Drinkwater, A; Palmer, P I; Feng, L; Arnold, T; Lan, X; Michel, S E; Parker, R; Boesch, H (2023) Atmospheric data support a multi-decadal shift in the global methane budget towards natural tropical emissions. Atmospheric Chemistry and Physics, 23 (14). pp. 8429-8452. ISSN 1680-7324

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Abstract

We use the GEOS-Chem global 3-D model and a Maximum A Posteriori inverse method to infer regional methane emissions and the corresponding carbon stable isotope source signatures, 2004–2020, across the globe using in situ and satellite remote sensing data. Over our study period, we find consistent evidence from both atmospheric CH4 datasets of a progressive increase of methane emissions at tropical (30◦N to 30 ◦S) latitudes (+3.80 Tg/yr/yr), accompanied by a progressively lighter 5 atmospheric δ13C signature, consistent with increasing natural emissions. The satellite remote sensing data provide evidence of higher spatially resolved hotspots of methane that are consistent with the location and seasonal timing of wetland emissions, limiting the hypothesis about the hydroxyl radical (OH) sink for methane playing a significant role in observed global growth in atmospheric methane. We find that since 2004, the largest growing regional contributions (2004–2020) are from North Africa (+19.9 Tg/yr), China (+21.6 Tg/yr), and Tropical South America (+14.2 Tg/yr). To quantify the influence of our results to 10 changes in OH, we also report regional emission estimates using an alternative scenario of a 0.5%/yr decrease in OH since 2004, followed by a 5 % drop in 2020 during the first COVID-19 lockdown. We find that our main findings are robust against those year-to-year changes in OH.

Item Type:	Article
Subjects:	Environmental Measurement > Atmospheric Science, Emission and Security
Divisions:	Atmospheric Environmental Sciences
Identification number/DOI:	10.5194/acp-23-8429-2023
Last Modified:	10 Jun 2026 10:50
URI:	https://eprintspublications.npl.co.uk/id/eprint/10431