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 synthesize data sets 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), mainly deforestation, 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
data products. The terrestrial CO2 sink (SLAND) is estimated with
dynamic global vegetation models. The resulting carbon budget imbalance
(BIM), 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 ±1σ. For the year 2021, EFOS increased by 5.1 % relative to 2020, with
fossil emissions at 10.1 ± 0.5 GtC yr−1 (9.9 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.1 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission
(including the cement carbonation sink) of 10.9 ± 0.8 GtC yr−1
(40.0 ± 2.9 GtCO2). Also, for 2021, GATM was 5.2 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.9 ± 0.4 GtC yr−1, and SLAND was 3.5 ± 0.9 GtC yr−1, with a
BIM of −0.6 GtC yr−1 (i.e. the total estimated sources were too low or
sinks were too high). The global atmospheric CO2 concentration averaged over
2021 reached 414.71 ± 0.1 ppm. Preliminary data for 2022 suggest an
increase in EFOS relative to 2021 of +1.0 % (0.1 % to 1.9 %)
globally and atmospheric CO2 concentration reaching 417.2 ppm, more
than 50 % above pre-industrial levels (around 278 ppm). Overall, the mean
and trend in the components of the global carbon budget are consistently
estimated over the period 1959–2021, but discrepancies of up to 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 change emissions, (2) a low agreement between the
different methods on the magnitude of the land CO2 flux in the northern
extratropics, 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 data sets used in this new global
carbon budget and the progress in understanding of the global carbon cycle
compared with previous publications of this data set. The data presented in
this work are available at https://doi.org/10.18160/GCP-2022 (Friedlingstein et al., 2022b).
