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<p>Accurate assessment of anthropogenic carbon dioxide (CO<span class="inline-formula">₂</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 methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO<span class="inline-formula">₂</span> emissions (<span class="inline-formula"><i>E</i>_FOS</span>) are based on energy statistics and cement production data, while emissions from land-use change (<span class="inline-formula"><i>E</i>_LUC</span>), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO<span class="inline-formula">₂</span> concentration is measured directly, and its growth rate (<span class="inline-formula"><i>G</i>_ATM</span>) is computed from the annual changes in concentration. The ocean CO<span class="inline-formula">₂</span> sink (<span class="inline-formula"><i>S</i>_OCEAN</span>) is estimated with global ocean biogeochemistry models and observation-based data products. The terrestrial CO<span class="inline-formula">₂</span> sink (<span class="inline-formula"><i>S</i>_LAND</span>) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (<span class="inline-formula"><i>B</i>_IM</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">±</span>1<span class="inline-formula"><i>σ</i></span>. For the first time, an approach is shown to reconcile the difference in our <span class="inline-formula"><i>E</i>_LUC</span> estimate with the one from national greenhouse gas inventories, supporting the assessment of collective countries' climate progress.</p> <p>For the year 2020, <span class="inline-formula"><i>E</i>_FOS</span> declined by 5.4 % relative to 2019, with fossil emissions at 9.5 <span class="inline-formula">±</span> 0.5 GtC yr<span class="inline-formula">⁻¹</span> (9.3 <span class="inline-formula">±</span> 0.5 GtC yr<span class="inline-formula">⁻¹</span> when the cement carbonation sink is included), and <span class="inline-formula"><i>E</i>_LUC</span> was 0.9 <span class="inline-formula">±</span> 0.7 GtC yr<span class="inline-formula">⁻¹</span>, for a total anthropogenic CO<span class="inline-formula">₂</span> emission of 10.2 <span class="inline-formula">±</span> 0.8 GtC yr<span class="inline-formula">⁻¹</span> (37.4 <span class="inline-formula">±</span> 2.9 GtCO<span class="inline-formula">₂</span>). Also, for 2020, <span class="inline-formula"><i>G</i>_ATM</span> was 5.0 <span class="inline-formula">±</span> 0.2 GtC yr<span class="inline-formula">⁻¹</span> (2.4 <span class="inline-formula">±</span> 0.1 ppm yr<span class="inline-formula">⁻¹</span>), <span class="inline-formula"><i>S</i>_OCEAN</span> was 3.0 <span class="inline-formula">±</span> 0.4 GtC yr<span class="inline-formula">⁻¹</span>, and <span class="inline-formula"><i>S</i>_LAND</span> was 2.9 <span class="inline-formula">±</span> 1 GtC yr<span class="inline-formula">⁻¹</span>, with a <span class="inline-formula"><i>B</i>_IM</span> of <span class="inline-formula">−</span>0.8 GtC yr<span class="inline-formula">⁻¹</span>. The global atmospheric CO<span class="inline-formula">₂</span> concentration averaged over 2020 reached 412.45 <span class="inline-formula">±</span> 0.1 ppm. Preliminary data for 2021 suggest a rebound in <span class="inline-formula"><i>E</i>_FOS</span> relative to 2020 of <span class="inline-formula">+</span>4.8 % (4.2 % to 5.4 %) globally.</p> <p>Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2020, but discrepancies of up to 1 GtC yr<span class="inline-formula">⁻¹</span> persist for the representation of annual to semi-decadal variability in CO<span class="inline-formula">₂</span> 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 CO<span class="inline-formula">₂</span> flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and datasets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this dataset (Friedlingstein et al., 2020, 2019; Le Quéré et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at <a href="https://doi.org/10.18160/gcp-2021">https://doi.org/10.18160/gcp-2021</a> (Friedlingstein et al., 2021).</p>