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Abstract

Accurate assessment of anthropogenic carbon dioxide(CO2) emissions and their redistribution among the atmosphere,ocean, and terrestrial biosphere – the “global carbon budget” – isimportant to better understand the global carbon cycle, support thedevelopment of climate policies, and project future climate change. Here wedescribe data sets and methodology to quantify the five major components ofthe global carbon budget and their uncertainties. Fossil CO2emissions (EFF) are based on energy statistics and cementproduction data, while emissions from land use and land-use change (ELUC),mainly deforestation, are based on land use and land-use change data andbookkeeping models. Atmospheric CO2 concentration is measureddirectly and its growth rate (GATM) is computed from the annualchanges in concentration. The ocean CO2 sink (SOCEAN)and terrestrial CO2 sink (SLAND) are estimated withglobal process models constrained by observations. The resulting carbonbudget imbalance (BIM), the difference between the estimatedtotal emissions and the estimated changes in the atmosphere, ocean, andterrestrial biosphere, is a measure of imperfect data and understanding ofthe contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was9.4±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 of0.5 GtC yr−1 indicating overestimated emissions and/or underestimatedsinks. 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 atmosphericCO2 concentration reached 405.0±0.1 ppm averaged over 2017.For 2018, preliminary data for the first 6–9 months indicate a renewedgrowth in EFF of +2.7 % (range of 1.8 % to 3.7 %) basedon national emission projections for China, the US, the EU, and India andprojections of gross domestic product corrected for recent changes in thecarbon intensity of the economy for the rest of the world. The analysispresented here shows that the mean and trend in the five components of theglobal carbon budget are consistently estimated over the period of 1959–2017,but discrepancies of up to 1 GtC yr−1 persist for the representationof semi-decadal variability in CO2 fluxes. A detailed comparisonamong individual estimates and the introduction of a broad range ofobservations show (1) no consensus in the mean and trend in land-use changeemissions, (2) a persistent low agreement among the different methods onthe magnitude of the land CO2 flux in the northern extra-tropics,and (3) an apparent underestimation of the CO2 variability by oceanmodels, originating outside the tropics. This living data update documentschanges in the methods and data sets used in this new global carbon budgetand the progress in understanding the global carbon cycle compared withprevious publications of this data set (Le Quéré et al., 2018, 2016,2015a, b, 2014, 2013). All results presented here can be downloaded fromhttps://doi.org/10.18160/GCP-2018.

Item Type:	Article
Authors/Creators:	Le Quere, C and Andrew, RM and Friedlingstein, P and Sitch, S and Hauck, J and Pongratz, J and Pickers, PA and Korsbakken, JI and Peters, GP and Canadell, JG and Arneth, A and Arora, VK and Barbero, L and Bastos, A and Bopp, L and Chevallier, F and Chini, LP and Ciais, P and Doney, SC and Gkritzalis, T and Goll, D and Harris, I and Haverd, V and Hoffman, FM and Hoppema, M and Houghton, R and Hurtt, G and Ilyina, T and Jain, A and Johannessen, T and Jones, C and Kato, E and Keeling, R and Klein Goldewijk, K and Landschutzer, P and Lefevre, N and Lienert, S and Liu, Z and Lombardozzi, D and Metzl, N and Munro, DR and Nabel, JEMS and Nakaoka, SI and Neill, C and Olsen, A and Ono, T and Patra, P and Peregon, A and Peters, W and Peylin, P and Pfeil, B and Pierrot, D and Poulter, B and Rehder, G and Resplandy, L and Robertson, E and Rocher, M and Rodenbeck, C and Schuster, U and Skjelvan, I and Seferian, R and Steinhoff, T and Sutton, A and Tans, P and Tian, H and Tilbrook, B and Tubiello, F and van der Laan-Luijkx, IT and van der Werf, GR and Viovy, N and Walker, A and Wiltshire, A and Wright, R and Zaehle, S and Zheng, B
Keywords:	global carbon budget, CO2 emissions, carbon cycle, climate change
Journal or Publication Title:	Earth System Science Data
Publisher:	Copernicus GmbH
ISSN:	1866-3508
DOI / ID Number:	10.5194/essd-10-2141-2018
Copyright Information:	© Author(s) 2018. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) http://creativecommons.org/licenses/by/4.0/
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