Global Carbon Budget 2018

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.

Keywords

Affiliated Institutions

• Institut Pierre-Simon Laplace FR
• National Institute for Environmental Studies JP
• NSF NCAR Climate and Global Dynamics Laboratory US
• University of Virginia US
• Sorbonne Université FR
• University of Exeter GB
• Wageningen University & Research NL
• Scripps Institution of Oceanography US
• Japan Agency for Marine-Earth Science and Technology JP
• Karlsruhe Institute of Technology DE
• University of Groningen NL
• NOAA Earth System Research Laboratory US
• Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung DE
• Oeschger Centre for Climate Change Research CH
• Ludwig-Maximilians-Universität München DE
• Japan Fisheries Research and Education Agency JP
• NORCE Research AS
• Centre National de la Recherche Scientifique FR
• Met Office GB
• University of Illinois Urbana-Champaign US
• GEOMAR Helmholtz Centre for Ocean Research Kiel DE
• Météo-France FR
• University of East Anglia GB
• CSIRO Oceans and Atmosphere AU
• Food and Agriculture Organization of the United Nations IT
• Institut de Recherche pour le Développement FR
• Leibniz Institute for Baltic Sea Research Warnemünde DE
• Tsinghua University CN
• Vrije Universiteit Amsterdam NL
• Tyndall Centre GB
• Max Planck Institute for Biogeochemistry DE
• Woodwell Climate Research Center US
• Flanders Marine Institute BE
• Commissariat à l'Énergie Atomique et aux Énergies Alternatives FR
• NOAA Pacific Marine Environmental Laboratory US
• National Oceanic and Atmospheric Administration US
• NSF National Center for Atmospheric Research US
• Norwich Research Park GB
• Netherlands Environmental Assessment Agency NL
• Université de Versailles Saint-Quentin-en-Yvelines FR
• Environment and Climate Change Canada CA
• Laboratoire des Sciences du Climat et de l'Environnement FR
• Bjerknes Centre for Climate Research
• Antarctic Climate and Ecosystems Cooperative Research Centre AU
• Auburn University US
• University of Miami US
• University of Maryland, College Park US
• NOAA Atlantic Oceanographic and Meteorological Laboratories US
• Laboratoire de Météorologie Dynamique FR
• Oak Ridge National Laboratory US
• Centre National de Recherches Météorologiques FR
• Institute of Applied Energy JP
• University of California, San Diego US
• Princeton University US
• University of Bern CH
• Max Planck Institute for Meteorology DE
• Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques FR
• University of Bergen
• Goddard Space Flight Center US
• University of Tasmania AU
• CICERO Center for International Climate Research
• Institute of Arctic and Alpine Research US

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