Abstract. We use satellite (GOSAT) and in situ (GLOBALVIEWplus CH4 ObsPack)
observations of atmospheric methane in a joint global inversion of methane
sources, sinks, and trends for the 2010–2017 period. The inversion is done
by analytical solution to the Bayesian optimization problem, yielding
closed-form estimates of information content to assess the consistency and
complementarity (or redundancy) of the satellite and in situ data sets. We
find that GOSAT and in situ observations are to a large extent
complementary, with GOSAT providing a stronger overall constraint on the
global methane distributions, but in situ observations being more important
for northern midlatitudes and for relaxing global error correlations
between methane emissions and the main methane sink (oxidation by OH
radicals). The in-situ-only and the GOSAT-only inversions alone achieve 113 and 212 respective independent pieces of information (DOFS) for
quantifying mean 2010–2017 anthropogenic emissions on 1009 global model grid
elements, and respective DOFS of 67 and 122 for 2010–2017 emission trends. The joint
GOSAT+ in situ inversion achieves DOFS of 262 and 161 for
mean emissions and trends, respectively. Thus, the in situ data increase the global
information content from the GOSAT-only inversion by 20 %–30 %. The
in-situ-only and GOSAT-only inversions show consistent corrections to
regional methane emissions but are less consistent in optimizing the global
methane budget. The joint inversion finds that oil and gas emissions in the US
and Canada are underestimated relative to the values reported by these
countries to the United Nations Framework Convention on Climate Change
(UNFCCC) and used here as prior estimates, whereas coal emissions in China are
overestimated. Wetland emissions in North America are much lower than in the
mean WetCHARTs inventory used as a prior estimate. Oil and gas emissions in the US
increase over the 2010–2017 period but decrease in Canada and Europe. The
joint inversion yields a global methane emission of 551 Tg a−1 averaged
over 2010–2017 and a methane lifetime of 11.2 years against oxidation by
tropospheric OH (86 % of the methane sink).