Articles | Volume 23, issue 8
https://doi.org/10.5194/acp-23-4863-2023
https://doi.org/10.5194/acp-23-4863-2023
Research article
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25 Apr 2023
Research article | Highlight paper |  | 25 Apr 2023

Methane emissions are predominantly responsible for record-breaking atmospheric methane growth rates in 2020 and 2021

Liang Feng, Paul I. Palmer, Robert J. Parker, Mark F. Lunt, and Hartmut Bösch

Data sets

University of Leicester GOSAT Proxy XCH4 v9.0 Robert Parker and Hartmut Boesch https://doi.org/10.5285/18ef8247f52a4cb6a14013f8235cc1eb

Multi-laboratory compilation of atmospheric carbon dioxide data for the period 1983–2021; obspack_ch4_1_GLOBALVIEWplus_v5.0_2022-10-17 K. N. Schuldt, T. Aalto, A. Andrews, et al. https://doi.org/10.25925/20221001

Multi-laboratory compilation of atmospheric carbon dioxide data for the period 1957–2021; obspack_co2_1_GLOBALVIEWplus_v8.0_2022-08-27 K. N. Schuldt, J. Mund, I. T. Luijkx, et al. https://doi.org/10.25925/20220808

MERRA-2 instM_2d_asm_Nx: 2d,Monthly mean,Single-Level,Assimilation,Single-Level Diagnostics V5.12.4 Global Modeling and Assimilation Office (GMAO) https://doi.org/10.5067/5ESKGQTZG7FO

JPL GRACE Mascon Ocean, Ice, and Hydrology Equivalent Water Height RL06 CRI Filtered Version 1 D. N. Wiese, D.-N. Yuan, C. Boening, F. W. Landerer, and M. M. Watkins https://doi.org/10.5067/TEMSC-3MJC6

2020 TCCON Data Release (Version GGG2020) Total Carbon Column Observing Network (TCCON) Team https://doi.org/10.14291/TCCON.GGG2020

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Executive editor
After a period of near-zero growth of atmospheric methane, a major greenhouse gas, its growth rates have increased, with values in 2020 and 2021 exceeding all prior values since the beginning of systematic measurements in 1983. This recent acceleration, particularly during the covid-19 years 2020 and 2021, raises the question whether the methane increase was due to stronger sources or reduced sinks in the troposphere. A reduction of the tropospheric abundance of the hydroxyl radical (OH), the reaction of which is the main tropospheric methane sink, could be plausibly explained by global-scale reductions in nitrogen oxides due to pandemic-related industry shutdowns. Using an inversion scheme, Feng et al. demonstrate that such a reduction only accounts for about 34% in 2020 and 10% in 2021 of the observed methane rise. Instead, the authors attribute increased methane emissions to hydrological anomalies and microbial sources over the tropics, i.e., Eastern Africa and tropical South America, and temperate North America. The study demonstrates the importance of simultaneously accounting for changes in methane emissions and sinks for an improved quantitative understanding of the evolution of the methane concentrations to assess the role of greenhouse gases in climate change and tropospheric composition.
Short summary
Our understanding of recent changes in atmospheric methane has defied explanation. Since 2007, the atmospheric growth of methane has accelerated to record-breaking values in 2020 and 2021. We use satellite observations of methane to show that (1) increasing emissions over the tropics are mostly responsible for these recent atmospheric changes, and (2) changes in the OH sink during the 2020 Covid-19 lockdown can explain up to 34% of changes in atmospheric methane for that year.
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