Global Carbon Budget 2017
Authors: Le Quéré Corinne , Andrew Robbie M. , Friedlingstein Pierre , Sitch Stephen , Pongratz Julia , Manning Andrew C. , Korsbakken Jan Ivar , Peters Glen P. , Canadell Josep G. , Jackson Robert B. , Boden Thomas A. , Tans Pieter P. , Andrews Oliver D. , Arora Vivek K. , Bakker Dorothee C. E. , Barbero Leticia , Becker Meike , Betts Richard A. , Bopp Laurent , Chevallier Frédéric , Chini Louise P. , Ciais Philippe , Cosca Catherine E. , Cross Jessica , Currie Kim , Gasser Thomas , Harris Ian , Hauck Judith , Haverd Vanessa , Houghton Richard A. , Hunt Christopher W. , Hurtt George , Ilyina Tatiana , Jain Atul K. , Kato Etsushi , Kautz Markus , Keeling Ralph F. , Klein Goldewijk Kees , Körtzinger Arne , Landschützer Peter , Lefèvre Nathalie , Lenton Andrew , Lienert Sebastian , Lima Ivan , Lombardozzi Danica , Metzl Nicolas , Millero Frank , Monteiro Pedro M. S. , Munro David R. , Nabel Julia E. M. S. , Nakaoka Shin-ichiro , Nojiri Yukihiro , Padín X. Antoni , Peregon Anna , Pfeil Benjamin , Pierrot Denis , Poulter Benjamin , Rehder Gregor , Reimer Janet , Rödenbeck Christian , Schwinger Jörg , Séférian Roland , Skjelvan Ingunn , Stocker Benjamin D. , Tian Hanqin , Tilbrook Bronte , van der Laan-Luijkx Ingrid T. , van der Werf Guido R. , van Heuven Steven , Viovy Nicolas , Vuichard Nicolas , Walker Anthony P. , Watson Andrew J. , Wiltshire Andrew J. , Zaehle Sönke , Zhu Dan 
Published: November 2017

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 our 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 higher fossil emissions and smaller SLAND for that year consistent with El Niño conditions. The global atmospheric CO2 concentration reached 402.8 ± 0.1 ppm averaged over 2016. For 2017, preliminary data 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 corrected for recent changes in the carbon intensity of the economy for the rest of the world. For 2017, initial data indicate an increase in atmospheric CO2 concentration of around 5.3 GtC (2.5 ppm), attributed to a combination of increasing emissions and receding El Niño conditions. 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; 2015a; 2014; 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017.