Global Carbon Budget 2019

Friedlingstein, Pierre ; Jones, Matthew W. ; O'Sullivan, Michael ; Andrew, Robbie M. ; Hauck, Judith ; Peters, Glen P. ; Peters, Wouter ; Pongratz, Julia ; Sitch, Stephen ; Le Quéré, Corinne ; Bakker, Dorothee C. E. ; Canadell, Josep G. ; Ciais, Philippe ; Jackson, Robert B. ; Anthoni, Peter ; Barbero, Leticia ; Bastos, Ana ; Bastrikov, Vladislav ; Becker, Meike ; Bopp, Laurent ; Buitenhuis, Erik ; Chandra, Naveen ; Chevallier, Frédéric ; Chini, Louise P. ; Currie, Kim I. ; Feely, Richard A. ; Gehlen, Marion ; Gilfillan, Dennis ; Gkritzalis, Thanos ; Goll, Daniel S. ; Gruber, Nicolas ; Gutekunst, Sören ; Harris, Ian ; Haverd, Vanessa ; Houghton, Richard A. ; Hurtt, George ; Ilyina, Tatiana ; Jain, Atul K. ; Joetzjer, Emilie ; Kaplan, Jed O. ; Kato, Etsushi ; Klein Goldewijk, Kees ; Korsbakken, Jan Ivar ; Landschützer, Peter ; Lauvset, Siv K. ; Lefèvre, Nathalie ; Lenton, Andrew ; Lienert, Sebastian ; Lombardozzi, Danica ; Marland, Gregg ; McGuire, Patrick C. ; Melton, Joe R. ; Metzl, Nicolas ; Munro, David R. ; Nabel, Julia E. M. S. ; Nakaoka, Shin-Ichiro ; Neill, Craig ; Omar, Abdirahman M. ; Ono, Tsuneo ; Peregon, Anna ; Pierrot, Denis ; Poulter, Benjamin ; Rehder, Gregor ; Resplandy, Laure ; Robertson, Eddy ; Rödenbeck, Christian ; Séférian, Roland ; Schwinger, Jörg ; Smith, Naomi ; Tans, Pieter P. ; Tian, Hanqin ; Tilbrook, Bronte ; Tubiello, Francesco N. ; van der Werf, Guido R. ; Wiltshire, Andrew J. ; Zaehle, Sönke

Année de publication
<p align=justify><strong>Abstract.</strong> Accurate assessment of anthropogenic carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) 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 <span class="inline-formula">CO<sub>2</sub></span> emissions (<span class="inline-formula"><i>E</i><sub>FF</sub></span>) are based on energy statistics and cement production data, while emissions from land use change (<span class="inline-formula"><i>E</i><sub>LUC</sub></span>), mainly deforestation, are based on land use and land use change data and bookkeeping models. Atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentration is measured directly and its growth rate (<span class="inline-formula"><i>G</i><sub>ATM</sub></span>) is computed from the annual changes in concentration. The ocean <span class="inline-formula">CO<sub>2</sub></span> sink (<span class="inline-formula"><i>S</i><sub>OCEAN</sub></span>) and terrestrial <span class="inline-formula">CO<sub>2</sub></span> sink (<span class="inline-formula"><i>S</i><sub>LAND</sub></span>) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (<span class="inline-formula"><i>B</i><sub>IM</sub></span>), 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 <span class="inline-formula">±1<i>σ</i></span>. For the last decade available (2009-2018), <span class="inline-formula"><i>E</i><sub>FF</sub></span> was <span class="inline-formula">9.5±0.5</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, <span class="inline-formula"><i>E</i><sub>LUC</sub></span> <span class="inline-formula">1.5±0.7</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, <span class="inline-formula"><i>G</i><sub>ATM</sub></span> <span class="inline-formula">4.9±0.02</span> GtC yr<span class="inline-formula"><sup>-1</sup></span> (<span class="inline-formula">2.3±0.01</span> ppm yr<span class="inline-formula"><sup>-1</sup></span>), <span class="inline-formula"><i>S</i><sub>OCEAN</sub></span> <span class="inline-formula">2.5±0.6</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, and <span class="inline-formula"><i>S</i><sub>LAND</sub></span> <span class="inline-formula">3.2±0.6</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, with a budget imbalance <span class="inline-formula"><i>B</i><sub>IM</sub></span> of 0.4 GtC yr<span class="inline-formula"><sup>-1</sup></span> indicating overestimated emissions and/or underestimated sinks. For the year 2018 alone, the growth in <span class="inline-formula"><i>E</i><sub>FF</sub></span> was about 2.1 % and fossil emissions increased to <span class="inline-formula">10.0±0.5</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, reaching 10 GtC yr<span class="inline-formula"><sup>-1</sup></span> for the first time in history, <span class="inline-formula"><i>E</i><sub>LUC</sub></span> was <span class="inline-formula">1.5±0.7</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, for total anthropogenic <span class="inline-formula">CO<sub>2</sub></span> emissions of <span class="inline-formula">11.5±0.9</span> GtC yr<span class="inline-formula"><sup>-1</sup></span> (<span class="inline-formula">42.5±3.3</span> <span class="inline-formula">GtCO<sub>2</sub></span>). Also for 2018, <span class="inline-formula"><i>G</i><sub>ATM</sub></span> was <span class="inline-formula">5.1±0.2</span> GtC yr<span class="inline-formula"><sup>-1</sup></span> (<span class="inline-formula">2.4±0.1</span> ppm yr<span class="inline-formula"><sup>-1</sup></span>), <span class="inline-formula"><i>S</i><sub>OCEAN</sub></span> was <span class="inline-formula">2.6±0.6</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, and <span class="inline-formula"><i>S</i><sub>LAND</sub></span> was <span class="inline-formula">3.5±0.7</span> GtC yr<span class="inline-formula"><sup>-1</sup></span>, with a <span class="inline-formula"><i>B</i><sub>IM</sub></span> of 0.3 GtC. The global atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentration reached <span class="inline-formula">407.38±0.1</span> ppm averaged over 2018. For 2019, preliminary data for the first 6-10 months indicate a reduced growth in <span class="inline-formula"><i>E</i><sub>FF</sub></span> of <span class="inline-formula">+0.6</span> % (range of <span class="inline-formula">-0.2</span> % 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<span class="inline-formula"><sup>-1</sup></span> persist for the representation of semi-decadal variability in <span class="inline-formula">CO<sub>2</sub></span> 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 <span class="inline-formula">CO<sub>2</sub></span> flux in the northern extra-tropics, and (3) an apparent underestimation of the <span class="inline-formula">CO<sub>2</sub></span> 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 <a href="" target="_blank"></a> (Friedlingstein et al., 2019).</p>
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