Global Carbon Budget 2024
<p>Accurate assessment of anthropogenic carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the glo...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2025-03-01
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| Series: | Earth System Science Data |
| Online Access: | https://essd.copernicus.org/articles/17/965/2025/essd-17-965-2025.pdf |
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| Summary: | <p>Accurate assessment of anthropogenic carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) 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<span class="inline-formula"><sub>2</sub></span> emissions (<span class="inline-formula"><i>E</i><sub>FOS</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>) are based on land-use and land-use change data and bookkeeping models. Atmospheric CO<span class="inline-formula"><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 global net uptake of CO<span class="inline-formula"><sub>2</sub></span> by the ocean (<span class="inline-formula"><i>S</i><sub>OCEAN</sub></span>, called the ocean sink) is estimated with global ocean biogeochemistry models and observation-based <span class="inline-formula"><i>f</i></span>CO<span class="inline-formula"><sub>2</sub></span> products (<span class="inline-formula"><i>f</i></span>CO<span class="inline-formula"><sub>2</sub></span> is the fugacity of CO<span class="inline-formula"><sub>2</sub></span>). The global net uptake of CO<span class="inline-formula"><sub>2</sub></span> by the land (<span class="inline-formula"><i>S</i><sub>LAND</sub></span>, 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 (<span class="inline-formula"><i>B</i><sub>IM</sub></span>), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as <span class="inline-formula">±1<i>σ</i></span>.</p>
<p>For the year 2023, <span class="inline-formula"><i>E</i><sub>FOS</sub></span> increased by 1.3 % relative to 2022, with fossil emissions at 10.1 <span class="inline-formula">±</span> 0.5 GtC yr<span class="inline-formula"><sup>−1</sup></span> (10.3 <span class="inline-formula">±</span> 0.5 GtC yr<span class="inline-formula"><sup>−1</sup></span> when the cement carbonation sink is not included), and <span class="inline-formula"><i>E</i><sub>LUC</sub></span> was 1.0 <span class="inline-formula">±</span> 0.7 GtC yr<span class="inline-formula"><sup>−1</sup></span>, for a total anthropogenic CO<span class="inline-formula"><sub>2</sub></span> emission (including the cement carbonation sink) of 11.1 <span class="inline-formula">±</span> 0.9 GtC yr<span class="inline-formula"><sup>−1</sup></span> (40.6 <span class="inline-formula">±</span> 3.2 GtCO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>). Also, for 2023, <span class="inline-formula"><i>G</i><sub>ATM</sub></span> was 5.9 <span class="inline-formula">±</span> 0.2 GtC yr<span class="inline-formula"><sup>−1</sup></span> (2.79 <span class="inline-formula">±</span> 0.1 ppm yr<span class="inline-formula"><sup>−1</sup></span>; ppm denotes parts per million), <span class="inline-formula"><i>S</i><sub>OCEAN</sub></span> was 2.9 <span class="inline-formula">±</span> 0.4 GtC yr<span class="inline-formula"><sup>−1</sup></span>, and <span class="inline-formula"><i>S</i><sub>LAND</sub></span> was 2.3 <span class="inline-formula">±</span> 1.0 GtC yr<span class="inline-formula"><sup>−1</sup></span>, with a near-zero <span class="inline-formula"><i>B</i><sub>IM</sub></span> (<span class="inline-formula">−</span>0.02 GtC yr<span class="inline-formula"><sup>−1</sup></span>). The global atmospheric CO<span class="inline-formula"><sub>2</sub></span> concentration averaged over 2023 reached 419.31 <span class="inline-formula">±</span> 0.1 ppm. Preliminary data for 2024 suggest an increase in <span class="inline-formula"><i>E</i><sub>FOS</sub></span> relative to 2023 of <span class="inline-formula">+</span>0.8 % (<span class="inline-formula">−</span>0.2 % to 1.7 %) globally and an atmospheric CO<span class="inline-formula"><sub>2</sub></span> 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<span class="inline-formula"><sup>−1</sup></span> persist for the representation of annual to semi-decadal variability in CO<span class="inline-formula"><sub>2</sub></span> 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<span class="inline-formula"><sub>2</sub></span> flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the mean ocean sink.</p>
<p>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 <a href="https://doi.org/10.18160/GCP-2024">https://doi.org/10.18160/GCP-2024</a> (Friedlingstein et al., 2024).</p> |
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| ISSN: | 1866-3508 1866-3516 |