Estimating Emissions of Methane Consistent with Atmospheric Measurements of Methane and δ13C of Methane Journal Article uri icon



  • Abstract. We have constructed an atmospheric inversion framework based on TM5 4DVAR to jointly assimilate measurements of methane and δ13C of methane in order to estimate source-specific methane emissions. Here we present global emission estimates from this framework for the period 1999–2016. We assimilate a newly constructed, multi-agency database of CH4 and δ13CH4 measurements. We find that traditional CH4-only atmospheric inversions are unlikely to estimate emissions consistent with atmospheric δ13CH4 data, and assimilating δ13CH4 data is necessary to deriving emissions consistent with both measurements. Our framework attributes ca. 85 % of the post-2007 growth in atmospheric methane to microbial sources, with about half of that coming from the Tropics between 23.5° N and 23.5° S. This contradicts the attribution of the recent growth in the methane budget of the Global Carbon Project (GCP). We find that the GCP attribution is only consistent with our top-down estimate in the absence of δ13CH4 data. We find that at global and continental scales, δ13CH4 data can separate microbial from fossil methane emissions much better than CH4 data alone can, and at smaller scales this ability is limited by the current δ13CH4 measurement coverage. Finally, we find that the largest uncertainty in using δ13CH4 data to separate different methane source types comes from our knowledge of atmospheric chemistry, specifically the distribution of tropospheric chlorine and the isotopic discrimination of the methane sink.;

publication date

  • July 5, 2022

has restriction

  • green

Date in CU Experts

  • July 5, 2022 12:13 PM

Full Author List

  • Basu S; Lan X; Dlugokencky E; Michel S; Schwietzke S; Miller JB; Bruhwiler L; Oh Y; Tans PP; Apadula F

author count

  • 19

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