Global Carbon Budget 2024
Authors: Friedlingstein Pierre , O'Sullivan Michael , Jones Matthew W. , Andrew Robbie M. , Hauck Judith , Landschützer Peter , Le Quéré Corinne , Li Hongmei , Luijkx Ingrid T. , Olsen Are , Peters Glen P. , Peters Wouter , Pongratz Julia , Schwingshackl Clemens , Sitch Stephen , Canadell Josep G. , Ciais Philippe , Jackson Robert B. , Alin Simone R. , Arneth Almut , Arora Vivek , Bates Nicholas R. , Becker Meike , Bellouin Nicolas , Berghoff Carla F. , Bittig Henry C. , Bopp Laurent , Cadule Patricia , Campbell Katie , Chamberlain Matthew A. , Chandra Naveen , Chevallier Frédéric , Chini Louise P. , Colligan Thomas , Decayeux Jeanne , Djeutchouang Laique , Dou Xinyu , Duran Rojas Carolina , Enyo Kazutaka , Evans Wiley , Fay Amanda , Feely Richard A. , Ford Daniel J. , Foster Adrianna , Gasser Thomas , Gehlen Marion , Gkritzalis Thanos , Grassi Giacomo , Gregor Luke , Gruber Nicolas , Gürses Özgür , Harris Ian , Hefner Matthew , Heinke Jens , Hurtt George C. , Iida Yosuke , Ilyina Tatiana , Jacobson Andrew R. , Jain Atul , Jarníková Tereza , Jersild Annika , Jiang Fei , Jin Zhe , Kato Etsushi , Keeling Ralph F. , Klein Goldewijk Kees , Knauer Jürgen , Korsbakken Jan Ivar , Lauvset Siv K. , Lefèvre Nathalie , Liu Zhu , Liu Junjie , Ma Lei , Maksyutov Shamil , Marland Gregg , Mayot Nicolas , McGuire Patrick , Metzl Nicolas , Monacci Natalie M. , Morgan Eric J. , Nakaoka Shin-Ichiro , Neill Craig , Niwa Yosuke , Nützel Tobias , Olivier Lea , Ono Tsuneo , Palmer Paul I. , Pierrot Denis , Qin Zhangcai , Resplandy Laure , Roobaert Alizée , Rosan Thais M. , Rödenbeck Christian , Schwinger Jörg , Smallman T. Luke , Smith Stephen , Sospedra-Alfonso Reinel , Steinhoff Tobias , Sun Qing , Sutton Adrienne J. , Séférian Roland , Takao Shintaro , Tatebe Hiroaki , Tian Hanqin , Tilbrook Bronte , Torres Olivier , Tourigny Etienne , Tsujino Hiroyuki , Tubiello Francesco , van der Werf Guido , Wanninkhof Rik , Wang Xuhui , Yang Dongxu , Yang Xiaojuan , Yu Zhen , Yuan Wenping , Yue Xu , Zaehle Sönke , Zeng Ning , Zeng Jiye 
Published: November 2024

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 synthesise datasets 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) 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 sum of all sources and sinks results in the carbon budget imbalance (BIM), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2023, EFOS increased by 1.3 % relative to 2022, with fossil emissions at 10.1 ± 0.5 GtC yr-1 (10.3 ± 0.5 GtC yr-1 when the cement carbonation sink is not included), ELUC was 1.0 ± 0.7 GtC yr-1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 11.1 ± 0.9 GtC yr-1 (40.6 ± 3.2 GtCO2 yr-1). Also, for 2023, GATM was 5.9 ± 0.2 GtC yr-1 (2.79 ± 0.1 ppm yr-1), SOCEAN was 2.9 ± 0.4 GtC yr-1 and SLAND was 2.3 ± 1.0 GtC yr-1, with a near zero BIM (-0.02 GtC yr-1). The global atmospheric CO2 concentration averaged over 2023 reached 419.3 ± 0.1 ppm. Preliminary data for 2024, suggest an increase in EFOS relative to 2023 of +0.8 % (-0.3 % to 1.9 %) globally, and atmospheric CO2 concentration increased by 2.8 ppm reaching 422.5 ppm, 52 % above pre-industrial level (around 278 ppm in 1750). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2023, with a near-zero overall budget imbalance, although discrepancies of up to around 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 mean ocean sink. This living data update documents changes in methods and datasets 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-2024 (Friedlingstein et al., 2024).