Accurate assessment of anthropogenic carbon dioxide (CO
2) emissions and
their redistribution among the atmosphere, ocean, and terrestrial biosphere
– the
global carbon budget
– is important to better understand the
global carbon cycle, support the development of climate policies, and project
future climate change. Here we describe data sets and methodology to quantify
the five major components of the global carbon budget and their
uncertainties. CO
2 emissions from fossil fuels and industry
(
EFF) are based on energy statistics and cement production data,
respectively, while emissions from land-use change (
ELUC), mainly
deforestation, are based on land-cover change data and bookkeeping models.
The global atmospheric CO
2 concentration is measured directly and its
rate of growth (
GATM) is computed from the annual changes in
concentration. The ocean CO
2 sink (
SOCEAN) and terrestrial
CO
2 sink (
SLAND) are estimated with global process models
constrained by observations. 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 ±1
σ. For the last decade
available (2007–2016),
EFF was 9.4 ± 0.5 GtC yr
−1,
ELUC 1.3 ± 0.7 GtC yr
−1,
GATM
4.7 ± 0.1 GtC yr
−1,
SOCEAN
2.4 ± 0.5 GtC yr
−1, and
SLAND
3.0 ± 0.8 GtC yr
−1, with a budget imbalance
BIM of
0.6 GtC yr
−1 indicating overestimated emissions and/or underestimated
sinks. For year 2016 alone, the growth in
EFF was approximately
zero and emissions remained at 9.9 ± 0.5 GtC yr
−1. Also for
2016,
ELUC was 1.3 ± 0.7 GtC yr
−1,
GATM
was 6.1 ± 0.2 GtC yr
−1,
SOCEAN was
2.6 ± 0.5 GtC yr
−1, and
SLAND was
2.7 ± 1.0 GtC yr
−1, with a small
BIM of −0.3 GtC.
GATM continued to be higher in 2016 compared to the past decade
(2007–2016), reflecting in part the high fossil emissions and the small
SLAND consistent with El Niño
conditions. The global atmospheric
CO
2 concentration reached 402.8 ± 0.1 ppm averaged over 2016. For
2017, preliminary data for the first 6–9 months indicate a
renewed growth in
EFF of +2.0 % (range of 0.8 to 3.0 %)
based on national emissions projections for China, USA, and India, and
projections of gross domestic product (GDP) corrected for recent changes in
the carbon intensity of the economy for the rest of the world. This living
data update documents changes in the methods and data sets used in this new
global carbon budget compared with previous publications of this data set (Le
Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here
can be downloaded from
https://doi.org/10.18160/GCP-2017 (GCP, 2017).