Global Carbon Budget 2021

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, terrestrial biosphere in a changing climate is critical to better understand global cycle, support development policies, project future change. Here we describe synthesize datasets methodology quantify five major components budget uncertainties. Fossil CO2 (EFOS) are based on energy statistics cement production data, while from land-use change (ELUC), mainly deforestation, land use data bookkeeping models. Atmospheric concentration measured directly, its growth rate (GATM) computed annual changes concentration. The ocean sink (SOCEAN) estimated with biogeochemistry models observation-based products. (SLAND) dynamic vegetation resulting imbalance (BIM), difference between total biosphere, measure imperfect understanding contemporary cycle. All uncertainties reported as ±1?. For first time, an approach shown reconcile our ELUC estimate one national greenhouse gas inventories, supporting collective countries' progress. year 2020, EFOS declined by 5.4 % relative 2019, fossil at 9.5 ± 0.5 GtC yr?1 (9.3 when carbonation included), was 0.9 0.7 yr?1, for emission 10.2 0.8 (37.4 2.9 GtCO2). Also, GATM 5.0 0.2 (2.4 0.1 ppm yr?1), SOCEAN 3.0 0.4 SLAND 1 BIM ?0.8 yr?1. atmospheric averaged over 2020 reached 412.45 ppm. Preliminary 2021 suggest rebound +4.8 (4.2 %) globally. Overall, mean trend consistently period 1959–2020, but discrepancies up persist representation semi-decadal variability fluxes. Comparison estimates multiple approaches observations shows (1) persistent large uncertainty emissions, (2) low agreement different methods magnitude flux northern extra-tropics, (3) discrepancy strength last decade. This living update documents used this new progress cycle compared previous publications dataset (Friedlingstein et al., 2019; Le Quéré 2018b, a, 2016, 2015b, 2014, 2013). presented work available https://doi.org/10.18160/gcp-2021 2021).