Accelerating methane growth rate from 2010 to 2017: leading contributions from the tropics and East Asia

Creators: Yin, Yi; Chevallier, Frederic; Ciais, Philippe; Bousquet, Philippe; Saunois, Marielle; Zheng, Bo; Worden, John; Bloom, A. Anthony; Parker, Robert J.; Jacob, Daniel J.; Dlugokencky, Edward J.; Frankenberg, Christian

Abstract

After stagnating in the early 2000s, the atmospheric methane growth rate has been positive since 2007 with a significant acceleration starting in 2014. While the causes for previous growth rate variations are still not well determined, this recent increase can be studied with dense surface and satellite observations. Here, we use an ensemble of six multi-species atmospheric inversions that have the capacity to assimilate observations of the main species in the methane oxidation chain – namely, methane, formaldehyde, and carbon monoxide – to simultaneously optimize both the methane sources and sinks at each model grid. We show that the surge of the atmospheric growth rate between 2010–2013 and 2014–2017 is most likely explained by an increase of global CH₄ emissions by 17.5±1.5 Tg yr⁻¹ (mean ± 1σ), while variations in the hydroxyl radicals (OH) remained small. The inferred emission increase is consistently supported by both surface and satellite observations, with leading contributions from the tropical wetlands (∼ 35 %) and anthropogenic emissions in China (∼ 20 %). Such a high consecutive atmospheric growth rate has not been observed since the 1980s and corresponds to unprecedented global total CH₄ emissions.

Additional Information

© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 29 June 2020 – Discussion started: 10 July 2020; Revised: 12 June 2021 – Accepted: 16 June 2021 – Published: 25 August 2021. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We acknowledge the University of Leicester for the GOSAT X_(CH4) retrievals, the NCAR MOPITT group for the CO retrievals, and the Goddard Earth Sciences Data and Information Services Center for the SAO OMI HCHO retrievals. We thank the WDCGG, NOAA, AGAGE, and TCCON archives for publishing the ground-based observations and we are very grateful to all the people involved in maintaining the networks and archiving the data. Specifically, we acknowledge the following networks for making the measurements available: NOAA, CSIRO, ECCC, AGAGE, JMA, UBAG, NIWA, LSCE, MGO, DMC, Empa, FMI, KMA, RSE, SAWS, UMLT, UNIURB, and VNMHA. The Mace Head, Trinidad Head, Ragged Point, Cape Matatula, and Cape Grim AGAGE stations are supported by the National Aeronautics and Space Administration (NASA) (grants NNX16AC98G to MIT, and NNX16AC97G and NNX16AC96G to SIO). Support also comes from the UK Department for Business, Energy & Industrial Strategy (BEIS) for Mace Head, the National Oceanic and Atmospheric Administration (NOAA) for Barbados, and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Bureau of Meteorology (Australia) for Cape Grim. RJP is funded via the UK National Centre for Earth Observation (NE/N018079/1). This research used the ALICE high-performance computing facility at the University of Leicester for the GOSAT retrievals. We thank the Japanese Aerospace Exploration Agency, National Institute for Environmental Studies, and the Ministry of the Environment for the GOSAT data and their continuous support as part of the joint research agreement. We also thank François Marabelle and the LSCE IT team for computing support at LSCE. This research is supported by NASA ROSES IDS (grant no. 80NM0018F0583), the NASA Carbon Monitoring System (grant no. 80NM0018F0583), and a grant from the Grantham Foundation. This work also benefited from HPC resources from GENCI-TGCC (grant no. 2018-A0050102201). Review statement: This paper was edited by Bryan N. Duncan and reviewed by two anonymous referees. Data availability: LMDz-PYVAR global inversion results presented in this study are available for download from the Caltech Data Center (https://doi.org/10.22002/D1.2079, Yin, 2021). Supplement: The supplement related to this article is available online at: https://doi.org/10.5194/acp-21-12631-2021-supplement. Author contributions: YY and FC designed the study. YY implemented changes to the inverse system and performed the analysis. The manuscript was written by YY and revised and discussed by all coauthors. The authors declare that they have no conflict of interest.

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