Global Carbon Budget 2024

Accurate assessment of anthropogenic carbon dioxide (CO 2 ) 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 synthesize datasets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO 2 emissions ( E FOS ) are based on energy statistics and cement production data, while emissions from land-use change ( E LUC ) are based on land-use and land-use change data and bookkeeping models. Atmospheric CO 2 concentration is measured directly, and its growth rate ( G ATM ) is computed from the annual changes in concentration. The global net uptake of CO 2 by the ocean ( S OCEAN , called the ocean sink) is estimated with global ocean biogeochemistry models and observation-based f CO 2 products ( f CO 2 is the fugacity of CO 2 ). The global net uptake of CO 2 by the land ( S LAND , called the land sink) 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 ( B IM ), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1 σ . For the year 2023, E FOS 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), and E LUC was 1.0 ± 0.7 GtC yr −1 , for a total anthropogenic CO 2 emission (including the cement carbonation sink) of 11.1 ± 0.9 GtC yr −1 (40.6 ± 3.2 GtCO 2 yr −1 ). Also, for 2023, G ATM was 5.9 ± 0.2 GtC yr −1 (2.79 ± 0.1 ppm yr −1 ; ppm denotes parts per million), S OCEAN was 2.9 ± 0.4 GtC yr −1 , and S LAND was 2.3 ± 1.0 GtC yr −1 , with a near-zero B IM (−0.02 GtC yr −1 ). The global atmospheric CO 2 concentration averaged over 2023 reached 419.31 ± 0.1 ppm. Preliminary data for 2024 suggest an increase in E FOS relative to 2023 of +0.8 % (−0.2 % to 1.7 %) globally and an atmospheric CO 2 concentration increase by 2.87 ppm, reaching 422.45 ppm, 52 % above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of 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 CO 2 fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) low agreement between the different methods on the magnitude of the land CO 2 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).