Gus and Woodwell, George M.",
    title = {Changes in the Carbon Content of Terrestrial Biota and Soils between 1860 and 1980: A Net Release of CO"2 to the Atmosphere},
    year = "1983",
    journal = "Ecological Monographs",
    abstract = "Changes in land use over the past two centuries have caused a significant release of CO 2 to the atmosphere from the terrestrial biota and soils. An analysis of this release is based on amounts of organic carbon within an ecosystem following changes such as harvest of forests; it is also based on rates of changes, such as conversion of forest to agriculture, deduced from agricultural and forestry statistics. A model is used to calculate the net amount of carbon stored or released each year by the biota and soils of 69 regional ecosystems. Some of the changes, such as afforestation, the growth of harvested forests, and buildup of soil organic matter, result in a storage of carbon; others, such as harvest of forests and increase in pasture and agricultural areas, result in a loss of carbon to the atmosphere. According to this analysis, there has been a net release of carbon from terrestrial ecosystems worldwide since at least 1860. Until °1960, the annual release was greater than release of carbon from fossil fuels. The total net release of carbon from terrestrial ecosystems since 1860 is estimated to have been 180 x 10 1 5 g (a range of estimates is 135—228 x 10 1 5 g). The estimated net release of carbon in 1980 was 1.8—4.7 x 10 1 5 g; for the 22 yr since 1958 the release of C was 38—76 x 10 1 5 g. The ranges reflect the differences among various estimates of forest biomass, soil carbon, and agricultural clearing. Improvements in the data on the clearing of tropical forests alone would reduce the range of estimates for 1980 by almost 60\%. Estimates of the other major terms in the global carbon budget, the atmospheric increase in CO 2, the fossil fuel release of CO 2, and the oceanic uptake of CO 2, are all subject to uncertainties. The combined errors in these estimates are large enough that the global carbon budget appears balanced if the low estimate for the biotic release of carbon given above is used (1.8 x 10 1 5 g released in 1980) with the higher estimates of oceanic uptake. If higher estimates for biotic release are used, then the carbon budget does not balance, and the estimates of oceanic uptake or of other factors require revision.",
    url = "https://doi.org/10.2307/1942531",
    doi = "10.2307/1942531",
    openalex = "W2084211992",
    references = "doi101126science1994325141"
}

With growing concern about climatic changes that could result from increased atmospheric carbon dioxide, it is appropriate to use the improved statistics on the production and use of fossil fuels which are now available and to review the CO2 discharges to the atmosphere from fossil fuel burning. Data on global fuel production and the chemical composition of these fuels have been re-examined and an attempt has been made to estimate the fraction of fuel which is used in the petrochemicals industry or otherwise not soon oxidized. Available statistics now permit more systematic treatment of natural gas liquids than in earlier calculations. Values used for combustion efficiency and non-fuel use on a global scale still require some estimation and extrapolation from United States data but can be bounded with sufficient precision that they add little uncertainty to the calculation of global CO2 emissions. Data now available permit the computation to be made with confidence that there are no major oversights. The differences from earlier calculations of CO2 emissions are minor, well within the uncertainty limits in the data available. The fundamental problems of assembling a data set on global fuel production limit the utility of striving for too much precision at other steps in the calculation. Annual CO2 emissions retain an uncertainty of 6-10%.Results of the calculations for 1980 through 1982 show decreases from 1979 CO2 emissions. This is the first time since the end of World War I1 that the emissions have decreased 3 years in succession. During the period following the 1973 escalation of fuel prices, the growth rate of emissions has been less than half what it was during the 1950s and 1960s (1.5%/year since 1973 as opposed to 4.5%/year through the 1950s and 1960s). Most of the change is a result of decreased growth in the use of oil.

@article{doi103402tellusbv36i414907,
    author = "Marland, Gregg and Rotty, Ralph M.",
    title = "Carbon dioxide emissions from fossil fuels: a procedure for estimation and results for 1950-1982",
    year = "1984",
    journal = "Tellus B",
    abstract = "With growing concern about climatic changes that could result from increased atmospheric carbon dioxide, it is appropriate to use the improved statistics on the production and use of fossil fuels which are now available and to review the CO2 discharges to the atmosphere from fossil fuel burning. Data on global fuel production and the chemical composition of these fuels have been re-examined and an attempt has been made to estimate the fraction of fuel which is used in the petrochemicals industry or otherwise not soon oxidized. Available statistics now permit more systematic treatment of natural gas liquids than in earlier calculations. Values used for combustion efficiency and non-fuel use on a global scale still require some estimation and extrapolation from United States data but can be bounded with sufficient precision that they add little uncertainty to the calculation of global CO2 emissions. Data now available permit the computation to be made with confidence that there are no major oversights. The differences from earlier calculations of CO2 emissions are minor, well within the uncertainty limits in the data available. The fundamental problems of assembling a data set on global fuel production limit the utility of striving for too much precision at other steps in the calculation. Annual CO2 emissions retain an uncertainty of 6-10\%.Results of the calculations for 1980 through 1982 show decreases from 1979 CO2 emissions. This is the first time since the end of World War I1 that the emissions have decreased 3 years in succession. During the period following the 1973 escalation of fuel prices, the growth rate of emissions has been less than half what it was during the 1950s and 1960s (1.5\%/year since 1973 as opposed to 4.5\%/year through the 1950s and 1960s). Most of the change is a result of decreased growth in the use of oil.",
    url = "https://doi.org/10.3402/tellusb.v36i4.14907",
    doi = "10.3402/tellusb.v36i4.14907",
    openalex = "W2066964481"
}

New data on the three major determinants of the carbon release from tropical forest clearing are used in a computer model that simulates land use change and its effects on the carbon content of vegetation and soil in order to calculate the net flux of carbon dioxide between tropical ecosystems and the atmosphere. The model also permits testing the sensitivity of the calculated flux to uncertainties in these data. The tropics were a net source of at least 0.4 x 10(15) grams but not more than 1.6 x 10(15) grams of carbon in 1980, considerably less than previous estimates. Decreases in soil organic matter were responsible for 0.1 x 10(15) to 0.3 x 10(15) grams of the release, while the burning and decay of cleared vegetation accounted for 0.3 x 10(15) to 1.3 x 10(15) grams. These estimates are lower than many previous ones because lower biomass estimates and slightly lower land clearing rates were used and because ecosystem recovery processes were included. These new estimates of the biotic release allow for the possibility of a balanced global budget given the large remaining uncertainties in the marine, terrestrial, and fossil fuel components of the carbon cycle.

@article{doi101126science239483542,
    author = "Detwiler, R. P. and Hall, Charles A. S.",
    title = "Tropical Forests and the Global Carbon Cycle",
    year = "1988",
    journal = "Science",
    abstract = "New data on the three major determinants of the carbon release from tropical forest clearing are used in a computer model that simulates land use change and its effects on the carbon content of vegetation and soil in order to calculate the net flux of carbon dioxide between tropical ecosystems and the atmosphere. The model also permits testing the sensitivity of the calculated flux to uncertainties in these data. The tropics were a net source of at least 0.4 x 10(15) grams but not more than 1.6 x 10(15) grams of carbon in 1980, considerably less than previous estimates. Decreases in soil organic matter were responsible for 0.1 x 10(15) to 0.3 x 10(15) grams of the release, while the burning and decay of cleared vegetation accounted for 0.3 x 10(15) to 1.3 x 10(15) grams. These estimates are lower than many previous ones because lower biomass estimates and slightly lower land clearing rates were used and because ecosystem recovery processes were included. These new estimates of the biotic release allow for the possibility of a balanced global budget given the large remaining uncertainties in the marine, terrestrial, and fossil fuel components of the carbon cycle.",
    url = "https://doi.org/10.1126/science.239.4835.42",
    doi = "10.1126/science.239.4835.42",
    openalex = "W1976873738"
}

The first 12 years (1974–1985) of continuous atmospheric CO 2 measurements from the NOAA GMCC program at the Mauna Loa Observatory in Hawaii are analyzed. Hourly and daily variations in the concentration of CO 2 due to local sources and sinks are described, with subsequent selection of data representing background concentrations. A digital filtering technique using the fast Fourier transform and low‐pass filters was used to smooth the selected data and to separate the seasonal cycle from the long‐term increase in CO 2. The amplitude of the seasonal cycle was found to be increasing at a rate of 0.05±0.02 ppm yr −1. The average growth rate of CO 2 was 1.42±0.02 ppm yr −1, and the fraction of CO 2 remaining in the atmosphere from fossil fuel combustion was 59%. A comparison between the Mauna Loa continuous CO 2 data and the CO 2 flask sample data from the sea level site at Cape Kumukahi, Hawaii, showed that the amplitude of the seasonal cycle at Cape Kumukahi was 23% larger than at Mauna Loa, with the phase of the cycle at Mauna Loa lagging the cycle at Cape Kumukahi by about 1–2 weeks.

@article{doi101029jd094id06p08549,
    author = "Thoning, K. W. and Tans, Pieter P. and Komhyr, W. D.",
    title = "Atmospheric carbon dioxide at Mauna Loa Observatory: 2. Analysis of the NOAA GMCC data, 1974–1985",
    year = "1989",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The first 12 years (1974–1985) of continuous atmospheric CO 2 measurements from the NOAA GMCC program at the Mauna Loa Observatory in Hawaii are analyzed. Hourly and daily variations in the concentration of CO 2 due to local sources and sinks are described, with subsequent selection of data representing background concentrations. A digital filtering technique using the fast Fourier transform and low‐pass filters was used to smooth the selected data and to separate the seasonal cycle from the long‐term increase in CO 2. The amplitude of the seasonal cycle was found to be increasing at a rate of 0.05±0.02 ppm yr −1. The average growth rate of CO 2 was 1.42±0.02 ppm yr −1, and the fraction of CO 2 remaining in the atmosphere from fossil fuel combustion was 59\%. A comparison between the Mauna Loa continuous CO 2 data and the CO 2 flask sample data from the sea level site at Cape Kumukahi, Hawaii, showed that the amplitude of the seasonal cycle at Cape Kumukahi was 23\% larger than at Mauna Loa, with the phase of the cycle at Mauna Loa lagging the cycle at Cape Kumukahi by about 1–2 weeks.",
    url = "https://doi.org/10.1029/jd094id06p08549",
    doi = "10.1029/jd094id06p08549",
    openalex = "W2039731403",
    references = "doi101007bf02162161, doi101016c20130074075, doi101029jc086ic06p05238, doi101029jd090id06p10529, doi101029jz070i024p06053, doi101038261116a0, doi10106314823194, doi101109tsmc19774309709, doi101111j215334901976tb00701x, doi1023072669794"
}

Observed atmospheric concentrations of CO(2) and data on the partial pressures of CO(2) in surface ocean waters are combined to identify globally significant sources and sinks of CO(2). The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO(2) are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO(2) in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO(2). Therefore, a large amount of the CO(2) is apparently absorbed on the continents by terrestrial ecosystems.

@article{doi101126science24749491431,
    author = "Tans, Pieter P. and Fung, Inez and Takahashi, Taro",
    title = "Observational Contrains on the Global Atmospheric Co 2 Budget",
    year = "1990",
    journal = "Science",
    abstract = "Observed atmospheric concentrations of CO(2) and data on the partial pressures of CO(2) in surface ocean waters are combined to identify globally significant sources and sinks of CO(2). The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO(2) are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO(2) in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO(2). Therefore, a large amount of the CO(2) is apparently absorbed on the continents by terrestrial ecosystems.",
    url = "https://doi.org/10.1126/science.247.4949.1431",
    doi = "10.1126/science.247.4949.1431",
    openalex = "W2074247901",
    references = "broecker1979fate, doi101007bf01054491, doi101029jd093id08p09341, doi101038319109a0, doi101126science1994325141, doi101126science2064417409, doi101126science239483542, doi101126science2404850293, doi1011751520049319831110609etdgmf20co2, doi103402tellusav27i29900, doi103402tellusbv36i414907"
}

@article{doi101016003101829290207l,
    author = "Walker, James C. G. and Kasting, James F.",
    title = "Effects of fuel and forest conservation on future levels of atmospheric carbon dioxide",
    year = "1992",
    journal = "Palaeogeography Palaeoclimatology Palaeoecology",
    url = "https://doi.org/10.1016/0031-0182(92)90207-l",
    doi = "10.1016/0031-0182(92)90207-l",
    openalex = "W2021085441",
    references = "doi1010160012821x74900788, doi1010160016703779900590, doi101029gm032, doi101029jc086ic10p09776, doi101029jc091ic04p05037, doi101126science243488757, doi101126science24749491431, doi102475ajs2824451, doi102475ajs2837641, openalexw1552913007"
}

@article{doi101016092181819290009y,
    author = "Walker, James C. G. and Kasting, James F.",
    title = "Effects of fuel and forest conservation on future levels of atmospheric carbon dioxide",
    year = "1992",
    journal = "Global and Planetary Change",
    url = "https://doi.org/10.1016/0921-8181(92)90009-y",
    doi = "10.1016/0921-8181(92)90009-y",
    openalex = "W4231752810",
    references = "doi1010160012821x74900788, doi1010160016703779900590, doi101029gm032, doi101029jc086ic10p09776, doi101029jc091ic04p05037, doi101038324237a0, doi101126science243488757, doi101126science24749491431, doi102475ajs2824451, doi102475ajs2837641"
}

@article{garrett1992on,
    author = "Garrett, Charles W.",
    title = "On global climate change, carbon dioxide, and fossil fuel combustion",
    year = "1992",
    journal = "Progress in Energy and Combustion Science",
    url = "https://doi.org/10.1016/0360-1285(92)90007-n",
    doi = "10.1016/0360-1285(92)90007-n",
    number = "5",
    openalex = "W1979461900",
    pages = "369-407",
    volume = "18",
    references = "doi101038315021a0, doi101038329408a0, doi101038344529a0, doi10108014786449608620846, doi101126science243488757, doi101126science24749491431, doi101126science2555043423, doi1011751520047719900710988roicci20co2, doi1015159780295741406007, doi1023071971875"
}

The increase in atmospheric CO 2 levels during the last deglaciation was comparable in magnitude to the recent historical increase. However, global CO 2 budgets for these changes reflect fundamental differences in rates and in sources and sinks. The modern oceans are a rapid net CO 2 sink, whereas the oceans were a gradual source during the deglaciation. Unidentified terrestrial CO 2 sinks are important uncertainties in both the deglacial and recent CO 2 budgets. The deglacial CO 2 budget represents a complexity of long-term dynamic behavior that is not adequately addressed by current models used to forecast future atmospheric CO 2 levels.

@article{doi101126science2595097934,
    author = "Sundquist, Eric T.",
    title = "The Global Carbon Dioxide Budget",
    year = "1993",
    journal = "Science",
    abstract = "The increase in atmospheric CO 2 levels during the last deglaciation was comparable in magnitude to the recent historical increase. However, global CO 2 budgets for these changes reflect fundamental differences in rates and in sources and sinks. The modern oceans are a rapid net CO 2 sink, whereas the oceans were a gradual source during the deglaciation. Unidentified terrestrial CO 2 sinks are important uncertainties in both the deglacial and recent CO 2 budgets. The deglacial CO 2 budget represents a complexity of long-term dynamic behavior that is not adequately addressed by current models used to forecast future atmospheric CO 2 levels.",
    url = "https://doi.org/10.1126/science.259.5097.934",
    doi = "10.1126/science.259.5097.934",
    openalex = "W2059290031",
    references = "doi101016003101829290207l"
}

The distribution and variations of atmospheric CO 2 from 1981 to 1992 were determined by measuring CO 2 mixing ratios in samples collected weekly at a cooperative global air sampling network. The results constitute the most geographically extensive, carefully calibrated, internally consistent CO 2 data set available. Analysis of the data reveals that the global CO 2 growth rate has declined from a peak of ∼2.5 ppm yr −1 in 1987–1988 to ∼0.6 ppm yr −1 in 1992. In 1992 we find no increase in atmospheric CO 2 from 30° to 90°N. Variations in fossil fuel CO 2 emissions cannot explain this result. The north pole‐south pole CO 2 difference increased from ∼3 ppm during 1981–1987 to ∼4 ppm during 1988–1991. In 1992 the difference was again ∼3 ppm. A two‐dimensional model analysis of the data indicates that the low CO 2 growth rate in 1992 is mainly due to an increase in the northern hemisphere CO 2 sink from 3.9 Gt C yr −1 in 1991 to 5.0 Gt C yr −1 in 1992. The increase in the north pole‐south pole CO 2 difference appears to result from an increase in the southern hemisphere CO 2 sink from ∼0.5 to ∼1.5 Gt C yr −1.

@article{doi10102994jd01951,
    author = "Conway, T. J. and Tans, Pieter P. and Waterman, Lee S. and Thoning, K. W. and Kitzis, Duane and Masarie, K. A. and Zhang, Ni",
    title = "Evidence for interannual variability of the carbon cycle from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network",
    year = "1994",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The distribution and variations of atmospheric CO 2 from 1981 to 1992 were determined by measuring CO 2 mixing ratios in samples collected weekly at a cooperative global air sampling network. The results constitute the most geographically extensive, carefully calibrated, internally consistent CO 2 data set available. Analysis of the data reveals that the global CO 2 growth rate has declined from a peak of ∼2.5 ppm yr −1 in 1987–1988 to ∼0.6 ppm yr −1 in 1992. In 1992 we find no increase in atmospheric CO 2 from 30° to 90°N. Variations in fossil fuel CO 2 emissions cannot explain this result. The north pole‐south pole CO 2 difference increased from ∼3 ppm during 1981–1987 to ∼4 ppm during 1988–1991. In 1992 the difference was again ∼3 ppm. A two‐dimensional model analysis of the data indicates that the low CO 2 growth rate in 1992 is mainly due to an increase in the northern hemisphere CO 2 sink from 3.9 Gt C yr −1 in 1991 to 5.0 Gt C yr −1 in 1992. The increase in the north pole‐south pole CO 2 difference appears to result from an increase in the southern hemisphere CO 2 sink from ∼0.5 to ∼1.5 Gt C yr −1.",
    url = "https://doi.org/10.1029/94jd01951",
    doi = "10.1029/94jd01951",
    openalex = "W2131648183",
    references = "doi101029jd094id06p08549"
}

While ecologists involved in management or policy often are advised to learn to deal with uncertainty, there are a number of components of global environmental change of which we are certain–certain that they are going on, and certain that they are human—caused. Some of these are largely ecological changes, and all have important ecological consequences. Three of the well—documented global changes are: increasing concentrations of carbon dioxide in the atmosphere; alterations in the biogeochemistry of the global nitrogen cycle; and ongoing land use/land cover change. Human activity–now primarily fossil fuel combustion– has increased carbon dioxide concentrations from °280 to 355 mL/L since 1800; the increase is unique, at least in the past 160 000 yr, and several lines of evidence demonstrate unequivocally that it is human—caused. This increase is likely to have climatic consequences–and certainly it has direct effects on biota in all Earth's terrestrial ecosystems. The global nitrogen cycle has been altered by human activity to such an extent that more nitrogen is fixed annually by humanity (primarily for nitrogen fertilizer, also by legume crops and as a by product of fossil fuel combustion) than by all natural pathways combined. This added nitrogen alters the chemistry of the atmosphere and of aquatic ecosystems, contributes to eutrophiction of the biosphere, and has substantial regional effects on biological diversity in the most affected areas. Finally, human land use/land cover change has transformed one—their to one—half of Earth's ice—free surface. This in and of itself probably represents the most important component of global change now and will for some decades to come; it has profound effects on biological diversity on land and on ecosystems downwind and downstream of affected areas. Overall, any clear dichotomy between pristine ecosystems and human—altered areas that may have existed in the past has vanished, and ecological research should account for this reality. These three and other equally certain components of global environmental change are the primary causes of anticipated changes in climate, and of ongoing losses of biological diversity. They are caused in turn by the extraordinary growth in size and resource use of the human population. On a broad scale, there is little uncertainty about any of these components of change or their causes. However, much of the public believes the causes–even the existence–of global change to be uncertain and contentious topics. By speaking out effectively, we can help to shift the focus of public discussion towards what can and should be done about global environmental change.

@article{doi1023071941591,
    author = "Vitousek, Peter M.",
    title = "Beyond Global Warming: Ecology and Global Change",
    year = "1994",
    journal = "Ecology",
    abstract = "While ecologists involved in management or policy often are advised to learn to deal with uncertainty, there are a number of components of global environmental change of which we are certain–certain that they are going on, and certain that they are human—caused. Some of these are largely ecological changes, and all have important ecological consequences. Three of the well—documented global changes are: increasing concentrations of carbon dioxide in the atmosphere; alterations in the biogeochemistry of the global nitrogen cycle; and ongoing land use/land cover change. Human activity–now primarily fossil fuel combustion– has increased carbon dioxide concentrations from °280 to 355 mL/L since 1800; the increase is unique, at least in the past 160 000 yr, and several lines of evidence demonstrate unequivocally that it is human—caused. This increase is likely to have climatic consequences–and certainly it has direct effects on biota in all Earth's terrestrial ecosystems. The global nitrogen cycle has been altered by human activity to such an extent that more nitrogen is fixed annually by humanity (primarily for nitrogen fertilizer, also by legume crops and as a by product of fossil fuel combustion) than by all natural pathways combined. This added nitrogen alters the chemistry of the atmosphere and of aquatic ecosystems, contributes to eutrophiction of the biosphere, and has substantial regional effects on biological diversity in the most affected areas. Finally, human land use/land cover change has transformed one—their to one—half of Earth's ice—free surface. This in and of itself probably represents the most important component of global change now and will for some decades to come; it has profound effects on biological diversity on land and on ecosystems downwind and downstream of affected areas. Overall, any clear dichotomy between pristine ecosystems and human—altered areas that may have existed in the past has vanished, and ecological research should account for this reality. These three and other equally certain components of global environmental change are the primary causes of anticipated changes in climate, and of ongoing losses of biological diversity. They are caused in turn by the extraordinary growth in size and resource use of the human population. On a broad scale, there is little uncertainty about any of these components of change or their causes. However, much of the public believes the causes–even the existence–of global change to be uncertain and contentious topics. By speaking out effectively, we can help to shift the focus of public discussion towards what can and should be done about global environmental change.",
    url = "https://doi.org/10.2307/1941591",
    doi = "10.2307/1941591",
    openalex = "W2138958034",
    references = "doi1010160006320787901224, doi101038344529a0, doi101126science1223166415a, doi101126science2394836149, doi101126science24148691043, doi101126science2555043423, doi101126science261511778, doi1023071310258, doi1023071971875, doi105860choice301495"
}

Abstract The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel Assessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potential feedbacks from climate, changing CO 2, and other factors; this paper presents the key results from that assessment, together with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y −1. During the same period, the atmosphere gained 3.2 Gt C y −1 and the oceans are believed to have absorbed 2.0 Gt C y −1. The regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y −1 during this period. Meanwhile, tropical deforestation is thought to have released an average 1.6 Gt C y −1 over the 1980s. While the fluxes among the four pools should balance, the average 198Ds values lead to a ‘missing sink’ of 1.4 Gt C y −1 Several processes, including forest regrowth, CO 2 fertilization of plant growth (c. 1.0 Gt C y −1), N deposition (c. 0.6 Gt C y −1), and their interactions, may account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interactive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper presents detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties. Lack of knowledge about positive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO 2 concentrations. Analyses of the atmospheric gradients of CO 2 and 13 CO 2 concentrations provide increasingly strong evidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive detection in direct biomass and soil measurements remains elusive. Current regional‐to‐global terrestrial ecosystem models with coupled carbon and nitrogen cycles represent the effects of CO 2 fertilization differently, but all suggest longterm responses to CO 2 that are substantially smaller than potential leaf‐ or laboratory whole plant‐level responses. Analyses of emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO 2 concentrations are sensitive to the way in which biospheric feedbacks are modeled by c. 15%. Decisions about land use can have effects of 100s of Gt C over the next few centuries, with similarly significant effects on the atmosphere. Critical areas for future research are continued measurements and analyses of atmospheric data (CO 2 and 13 CO 2) to serve as large‐scale constraints, process studies of the scaling from the photosynthetic response to CO 2 to whole‐ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.

@article{doi101111j136524861995tb00008x,
    author = "Schimel, David",
    title = "Terrestrial ecosystems and the carbon cycle",
    year = "1995",
    journal = "Global Change Biology",
    abstract = "Abstract The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel Assessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potential feedbacks from climate, changing CO 2, and other factors; this paper presents the key results from that assessment, together with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y −1. During the same period, the atmosphere gained 3.2 Gt C y −1 and the oceans are believed to have absorbed 2.0 Gt C y −1. The regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y −1 during this period. Meanwhile, tropical deforestation is thought to have released an average 1.6 Gt C y −1 over the 1980s. While the fluxes among the four pools should balance, the average 198Ds values lead to a ‘missing sink’ of 1.4 Gt C y −1 Several processes, including forest regrowth, CO 2 fertilization of plant growth (c. 1.0 Gt C y −1), N deposition (c. 0.6 Gt C y −1), and their interactions, may account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interactive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper presents detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties. Lack of knowledge about positive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO 2 concentrations. Analyses of the atmospheric gradients of CO 2 and 13 CO 2 concentrations provide increasingly strong evidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive detection in direct biomass and soil measurements remains elusive. Current regional‐to‐global terrestrial ecosystem models with coupled carbon and nitrogen cycles represent the effects of CO 2 fertilization differently, but all suggest longterm responses to CO 2 that are substantially smaller than potential leaf‐ or laboratory whole plant‐level responses. Analyses of emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO 2 concentrations are sensitive to the way in which biospheric feedbacks are modeled by c. 15\%. Decisions about land use can have effects of 100s of Gt C over the next few centuries, with similarly significant effects on the atmosphere. Critical areas for future research are continued measurements and analyses of atmospheric data (CO 2 and 13 CO 2) to serve as large‐scale constraints, process studies of the scaling from the photosynthetic response to CO 2 to whole‐ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.",
    url = "https://doi.org/10.1111/j.1365-2486.1995.tb00008.x",
    doi = "10.1111/j.1365-2486.1995.tb00008.x",
    openalex = "W1970527729",
    references = "broecker1979fate, doi101007bf00002772, doi10102991gb01778, doi10102993gb02725, doi101038361520a0, doi101038363234a0, doi101126science2064417409, doi101126science24749491431, doi101126science26051161905, doi101126science2635144185, doi102136sssaj199303615995005700010034x, doi1023071311067, openalexw1759145845"
}

Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.

@article{doi101126science1072357,
    author = "Hoffert, Martin I. and Caldeira, K. and Benford, Gregory and Criswell, David R. and Green, Christopher and Herzog, Howard J. and Jain, Atul K. and Kheshgi, Haroon S. and Lackner, Klaus S. and Lewis, John S. and Lightfoot, H. Douglas and Manheimer, Wallace M. and Mankins, John C. and Mauel, M. E. and Perkins, L.J. and Schlesinger, Michael E. and Volk, Tyler and Wigley, T. M. L.",
    title = "Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet",
    year = "2002",
    journal = "Science",
    abstract = "Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.",
    url = "https://doi.org/10.1126/science.1072357",
    doi = "10.1126/science.1072357",
    openalex = "W2098442460",
    references = "doi10108014786449608620846"
}

Long‐term atmospheric 14 CO 2 observations are used to quantify fossil fuel‐derived CO 2 concentrations at a regional polluted site, and at a continental mountain station in southwest Germany. Fossil fuel CO 2 emission rates for the relevant catchment areas are obtained by applying the Radon‐Tracer‐Method. They compare well with statistical emissions inventories but reveal a larger seasonality than earlier assumed, thus contributing significantly to the observed CO 2 seasonal cycle over Europe. Based on the present approach, emissions reductions on the order of 5–10% are detectable for catchment areas of several hundred kilometres radius, as anticipated within a five‐years commitment period of the Kyoto Protocol. Still, no significant change of fossil fuel CO 2 emissions is observed at the two sites over the last 16 years.

@article{doi1010292003gl018477,
    author = "Levin, Ingeborg and Kromer, Bernd and Schmidt, Martina and Sartorius, H.",
    title = "A novel approach for independent budgeting of fossil fuel CO 2 over Europe by 14 CO 2 observations",
    year = "2003",
    journal = "Geophysical Research Letters",
    abstract = "Long‐term atmospheric 14 CO 2 observations are used to quantify fossil fuel‐derived CO 2 concentrations at a regional polluted site, and at a continental mountain station in southwest Germany. Fossil fuel CO 2 emission rates for the relevant catchment areas are obtained by applying the Radon‐Tracer‐Method. They compare well with statistical emissions inventories but reveal a larger seasonality than earlier assumed, thus contributing significantly to the observed CO 2 seasonal cycle over Europe. Based on the present approach, emissions reductions on the order of 5–10\% are detectable for catchment areas of several hundred kilometres radius, as anticipated within a five‐years commitment period of the Kyoto Protocol. Still, no significant change of fossil fuel CO 2 emissions is observed at the two sites over the last 16 years.",
    url = "https://doi.org/10.1029/2003gl018477",
    doi = "10.1029/2003gl018477",
    openalex = "W2148708766",
    references = "doi101126science1223166415b"
}

CO2 emissions from fossil-fuel burning and industrial processes have been accelerating at a global scale, with their growth rate increasing from 1.1% y(-1) for 1990-1999 to >3% y(-1) for 2000-2004. The emissions growth rate since 2000 was greater than for the most fossil-fuel intensive of the Intergovernmental Panel on Climate Change emissions scenarios developed in the late 1990s. Global emissions growth since 2000 was driven by a cessation or reversal of earlier declining trends in the energy intensity of gross domestic product (GDP) (energy/GDP) and the carbon intensity of energy (emissions/energy), coupled with continuing increases in population and per-capita GDP. Nearly constant or slightly increasing trends in the carbon intensity of energy have been recently observed in both developed and developing regions. No region is decarbonizing its energy supply. The growth rate in emissions is strongest in rapidly developing economies, particularly China. Together, the developing and least-developed economies (forming 80% of the world's population) accounted for 73% of global emissions growth in 2004 but only 41% of global emissions and only 23% of global cumulative emissions since the mid-18th century. The results have implications for global equity.

@article{doi101073pnas0700609104,
    author = "Raupach, Michael and Marland, Gregg and Ciais, Philippe and Quéré, Corinne Le and Canadell, Josep G. and Klepper, Gernot and Field, Christopher B.",
    title = "Global and regional drivers of accelerating CO 2 emissions",
    year = "2007",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "CO2 emissions from fossil-fuel burning and industrial processes have been accelerating at a global scale, with their growth rate increasing from 1.1\% y(-1) for 1990-1999 to >3\% y(-1) for 2000-2004. The emissions growth rate since 2000 was greater than for the most fossil-fuel intensive of the Intergovernmental Panel on Climate Change emissions scenarios developed in the late 1990s. Global emissions growth since 2000 was driven by a cessation or reversal of earlier declining trends in the energy intensity of gross domestic product (GDP) (energy/GDP) and the carbon intensity of energy (emissions/energy), coupled with continuing increases in population and per-capita GDP. Nearly constant or slightly increasing trends in the carbon intensity of energy have been recently observed in both developed and developing regions. No region is decarbonizing its energy supply. The growth rate in emissions is strongest in rapidly developing economies, particularly China. Together, the developing and least-developed economies (forming 80\% of the world's population) accounted for 73\% of global emissions growth in 2004 but only 41\% of global emissions and only 23\% of global cumulative emissions since the mid-18th century. The results have implications for global equity.",
    url = "https://doi.org/10.1073/pnas.0700609104",
    doi = "10.1073/pnas.0700609104",
    openalex = "W2131665065",
    references = "doi10100797836620308372, doi1010179781316577226067, doi101017cbo9780511817434, doi10102995jd03410, doi101126science1072357, doi101256004316502320517344, doi1015159783110874815048, doi10230720033020, openalexw1621450917, openalexw2743166207"
}

The growth rate of atmospheric carbon dioxide (CO(2)), the largest human contributor to human-induced climate change, is increasing rapidly. Three processes contribute to this rapid increase. Two of these processes concern emissions. Recent growth of the world economy combined with an increase in its carbon intensity have led to rapid growth in fossil fuel CO(2) emissions since 2000: comparing the 1990s with 2000-2006, the emissions growth rate increased from 1.3% to 3.3% y(-1). The third process is indicated by increasing evidence (P = 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of CO(2) emissions, implying a decline in the efficiency of CO(2) sinks on land and oceans in absorbing anthropogenic emissions. Since 2000, the contributions of these three factors to the increase in the atmospheric CO(2) growth rate have been approximately 65 +/- 16% from increasing global economic activity, 17 +/- 6% from the increasing carbon intensity of the global economy, and 18 +/- 15% from the increase in AF. An increasing AF is consistent with results of climate-carbon cycle models, but the magnitude of the observed signal appears larger than that estimated by models. All of these changes characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing.

@article{doi101073pnas0702737104,
    author = "Canadell, Josep G. and Quéré, Corinne Le and Raupach, Michael and Field, Christopher B. and Buitenhuis, Erik T. and Ciais, Philippe and Conway, T. J. and Gillett, Nathan P. and Houghton, R. A. and Marland, Gregg",
    title = "Contributions to accelerating atmospheric CO 2 growth from economic activity, carbon intensity, and efficiency of natural sinks",
    year = "2007",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "The growth rate of atmospheric carbon dioxide (CO(2)), the largest human contributor to human-induced climate change, is increasing rapidly. Three processes contribute to this rapid increase. Two of these processes concern emissions. Recent growth of the world economy combined with an increase in its carbon intensity have led to rapid growth in fossil fuel CO(2) emissions since 2000: comparing the 1990s with 2000-2006, the emissions growth rate increased from 1.3\% to 3.3\% y(-1). The third process is indicated by increasing evidence (P = 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of CO(2) emissions, implying a decline in the efficiency of CO(2) sinks on land and oceans in absorbing anthropogenic emissions. Since 2000, the contributions of these three factors to the increase in the atmospheric CO(2) growth rate have been approximately 65 +/- 16\% from increasing global economic activity, 17 +/- 6\% from the increasing carbon intensity of the global economy, and 18 +/- 15\% from the increase in AF. An increasing AF is consistent with results of climate-carbon cycle models, but the magnitude of the observed signal appears larger than that estimated by models. All of these changes characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing.",
    url = "https://doi.org/10.1073/pnas.0702737104",
    doi = "10.1073/pnas.0702737104",
    openalex = "W2133920545",
    references = "doi10103820859, doi10103835021000, doi101038nature03972, doi101049ep19770180, doi101073pnas0505734102, doi101073pnas0700609104, doi101175jcli38001, doi10230720033020, doi1023073324639, openalexw2939474406"
}

We present an estimate of net CO(2) exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO(2) mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO(2) called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO(2) in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed -0.65 PgC/yr (1 petagram = 10(15) g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of -0.4 to -1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to -0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.

@article{doi101073pnas0708986104,
    author = "Peters, Wouter and Jacobson, A. R. and Sweeney, Colm and Andrews, A. E. and Conway, T. J. and Masarie, K. A. and Miller, J. B. and Bruhwiler, L. M. and Pétron, Gabrielle and Hirsch, A. and Worthy, Douglas E. J. and van der Werf, Guido R. and Randerson, James T. and Wennberg, P. O. and Krol, Maarten and Tans, Pieter P.",
    title = "An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker",
    year = "2007",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "We present an estimate of net CO(2) exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO(2) mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO(2) called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO(2) in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed -0.65 PgC/yr (1 petagram = 10(15) g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of -0.4 to -1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32\%) and the boreal coniferous forests (22\%). Terrestrial uptake fell to -0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.",
    url = "https://doi.org/10.1073/pnas.0708986104",
    doi = "10.1073/pnas.0708986104",
    openalex = "W2166165736",
    references = "doi101007s1058400553522, doi1010292004gb002439, doi101038415626a, doi101038nature03972, doi101126science1057320, doi101126science1137004, doi101126science2825388442, doi105194acp319192003, doi105194acp54172005, doi105194acp634232006"
}

The global carbon budget is, of course, balanced. The conservation of carbon and the first law of thermodynamics are intact. “Balancing the carbon budget” refers to the state of the science in evaluating the terms of the global carbon equation. The annual increases in the amount of carbon in the atmosphere, oceans, and land should balance the emissions of carbon from fossil fuels and deforestation. Balancing the carbon budget is not the real issue, however. The real issue is understanding the processes responsible for net sources and sinks of carbon. Such understanding should lead to more accurate predictions of future concentrations of CO 2 and more accurate predictions of the rate and extent of climatic change. The recent past may be insufficient for prediction, however. Oceanic and terrestrial sinks that have lessened the rate of growth in atmospheric CO 2 until now may diminish as feedbacks between the carbon cycle and climate become more prominent.

@article{doi101146annurevearth35031306140057,
    author = "Houghton, R. A.",
    title = "Balancing the Global Carbon Budget",
    year = "2007",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "The global carbon budget is, of course, balanced. The conservation of carbon and the first law of thermodynamics are intact. “Balancing the carbon budget” refers to the state of the science in evaluating the terms of the global carbon equation. The annual increases in the amount of carbon in the atmosphere, oceans, and land should balance the emissions of carbon from fossil fuels and deforestation. Balancing the carbon budget is not the real issue, however. The real issue is understanding the processes responsible for net sources and sinks of carbon. Such understanding should lead to more accurate predictions of future concentrations of CO 2 and more accurate predictions of the rate and extent of climatic change. The recent past may be insufficient for prediction, however. Oceanic and terrestrial sinks that have lessened the rate of growth in atmospheric CO 2 until now may diminish as feedbacks between the carbon cycle and climate become more prominent.",
    url = "https://doi.org/10.1146/annurev.earth.35.031306.140057",
    doi = "10.1146/annurev.earth.35.031306.140057",
    openalex = "W2148979610",
    references = "broecker1979fate, doi101038298156a0, doi10103835041539, doi101038386698a0, doi101038nature03972, doi101038nature04514, doi101126science1097403, doi101126science2064417409, doi101126science2815374200, doi101175jcli38001, doi101256004316502320517344, doi1018901051076120000100423tvdoso20co2"
}

@misc{crossref2008fossil,
    title = "FOSSIL FUELS, CARBON DIOXIDE, AND GLOBAL WARMING",
    year = "2008",
    booktitle = "Power Struggle",
    url = "https://doi.org/10.5040/9798400699856.0012",
    doi = "10.5040/9798400699856.0012",
    openalex = "W4399955499",
    pages = "125-148"
}

Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time can new fossil fuels be formed naturally. In contrast, chemical recycling of carbon dioxide from natural and industrial sources as well as varied human activities or even from the air itself to methanol or dimethyl ether (DME) and their varied products can be achieved via its capture and subsequent reductive hydrogenative conversion. The present Perspective reviews this new approach and our research in the field over the last 15 years. Carbon recycling represents a significant aspect of our proposed Methanol Economy. Any available energy source (alternative energies such as solar, wind, geothermal, and atomic energy) can be used for the production of needed hydrogen and chemical conversion of CO(2). Improved new methods for the efficient reductive conversion of CO(2) to methanol and/or DME that we have developed include bireforming with methane and ways of catalytic or electrochemical conversions. Liquid methanol is preferable to highly volatile and potentially explosive hydrogen for energy storage and transportation. Together with the derived DME, they are excellent transportation fuels for internal combustion engines (ICE) and fuel cells as well as convenient starting materials for synthetic hydrocarbons and their varied products. Carbon dioxide thus can be chemically transformed from a detrimental greenhouse gas causing global warming into a valuable, renewable and inexhaustible carbon source of the future allowing environmentally neutral use of carbon fuels and derived hydrocarbon products.

@article{doi101021jo801260f,
    author = "Olah, George A. and Goeppert, Alain and Prakash, G. K. Surya",
    title = "Chemical Recycling of Carbon Dioxide to Methanol and Dimethyl Ether: From Greenhouse Gas to Renewable, Environmentally Carbon Neutral Fuels and Synthetic Hydrocarbons",
    year = "2008",
    journal = "The Journal of Organic Chemistry",
    abstract = "Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time can new fossil fuels be formed naturally. In contrast, chemical recycling of carbon dioxide from natural and industrial sources as well as varied human activities or even from the air itself to methanol or dimethyl ether (DME) and their varied products can be achieved via its capture and subsequent reductive hydrogenative conversion. The present Perspective reviews this new approach and our research in the field over the last 15 years. Carbon recycling represents a significant aspect of our proposed Methanol Economy. Any available energy source (alternative energies such as solar, wind, geothermal, and atomic energy) can be used for the production of needed hydrogen and chemical conversion of CO(2). Improved new methods for the efficient reductive conversion of CO(2) to methanol and/or DME that we have developed include bireforming with methane and ways of catalytic or electrochemical conversions. Liquid methanol is preferable to highly volatile and potentially explosive hydrogen for energy storage and transportation. Together with the derived DME, they are excellent transportation fuels for internal combustion engines (ICE) and fuel cells as well as convenient starting materials for synthetic hydrocarbons and their varied products. Carbon dioxide thus can be chemically transformed from a detrimental greenhouse gas causing global warming into a valuable, renewable and inexhaustible carbon source of the future allowing environmentally neutral use of carbon fuels and derived hydrocarbon products.",
    url = "https://doi.org/10.1021/jo801260f",
    doi = "10.1021/jo801260f",
    openalex = "W2113086422",
    references = "doi1010179781316577226067, openalexw1573748297"
}

CO 2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO 2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO 3. Common measures of the atmospheric lifetime of CO 2, including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO 2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20–35% of the CO 2 remains in the atmosphere after equilibration with the ocean (2–20 centuries). Neutralization by CaCO 3 draws the airborne fraction down further on timescales of 3 to 7 kyr.

@article{archer2009atmospheric,
    author = "Archer, David and Eby, Michael and Brovkin, Victor and Ridgwell, Andy and Cao, Long and Mikolajewicz, Uwe and Caldeira, Ken and Matsumoto, Katsumi and Munhoven, Guy and Montenegro, Alvaro and Tokos, Kathy",
    title = "Atmospheric Lifetime of Fossil Fuel Carbon Dioxide",
    year = "2009",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "CO 2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO 2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO 3. Common measures of the atmospheric lifetime of CO 2, including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO 2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20–35\% of the CO 2 remains in the atmosphere after equilibration with the ocean (2–20 centuries). Neutralization by CaCO 3 draws the airborne fraction down further on timescales of 3 to 7 kyr.",
    url = "https://doi.org/10.1146/annurev.earth.031208.100206",
    doi = "10.1146/annurev.earth.031208.100206",
    number = "1",
    openalex = "W2149521176",
    pages = "117-134",
    volume = "37",
    references = "doi101016003101829290207l, doi101016s0038071703001238, doi101029jc086ic10p09776, doi10103834839, doi101038353225a0, doi101046j13652486200100383x, doi101046j13652486200300569x, doi101126science24749491431, doi101175jcli38001, doi1023071971875, doi102475ajs2837641, doi102475ajs294156, openalexw2939474406"
}

The lack of temporal information is an important limitation of life cycle assessment (LCA). A dynamic LCA approach is proposed to improve the accuracy of LCA by addressing the inconsistency of temporal assessment. This approach consists of first computing a dynamic life cycle inventory (LCI), considering the temporal profile of emissions. Then, time-dependent characterization factors are calculated to assess the dynamic LCI in real-time impact scores for any given time horizon. Although generally applicable to any impact category, this approach is developed here for global warming, based on the radiative forcing concept. This case study demonstrates that the use of global warming potentials for a given time horizon to characterize greenhouse gas emissions leads to an inconsistency between the time frame chosen for the analysis and the time period covered by the LCA results. Dynamic LCA is applied to the US EPA LCA on renewable fuels, which compares the life cycle greenhouse gas emissions of different biofuels with fossil fuels including land-use change emissions. The comparison of the results obtained with both traditional and dynamic LCA approaches shows that the difference can be important enough to change the conclusions on whether or not a biofuel meets some given global warming reduction targets.

@article{doi101021es9030003,
    author = "Levasseur, Annie and Lesage, Pascal and Margni, Manuele and Deschênes, Louise and Samson, Réjean",
    title = "Considering Time in LCA: Dynamic LCA and Its Application to Global Warming Impact Assessments",
    year = "2010",
    journal = "Environmental Science \& Technology",
    abstract = "The lack of temporal information is an important limitation of life cycle assessment (LCA). A dynamic LCA approach is proposed to improve the accuracy of LCA by addressing the inconsistency of temporal assessment. This approach consists of first computing a dynamic life cycle inventory (LCI), considering the temporal profile of emissions. Then, time-dependent characterization factors are calculated to assess the dynamic LCI in real-time impact scores for any given time horizon. Although generally applicable to any impact category, this approach is developed here for global warming, based on the radiative forcing concept. This case study demonstrates that the use of global warming potentials for a given time horizon to characterize greenhouse gas emissions leads to an inconsistency between the time frame chosen for the analysis and the time period covered by the LCA results. Dynamic LCA is applied to the US EPA LCA on renewable fuels, which compares the life cycle greenhouse gas emissions of different biofuels with fossil fuels including land-use change emissions. The comparison of the results obtained with both traditional and dynamic LCA approaches shows that the difference can be important enough to change the conclusions on whether or not a biofuel meets some given global warming reduction targets.",
    url = "https://doi.org/10.1021/es9030003",
    doi = "10.1021/es9030003",
    openalex = "W2065202886",
    references = "doi101038344529a0"
}

@article{andres2011monthly,
    author = "Andres, R. J. and Gregg, J. S. and Losey, L. and Marland, G. and Boden, T. A.",
    title = "Monthly, global emissions of carbon dioxide from fossil fuel consumption",
    year = "2011",
    journal = "Tellus B: Chemical and Physical Meteorology",
    url = "https://doi.org/10.1111/j.1600-0889.2011.00530.x",
    doi = "10.1111/j.1600-0889.2011.00530.x",
    number = "3",
    openalex = "W2168433360",
    pages = "309",
    volume = "63",
    references = "doi1010179781316577226067, doi101017cbo9780511664885043, doi101029jd094id06p08549, doi101038382146a0, doi101038ngeo689, doi105194acp115432011, openalexw1575579655, openalexw1909570941, openalexw2939474406"
}

Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time, millions of years, can new fossil fuels be formed naturally. The burning of our diminishing fossil fuel reserves is accompanied by large anthropogenic CO(2) release, which is outpacing nature's CO(2) recycling capability, causing significant environmental harm. To supplement the natural carbon cycle, we have proposed and developed a feasible anthropogenic chemical recycling of carbon dioxide. Carbon dioxide is captured by absorption technologies from any natural or industrial source, from human activities, or even from the air itself. It can then be converted by feasible chemical transformations into fuels such as methanol, dimethyl ether, and varied products including synthetic hydrocarbons and even proteins for animal feed, thus supplementing our food chain. This concept of broad scope and framework is the basis of what we call the Methanol Economy. The needed renewable starting materials, water and CO(2), are available anywhere on Earth. The required energy for the synthetic carbon cycle can come from any alternative energy source such as solar, wind, geothermal, and even hopefully safe nuclear energy. The anthropogenic carbon dioxide cycle offers a way of assuring a sustainable future for humankind when fossil fuels become scarce. While biosources can play a limited role in supplementing future energy needs, they increasingly interfere with the essentials of the food chain. We have previously reviewed aspects of the chemical recycling of carbon dioxide to methanol and dimethyl ether. In the present Perspective, we extend the discussion of the innovative and feasible anthropogenic carbon cycle, which can be the basis of progressively liberating humankind from its dependence on diminishing fossil fuel reserves while also controlling harmful CO(2) emissions to the atmosphere. We also discuss in more detail the essential stages and the significant aspects of carbon capture and subsequent recycling. Our ability to develop a feasible anthropogenic chemical carbon cycle supplementing nature's photosynthesis also offers a new solution to one of the major challenges facing humankind.

@article{doi101021ja202642y,
    author = "Olah, George A. and Prakash, G. K. Surya and Goeppert, Alain",
    title = "Anthropogenic Chemical Carbon Cycle for a Sustainable Future",
    year = "2011",
    journal = "Journal of the American Chemical Society",
    abstract = "Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time, millions of years, can new fossil fuels be formed naturally. The burning of our diminishing fossil fuel reserves is accompanied by large anthropogenic CO(2) release, which is outpacing nature's CO(2) recycling capability, causing significant environmental harm. To supplement the natural carbon cycle, we have proposed and developed a feasible anthropogenic chemical recycling of carbon dioxide. Carbon dioxide is captured by absorption technologies from any natural or industrial source, from human activities, or even from the air itself. It can then be converted by feasible chemical transformations into fuels such as methanol, dimethyl ether, and varied products including synthetic hydrocarbons and even proteins for animal feed, thus supplementing our food chain. This concept of broad scope and framework is the basis of what we call the Methanol Economy. The needed renewable starting materials, water and CO(2), are available anywhere on Earth. The required energy for the synthetic carbon cycle can come from any alternative energy source such as solar, wind, geothermal, and even hopefully safe nuclear energy. The anthropogenic carbon dioxide cycle offers a way of assuring a sustainable future for humankind when fossil fuels become scarce. While biosources can play a limited role in supplementing future energy needs, they increasingly interfere with the essentials of the food chain. We have previously reviewed aspects of the chemical recycling of carbon dioxide to methanol and dimethyl ether. In the present Perspective, we extend the discussion of the innovative and feasible anthropogenic carbon cycle, which can be the basis of progressively liberating humankind from its dependence on diminishing fossil fuel reserves while also controlling harmful CO(2) emissions to the atmosphere. We also discuss in more detail the essential stages and the significant aspects of carbon capture and subsequent recycling. Our ability to develop a feasible anthropogenic chemical carbon cycle supplementing nature's photosynthesis also offers a new solution to one of the major challenges facing humankind.",
    url = "https://doi.org/10.1021/ja202642y",
    doi = "10.1021/ja202642y",
    openalex = "W1974801467",
    references = "doi10108014786449608620846"
}

[1] We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global scale using the machine learning technique, model tree ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5° × 0.5° spatial resolution and a monthly temporal resolution from 1982 to 2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were not as strong (MEf between 0.29 and 0.52). Improved accounting of disturbance and lagged environmental effects, along with improved characterization of errors in the training data set, would contribute most to further reducing uncertainties. Our global estimates of LE (158 ± 7 J × 1018 yr−1), H (164 ± 15 J × 1018 yr−1), and GPP (119 ± 6 Pg C yr−1) were similar to independent estimates. Our global TER estimate (96 ± 6 Pg C yr−1) was likely underestimated by 5–10%. Hot spot regions of interannual variability in carbon fluxes occurred in semiarid to semihumid regions and were controlled by moisture supply. Overall, GPP was more important to interannual variability in NEE than TER. Our empirically derived fluxes may be used for calibration and evaluation of land surface process models and for exploratory and diagnostic assessments of the biosphere.

@article{doi1010292010jg001566,
    author = "Jung, Martin and Reichstein, Markus and Margolis, Hank A. and Cescatti, Alessandro and Richardson, Andrew D. and Arain, M. Altaf and Arneth, Almut and Bernhofer, Christian and Bonal, Damien and Chen, Jiquan and Gianelle, Damiano and Gobron, Nadine and Kiely, Gerard and Kutsch, Werner L. and Lasslop, Gitta and Law, B. E. and Lindroth, Anders and Merbold, Lutz and Montagnani, Leonardo and Moors, Eddy and Papale, Dario and Sottocornola, Matteo and Vaccari, Francesco Primo and Williams, C. A.",
    title = "Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations",
    year = "2011",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "[1] We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global scale using the machine learning technique, model tree ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5° × 0.5° spatial resolution and a monthly temporal resolution from 1982 to 2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were not as strong (MEf between 0.29 and 0.52). Improved accounting of disturbance and lagged environmental effects, along with improved characterization of errors in the training data set, would contribute most to further reducing uncertainties. Our global estimates of LE (158 ± 7 J × 1018 yr−1), H (164 ± 15 J × 1018 yr−1), and GPP (119 ± 6 Pg C yr−1) were similar to independent estimates. Our global TER estimate (96 ± 6 Pg C yr−1) was likely underestimated by 5–10\%. Hot spot regions of interannual variability in carbon fluxes occurred in semiarid to semihumid regions and were controlled by moisture supply. Overall, GPP was more important to interannual variability in NEE than TER. Our empirically derived fluxes may be used for calibration and evaluation of land surface process models and for exploratory and diagnostic assessments of the biosphere.",
    url = "https://doi.org/10.1029/2010jg001566",
    doi = "10.1029/2010jg001566",
    openalex = "W2126479957",
    references = "doi1011752008bams26341, openalexw1909570941"
}

Recent research has highlighted the valuable role that coastal and marine ecosystems play in sequestering carbon dioxide (CO 2). The carbon (C) sequestered in vegetated coastal ecosystems, specifically mangrove forests, seagrass beds, and salt marshes, has been termed “blue carbon”. Although their global area is one to two orders of magnitude smaller than that of terrestrial forests, the contribution of vegetated coastal habitats per unit area to long‐term C sequestration is much greater, in part because of their efficiency in trapping suspended matter and associated organic C during tidal inundation. Despite the value of mangrove forests, seagrass beds, and salt marshes in sequestering C, and the other goods and services they provide, these systems are being lost at critical rates and action is urgently needed to prevent further degradation and loss. Recognition of the C sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration; however, it is necessary to improve scientific understanding of the underlying mechanisms that control C sequestration in these ecosystems. Here, we identify key areas of uncertainty and specific actions needed to address them.

@article{doi101890110004,
    author = "Mcleod, Elizabeth and Chmura, Gail L. and Bouillon, Steven and Salm, Rodney V. and Björk, Mats and Duarte, Carlos M. and Lovelock, Catherine E. and Schlesinger, William H. and Silliman, Brian R.",
    title = "A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO 2",
    year = "2011",
    journal = "Frontiers in Ecology and the Environment",
    abstract = "Recent research has highlighted the valuable role that coastal and marine ecosystems play in sequestering carbon dioxide (CO 2). The carbon (C) sequestered in vegetated coastal ecosystems, specifically mangrove forests, seagrass beds, and salt marshes, has been termed “blue carbon”. Although their global area is one to two orders of magnitude smaller than that of terrestrial forests, the contribution of vegetated coastal habitats per unit area to long‐term C sequestration is much greater, in part because of their efficiency in trapping suspended matter and associated organic C during tidal inundation. Despite the value of mangrove forests, seagrass beds, and salt marshes in sequestering C, and the other goods and services they provide, these systems are being lost at critical rates and action is urgently needed to prevent further degradation and loss. Recognition of the C sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration; however, it is necessary to improve scientific understanding of the underlying mechanisms that control C sequestration in these ecosystems. Here, we identify key areas of uncertainty and specific actions needed to address them.",
    url = "https://doi.org/10.1890/110004",
    doi = "10.1890/110004",
    openalex = "W1999803596",
    references = "doi101016c20120016547, doi101038387253a0, doi101038nature06949, doi101038ngeo1123, doi101073pnas0905620106, doi101111j14668238201000584x, doi101126science1097403, openalexw1520428197, openalexw2939474406, openalexw75231382"
}

Abstract. Emissions of CO2 from fossil fuel combustion are a critical quantity that must be accurately given in established flux inversion frameworks. Work with emerging satellite-based inversions requires spatiotemporally-detailed inventories that permit analysis of regional natural sources and sinks. Conventional approaches for disaggregating national emissions beyond the country and city levels based on population distribution have certain difficulties in their application. We developed a global 1 km×1 km annual fossil fuel CO2 emission inventory for the years 1980–2007 by combining a worldwide point source database and satellite observations of the global nightlight distribution. In addition to estimating the national emissions using global energy consumption statistics, emissions from point sources were estimated separately and were spatially allocated to exact locations indicated by the point source database. Emissions from other sources were distributed using a special nightlight dataset that had fewer saturated pixels compared with regular nightlight datasets. The resulting spatial distributions differed in several ways from those derived using conventional population-based approaches. Because of the inherent characteristics of the nightlight distribution, source regions corresponding to human settlements and land transportation were well articulated. Our distributions showed good agreement with a high-resolution inventory across the US at spatial resolutions that were adequate for regional flux inversions. The inventory can be extended to the future using updated data, and is expected to be incorporated into models for operational flux inversions that use observational data from the Japanese Greenhouse Gases Observing SATellite (GOSAT).

@article{doi105194acp115432011,
    author = "Oda, Tomohiro and Maksyutov, Shamil",
    title = "A very high-resolution (1 km×1 km) global fossil fuel CO 2 emission inventory derived using a point source database and satellite observations of nighttime lights",
    year = "2011",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. Emissions of CO2 from fossil fuel combustion are a critical quantity that must be accurately given in established flux inversion frameworks. Work with emerging satellite-based inversions requires spatiotemporally-detailed inventories that permit analysis of regional natural sources and sinks. Conventional approaches for disaggregating national emissions beyond the country and city levels based on population distribution have certain difficulties in their application. We developed a global 1 km×1 km annual fossil fuel CO2 emission inventory for the years 1980–2007 by combining a worldwide point source database and satellite observations of the global nightlight distribution. In addition to estimating the national emissions using global energy consumption statistics, emissions from point sources were estimated separately and were spatially allocated to exact locations indicated by the point source database. Emissions from other sources were distributed using a special nightlight dataset that had fewer saturated pixels compared with regular nightlight datasets. The resulting spatial distributions differed in several ways from those derived using conventional population-based approaches. Because of the inherent characteristics of the nightlight distribution, source regions corresponding to human settlements and land transportation were well articulated. Our distributions showed good agreement with a high-resolution inventory across the US at spatial resolutions that were adequate for regional flux inversions. The inventory can be extended to the future using updated data, and is expected to be incorporated into models for operational flux inversions that use observational data from the Japanese Greenhouse Gases Observing SATellite (GOSAT).",
    url = "https://doi.org/10.5194/acp-11-543-2011",
    doi = "10.5194/acp-11-543-2011",
    openalex = "W2111195126",
    references = "doi101016s0034425798000984, doi1010292000gl011912, doi1010292004gb002439, doi101038415626a, doi101126science1137004, doi102151sola2009041, doi1023073324639, doi105194acp744192007, myhre2009a, openalexw1007704209, openalexw2105244019"
}

@article{doi101016jenpol201210046,
    author = "Höök, Mikael and Tang, Xu",
    title = "Depletion of fossil fuels and anthropogenic climate change—A review",
    year = "2012",
    journal = "Energy Policy",
    url = "https://doi.org/10.1016/j.enpol.2012.10.046",
    doi = "10.1016/j.enpol.2012.10.046",
    openalex = "W2121393448",
    references = "doi10108014786449608620846, doi1015159780295741406007"
}

Abstract. This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts on inventorying them; their global, regional, and national totals at different spatial and temporal scales; how they are distributed on global grids (i.e., maps); how they are transported in models; and the uncertainties associated with these different aspects of the emissions. The magnitude of emissions from the combustion of fossil fuels has been almost continuously increasing with time since fossil fuels were first used by humans. Despite events in some nations specifically designed to reduce emissions, or which have had emissions reduction as a byproduct of other events, global total emissions continue their general increase with time. Global total fossil-fuel carbon dioxide emissions are known to within 10 % uncertainty (95 % confidence interval). Uncertainty on individual national total fossil-fuel carbon dioxide emissions range from a few percent to more than 50 %. This manuscript concludes that carbon dioxide emissions from fossil-fuel combustion continue to increase with time and that while much is known about the overall characteristics of these emissions, much is still to be learned about the detailed characteristics of these emissions.

@article{doi105194bg918452012,
    author = "Andres, R. J. and Boden, T. A. and Bréon, François‐Marie and Ciais, Philippe and Davis, Steven J. and Erickson, Darin J. and Gregg, Jay Sterling and Jacobson, A. R. and Marland, Gregg and Miller, J. B. and Oda, Tomohiro and Olivier, J. G. J. and Raupach, Michael and Rayner, P. J. and Treanton, K.",
    title = "A synthesis of carbon dioxide emissions from fossil-fuel combustion",
    year = "2012",
    journal = "Biogeosciences",
    abstract = "Abstract. This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts on inventorying them; their global, regional, and national totals at different spatial and temporal scales; how they are distributed on global grids (i.e., maps); how they are transported in models; and the uncertainties associated with these different aspects of the emissions. The magnitude of emissions from the combustion of fossil fuels has been almost continuously increasing with time since fossil fuels were first used by humans. Despite events in some nations specifically designed to reduce emissions, or which have had emissions reduction as a byproduct of other events, global total emissions continue their general increase with time. Global total fossil-fuel carbon dioxide emissions are known to within 10 \% uncertainty (95 \% confidence interval). Uncertainty on individual national total fossil-fuel carbon dioxide emissions range from a few percent to more than 50 \%. This manuscript concludes that carbon dioxide emissions from fossil-fuel combustion continue to increase with time and that while much is known about the overall characteristics of these emissions, much is still to be learned about the detailed characteristics of these emissions.",
    url = "https://doi.org/10.5194/bg-9-1845-2012",
    doi = "10.5194/bg-9-1845-2012",
    openalex = "W2139243186",
    references = "doi105194acp115432011"
}

Abstract Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black‐carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom‐up inventory methods are 7500 Gg yr −1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial‐era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m −2 with 90% uncertainty bounds of (+0.08, +1.27) W m −2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m −2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial‐era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m −2 with 90% uncertainty bounds of +0.17 to +2.1 W m −2. Thus, there is a very high probability that black carbon emissions, independent of co‐emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m −2, is the second most important human emission in terms of its climate forcing in the present‐day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short‐lived species that may either cool or warm climate. Climate forcings from co‐emitted species are estimated and used in the framework described herein. When the principal effects of short‐lived co‐emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy‐related sources (fossil fuel and biofuel) have an industrial‐era climate forcing of +0.22 (−0.50 to +1.08) W m −2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short‐lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial‐era climate forcing by all short‐lived species from black‐carbon‐rich sources becomes slightly negative (−0.06 W m −2 with 90% uncertainty bounds of −1.45 to +1.29 W m −2). The uncertainties in net climate forcing from black‐carbon‐rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co‐emitted organic carbon. In prioritizing potential black‐carbon mitigation actions, non‐science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near‐term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black‐carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

@article{doi101002jgrd50171,
    author = "Bond, Tami C. and Doherty, Sarah J. and Fahey, D. W. and Forster, Piers and Berntsen, Terje K. and DeAngelo, B. J. and Flanner, M. and Ghan, S. J. and Kärcher, B. and Koch, D. and Kinne, S. and Kondo, Y. and Quinn, Patricia K. and Sarofim, Marcus C. and Schultz, Martin G. and Schulz, Michael and Venkataraman, Chandra and Zhang, H. and Zhang, Xiaofeng and Bellouin, Nicolas and Guttikunda, Sarath and Hopke, Philip K. and Jacobson, Mark Z. and Kaiser, Johannes W. and Klimont, Zbigniew and Lohmann, Ulrike and Schwarz, J. P. and Shindell, Drew and Storelvmo, Trude and Warren, Stephen G. and Zender, Charles S.",
    title = "Bounding the role of black carbon in the climate system: A scientific assessment",
    year = "2013",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Abstract Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black‐carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom‐up inventory methods are 7500 Gg yr −1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial‐era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m −2 with 90\% uncertainty bounds of (+0.08, +1.27) W m −2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m −2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial‐era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m −2 with 90\% uncertainty bounds of +0.17 to +2.1 W m −2. Thus, there is a very high probability that black carbon emissions, independent of co‐emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m −2, is the second most important human emission in terms of its climate forcing in the present‐day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short‐lived species that may either cool or warm climate. Climate forcings from co‐emitted species are estimated and used in the framework described herein. When the principal effects of short‐lived co‐emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy‐related sources (fossil fuel and biofuel) have an industrial‐era climate forcing of +0.22 (−0.50 to +1.08) W m −2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short‐lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial‐era climate forcing by all short‐lived species from black‐carbon‐rich sources becomes slightly negative (−0.06 W m −2 with 90\% uncertainty bounds of −1.45 to +1.29 W m −2). The uncertainties in net climate forcing from black‐carbon‐rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co‐emitted organic carbon. In prioritizing potential black‐carbon mitigation actions, non‐science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near‐term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black‐carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.",
    url = "https://doi.org/10.1002/jgrd.50171",
    doi = "10.1002/jgrd.50171",
    openalex = "W1907369419",
    references = "doi1010160960168693901047, doi101016s0169743996000445, doi1010292005jd006653, doi10102993jd02916, doi101038nature08823, doi101126science22246301283, doi105194acp10117072010, doi105194acp119312011, openalexw2907110490, openalexw2939474406, openalexw617039848"
}

@article{doi101016jpecs201305001,
    author = "Zhao, Chuanwen and Chen, Xiaoping and Anthony, Edward J. and Jiang, Xi and Duan, Lunbo and Wu, Ye and Dong, Wei and Zhao, Changsui",
    title = "Capturing CO2 in flue gas from fossil fuel-fired power plants using dry regenerable alkali metal-based sorbent",
    year = "2013",
    journal = "Progress in Energy and Combustion Science",
    url = "https://doi.org/10.1016/j.pecs.2013.05.001",
    doi = "10.1016/j.pecs.2013.05.001",
    openalex = "W1982073923",
    references = "garrett1992on"
}

@article{doi101038nature14677,
    author = "Liu, Zhu and Guan, Dabo and Wei, Wei and Davis, Steven J. and Ciais, Philippe and Bai, Jin and Peng, Shushi and Zhang, Qiang and Hubacek, Klaus and Marland, Gregg and Andres, R. J. and Crawford‐Brown, Douglas and Lin, Jintai and Zhao, Hongyan and Hong, Chaopeng and Boden, Thomas A. and Feng, Kuishuang and Peters, Glen P. and Xi, Fengming and Liu, Junguo and Li, Yuan and Zhao, Yu and Zeng, Ning and He, Kebin",
    title = "Reduced carbon emission estimates from fossil fuel combustion and cement production in China",
    year = "2015",
    journal = "Nature",
    url = "https://doi.org/10.1038/nature14677",
    doi = "10.1038/nature14677",
    openalex = "W2119642490"
}

Abstract. The land and ocean absorb on average just over half of the anthropogenic emissions of carbon dioxide (CO2) every year. These CO2 "sinks" are modulated by climate change and variability. Here we use a suite of nine dynamic global vegetation models (DGVMs) and four ocean biogeochemical general circulation models (OBGCMs) to estimate trends driven by global and regional climate and atmospheric CO2 in land and oceanic CO2 exchanges with the atmosphere over the period 1990–2009, to attribute these trends to underlying processes in the models, and to quantify the uncertainty and level of inter-model agreement. The models were forced with reconstructed climate fields and observed global atmospheric CO2; land use and land cover changes are not included for the DGVMs. Over the period 1990–2009, the DGVMs simulate a mean global land carbon sink of −2.4 ± 0.7 Pg C yr−1 with a small significant trend of −0.06 ± 0.03 Pg C yr−2 (increasing sink). Over the more limited period 1990–2004, the ocean models simulate a mean ocean sink of −2.2 ± 0.2 Pg C yr−1 with a trend in the net C uptake that is indistinguishable from zero (−0.01 ± 0.02 Pg C yr−2). The two ocean models that extended the simulations until 2009 suggest a slightly stronger, but still small, trend of −0.02 ± 0.01 Pg C yr−2. Trends from land and ocean models compare favourably to the land greenness trends from remote sensing, atmospheric inversion results, and the residual land sink required to close the global carbon budget. Trends in the land sink are driven by increasing net primary production (NPP), whose statistically significant trend of 0.22 ± 0.08 Pg C yr−2 exceeds a significant trend in heterotrophic respiration of 0.16 ± 0.05 Pg C yr−2 – primarily as a consequence of widespread CO2 fertilisation of plant production. Most of the land-based trend in simulated net carbon uptake originates from natural ecosystems in the tropics (−0.04 ± 0.01 Pg C yr−2), with almost no trend over the northern land region, where recent warming and reduced rainfall offsets the positive impact of elevated atmospheric CO2 and changes in growing season length on carbon storage. The small uptake trend in the ocean models emerges because climate variability and change, and in particular increasing sea surface temperatures, tend to counter\\-act the trend in ocean uptake driven by the increase in atmospheric CO2. Large uncertainty remains in the magnitude and sign of modelled carbon trends in several regions, as well as regarding the influence of land use and land cover changes on regional trends.

@article{doi105194bg126532015,
    author = "Sitch, Stephen and Friedlingstein, Pierre and Gruber, Nicolas and Jones, S. D. M. and Murray‐Tortarolo, Guillermo N. and Ahlström, Anders and Doney, Scott C. and Graven, Heather and Heinze, Christoph and Huntingford, Chris and Levis, Samuel and Levy, Peter and Lomas, M. and Poulter, Benjamin and Viovy, Nicolas and Zaehle, Sönke and Zeng, Ning and Arneth, Almut and Bonan, Gordon B. and Bopp, Laurent and Canadell, Josep G. and Chevallier, Frédéric and Ciais, Philippe and Ellis, Rich and Gloor, Manuel and Peylin, Philippe and Piao, Shilong and Quéré, Corinne Le and Smith, Benjamin and Zhu, Zaichun and Myneni, Ranga B.",
    title = "Recent trends and drivers of regional sources and sinks of carbon dioxide",
    year = "2015",
    journal = "Biogeosciences",
    abstract = {Abstract. The land and ocean absorb on average just over half of the anthropogenic emissions of carbon dioxide (CO2) every year. These CO2 "sinks" are modulated by climate change and variability. Here we use a suite of nine dynamic global vegetation models (DGVMs) and four ocean biogeochemical general circulation models (OBGCMs) to estimate trends driven by global and regional climate and atmospheric CO2 in land and oceanic CO2 exchanges with the atmosphere over the period 1990–2009, to attribute these trends to underlying processes in the models, and to quantify the uncertainty and level of inter-model agreement. The models were forced with reconstructed climate fields and observed global atmospheric CO2; land use and land cover changes are not included for the DGVMs. Over the period 1990–2009, the DGVMs simulate a mean global land carbon sink of −2.4 ± 0.7 Pg C yr−1 with a small significant trend of −0.06 ± 0.03 Pg C yr−2 (increasing sink). Over the more limited period 1990–2004, the ocean models simulate a mean ocean sink of −2.2 ± 0.2 Pg C yr−1 with a trend in the net C uptake that is indistinguishable from zero (−0.01 ± 0.02 Pg C yr−2). The two ocean models that extended the simulations until 2009 suggest a slightly stronger, but still small, trend of −0.02 ± 0.01 Pg C yr−2. Trends from land and ocean models compare favourably to the land greenness trends from remote sensing, atmospheric inversion results, and the residual land sink required to close the global carbon budget. Trends in the land sink are driven by increasing net primary production (NPP), whose statistically significant trend of 0.22 ± 0.08 Pg C yr−2 exceeds a significant trend in heterotrophic respiration of 0.16 ± 0.05 Pg C yr−2 – primarily as a consequence of widespread CO2 fertilisation of plant production. Most of the land-based trend in simulated net carbon uptake originates from natural ecosystems in the tropics (−0.04 ± 0.01 Pg C yr−2), with almost no trend over the northern land region, where recent warming and reduced rainfall offsets the positive impact of elevated atmospheric CO2 and changes in growing season length on carbon storage. The small uptake trend in the ocean models emerges because climate variability and change, and in particular increasing sea surface temperatures, tend to counter\\-act the trend in ocean uptake driven by the increase in atmospheric CO2. Large uncertainty remains in the magnitude and sign of modelled carbon trends in several regions, as well as regarding the influence of land use and land cover changes on regional trends.},
    url = "https://doi.org/10.5194/bg-12-653-2015",
    doi = "10.5194/bg-12-653-2015",
    openalex = "W2035962295",
    references = "doi1010292006gb002784, doi105194bg1066992013"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover-change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2, and land-cover-change (some including nitrogen–carbon interactions). We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2004–2013), EFF was 8.9 ± 0.4 GtC yr−1, ELUC 0.9 ± 0.5 GtC yr−1, GATM 4.3 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 2.9 ± 0.8 GtC yr−1. For year 2013 alone, EFF grew to 9.9 ± 0.5 GtC yr−1, 2.3% above 2012, continuing the growth trend in these emissions, ELUC was 0.9 ± 0.5 GtC yr−1, GATM was 5.4 ± 0.2 GtC yr−1, SOCEAN was 2.9 ± 0.5 GtC yr−1, and SLAND was 2.5 ± 0.9 GtC yr−1. GATM was high in 2013, reflecting a steady increase in EFF and smaller and opposite changes between SOCEAN and SLAND compared to the past decade (2004–2013). The global atmospheric CO2 concentration reached 395.31 ± 0.10 ppm averaged over 2013. We estimate that EFF will increase by 2.5% (1.3–3.5%) to 10.1 ± 0.6 GtC in 2014 (37.0 ± 2.2 GtCO2 yr−1), 65% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the global economy. From this projection of EFF and assumed constant ELUC for 2014, cumulative emissions of CO2 will reach about 545 ± 55 GtC (2000 ± 200 GtCO2) for 1870–2014, about 75% from EFF and 25% from ELUC. This paper documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this living data set (Le Quéré et al., 2013, 2014). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2014).

@article{doi105194essd7472015,
    author = "Quéré, Corinne Le and Moriarty, R. and Andrew, Robbie M. and Peters, Glen P. and Ciais, Philippe and Friedlingstein, Pierre and Jones, S. D. M. and Sitch, Stephen and Tans, Pieter P. and Arneth, Almut and Boden, T. A. and Bopp, Laurent and Bozec, Yann and Canadell, Josep G. and Chini, Louise and Chevallier, Frédéric and Cosca, Catherine E and Harris, Ian and Hoppema, Mario and Houghton, R. A. and House, Joanna I. and Jain, Atul K. and Johannessen, Truls and Kato, Etsushi and Keeling, Ralph F. and Kitidis, Vassilis and Goldewijk, Kees Klein and Koven, Charles D. and Landa, Camilla S. and Landschützer, Peter and Lenton, Andrew and Lima, Ivan D. and Marland, Gregg and Mathis, Jeremy T. and Metzl, Nicolas and Nojiri, Yukihiro and Olsen, Are and Ono, Tsuneo and Peng, Shushi and Peters, Wouter and Pfeil, Benjamin and Poulter, Benjamin and Raupach, Michael and Regnier, Pierre and Rödenbeck, Christian and Saito, Shu and Salisbury, J. and Schuster, Ute and Schwinger, Jörg and Séférian, Roland and Segschneider, Joachim and Steinhoff, Tobias and Stocker, Benjamin D. and Sutton, Adrienne J. and Takahashi, Taro and Tilbrook, Bronte and van der Werf, Guido R. and Viovy, Nicolas and Wang, Ying‐Ping and Wanninkhof, Rik and Wiltshire, A. and Zeng, Ning",
    title = "Global carbon budget 2014",
    year = "2015",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover-change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2, and land-cover-change (some including nitrogen–carbon interactions). We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2004–2013), EFF was 8.9 ± 0.4 GtC yr−1, ELUC 0.9 ± 0.5 GtC yr−1, GATM 4.3 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 2.9 ± 0.8 GtC yr−1. For year 2013 alone, EFF grew to 9.9 ± 0.5 GtC yr−1, 2.3\% above 2012, continuing the growth trend in these emissions, ELUC was 0.9 ± 0.5 GtC yr−1, GATM was 5.4 ± 0.2 GtC yr−1, SOCEAN was 2.9 ± 0.5 GtC yr−1, and SLAND was 2.5 ± 0.9 GtC yr−1. GATM was high in 2013, reflecting a steady increase in EFF and smaller and opposite changes between SOCEAN and SLAND compared to the past decade (2004–2013). The global atmospheric CO2 concentration reached 395.31 ± 0.10 ppm averaged over 2013. We estimate that EFF will increase by 2.5\% (1.3–3.5\%) to 10.1 ± 0.6 GtC in 2014 (37.0 ± 2.2 GtCO2 yr−1), 65\% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the global economy. From this projection of EFF and assumed constant ELUC for 2014, cumulative emissions of CO2 will reach about 545 ± 55 GtC (2000 ± 200 GtCO2) for 1870–2014, about 75\% from EFF and 25\% from ELUC. This paper documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this living data set (Le Quéré et al., 2013, 2014). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP\_2014).",
    url = "https://doi.org/10.5194/essd-7-47-2015",
    doi = "10.5194/essd-7-47-2015",
    openalex = "W2154981955",
    references = "doi1010292006gb002784, doi105194bg1066992013"
}

@misc{canadell2016fossil,
    author = "Canadell, Pep and Peters, Glen and Jackson, Rob and Quéré, Corinne",
    title = "Fossil fuel emissions have stalled: Global Carbon Budget 2016",
    year = "2016",
    url = "https://doi.org/10.64628/aa.a35hdgvhk",
    doi = "10.64628/aa.a35hdgvhk",
    openalex = "W4413718775"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), EFF was 9.3 ± 0.5 GtC yr−1, ELUC 1.0 ± 0.5 GtC yr−1, GATM 4.5 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 3.1 ± 0.9 GtC yr−1. For year 2015 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr−1 that took place during 2006–2015. Also, for 2015, ELUC was 1.3 ± 0.5 GtC yr−1, GATM was 6.3 ± 0.2 GtC yr−1, SOCEAN was 3.0 ± 0.5 GtC yr−1, and SLAND was 1.9 ± 0.9 GtC yr−1. GATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller SLAND for that year. The global atmospheric CO2 concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in EFF with +0.2 % (range of −1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of EFF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Niño conditions of 2015–2016. From this projection of EFF and assumed constant ELUC for 2016, cumulative emissions of CO2 will reach 565 ± 55 GtC (2075 ± 205 GtCO2) for 1870–2016, about 75 % from EFF and 25 % from ELUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).

@article{doi105194essd86052016,
    author = "Quéré, Corinne Le and Andrew, Robbie M. and Canadell, Josep G. and Sitch, Stephen and Korsbakken, Jan Ivar and Peters, Glen P. and Manning, Andrew C. and Boden, Thomas A. and Tans, Pieter P. and Houghton, R. A. and Keeling, Ralph F. and Alin, Simone R. and Andrews, Oliver and Anthoni, Peter and Barbero, Leticia and Bopp, Laurent and Chevallier, Frédéric and Chini, Louise and Ciais, Philippe and Currie, Kim and Delire, Christine and Doney, Scott C. and Friedlingstein, Pierre and Gkritzalis, Thanos and Harris, Ian and Hauck, Judith and Haverd, Vanessa and Hoppema, Mario and Goldewijk, Kees Klein and Jain, Atul K. and Kato, Etsushi and Körtzinger, Arne and Landschützer, Peter and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Lombardozzi, Danica and Melton, Joe R. and Metzl, Nicolas and Millero, Frank J. and Monteiro, Pedro M. S. and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and O’Brien, Kevin and Olsen, Are and Omar, Abdirahman M and Ono, Tsuneo and Pierrot, Denis and Poulter, Benjamin and Rödenbeck, Christian and Salisbury, Joe and Schuster, Ute and Schwinger, Jörg and Séférian, Roland and Skjelvan, Ingunn and Stocker, Benjamin D. and Sutton, Adrienne J. and Takahashi, Taro and Tian, Hanqin and Tilbrook, Bronte and Luijkx, Ingrid T. and van der Werf, Guido R. and Viovy, Nicolas and Walker, Anthony P. and Wiltshire, A. and Zaehle, Sönke",
    title = "Global Carbon Budget 2016",
    year = "2016",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), EFF was 9.3 ± 0.5 GtC yr−1, ELUC 1.0 ± 0.5 GtC yr−1, GATM 4.5 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 3.1 ± 0.9 GtC yr−1. For year 2015 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 \% yr−1 that took place during 2006–2015. Also, for 2015, ELUC was 1.3 ± 0.5 GtC yr−1, GATM was 6.3 ± 0.2 GtC yr−1, SOCEAN was 3.0 ± 0.5 GtC yr−1, and SLAND was 1.9 ± 0.9 GtC yr−1. GATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller SLAND for that year. The global atmospheric CO2 concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in EFF with +0.2 \% (range of −1.0 to +1.8 \%) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of EFF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Niño conditions of 2015–2016. From this projection of EFF and assumed constant ELUC for 2016, cumulative emissions of CO2 will reach 565 ± 55 GtC (2075 ± 205 GtCO2) for 1870–2016, about 75 \% from EFF and 25 \% from ELUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP\_2016).",
    url = "https://doi.org/10.5194/essd-8-605-2016",
    doi = "10.5194/essd-8-605-2016",
    openalex = "W2916961622",
    references = "doi1010292006gb002784, myhre2009a"
}

Abstract. The global methane (CH4) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH4 over the past decade. Emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH4 sources that overlap geographically, and from the destruction of CH4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (∼ biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). For the 2003–2012 decade, global methane emissions are estimated by top-down inversions at 558 Tg CH4 yr−1, range 540–568. About 60 % of global emissions are anthropogenic (range 50–65 %). Since 2010, the bottom-up global emission inventories have been closer to methane emissions in the most carbon-intensive Representative Concentrations Pathway (RCP8.5) and higher than all other RCP scenarios. Bottom-up approaches suggest larger global emissions (736 Tg CH4 yr−1, range 596–884) mostly because of larger natural emissions from individual sources such as inland waters, natural wetlands and geological sources. Considering the atmospheric constraints on the top-down budget, it is likely that some of the individual emissions reported by the bottom-up approaches are overestimated, leading to too large global emissions. Latitudinal data from top-down emissions indicate a predominance of tropical emissions (∼ 64 % of the global budget, < 30° N) as compared to mid (∼ 32 %, 30–60° N) and high northern latitudes (∼ 4 %, 60–90° N). Top-down inversions consistently infer lower emissions in China (∼ 58 Tg CH4 yr−1, range 51–72, −14 %) and higher emissions in Africa (86 Tg CH4 yr−1, range 73–108, +19 %) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models. The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30–40 % on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions. The data presented here can be downloaded from the Carbon Dioxide Information Analysis Center (http://doi.org/10.3334/CDIAC/GLOBAL_METHANE_BUDGET_2016_V1.1) and the Global Carbon Project.

@article{doi105194essd86972016,
    author = "Saunois, Marielle and Bousquet, Philippe and Poulter, Benjamin and Peregon, Anna and Ciais, Philippe and Canadell, Josep G. and Dlugokencky, Edward J. and Etiope, Giuseppe and Bastviken, David and Houweling, Sander and Janssens‐Maenhout, Greet and Tubiello, Francesco N. and Castaldi, Simona and Jackson, Robert B. and Alexe, Mihai and Arora, Vivek K. and Beerling, David J. and Bergamaschi, P. and Blake, D. R. and Brailsford, Gordon and Brovkin, Victor and Bruhwiler, Lori and Crévoisier, Cyril and Crill, Patrick and Covey, Kristofer and Curry, Charles L. and Frankenberg, Christian and Gedney, Nicola and Höglund-Isaksson, Lena and Ishizawa, Misa and Ito, Akihiko and Joos, Fortunat and Kim, Heon-Sook and Kleinen, Thomas and Krummel, Paul B. and Lamarque, Jean‐François and Langenfelds, R. L. and Locatelli, Robin and Machida, Toshinobu and Maksyutov, Shamil and McDonald, K. C. and Marshall, Julia and Melton, Joe R. and Morino, Isamu and Naïk, Vaishali and O’Doherty, Simon and Parmentier, Frans‐Jan W. and Patra, Prabir K. and Peng, Changhui and Peng, Shushi and Peters, Glen P. and Pison, Isabelle and Prigent, Catherine and Prinn, Ronald G. and Ramonet, Michel and Riley, W. J. and Saito, Makoto and Santini, Monia and Schroeder, R. and Simpson, Isobel J. and Spahni, Renato and Steele, P. and Takizawa, Atsushi and Thornton, Brett F. and Tian, Hanqin and Tohjima, Yasunori and Viovy, Nicolas and Voulgarakis, Apostolos and van Weele, Michiel and van der Werf, Guido R. and Weiss, Ray F. and Wiedinmyer, Christine and Wilton, David J. and Wiltshire, Andy and Worthy, Doug and Wunch, Debra and Xu, Xiyan and Yoshida, Yukio and Zhang, Bowen and Zhang, Zhen and Zhu, Qiuan",
    title = "The global methane budget 2000–2012",
    year = "2016",
    journal = "Earth system science data",
    abstract = "Abstract. The global methane (CH4) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH4 over the past decade. Emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH4 sources that overlap geographically, and from the destruction of CH4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (∼ biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). For the 2003–2012 decade, global methane emissions are estimated by top-down inversions at 558 Tg CH4 yr−1, range 540–568. About 60 \% of global emissions are anthropogenic (range 50–65 \%). Since 2010, the bottom-up global emission inventories have been closer to methane emissions in the most carbon-intensive Representative Concentrations Pathway (RCP8.5) and higher than all other RCP scenarios. Bottom-up approaches suggest larger global emissions (736 Tg CH4 yr−1, range 596–884) mostly because of larger natural emissions from individual sources such as inland waters, natural wetlands and geological sources. Considering the atmospheric constraints on the top-down budget, it is likely that some of the individual emissions reported by the bottom-up approaches are overestimated, leading to too large global emissions. Latitudinal data from top-down emissions indicate a predominance of tropical emissions (∼ 64 \% of the global budget, < 30° N) as compared to mid (∼ 32 \%, 30–60° N) and high northern latitudes (∼ 4 \%, 60–90° N). Top-down inversions consistently infer lower emissions in China (∼ 58 Tg CH4 yr−1, range 51–72, −14 \%) and higher emissions in Africa (86 Tg CH4 yr−1, range 73–108, +19 \%) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models. The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30–40 \% on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions. The data presented here can be downloaded from the Carbon Dioxide Information Analysis Center (http://doi.org/10.3334/CDIAC/GLOBAL\_METHANE\_BUDGET\_2016\_V1.1) and the Global Carbon Project.",
    url = "https://doi.org/10.5194/essd-8-697-2016",
    doi = "10.5194/essd-8-697-2016",
    openalex = "W2427928079",
    references = "doi101029jd094id06p08549, doi101073pnas0708986104, doi10108010889370802175895"
}

Abstract. The global production of cement has grown very rapidly in recent years, and after fossil fuels and land-use change, it is the third-largest source of anthropogenic emissions of carbon dioxide. The required data for estimating emissions from global cement production are poor, and it has been recognised that some global estimates are significantly inflated. Here we assemble a large variety of available datasets and prioritise official data and emission factors, including estimates submitted to the UNFCCC plus new estimates for China and India, to present a new analysis of global process emissions from cement production. We show that global process emissions in 2016 were 1.45±0.20 Gt CO2, equivalent to about 4 % of emissions from fossil fuels. Cumulative emissions from 1928 to 2016 were 39.3±2.4 Gt CO2, 66 % of which have occurred since 1990. Emissions in 2015 were 30 % lower than those recently reported by the Global Carbon Project. The data associated with this article can be found at https://doi.org/10.5281/zenodo.831455.

@article{doi105194essd101952018,
    author = "Andrew, Robbie M.",
    title = "Global CO 2 emissions from cement production",
    year = "2018",
    journal = "Earth system science data",
    abstract = "Abstract. The global production of cement has grown very rapidly in recent years, and after fossil fuels and land-use change, it is the third-largest source of anthropogenic emissions of carbon dioxide. The required data for estimating emissions from global cement production are poor, and it has been recognised that some global estimates are significantly inflated. Here we assemble a large variety of available datasets and prioritise official data and emission factors, including estimates submitted to the UNFCCC plus new estimates for China and India, to present a new analysis of global process emissions from cement production. We show that global process emissions in 2016 were 1.45±0.20 Gt CO2, equivalent to about 4 \% of emissions from fossil fuels. Cumulative emissions from 1928 to 2016 were 39.3±2.4 Gt CO2, 66 \% of which have occurred since 1990. Emissions in 2015 were 30 \% lower than those recently reported by the Global Carbon Project. The data associated with this article can be found at https://doi.org/10.5281/zenodo.831455.",
    url = "https://doi.org/10.5194/essd-10-195-2018",
    doi = "10.5194/essd-10-195-2018",
    openalex = "W2748635950"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use and land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.7±0.02 GtC yr−1, SOCEAN 2.4±0.5 GtC yr−1, and SLAND 3.2±0.8 GtC yr−1, with a budget imbalance BIM of 0.5 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 % and emissions increased to 9.9±0.5 GtC yr−1. Also for 2017, ELUC was 1.4±0.7 GtC yr−1, GATM was 4.6±0.2 GtC yr−1, SOCEAN was 2.5±0.5 GtC yr−1, and SLAND was 3.8±0.8 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018.

@article{doi105194essd1021412018,
    author = "Quéré, Corinne Le and Andrew, Robbie M. and Friedlingstein, Pierre and Sitch, Stephen and Hauck, Judith and Pongratz, Julia and Pickers, Penelope A. and Korsbakken, Jan Ivar and Peters, Glen P. and Canadell, Josep G. and Arneth, Almut and Arora, Vivek K. and Barbero, Leticia and Bastos, Ana and Bopp, Laurent and Chevallier, Frédéric and Chini, Louise and Ciais, Philippe and Doney, Scott C. and Gkritzalis, Thanos and Goll, Daniel S. and Harris, Ian and Haverd, Vanessa and Hoffman, Forrest M. and Hoppema, Mario and Houghton, R. A. and Hurtt, G. C. and Ilyina, Tatiana and Jain, Atul K. and Johannessen, Truls and Jones, Chris and Kato, Etsushi and Keeling, Ralph F. and Goldewijk, Kees Klein and Landschützer, Peter and Lefèvre, Nathalie and Lienert, Sebastian and Liu, Zhu and Lombardozzi, Danica and Metzl, Nicolas and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and Neill, Craig and Olsen, Are and Ono, Tsueno and Patra, Prabir K. and Peregon, Anna and Peters, Wouter and Peylin, Philippe and Pfeil, Benjamin and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Resplandy, Laure and Robertson, Eddy and Rocher, Matthias and Rödenbeck, Christian and Schuster, Ute and Schwinger, Jörg and Séférian, Roland and Skjelvan, Ingunn and Steinhoff, Tobias and Sutton, Adrienne J. and Tans, Pieter P. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and Luijkx, Ingrid T. and van der Werf, Guido R. and Viovy, Nicolas and Walker, Anthony P. and Wiltshire, A. and Wright, Rebecca and Zaehle, Sönke and Zheng, Bo",
    title = "Global Carbon Budget 2018",
    year = "2018",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use and land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.7±0.02 GtC yr−1, SOCEAN 2.4±0.5 GtC yr−1, and SLAND 3.2±0.8 GtC yr−1, with a budget imbalance BIM of 0.5 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 \% and emissions increased to 9.9±0.5 GtC yr−1. Also for 2017, ELUC was 1.4±0.7 GtC yr−1, GATM was 4.6±0.2 GtC yr−1, SOCEAN was 2.5±0.5 GtC yr−1, and SLAND was 3.8±0.8 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.7 \% (range of 1.8 \% to 3.7 \%) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018.",
    url = "https://doi.org/10.5194/essd-10-2141-2018",
    doi = "10.5194/essd-10-2141-2018",
    openalex = "W2915336810",
    references = "andres2011monthly, archer2009atmospheric, doi101002joc3711, doi1010292003gb002199, doi101038nature09396, doi101038ngeo1955, doi101038ngeo689, doi101073pnas1019576108, doi102151jmsj2015001, doi1023073324639, doi105194acp10117072010, doi105194bg1066992013, doi105194essd96972017, doi105194essd99272017, myhre2009a"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the global carbon budget – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2007–2016), EFF was 9.4 ± 0.5 GtC yr−1, ELUC 1.3 ± 0.7 GtC yr−1, GATM 4.7 ± 0.1 GtC yr−1, SOCEAN 2.4 ± 0.5 GtC yr−1, and SLAND 3.0 ± 0.8 GtC yr−1, with a budget imbalance BIM of 0.6 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1. Also for 2016, ELUC was 1.3 ± 0.7 GtC yr−1, GATM was 6.1 ± 0.2 GtC yr−1, SOCEAN was 2.6 ± 0.5 GtC yr−1, and SLAND was 2.7 ± 1.0 GtC yr−1, with a small BIM of −0.3 GtC. GATM continued to be higher in 2016 compared to the past decade (2007–2016), reflecting in part the high fossil emissions and the small SLAND consistent with El Niño conditions. The global atmospheric CO2 concentration reached 402.8 ± 0.1 ppm averaged over 2016. For 2017, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.0 % (range of 0.8 to 3.0 %) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world. This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set (Le Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).

@article{doi105194essd104052018,
    author = "Quéré, Corinne Le and Andrew, Robbie M. and Friedlingstein, Pierre and Sitch, Stephen and Pongratz, Julia and Manning, Andrew C. and Korsbakken, Jan Ivar and Peters, Glen P. and Canadell, Josep G. and Jackson, Robert B. and Boden, Thomas A. and Tans, Pieter P. and Andrews, Oliver and Arora, Vivek K. and Bakker, Dorothée C. E. and Barbero, Leticia and Becker, Meike and Betts, Richard and Bopp, Laurent and Chevallier, Frédéric and Chini, Louise and Ciais, Philippe and Cosca, Catherine E and Cross, Jessica and Currie, Kim and Gasser, Thomas and Harris, Ian and Hauck, Judith and Haverd, Vanessa and Houghton, R. A. and Hunt, Christopher W and Hurtt, G. C. and Ilyina, Tatiana and Jain, Atul K. and Kato, Etsushi and Kautz, Markus and Keeling, Ralph F. and Goldewijk, Kees Klein and Körtzinger, Arne and Landschützer, Peter and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Lima, Ivan D. and Lombardozzi, Danica and Metzl, Nicolas and Millero, Frank J. and Monteiro, Pedro M. S. and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and Nojiri, Yukihiro and Padín, X. A. and Peregon, Anna and Pfeil, Benjamin and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Reimer, Janet J. and Rödenbeck, Christian and Schwinger, Jörg and Séférian, Roland and Skjelvan, Ingunn and Stocker, Benjamin D. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and Luijkx, Ingrid T. and van der Werf, Guido R. and van Heuven, Steven and Viovy, Nicolas and Vuichard, Nicolas and Walker, Anthony P. and Watson, Andrew and Wiltshire, A. and Zaehle, Sönke and Zhu, Dan",
    title = "Global Carbon Budget 2017",
    year = "2018",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the global carbon budget – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2007–2016), EFF was 9.4 ± 0.5 GtC yr−1, ELUC 1.3 ± 0.7 GtC yr−1, GATM 4.7 ± 0.1 GtC yr−1, SOCEAN 2.4 ± 0.5 GtC yr−1, and SLAND 3.0 ± 0.8 GtC yr−1, with a budget imbalance BIM of 0.6 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1. Also for 2016, ELUC was 1.3 ± 0.7 GtC yr−1, GATM was 6.1 ± 0.2 GtC yr−1, SOCEAN was 2.6 ± 0.5 GtC yr−1, and SLAND was 2.7 ± 1.0 GtC yr−1, with a small BIM of −0.3 GtC. GATM continued to be higher in 2016 compared to the past decade (2007–2016), reflecting in part the high fossil emissions and the small SLAND consistent with El Niño conditions. The global atmospheric CO2 concentration reached 402.8 ± 0.1 ppm averaged over 2016. For 2017, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.0 \% (range of 0.8 to 3.0 \%) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world. This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set (Le Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).",
    url = "https://doi.org/10.5194/essd-10-405-2018",
    doi = "10.5194/essd-10-405-2018",
    openalex = "W2915841000",
    references = "archer2009atmospheric, myhre2009a"
}

The Open-source Data Inventory for Anthropogenic CO 2 (ODIAC) is a global high-spatial resolution gridded emission data product that distributes carbon dioxide (CO 2) emissions from fossil fuel combustion. The emission spatial distributions are estimated at a 1×1 km spatial resolution over land using power plant profiles (emission intensity and geographical location) and satellite-observed nighttime lights. This paper describes the year 2016 version of the ODIAC emission data product (ODIAC2016) and presents analyses that help guiding data users, especially for atmospheric CO 2 tracer transport simulations and flux inversion analysis. Since the original publication in 2011, we have made modifications to our emission modeling framework in order to deliver a comprehensive global gridded emission data product. Major changes from the 2011 publication are 1) the use of emissions estimates made by the Carbon Dioxide Information Analysis Center (CDIAC) at the Oak Ridge National Laboratory (ORNL) by fuel type (solid, liquid, gas, cement manufacturing, gas flaring and international aviation and marine bunkers), 2) the use of multiple spatial emission proxies by fuel type such as nightlight data specific to gas flaring and ship/aircraft fleet tracks and 3) the inclusion of emission temporal variations. Using global fuel consumption data, we extrapolated the CDIAC emissions estimates for the recent years and produced the ODIAC2016 emission data product that covers 2000-2015. Our emission data can be viewed as an extended version of CDIAC gridded emission data product, which should allow data users to impose global fossil fuel emissions in more comprehensive manner than original CDIAC product. Our new emission modeling framework allows us to produce future versions of ODIAC emission data product with a timely update. Such capability has become more significant given the CDIAC/ORNL's shutdown. ODIAC data product could play an important role to support carbon cycle science, especially modeling studies with space-based CO 2 data collected near real time by ongoing carbon observing missions such as Japanese Greenhouse Observing SATellite (GOSAT), NASA's Orbiting Carbon Observatory 2 (OCO-2) and upcoming future missions. The ODIAC emission data product including the latest version of the ODIAC emission data (ODIAC2017, 2000-2016), is distributed from http://db.cger.nies.go.jp/dataset/ODIAC/ with a DOI.

@article{doi105194essd10872018,
    author = "Oda, Tomohiro and Maksyutov, Shamil and Andres, R. J.",
    title = "The Open-source Data Inventory for Anthropogenic CO 2, version 2016 (ODIAC2016): a global monthly fossil fuel CO 2 gridded emissions data product for tracer transport simulations and surface flux inversions",
    year = "2018",
    journal = "Earth system science data",
    abstract = "The Open-source Data Inventory for Anthropogenic CO 2 (ODIAC) is a global high-spatial resolution gridded emission data product that distributes carbon dioxide (CO 2) emissions from fossil fuel combustion. The emission spatial distributions are estimated at a 1×1 km spatial resolution over land using power plant profiles (emission intensity and geographical location) and satellite-observed nighttime lights. This paper describes the year 2016 version of the ODIAC emission data product (ODIAC2016) and presents analyses that help guiding data users, especially for atmospheric CO 2 tracer transport simulations and flux inversion analysis. Since the original publication in 2011, we have made modifications to our emission modeling framework in order to deliver a comprehensive global gridded emission data product. Major changes from the 2011 publication are 1) the use of emissions estimates made by the Carbon Dioxide Information Analysis Center (CDIAC) at the Oak Ridge National Laboratory (ORNL) by fuel type (solid, liquid, gas, cement manufacturing, gas flaring and international aviation and marine bunkers), 2) the use of multiple spatial emission proxies by fuel type such as nightlight data specific to gas flaring and ship/aircraft fleet tracks and 3) the inclusion of emission temporal variations. Using global fuel consumption data, we extrapolated the CDIAC emissions estimates for the recent years and produced the ODIAC2016 emission data product that covers 2000-2015. Our emission data can be viewed as an extended version of CDIAC gridded emission data product, which should allow data users to impose global fossil fuel emissions in more comprehensive manner than original CDIAC product. Our new emission modeling framework allows us to produce future versions of ODIAC emission data product with a timely update. Such capability has become more significant given the CDIAC/ORNL's shutdown. ODIAC data product could play an important role to support carbon cycle science, especially modeling studies with space-based CO 2 data collected near real time by ongoing carbon observing missions such as Japanese Greenhouse Observing SATellite (GOSAT), NASA's Orbiting Carbon Observatory 2 (OCO-2) and upcoming future missions. The ODIAC emission data product including the latest version of the ODIAC emission data (ODIAC2017, 2000-2016), is distributed from http://db.cger.nies.go.jp/dataset/ODIAC/ with a DOI.",
    url = "https://doi.org/10.5194/essd-10-87-2018",
    doi = "10.5194/essd-10-87-2018",
    openalex = "W2738771715",
    references = "andres2011monthly, doi101038415626a, doi101038nature11299, doi101073pnas0708986104, doi101126science24749491431, doi102151sola2009041, doi103390en20300595, doi105194acp115432011, doi105194acp13110192013, doi105194bg1066992013, doi105194essd86052016, doi107125apan357, myhre2009a"
}

@article{doi101038s415860191554z,
    author = "Shindell, Drew and Smith, Chris",
    title = "Climate and air-quality benefits of a realistic phase-out of fossil fuels",
    year = "2019",
    journal = "Nature",
    url = "https://doi.org/10.1038/s41586-019-1554-z",
    doi = "10.1038/s41586-019-1554-z",
    openalex = "W2973307909",
    references = "doi105194acp1318532013"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use change (ELUC), mainly deforestation, are based on land use and land use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2009–2018), EFF was 9.5±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.9±0.02 GtC yr−1 (2.3±0.01 ppm yr−1), SOCEAN 2.5±0.6 GtC yr−1, and SLAND 3.2±0.6 GtC yr−1, with a budget imbalance BIM of 0.4 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2018 alone, the growth in EFF was about 2.1 % and fossil emissions increased to 10.0±0.5 GtC yr−1, reaching 10 GtC yr−1 for the first time in history, ELUC was 1.5±0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5±0.9 GtC yr−1 (42.5±3.3 GtCO2). Also for 2018, GATM was 5.1±0.2 GtC yr−1 (2.4±0.1 ppm yr−1), SOCEAN was 2.6±0.6 GtC yr−1, and SLAND was 3.5±0.7 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 407.38±0.1 ppm averaged over 2018. For 2019, preliminary data for the first 6–10 months indicate a reduced growth in EFF of +0.6 % (range of −0.2 % to 1.5 %) based on national emissions projections for China, the USA, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. Overall, the mean and trend in the five components of the global carbon budget are consistently estimated over the period 1959–2018, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations shows (1) no consensus in the mean and trend in land use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018a, b, 2016, 2015a, b, 2014, 2013). The data generated by this work are available at https://doi.org/10.18160/gcp-2019 (Friedlingstein et al., 2019).

@article{doi105194essd1117832019,
    author = "Friedlingstein, Pierre and Jones, Matthew W. and O’Sullivan, Michael and Andrew, Robbie M. and Hauck, Judith and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Sitch, Stephen and Quéré, Corinne Le and Bakker, Dorothée C. E. and Canadell, Josep G. and Ciais, Philippe and Jackson, Robert B. and Anthoni, Peter and Barbero, Leticia and Bastos, Ana and Bastrikov, Vladislav and Becker, Meike and Bopp, Laurent and Buitenhuis, Erik T. and Chandra, Naveen and Chevallier, Frédéric and Chini, Louise and Currie, Kim and Feely, Richard A. and Gehlen, Marion and Gilfillan, Dennis and Gkritzalis, Thanos and Goll, Daniel S. and Gruber, Nicolas and Gutekunst, Sören and Harris, Ian and Haverd, Vanessa and Houghton, R. A. and Hurtt, G. C. and Ilyina, Tatiana and Jain, Atul K. and Joetzjer, Émilie and Kaplan, Jed O. and Kato, Etsushi and Goldewijk, Kees Klein and Korsbakken, Jan Ivar and Landschützer, Peter and Lauvset, Siv K. and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Lombardozzi, Danica and Marland, Gregg and McGuire, Patrick and Melton, Joe R. and Metzl, Nicolas and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and Neill, Craig and Omar, Abdirahman M and Ono, Tsuneo and Peregon, Anna and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Séférian, Roland and Schwinger, Jörg and Smith, Naomi and Tans, Pieter P. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and van der Werf, Guido R. and Wiltshire, A. and Zaehle, Sönke",
    title = "Global Carbon Budget 2019",
    year = "2019",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use change (ELUC), mainly deforestation, are based on land use and land use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2009–2018), EFF was 9.5±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.9±0.02 GtC yr−1 (2.3±0.01 ppm yr−1), SOCEAN 2.5±0.6 GtC yr−1, and SLAND 3.2±0.6 GtC yr−1, with a budget imbalance BIM of 0.4 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2018 alone, the growth in EFF was about 2.1 \% and fossil emissions increased to 10.0±0.5 GtC yr−1, reaching 10 GtC yr−1 for the first time in history, ELUC was 1.5±0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5±0.9 GtC yr−1 (42.5±3.3 GtCO2). Also for 2018, GATM was 5.1±0.2 GtC yr−1 (2.4±0.1 ppm yr−1), SOCEAN was 2.6±0.6 GtC yr−1, and SLAND was 3.5±0.7 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 407.38±0.1 ppm averaged over 2018. For 2019, preliminary data for the first 6–10 months indicate a reduced growth in EFF of +0.6 \% (range of −0.2 \% to 1.5 \%) based on national emissions projections for China, the USA, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. Overall, the mean and trend in the five components of the global carbon budget are consistently estimated over the period 1959–2018, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations shows (1) no consensus in the mean and trend in land use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018a, b, 2016, 2015a, b, 2014, 2013). The data generated by this work are available at https://doi.org/10.18160/gcp-2019 (Friedlingstein et al., 2019).",
    url = "https://doi.org/10.5194/essd-11-1783-2019",
    doi = "10.5194/essd-11-1783-2019",
    openalex = "W2979653715",
    references = "archer2009atmospheric, doi101002joc3711, doi1010292003gb002199, doi101073pnas1019576108, doi101126science1097403, doi101126science1244693, doi102151jmsj2015001, doi1023073324639, doi105194acp10117072010, doi105194bg1066992013, doi105194essd1021412018, doi105194essd1117832019, doi105194essd96972017, myhre2009a, openalexw2883478268"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2010–2019), EFOS was 9.6 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.4 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.6 ± 0.7 GtC yr−1. For the same decade, GATM was 5.1 ± 0.02 GtC yr−1 (2.4 ± 0.01 ppm yr−1), SOCEAN 2.5 ± 0.6 GtC yr−1, and SLAND 3.4 ± 0.9 GtC yr−1, with a budget imbalance BIM of −0.1 GtC yr−1 indicating a near balance between estimated sources and sinks over the last decade. For the year 2019 alone, the growth in EFOS was only about 0.1 % with fossil emissions increasing to 9.9 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.7 ± 0.5 GtC yr−1 when cement carbonation sink is included), and ELUC was 1.8 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5 ± 0.9 GtC yr−1 (42.2 ± 3.3 GtCO2). Also for 2019, GATM was 5.4 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.6 ± 0.6 GtC yr−1, and SLAND was 3.1 ± 1.2 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 409.85 ± 0.1 ppm averaged over 2019. Preliminary data for 2020, accounting for the COVID-19-induced changes in emissions, suggest a decrease in EFOS relative to 2019 of about −7 % (median estimate) based on individual estimates from four studies of −6 %, −7 %, −7 % (−3 % to −11 %), and −13 %. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2019, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. Comparison of estimates from diverse approaches and observations shows (1) no consensus in the mean and trend in land-use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent discrepancy between the different methods for the ocean sink outside the tropics, particularly in the Southern Ocean. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2020 (Friedlingstein et al., 2020).

@article{doi105194essd1232692020,
    author = "Friedlingstein, Pierre and O’Sullivan, Michael and Jones, Matthew W. and Andrew, Robbie M. and Hauck, Judith and Olsen, Are and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Sitch, Stephen and Quéré, Corinne Le and Canadell, Josep G. and Ciais, Philippe and Jackson, Robert B. and Alin, Simone R. and Aragão, Luiz E. O. C. and Arneth, Almut and Arora, Vivek and Bates, Nicholas R. and Becker, Meike and Benoit-Cattin, Alice and Bittig, Henry C. and Bopp, Laurent and Bultan, Selma and Chandra, Naveen and Chevallier, Frédéric and Chini, Louise and Evans, Wiley and Florentie, Liesbeth and Forster, Piers and Gasser, Thomas and Gehlen, Marion and Gilfillan, Dennis and Gkritzalis, Thanos and Gregor, Luke and Gruber, Nicolas and Harris, Ian and Hartung, Kerstin and Haverd, Vanessa and Houghton, R. A. and Ilyina, Tatiana and Jain, Atul K. and Joetzjer, Émilie and Kadono, Koji and Kato, Etsushi and Kitidis, Vassilis and Korsbakken, Jan Ivar and Landschützer, Peter and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Liu, Zhu and Lombardozzi, Danica and Marland, Gregg and Metzl, Nicolas and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and Niwa, Yosuke and O’Brien, Kevin and Ono, Tsuneo and Palmer, Paul I. and Pierrot, Denis and Poulter, Benjamin and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Schwinger, Jörg and Séférian, Roland and Skjelvan, Ingunn and Smith, Adam J. P. and Sutton, Adrienne J. and Tanhua, Toste and Tans, Pieter P. and Tian, Hanqin and Tilbrook, Bronte and van der Werf, Guido R. and Vuichard, Nicolas and Walker, Anthony P. and Wanninkhof, Rik and Watson, Andrew and Willis, David and Wiltshire, A. and Yuan, Wenping and Yue, Xu and Zaehle, Sönke",
    title = "Global Carbon Budget 2020",
    year = "2020",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2010–2019), EFOS was 9.6 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.4 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.6 ± 0.7 GtC yr−1. For the same decade, GATM was 5.1 ± 0.02 GtC yr−1 (2.4 ± 0.01 ppm yr−1), SOCEAN 2.5 ± 0.6 GtC yr−1, and SLAND 3.4 ± 0.9 GtC yr−1, with a budget imbalance BIM of −0.1 GtC yr−1 indicating a near balance between estimated sources and sinks over the last decade. For the year 2019 alone, the growth in EFOS was only about 0.1 \% with fossil emissions increasing to 9.9 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.7 ± 0.5 GtC yr−1 when cement carbonation sink is included), and ELUC was 1.8 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5 ± 0.9 GtC yr−1 (42.2 ± 3.3 GtCO2). Also for 2019, GATM was 5.4 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.6 ± 0.6 GtC yr−1, and SLAND was 3.1 ± 1.2 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 409.85 ± 0.1 ppm averaged over 2019. Preliminary data for 2020, accounting for the COVID-19-induced changes in emissions, suggest a decrease in EFOS relative to 2019 of about −7 \% (median estimate) based on individual estimates from four studies of −6 \%, −7 \%, −7 \% (−3 \% to −11 \%), and −13 \%. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2019, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. Comparison of estimates from diverse approaches and observations shows (1) no consensus in the mean and trend in land-use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent discrepancy between the different methods for the ocean sink outside the tropics, particularly in the Southern Ocean. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2020 (Friedlingstein et al., 2020).",
    url = "https://doi.org/10.5194/essd-12-3269-2020",
    doi = "10.5194/essd-12-3269-2020",
    openalex = "W3093432062",
    references = "archer2009atmospheric, doi101002joc3711, doi101016jdsr2200812009, doi1010292003gb002199, doi10102992jc00188, doi101038nature25138, doi101038ngeo689, doi101038s41467020189227, doi101038s415580200797x, doi101038s4159702004533, doi101073pnas0700609104, doi101073pnas1019576108, doi101126science1097403, doi101126science1244693, doi1011751520047719960770437tnyrp20co2, doi102151jmsj2015001, doi1023073324639, doi1025607obp1342, doi105194acp10117072010, doi105194essd1021412018, doi105194essd1117832019, doi105194essd119592019, doi105194essd1232692020, doi105194essd96972017, doi105194essd99272017, doi105194gmd919372016, myhre2009a, openalexw2883478268"
}

Abstract. Human land use activities have resulted in large changes to the biogeochemical and biophysical properties of the Earth's surface, with consequences for climate and other ecosystem services. In the future, land use activities are likely to expand and/or intensify further to meet growing demands for food, fiber, and energy. As part of the World Climate Research Program Coupled Model Intercomparison Project (CMIP6), the international community has developed the next generation of advanced Earth system models (ESMs) to estimate the combined effects of human activities (e.g., land use and fossil fuel emissions) on the carbon–climate system. A new set of historical data based on the History of the Global Environment database (HYDE), and multiple alternative scenarios of the future (2015–2100) from Integrated Assessment Model (IAM) teams, is required as input for these models. With most ESM simulations for CMIP6 now completed, it is important to document the land use patterns used by those simulations. Here we present results from the Land-Use Harmonization 2 (LUH2) project, which smoothly connects updated historical reconstructions of land use with eight new future projections in the format required for ESMs. The harmonization strategy estimates the fractional land use patterns, underlying land use transitions, key agricultural management information, and resulting secondary lands annually, while minimizing the differences between the end of the historical reconstruction and IAM initial conditions and preserving changes depicted by the IAMs in the future. The new approach builds on a similar effort from CMIP5 and is now provided at higher resolution (0.25∘×0.25∘) over a longer time domain (850–2100, with extensions to 2300) with more detail (including multiple crop and pasture types and associated management practices) using more input datasets (including Landsat remote sensing data) and updated algorithms (wood harvest and shifting cultivation); it is assessed via a new diagnostic package. The new LUH2 products contain > 50 times the information content of the datasets used in CMIP5 and are designed to enable new and improved estimates of the combined effects of land use on the global carbon–climate system.

@article{doi105194gmd1354252020,
    author = "Hurtt, G. C. and Chini, Louise and Sahajpal, Ritvik and Frolking, Steve and Bodirsky, Benjamin Leon and Calvin, Katherine and Doelman, Jonathan and Fisk, J. and Fujimori, Shinichiro and Goldewijk, Kees Klein and Hasegawa, Tomoko and Havlík, Peter and Heinimann, Andreas and Humpenöder, Florian and Jungclaus, J. and Kaplan, Jed O. and Kennedy, Jennifer A. and Krisztin, Tamás and Lawrence, David M. and Lawrence, Peter and Ma, Lei and Mertz, Ole and Pongratz, Julia and Popp, Alexander and Poulter, Benjamin and Riahi, Keywan and Shevliakova, Elena and Stehfest, Elke and Thornton, Peter and Tubiello, Francesco N. and van Vuuren, Detlef P. and Zhang, Xin",
    title = "Harmonization of global land use change and management for the period 850–2100 (LUH2) for CMIP6",
    year = "2020",
    journal = "Geoscientific model development",
    abstract = "Abstract. Human land use activities have resulted in large changes to the biogeochemical and biophysical properties of the Earth's surface, with consequences for climate and other ecosystem services. In the future, land use activities are likely to expand and/or intensify further to meet growing demands for food, fiber, and energy. As part of the World Climate Research Program Coupled Model Intercomparison Project (CMIP6), the international community has developed the next generation of advanced Earth system models (ESMs) to estimate the combined effects of human activities (e.g., land use and fossil fuel emissions) on the carbon–climate system. A new set of historical data based on the History of the Global Environment database (HYDE), and multiple alternative scenarios of the future (2015–2100) from Integrated Assessment Model (IAM) teams, is required as input for these models. With most ESM simulations for CMIP6 now completed, it is important to document the land use patterns used by those simulations. Here we present results from the Land-Use Harmonization 2 (LUH2) project, which smoothly connects updated historical reconstructions of land use with eight new future projections in the format required for ESMs. The harmonization strategy estimates the fractional land use patterns, underlying land use transitions, key agricultural management information, and resulting secondary lands annually, while minimizing the differences between the end of the historical reconstruction and IAM initial conditions and preserving changes depicted by the IAMs in the future. The new approach builds on a similar effort from CMIP5 and is now provided at higher resolution (0.25∘×0.25∘) over a longer time domain (850–2100, with extensions to 2300) with more detail (including multiple crop and pasture types and associated management practices) using more input datasets (including Landsat remote sensing data) and updated algorithms (wood harvest and shifting cultivation); it is assessed via a new diagnostic package. The new LUH2 products contain > 50 times the information content of the datasets used in CMIP5 and are designed to enable new and improved estimates of the combined effects of land use on the global carbon–climate system.",
    url = "https://doi.org/10.5194/gmd-13-5425-2020",
    doi = "10.5194/gmd-13-5425-2020",
    openalex = "W3016282791",
    references = "doi101038nature15743, doi105194gmd45432011"
}

The concept of carbon neutrality is much emphasized in IPCC Spatial Report on Global Warming of 1.5 °C in order to achieve the long-term temperature goals as reflected in Paris Agreement. To keep these goals within reach, peaking the global carbon emissions as soon as possible and achieving carbon neutrality are urgently needed. However, global CO2 emissions continued to grow up to a record high of 43.1 Gt CO2 during 2019, with fossil CO2 emissions of 36.5 Gt CO2 and land-use change emissions of 6.6 Gt CO2. In such case, the global carbon emissions must drop 32 Gt CO2 (7.6% per year) from 2020 to 2030 for the 1.5 °C warming limit, which is even larger than the COVID-induced reduction (6.4%) in global CO2 emissions during 2020. Recently, China has announced scaling up its national commitments, aiming to peak its CO2 emissions before 2030 and achieve carbon neutrality before 2060. Achieving these goals requires rapid and far-reaching transitions in the whole society. On the one hand, deeper emissions reduction in all sectors includes decarbonization of energy, electrification, increasing share of renewables, energy efficiency, sustainable land management, decarbonization of transport, reducing food loss and waste, as well as behavior and lifestyles changes. On the other hand, possible actions by removing CO2 from the atmosphere involves enlarging land and ocean net carbon sink, CO2 removal technologies (such as Bioenergy with carbon capture and storage), and CO2 capture, utilization and storage technologies, but should be caution for their scales and tradeoffs.

@article{doi101016jaccre202103004,
    author = "Huang, Mengtian and Zhai, Panmao",
    title = "Achieving Paris Agreement temperature goals requires carbon neutrality by middle century with far-reaching transitions in the whole society",
    year = "2021",
    journal = "Advances in Climate Change Research",
    abstract = "The concept of carbon neutrality is much emphasized in IPCC Spatial Report on Global Warming of 1.5 °C in order to achieve the long-term temperature goals as reflected in Paris Agreement. To keep these goals within reach, peaking the global carbon emissions as soon as possible and achieving carbon neutrality are urgently needed. However, global CO2 emissions continued to grow up to a record high of 43.1 Gt CO2 during 2019, with fossil CO2 emissions of 36.5 Gt CO2 and land-use change emissions of 6.6 Gt CO2. In such case, the global carbon emissions must drop 32 Gt CO2 (7.6\% per year) from 2020 to 2030 for the 1.5 °C warming limit, which is even larger than the COVID-induced reduction (6.4\%) in global CO2 emissions during 2020. Recently, China has announced scaling up its national commitments, aiming to peak its CO2 emissions before 2030 and achieve carbon neutrality before 2060. Achieving these goals requires rapid and far-reaching transitions in the whole society. On the one hand, deeper emissions reduction in all sectors includes decarbonization of energy, electrification, increasing share of renewables, energy efficiency, sustainable land management, decarbonization of transport, reducing food loss and waste, as well as behavior and lifestyles changes. On the other hand, possible actions by removing CO2 from the atmosphere involves enlarging land and ocean net carbon sink, CO2 removal technologies (such as Bioenergy with carbon capture and storage), and CO2 capture, utilization and storage technologies, but should be caution for their scales and tradeoffs.",
    url = "https://doi.org/10.1016/j.accre.2021.03.004",
    doi = "10.1016/j.accre.2021.03.004",
    openalex = "W3138573286",
    references = "doi101038s41467020189227"
}

Global temperature is expected to rise by an average of 2 °C (optimistic scenario) to 4 °C (pessimistic scenario) by the year 2100 compared to the average temperature of the Industrial Revolution era (estimated by the IPCC Working Group 1). Technological advancement and population growth, powered by the exploitation of fossil fuel have led to a 68% rise in atmospheric CO2 concentrations and anthropogenic carbon emissions. While renewable energy production is on the rise, the consumption for non-renewable energy, especially fossil fuel is also on the rise due to increase in global population and rapid expansion of the global economy. Extant studies show that increase consumption of non-renewable energy leads to retardation in carbon emission abatement globally. The authors observed that there is limited discussion on both socio-technological transition perspective (particularly renewable energy) and emerging carbon abatement technologies. Limited options available to reduce energy-related CO2 emissions through a systematic review of academic studies is presented. This was achieved by discussing: socio-technological transition perspective particularly renewable energy; energy efficiency ways to eliminate energy waste; waste-energy technologies; emerging carbon abatement technologies. The study concludes that developing green and sustainable-energy economies requires innovative technologies and energy-environmental resolutions to reduce carbon footprints while transforming global economy.

@article{doi101016jclema2021100020,
    author = "Tetteh, Emmanuel Kweinor and Amankwa, M.O. and Amankwa, Mark Opoku and Yeboah, C. and Amankwa, Mark Opoku and Amankwa, M.O.",
    title = "Emerging carbon abatement technologies to mitigate energy-carbon footprint- a review",
    year = "2021",
    journal = "Cleaner Materials",
    abstract = "Global temperature is expected to rise by an average of 2 °C (optimistic scenario) to 4 °C (pessimistic scenario) by the year 2100 compared to the average temperature of the Industrial Revolution era (estimated by the IPCC Working Group 1). Technological advancement and population growth, powered by the exploitation of fossil fuel have led to a 68\% rise in atmospheric CO2 concentrations and anthropogenic carbon emissions. While renewable energy production is on the rise, the consumption for non-renewable energy, especially fossil fuel is also on the rise due to increase in global population and rapid expansion of the global economy. Extant studies show that increase consumption of non-renewable energy leads to retardation in carbon emission abatement globally. The authors observed that there is limited discussion on both socio-technological transition perspective (particularly renewable energy) and emerging carbon abatement technologies. Limited options available to reduce energy-related CO2 emissions through a systematic review of academic studies is presented. This was achieved by discussing: socio-technological transition perspective particularly renewable energy; energy efficiency ways to eliminate energy waste; waste-energy technologies; emerging carbon abatement technologies. The study concludes that developing green and sustainable-energy economies requires innovative technologies and energy-environmental resolutions to reduce carbon footprints while transforming global economy.",
    url = "https://doi.org/10.1016/j.clema.2021.100020",
    doi = "10.1016/j.clema.2021.100020",
    openalex = "W3206995047",
    references = "garrett1992on"
}

NASA's Orbiting Carbon Observatory-3 (OCO-3) was designed to support the quantification and monitoring of anthropogenic CO2 emissions. Its Snapshot Area Map (SAM) and target mode measurements provide an innovative dataset for carbon studies on sub-city scales. Unlike any other current space-based instrument, OCO-3 has the ability to scan large contiguous areas of emission hot spots like cities, power plants, and volcanoes. These measurements result in dense, fine-scale spatial maps of column averaged dry-air mole fractions of carbon dioxide (XCO2). For the first time, we present and analyze XCO2 distributions over the Los Angeles megacity (LA) derived from OCO-3 SAM and target mode observations. Urban XCO2 enhancements range from 0 − 6 ppm (median enhancements ≃ 2 ppm) relative to a clean background and show excellent agreement with nearby ground-based TCCON measurements of XCO2. OCO-3's dense observations reveal intra-urban variations of XCO2 over the city that have never been observed from space before. The spatial variations are mainly driven by the complex fossil fuel emission patterns and meteorological conditions in the LA Basin and are in good agreement with those from co-located TROPOMI measurements of co-emitted NO2. Differences between measured and simulated XCO2 enhancements from two models (WRF-Chem and X-STILT) are typically below 1 ppm with larger differences for some sub regions. Both models capture the observed intra-urban XCO2 gradients. Further, OCO-3's multi-swath measurements capture about three times as much of the city emissions compared to single-swath overpasses. OCO-3's frequent target and SAM mode observations will pave the way to constrain urban emissions at finer, sub-city scales.

@article{doi101016jrse2021112314,
    author = "Kiel, Matthäus and Eldering, A. and Roten, Dustin and Lin, John C. and Feng, Sha and Lei, Ruixue and Lauvaux, Thomas and Oda, Tomohiro and Roehl, Coleen M. and Blavier, J.-F. and Iraci, Laura T.",
    title = "Urban-focused satellite CO2 observations from the Orbiting Carbon Observatory-3: A first look at the Los Angeles megacity",
    year = "2021",
    journal = "Remote Sensing of Environment",
    abstract = "NASA's Orbiting Carbon Observatory-3 (OCO-3) was designed to support the quantification and monitoring of anthropogenic CO2 emissions. Its Snapshot Area Map (SAM) and target mode measurements provide an innovative dataset for carbon studies on sub-city scales. Unlike any other current space-based instrument, OCO-3 has the ability to scan large contiguous areas of emission hot spots like cities, power plants, and volcanoes. These measurements result in dense, fine-scale spatial maps of column averaged dry-air mole fractions of carbon dioxide (XCO2). For the first time, we present and analyze XCO2 distributions over the Los Angeles megacity (LA) derived from OCO-3 SAM and target mode observations. Urban XCO2 enhancements range from 0 − 6 ppm (median enhancements ≃ 2 ppm) relative to a clean background and show excellent agreement with nearby ground-based TCCON measurements of XCO2. OCO-3's dense observations reveal intra-urban variations of XCO2 over the city that have never been observed from space before. The spatial variations are mainly driven by the complex fossil fuel emission patterns and meteorological conditions in the LA Basin and are in good agreement with those from co-located TROPOMI measurements of co-emitted NO2. Differences between measured and simulated XCO2 enhancements from two models (WRF-Chem and X-STILT) are typically below 1 ppm with larger differences for some sub regions. Both models capture the observed intra-urban XCO2 gradients. Further, OCO-3's multi-swath measurements capture about three times as much of the city emissions compared to single-swath overpasses. OCO-3's frequent target and SAM mode observations will pave the way to constrain urban emissions at finer, sub-city scales.",
    url = "https://doi.org/10.1016/j.rse.2021.112314",
    doi = "10.1016/j.rse.2021.112314",
    openalex = "W3134417991",
    references = "doi105194essd10872018"
}

Global development has been heavily reliant on the overexploitation of natural resources since the Industrial Revolution. With the extensive use of fossil fuels, deforestation, and other forms of land-use change, anthropogenic activities have contributed to the ever-increasing concentrations of greenhouse gases (GHGs) in the atmosphere, causing global climate change. In response to the worsening global climate change, achieving carbon neutrality by 2050 is the most pressing task on the planet. To this end, it is of utmost importance and a significant challenge to reform the current production systems to reduce GHG emissions and promote the capture of CO2 from the atmosphere. Herein, we review innovative technologies that offer solutions achieving carbon (C) neutrality and sustainable development, including those for renewable energy production, food system transformation, waste valorization, C sink conservation, and C-negative manufacturing. The wealth of knowledge disseminated in this review could inspire the global community and drive the further development of innovative technologies to mitigate climate change and sustainably support human activities.

@article{doi101016jxinn2021100180,
    author = "Wang, Fang and Harindintwali, Jean Damascene and Yuan, Zhizhang and Wang, Min and Wang, Faming and Li, Sheng and Yin, Zhigang and Huang, Lei and Fu, Yuhao and Li, Lei and Chang, Scott X. and Zhang, Linjuan and Rinklebe, Jörg and Yuan, Zuoqiang and Zhu, Qinggong and Xiang, Leilei and Tsang, Daniel C.W. and Xu, Liang and Jiang, Xin and Liu, Jihua and Wei, Ning and Kästner, Matthias and Zou, Yang and Ok, Yong Sik and Shen, Jianlin and Peng, Dailiang and Zhang, Wei and Barceló, ‪Damià and Zhou, Yongjin J. and Bai, Zhaohai and Li, Boqiang and Zhang, Bin and Wei, Ke and Cao, Hujun and Tan, Zhiliang and Zhao, Liu‐Bin and He, Xiao and Zheng, Jinxing and Bolan, Nanthi and Liu, Xiaohong and Huang, Changping and Dietmann, Sabine and Luo, Ming and Sun, Nannan and Gong, Jirui and Gong, Yulie and Brahushi, Ferdi and Zhang, Tangtang and Xiao, Cunde and Li, Xianfeng and Chen, Wenfu and Jiao, Nianzhi and Lehmann, Johannes and Zhu, Yong‐Guan and Jin, Hongguang and Schäffer, Andreas and Tiedje, James M. and Chen, Jing M.",
    title = "Technologies and perspectives for achieving carbon neutrality",
    year = "2021",
    journal = "The Innovation",
    abstract = "Global development has been heavily reliant on the overexploitation of natural resources since the Industrial Revolution. With the extensive use of fossil fuels, deforestation, and other forms of land-use change, anthropogenic activities have contributed to the ever-increasing concentrations of greenhouse gases (GHGs) in the atmosphere, causing global climate change. In response to the worsening global climate change, achieving carbon neutrality by 2050 is the most pressing task on the planet. To this end, it is of utmost importance and a significant challenge to reform the current production systems to reduce GHG emissions and promote the capture of CO2 from the atmosphere. Herein, we review innovative technologies that offer solutions achieving carbon (C) neutrality and sustainable development, including those for renewable energy production, food system transformation, waste valorization, C sink conservation, and C-negative manufacturing. The wealth of knowledge disseminated in this review could inspire the global community and drive the further development of innovative technologies to mitigate climate change and sustainably support human activities.",
    url = "https://doi.org/10.1016/j.xinn.2021.100180",
    doi = "10.1016/j.xinn.2021.100180",
    openalex = "W3208259726",
    references = "doi101021acschemrev8b00705, doi101021cr300463y, doi101038s4146702020061y, doi101039d0cs00071j, doi101890110004, doi105194essd1232692020"
}

Ammonia, a molecule that is gaining more interest as a fueling vector, has been considered as a candidate to power transport, produce energy, and support heating applications for decades. However, the particular characteristics of the molecule always made it a chemical with low, if any, benefit once compared to conventional fossil fuels. Still, the current need to decarbonize our economy makes the search of new methods crucial to use chemicals, such as ammonia, that can be produced and employed without incurring in the emission of carbon oxides. Therefore, current efforts in this field are leading scientists, industries, and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis, this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector, moving through all of the steps in the production, distribution, utilization, safety, legal considerations, and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed, thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works, this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further, the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes, legal barriers that will be faced to achieve its deployment, safety and environmental considerations that impose a critical aspect for acceptance and wellbeing, and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein, this work sets the principles, research, practicalities, and future views of a transition toward a future where ammonia will be a major energy player.

@article{doi101021acsenergyfuels0c03685,
    author = "Valera-Medina, Agustín and Amer-Hatem, F. and Azad, A. K. and Dedoussi, Irene C. and de Joannon, Mara and Fernandes, R. X. and Glarborg, Peter and Hashemi, Hamid and He, Xiaoyu and Mashruk, Syed and McGowan, J.G. and Mounaim-Rouselle, Christine and Ortíz, A. and Ortiz-Valera, Adrián Esteban and Rossetti, Ilenia and Shu, Bo and Yehia, Mohamed and Xiao, Hua and Costa, Mário",
    title = "Review on Ammonia as a Potential Fuel: From Synthesis to Economics",
    year = "2021",
    journal = "Energy \& Fuels",
    abstract = "Ammonia, a molecule that is gaining more interest as a fueling vector, has been considered as a candidate to power transport, produce energy, and support heating applications for decades. However, the particular characteristics of the molecule always made it a chemical with low, if any, benefit once compared to conventional fossil fuels. Still, the current need to decarbonize our economy makes the search of new methods crucial to use chemicals, such as ammonia, that can be produced and employed without incurring in the emission of carbon oxides. Therefore, current efforts in this field are leading scientists, industries, and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis, this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector, moving through all of the steps in the production, distribution, utilization, safety, legal considerations, and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed, thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works, this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further, the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes, legal barriers that will be faced to achieve its deployment, safety and environmental considerations that impose a critical aspect for acceptance and wellbeing, and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein, this work sets the principles, research, practicalities, and future views of a transition toward a future where ammonia will be a major energy player.",
    url = "https://doi.org/10.1021/acs.energyfuels.0c03685",
    doi = "10.1021/acs.energyfuels.0c03685",
    openalex = "W3134967399",
    references = "doi101016jrser201812023"
}

This analysis presents system level analysis of three stages along the transition towards sustainable synthesis of ammonia.

@article{doi101039d0ee03808c,
    author = "Wang, Miao and Khan, Mohd Adnan and Mohsin, Imtinan and Wicks, Joshua and Ip, Alexander H. and Sumon, Kazi Z. and Dinh, Cao‐Thang and Sargent, Edward H. and Gates, Ian D. and Kibria, Md Golam",
    title = "Can sustainable ammonia synthesis pathways compete with fossil-fuel based Haber–Bosch processes?",
    year = "2021",
    journal = "Energy \& Environmental Science",
    abstract = "This analysis presents system level analysis of three stages along the transition towards sustainable synthesis of ammonia.",
    url = "https://doi.org/10.1039/d0ee03808c",
    doi = "10.1039/d0ee03808c",
    openalex = "W3139011216",
    references = "doi101016jrser201812023"
}

Our study evaluated the effectiveness of using eight pathways in combination for a complete to transition from fossil fuels to renewable energy by 2050. These pathways included renewable energy development; improving energy efficiency; increasing energy conservation; carbon taxes; more equitable balancing of human wellbeing and per capita energy use; cap and trade systems; carbon capture, utilization, and storage; and nuclear power development. We used the annual ‘British Petroleum statistical review of world energy 2021’ report as our primary database. Globally, fossil fuels, renewable (primarily hydro, wind and solar), nuclear energy accounted for 83%, 12.6%, and 6.3% of the total energy consumption in 2020. To achieve zero fossil fuel use by 2050, we found that renewable energy production will need to be increased by up to 6-fold or 8-fold if energy demand is held constant at, or increased 50% from, the 2020 energy demand level. Constraining 2050 world energy demand to a 25% increase over the 2020 level, improves the probability of achieving independence from fossil fuels. Improvements in energy efficiency need to accelerate beyond the current rate of ~1.5% per year. Aggressive application of energy conservation policies involving land use and taxation could potentially reduce world energy use by 10% or more by 2050. Our meta-analysis shows that the minimum level of per capita energy consumption that would allow 8 billion people to have a ‘Decent Living Standard’ is on average ~70 GJ per capita per year, which is 93% of the 2020 global average. Developed countries in temperate climates with high vehicle-dependency needed ~120 GJ per capita year−1, whereas equatorial countries with low vehicle-dependency needed 30 GJ per capita year−1. Our meta-analyses indicated replacement of fossil fuels with renewable energy by 2050 may be possible but will require aggressive application of all eight pathways, major lifestyle changes in developed countries, and close cooperation among all countries.

@article{doi103390su14084792,
    author = "Holechek, Jerry L. and Geli, Hatim M. E. and Sawalhah, Mohammed N. and Valdéz, Raul",
    title = "A Global Assessment: Can Renewable Energy Replace Fossil Fuels by 2050?",
    year = "2022",
    journal = "Sustainability",
    abstract = "Our study evaluated the effectiveness of using eight pathways in combination for a complete to transition from fossil fuels to renewable energy by 2050. These pathways included renewable energy development; improving energy efficiency; increasing energy conservation; carbon taxes; more equitable balancing of human wellbeing and per capita energy use; cap and trade systems; carbon capture, utilization, and storage; and nuclear power development. We used the annual ‘British Petroleum statistical review of world energy 2021’ report as our primary database. Globally, fossil fuels, renewable (primarily hydro, wind and solar), nuclear energy accounted for 83\%, 12.6\%, and 6.3\% of the total energy consumption in 2020. To achieve zero fossil fuel use by 2050, we found that renewable energy production will need to be increased by up to 6-fold or 8-fold if energy demand is held constant at, or increased 50\% from, the 2020 energy demand level. Constraining 2050 world energy demand to a 25\% increase over the 2020 level, improves the probability of achieving independence from fossil fuels. Improvements in energy efficiency need to accelerate beyond the current rate of \textasciitilde 1.5\% per year. Aggressive application of energy conservation policies involving land use and taxation could potentially reduce world energy use by 10\% or more by 2050. Our meta-analysis shows that the minimum level of per capita energy consumption that would allow 8 billion people to have a ‘Decent Living Standard’ is on average \textasciitilde 70 GJ per capita per year, which is 93\% of the 2020 global average. Developed countries in temperate climates with high vehicle-dependency needed \textasciitilde 120 GJ per capita year−1, whereas equatorial countries with low vehicle-dependency needed 30 GJ per capita year−1. Our meta-analyses indicated replacement of fossil fuels with renewable energy by 2050 may be possible but will require aggressive application of all eight pathways, major lifestyle changes in developed countries, and close cooperation among all countries.",
    url = "https://doi.org/10.3390/su14084792",
    doi = "10.3390/su14084792",
    openalex = "W4224246016",
    references = "doi101017cbo9780511546013, doi101038s4156002005798, doi101073pnas1810141115, doi1010801356346720191598964, doi10108817489326aa7541, doi101093bioscibiab079, doi101093bioscibix125, doi101371journalpone0006802, openalexw2334363480, openalexw2986345846"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize datasets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the first time, an approach is shown to reconcile the difference in our ELUC estimate with the one from national greenhouse gas inventories, supporting the assessment of collective countries' climate progress. For the year 2020, EFOS declined by 5.4 % relative to 2019, with fossil emissions at 9.5 ± 0.5 GtC yr−1 (9.3 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 0.9 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission of 10.2 ± 0.8 GtC yr−1 (37.4 ± 2.9 GtCO2). Also, for 2020, GATM was 5.0 ± 0.2 GtC yr−1 (2.4 ± 0.1 ppm yr−1), SOCEAN was 3.0 ± 0.4 GtC yr−1, and SLAND was 2.9 ± 1 GtC yr−1, with a BIM of −0.8 GtC yr−1. The global atmospheric CO2 concentration averaged over 2020 reached 412.45 ± 0.1 ppm. Preliminary data for 2021 suggest a rebound in EFOS relative to 2020 of +4.8 % (4.2 % to 5.4 %) globally. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2020, but discrepancies of up to 1 GtC yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and datasets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this dataset (Friedlingstein et al., 2020, 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2021 (Friedlingstein et al., 2021).

@article{doi105194essd1419172022,
    author = "Friedlingstein, Pierre and Jones, Matthew W. and O’Sullivan, Michael and Andrew, Robbie M. and Bakker, Dorothée C. E. and Hauck, Judith and Quéré, Corinne Le and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Sitch, Stephen and Canadell, Josep G. and Ciais, Philippe and Jackson, Robert B. and Alin, Simone R. and Anthoni, Peter and Bates, Nicholas R. and Becker, Meike and Bellouin, Nicolas and Bopp, Laurent and Chau, Thi Tuyet Trang and Chevallier, Frédéric and Chini, Louise and Cronin, Margot and Currie, Kim and Decharme, Bertrand and Djeutchouang, Laique and Dou, Xinyu and Evans, Wiley and Feely, Richard A. and Feng, Liang and Gasser, Thomas and Gilfillan, Dennis and Gkritzalis, Thanos and Grassi, Giacomo and Gregor, Luke and Gruber, Nicolas and Gürses, Özgür and Harris, Ian and Houghton, R. A. and Hurtt, G. C. and Iida, Yosuke and Ilyina, Tatiana and Luijkx, Ingrid T. and Jain, Atul K. and Jones, S. D. M. and Kato, Etsushi and Kennedy, Daniel and Goldewijk, Kees Klein and Knauer, Jürgen and Korsbakken, Jan Ivar and Körtzinger, Arne and Landschützer, Peter and Lauvset, Siv K. and Lefèvre, Nathalie and Lienert, Sebastian and Liu, Junjie and Marland, Gregg and McGuire, Patrick and Melton, Joe R. and Munro, David R. and Nabel, Julia E. M. S. and Nakaoka, Shin‐Ichiro and Niwa, Yosuke and Ono, Tsuneo and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Rosan, Thais M. and Schwinger, Jörg and Schwingshackl, Clemens and Séférian, Roland and Sutton, Adrienne J. and Sweeney, Colm and Tanhua, Toste and Tans, Pieter P. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and van der Werf, Guido R. and Vuichard, Nicolas and Wada, Chisato and Wanninkhof, Rik and Watson, Andrew and Willis, David and Wiltshire, A. and Yuan, Wenping and Yue, Chao and Yue, Xu and Zaehle, Sönke and Zeng, Jiye",
    title = "Global Carbon Budget 2021",
    year = "2022",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize datasets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the first time, an approach is shown to reconcile the difference in our ELUC estimate with the one from national greenhouse gas inventories, supporting the assessment of collective countries' climate progress. For the year 2020, EFOS declined by 5.4 \% relative to 2019, with fossil emissions at 9.5 ± 0.5 GtC yr−1 (9.3 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 0.9 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission of 10.2 ± 0.8 GtC yr−1 (37.4 ± 2.9 GtCO2). Also, for 2020, GATM was 5.0 ± 0.2 GtC yr−1 (2.4 ± 0.1 ppm yr−1), SOCEAN was 3.0 ± 0.4 GtC yr−1, and SLAND was 2.9 ± 1 GtC yr−1, with a BIM of −0.8 GtC yr−1. The global atmospheric CO2 concentration averaged over 2020 reached 412.45 ± 0.1 ppm. Preliminary data for 2021 suggest a rebound in EFOS relative to 2020 of +4.8 \% (4.2 \% to 5.4 \%) globally. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2020, but discrepancies of up to 1 GtC yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and datasets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this dataset (Friedlingstein et al., 2020, 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2021 (Friedlingstein et al., 2021).",
    url = "https://doi.org/10.5194/essd-14-1917-2022",
    doi = "10.5194/essd-14-1917-2022",
    openalex = "W4225004802",
    references = "archer2009atmospheric, doi101002joc3711, doi1010160016703782901107, doi101016jdsr2200812009, doi1010292003gb002199, doi1010292006gb002784, doi10102992jc00188, doi101038nature14283, doi101038nature25138, doi101038s41467020189227, doi101038s4159702004533, doi101126science1097403, doi101126science1244693, doi102151jmsj2015001, doi1025607obp1342, doi104060ca9825en, doi105194acp10117072010, doi105194essd1021412018, doi105194essd1117832019, doi105194essd119592019, doi105194essd1232692020, doi105194essd1419172022, doi105194essd96972017, doi105194essd99272017, doi105194gmd919372016"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2021, EFOS increased by 5.1 % relative to 2020, with fossil emissions at 10.1 ± 0.5 GtC yr−1 (9.9 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.1 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 10.9 ± 0.8 GtC yr−1 (40.0 ± 2.9 GtCO2). Also, for 2021, GATM was 5.2 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.9 ± 0.4 GtC yr−1, and SLAND was 3.5 ± 0.9 GtC yr−1, with a BIM of −0.6 GtC yr−1 (i.e. the total estimated sources were too low or sinks were too high). The global atmospheric CO2 concentration averaged over 2021 reached 414.71 ± 0.1 ppm. Preliminary data for 2022 suggest an increase in EFOS relative to 2021 of +1.0 % (0.1 % to 1.9 %) globally and atmospheric CO2 concentration reaching 417.2 ppm, more than 50 % above pre-industrial levels (around 278 ppm). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2021, but discrepancies of up to 1 GtC yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extratropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set. The data presented in this work are available at https://doi.org/10.18160/GCP-2022 (Friedlingstein et al., 2022b).

@article{doi105194essd1448112022,
    author = "Friedlingstein, Pierre and O’Sullivan, Michael and Jones, Matthew W. and Andrew, Robbie M. and Gregor, Luke and Hauck, Judith and Quéré, Corinne Le and Luijkx, Ingrid T. and Olsen, Are and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Schwingshackl, Clemens and Sitch, Stephen and Canadell, Josep G. and Ciais, Philippe and Jackson, Robert B. and Alin, Simone R. and Alkama, Ramdane and Arneth, Almut and Arora, Vivek and Bates, Nicholas R. and Becker, Meike and Bellouin, Nicolas and Bittig, Henry C. and Bopp, Laurent and Chevallier, Frédéric and Chini, Louise and Cronin, Margot and Evans, Wiley and Falk, Stefanie and Feely, Richard A. and Gasser, Thomas and Gehlen, Marion and Gkritzalis, Thanos and Gloege, Lucas and Grassi, Giacomo and Gruber, Nicolas and Gürses, Özgür and Harris, Ian and Hefner, Matthew and Houghton, R. A. and Hurtt, G. C. and Iida, Yosuke and Ilyina, Tatiana and Jain, Atul K. and Jersild, Annika and Kadono, Koji and Kato, Etsushi and Kennedy, Daniel and Goldewijk, Kees Klein and Knauer, Jürgen and Korsbakken, Jan Ivar and Landschützer, Peter and Lefèvre, Nathalie and Lindsay, Keith and Liu, Junjie and Liu, Zhu and Marland, Gregg and Mayot, Nicolas and McGrath, Matthew J. and Metzl, Nicolas and Monacci, Natalie and Munro, David R. and Nakaoka, Shin‐Ichiro and Niwa, Yosuke and O’Brien, Kevin and Ono, Tsuneo and Palmer, Paul I. and Pan, Naiqing and Pierrot, Denis and Pocock, Katie and Poulter, Benjamin and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Rodríguez, Carmen Dolores Arbelo and Rosan, Thais M. and Schwinger, Jörg and Séférian, Roland and Shutler, Jamie D. and Skjelvan, Ingunn and Steinhoff, Tobias and Sun, Qing and Sutton, Adrienne J. and Sweeney, Colm and Takao, Shintaro and Tanhua, Toste and Tans, Pieter P. and Tian, Xiangjun and Tian, Hanqin and Tilbrook, Bronte and Tsujino, Hiroyuki and Tubiello, Francesco N. and van der Werf, Guido R. and Walker, Anthony P. and Wanninkhof, Rik and Whitehead, Chris and Wranne, Anna Willstrand and Wright, Rebecca",
    title = "Global Carbon Budget 2022",
    year = "2022",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2021, EFOS increased by 5.1 \% relative to 2020, with fossil emissions at 10.1 ± 0.5 GtC yr−1 (9.9 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.1 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 10.9 ± 0.8 GtC yr−1 (40.0 ± 2.9 GtCO2). Also, for 2021, GATM was 5.2 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.9 ± 0.4 GtC yr−1, and SLAND was 3.5 ± 0.9 GtC yr−1, with a BIM of −0.6 GtC yr−1 (i.e. the total estimated sources were too low or sinks were too high). The global atmospheric CO2 concentration averaged over 2021 reached 414.71 ± 0.1 ppm. Preliminary data for 2022 suggest an increase in EFOS relative to 2021 of +1.0 \% (0.1 \% to 1.9 \%) globally and atmospheric CO2 concentration reaching 417.2 ppm, more than 50 \% above pre-industrial levels (around 278 ppm). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2021, but discrepancies of up to 1 GtC yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extratropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set. The data presented in this work are available at https://doi.org/10.18160/GCP-2022 (Friedlingstein et al., 2022b).",
    url = "https://doi.org/10.5194/essd-14-4811-2022",
    doi = "10.5194/essd-14-4811-2022",
    openalex = "W4308697725",
    references = "archer2009atmospheric, doi101002joc3711, doi1010160016703782901107, doi101016jdsr2200812009, doi1010179781009157896004, doi1010292003gb002199, doi10102992jc00188, doi101038nature14283, doi101038nature25138, doi101038s41467020189227, doi101038s4159702004533, doi101073pnas0700609104, doi101073pnas1019576108, doi101126science1244693, doi1011751520044220020151609aiisas20co2, doi102151jmsj2015001, doi1025607obp1342, doi104060ca9825en, doi105194acp10117072010, doi105194essd1021412018, doi105194essd1117832019, doi105194essd119592019, doi105194essd1232692020, doi105194essd1419172022, doi105194essd1448112022, doi105194essd96972017, doi105194essd99272017, doi105194gmd919372016"
}

. We report national contributions to global warming resulting from emissions of each gas, including a disaggregation to fossil and land use sectors. This dataset will be updated annually as national emissions datasets are updated.

@article{doi101038s41597023020411,
    author = "Jones, Matthew W. and Peters, Glen P. and Gasser, Thomas and Andrew, Robbie M. and Schwingshackl, Clemens and Gütschow, Johannes and Houghton, R. A. and Friedlingstein, Pierre and Pongratz, Julia and Quéré, Corinne Le",
    title = "National contributions to climate change due to historical emissions of carbon dioxide, methane, and nitrous oxide since 1850",
    year = "2023",
    journal = "Scientific Data",
    abstract = ". We report national contributions to global warming resulting from emissions of each gas, including a disaggregation to fossil and land use sectors. This dataset will be updated annually as national emissions datasets are updated.",
    url = "https://doi.org/10.1038/s41597-023-02041-1",
    doi = "10.1038/s41597-023-02041-1",
    openalex = "W4361198723",
    references = "doi1010179781009157896004, doi101038s4159702004622"
}

OBJECTIVES: To estimate all cause and cause specific deaths that are attributable to fossil fuel related air pollution and to assess potential health benefits from policies that replace fossil fuels with clean, renewable energy sources. DESIGN: Observational and modelling study. METHODS: An updated atmospheric composition model, a newly developed relative risk model, and satellite based data were used to determine exposure to ambient air pollution, estimate all cause and disease specific mortality, and attribute them to emission categories. DATA SOURCES: Data from the global burden of disease 2019 study, observational fine particulate matter and population data from National Aeronautics and Space Administration (NASA) satellites, and atmospheric chemistry, aerosol, and relative risk modelling for 2019. RESULTS: Globally, all cause excess deaths due to fine particulate and ozone air pollution are estimated at 8.34 million (95% confidence interval 5.63 to 11.19) deaths per year. Most (52%) of the mortality burden is related to cardiometabolic conditions, particularly ischaemic heart disease (30%). Stroke and chronic obstructive pulmonary disease both account for 16% of mortality burden. About 20% of all cause mortality is undefined, with arterial hypertension and neurodegenerative diseases possibly implicated. An estimated 5.13 million (3.63 to 6.32) excess deaths per year globally are attributable to ambient air pollution from fossil fuel use and therefore could potentially be avoided by phasing out fossil fuels. This figure corresponds to 82% of the maximum number of air pollution deaths that could be averted by controlling all anthropogenic emissions. Smaller reductions, rather than a complete phase-out, indicate that the responses are not strongly non-linear. Reductions in emission related to fossil fuels at all levels of air pollution can decrease the number of attributable deaths substantially. Estimates of avoidable excess deaths are markedly higher in this study than most previous studies for these reasons: the new relative risk model has implications for high income (largely fossil fuel intensive) countries and for low and middle income countries where the use of fossil fuels is increasing; this study accounts for all cause mortality in addition to disease specific mortality; and the large reduction in air pollution from a fossil fuel phase-out can greatly reduce exposure. CONCLUSION: Phasing out fossil fuels is deemed to be an effective intervention to improve health and save lives as part the United Nations' goal of climate neutrality by 2050. Ambient air pollution would no longer be a leading, environmental health risk factor if the use of fossil fuels were superseded by equitable access to clean sources of renewable energy.

@article{doi101136bmj2023077784,
    author = "Lelieveld, Jos and Haines, Andy and Burnett, Richard T. and Tonne, Cathryn and Klingmüller, Klaus and Münzel, Thomas and Pozzer, Andrea",
    title = "Air pollution deaths attributable to fossil fuels: observational and modelling study",
    year = "2023",
    journal = "BMJ",
    abstract = "OBJECTIVES: To estimate all cause and cause specific deaths that are attributable to fossil fuel related air pollution and to assess potential health benefits from policies that replace fossil fuels with clean, renewable energy sources. DESIGN: Observational and modelling study. METHODS: An updated atmospheric composition model, a newly developed relative risk model, and satellite based data were used to determine exposure to ambient air pollution, estimate all cause and disease specific mortality, and attribute them to emission categories. DATA SOURCES: Data from the global burden of disease 2019 study, observational fine particulate matter and population data from National Aeronautics and Space Administration (NASA) satellites, and atmospheric chemistry, aerosol, and relative risk modelling for 2019. RESULTS: Globally, all cause excess deaths due to fine particulate and ozone air pollution are estimated at 8.34 million (95\% confidence interval 5.63 to 11.19) deaths per year. Most (52\%) of the mortality burden is related to cardiometabolic conditions, particularly ischaemic heart disease (30\%). Stroke and chronic obstructive pulmonary disease both account for 16\% of mortality burden. About 20\% of all cause mortality is undefined, with arterial hypertension and neurodegenerative diseases possibly implicated. An estimated 5.13 million (3.63 to 6.32) excess deaths per year globally are attributable to ambient air pollution from fossil fuel use and therefore could potentially be avoided by phasing out fossil fuels. This figure corresponds to 82\% of the maximum number of air pollution deaths that could be averted by controlling all anthropogenic emissions. Smaller reductions, rather than a complete phase-out, indicate that the responses are not strongly non-linear. Reductions in emission related to fossil fuels at all levels of air pollution can decrease the number of attributable deaths substantially. Estimates of avoidable excess deaths are markedly higher in this study than most previous studies for these reasons: the new relative risk model has implications for high income (largely fossil fuel intensive) countries and for low and middle income countries where the use of fossil fuels is increasing; this study accounts for all cause mortality in addition to disease specific mortality; and the large reduction in air pollution from a fossil fuel phase-out can greatly reduce exposure. CONCLUSION: Phasing out fossil fuels is deemed to be an effective intervention to improve health and save lives as part the United Nations' goal of climate neutrality by 2050. Ambient air pollution would no longer be a leading, environmental health risk factor if the use of fossil fuels were superseded by equitable access to clean sources of renewable energy.",
    url = "https://doi.org/10.1136/bmj-2023-077784",
    doi = "10.1136/bmj-2023-077784",
    openalex = "W4389154806",
    references = "doi1010179781009157896"
}

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land-use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based fCO2 products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. Additional lines of evidence on land and ocean sinks are provided by atmospheric inversions, atmospheric oxygen measurements, and Earth system models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2022, EFOS increased by 0.9 % relative to 2021, with fossil emissions at 9.9±0.5 Gt C yr−1 (10.2±0.5 Gt C yr−1 when the cement carbonation sink is not included), and ELUC was 1.2±0.7 Gt C yr−1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 11.1±0.8 Gt C yr−1 (40.7±3.2 Gt CO2 yr−1). Also, for 2022, GATM was 4.6±0.2 Gt C yr−1 (2.18±0.1 ppm yr−1; ppm denotes parts per million), SOCEAN was 2.8±0.4 Gt C yr−1, and SLAND was 3.8±0.8 Gt C yr−1, with a BIM of −0.1 Gt C yr−1 (i.e. total estimated sources marginally too low or sinks marginally too high). The global atmospheric CO2 concentration averaged over 2022 reached 417.1±0.1 ppm. Preliminary data for 2023 suggest an increase in EFOS relative to 2022 of +1.1 % (0.0 % to 2.1 %) globally and atmospheric CO2 concentration reaching 419.3 ppm, 51 % above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of and trend in the components of the global carbon budget are consistently estimated over the period 1959–2022, with a near-zero overall budget imbalance, although discrepancies of up to around 1 Gt C yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living-data update documents changes in methods and data sets applied to this most recent global carbon budget as well as evolving community understanding of the global carbon cycle. The data presented in this work are available at https://doi.org/10.18160/GCP-2023 (Friedlingstein et al., 2023).

@article{doi105194essd1553012023,
    author = "Friedlingstein, Pierre and O’Sullivan, Michael and Jones, Matthew W. and Andrew, Robbie M. and Bakker, Dorothée C. E. and Hauck, Judith and Landschützer, Peter and Quéré, Corinne Le and Luijkx, Ingrid T. and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Schwingshackl, Clemens and Sitch, Stephen and Canadell, Josep G. and Ciais, Philippe and Jackson, Robert B. and Alin, Simone R. and Anthoni, Peter and Barbero, Leticia and Bates, Nicholas R. and Becker, Meike and Bellouin, Nicolas and Decharme, Bertrand and Bopp, Laurent and Brasika, Ida Bagus Mandhara and Cadule, Patricia and Chamberlain, Matthew A. and Chandra, Naveen and Chau, Thi Tuyet Trang and Chevallier, Frédéric and Chini, Louise and Cronin, Margot and Dou, Xinyu and Enyo, Kazutaka and Evans, Wiley and Falk, Stefanie and Feely, Richard A. and Feng, Liang and Ford, Daniel J. and Gasser, Thomas and Ghattas, Joséfine and Gkritzalis, Thanos and Grassi, Giacomo and Gregor, Luke and Gruber, Nicolas and Gürses, Özgür and Harris, Ian and Hefner, Matthew and Heinke, Jens and Houghton, R. A. and Hurtt, G. C. and Iida, Yosuke and Ilyina, Tatiana and Jacobson, A. R. and Jain, Atul K. and Jarníková, Tereza and Jersild, Annika and Jiang, Fei and Jin, Zhe and Joos, Fortunat and Kato, Etsushi and Keeling, Ralph F. and Kennedy, Daniel and Goldewijk, Kees Klein and Knauer, Jürgen and Korsbakken, Jan Ivar and Körtzinger, Arne and Lan, Xin and Lefèvre, Nathalie and Li, Hongmei and Liu, Junjie and Liu, Zhiqiang and Ma, Lei and Marland, G. and Mayot, Nicolas and McGuire, Patrick and McKinley, Galen A. and Meyer, Gesa and Morgan, Eric J. and Munro, David R. and Nakaoka, Shin‐Ichiro and Niwa, Yosuke and O'Brien, Kevin M. and Olsen, Are and Omar, Abdirahman M and Ono, Tsuneo and Paulsen, Melf and Pierrot, Denis and Pocock, Katie and Poulter, Benjamin and Powis, Carter M. and Rehder, Gregor and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Rosan, Thais M. and Schwinger, Jörg and Séférian, Roland and Smallman, T. Luke",
    title = "Global Carbon Budget 2023",
    year = "2023",
    journal = "Earth system science data",
    abstract = "Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land-use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based fCO2 products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. Additional lines of evidence on land and ocean sinks are provided by atmospheric inversions, atmospheric oxygen measurements, and Earth system models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2022, EFOS increased by 0.9 \% relative to 2021, with fossil emissions at 9.9±0.5 Gt C yr−1 (10.2±0.5 Gt C yr−1 when the cement carbonation sink is not included), and ELUC was 1.2±0.7 Gt C yr−1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 11.1±0.8 Gt C yr−1 (40.7±3.2 Gt CO2 yr−1). Also, for 2022, GATM was 4.6±0.2 Gt C yr−1 (2.18±0.1 ppm yr−1; ppm denotes parts per million), SOCEAN was 2.8±0.4 Gt C yr−1, and SLAND was 3.8±0.8 Gt C yr−1, with a BIM of −0.1 Gt C yr−1 (i.e. total estimated sources marginally too low or sinks marginally too high). The global atmospheric CO2 concentration averaged over 2022 reached 417.1±0.1 ppm. Preliminary data for 2023 suggest an increase in EFOS relative to 2022 of +1.1 \% (0.0 \% to 2.1 \%) globally and atmospheric CO2 concentration reaching 419.3 ppm, 51 \% above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of and trend in the components of the global carbon budget are consistently estimated over the period 1959–2022, with a near-zero overall budget imbalance, although discrepancies of up to around 1 Gt C yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living-data update documents changes in methods and data sets applied to this most recent global carbon budget as well as evolving community understanding of the global carbon cycle. The data presented in this work are available at https://doi.org/10.18160/GCP-2023 (Friedlingstein et al., 2023).",
    url = "https://doi.org/10.5194/essd-15-5301-2023",
    doi = "10.5194/essd-15-5301-2023",
    openalex = "W4389195056",
    references = "archer2009atmospheric, doi101016jdsr2200812009, doi1010179781009157896004, doi1010292003gb002199, doi1010292010jd015139, doi1010292019ms002010, doi101038nature14283, doi101038nature25138, doi101038ngeo689, doi101073pnas0702737104, doi105194acp10117072010, doi105194essd1021412018, doi105194essd1117832019, doi105194essd119592019, doi105194essd1232692020, doi105194essd1419172022, doi105194essd1448112022, doi105194essd1553012023, doi105194essd96972017, doi105194gmd113692018, doi105194gmd919372016"
}

@article{doi101016jjclepro2024142113,
    author = "Rahman, Arifur and Murad, S. M. Woahid and Mohsin, Abu Khair Mohammad and Wang, Xiaowen",
    title = "Does renewable energy proactively contribute to mitigating carbon emissions in major fossil fuels consuming countries?",
    year = "2024",
    journal = "Journal of Cleaner Production",
    url = "https://doi.org/10.1016/j.jclepro.2024.142113",
    doi = "10.1016/j.jclepro.2024.142113",
    openalex = "W4393999225",
    references = "doi103390su14084792"
}

@article{alagoz2026a,
    author = "Alagoz, Baris Baykant and Keles, Cemal and Baran, Burhan",
    title = "A note on effects of fossil fuel reduction policies on atmospheric carbon dioxide buildup and global warming",
    year = "2026",
    journal = "Journal of Atmospheric and Solar-Terrestrial Physics",
    url = "https://doi.org/10.1016/j.jastp.2026.106724",
    doi = "10.1016/j.jastp.2026.106724",
    openalex = "W7119118301",
    pages = "106724",
    volume = "279",
    references = "doi101016jgloenvcha201605009, doi1010179781009157896, doi101029gm029p0130, doi101038d41586019035950, doi101038nature08017, doi101073pnas0705414105, doi1011752008bams26341, doi103390su14084792, doi105194acp1318532013, doi105194gmd934612016"
}