Tropospheric oxidation chemistry and methane growth: a process-based attribution of OH variability (2003–2022)

Abstract. Earth system models that include interactive chemistry provide a mechanistic understanding of the hydroxyl radical (OH) sources and sinks. However, their use is often limited in the estimation of the global methane (CH4) budget. We conduct 20-year emission-driven methane simulations (2003–2022) with the Community Earth System Model Version 2.2 (CESM2.2) nudged to different meteorological datasets and input various chemical emissions, including the Seventh Coupled Model Intercomparison Project (CMIP7). Our evaluation includes in-situ observations from the NOAA Marine Boundary Layer Reference and airborne field studies, as well as ground-based and satellite remote sensing observations of carbon monoxide (CO) and CH4. We find that the model configurations with a lower OH bias have improved skill in reproducing both CO and CH4 spatial and temporal variations, including the CH4 annual growth rate. We quantify the OH impacts on the CH4 growth rate and derive a comprehensive attribution of OH changes to Earth System chemical processes. Despite an interannual variability lower than 4 %, changes in OH explains around 30 % of the interannual variability of the CH4 growth throughout the 2003–2022 period. The OH changes arise from both internal variability —via biogenic and lightning emission responses— and prescribed surface emissions, with remaining uncertainties. We find that OH is well buffered against chemistry perturbations, as increased chemical complexity raises the OH recycling probability. Consequently, studies relying on simplified and prescribed OH representations may neglect these complex chemical feedbacks and overestimate the role of OH changes in driving the CH4 growth rate.

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Publication Details

Journal
Atmospheric chemistry and physics
Published
2026-11-09
DOI
https://doi.org/10.5194/acp-26-15683-2026
Citations
1
Primary Topic
Atmospheric and Environmental Gas Dynamics
Type
article
Field-Weighted Citation Impact
1.71

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article

Tropospheric oxidation chemistry and methane growth: a process-based attribution of OH variability (2003–2022)

Yangyang Xu, Rafael P. Fernández, Avelino F. Arellano, Carlos Alberto Cuevas et al.
1 citations
Atmospheric chemistry and physics
Atmospheric and Environmental Gas Dynamics
1.71
article

Tropospheric oxidation chemistry and methane growth: a process-based attribution of OH variability (2003–2022)

Yangyang Xu, Rafael P. Fernández, Avelino F. Arellano, Carlos Alberto Cuevas, Gabrielle Pétron, John J. Orlando, Alfonso Saiz‐Lopez, Idir Bouarar, L. K. Emmons, Iván Ortega, Lori Bruhwiler, Guy Pierre Brasseur, Mohammad Amin Mirrezaei, Xin Lan, Nicolas Zilbermann, Claire Granier, Benjamin Gaubert, Chuan Feng, Youmi Oh, Shuo Chen
article en
1 citations

Abstract

Abstract. Earth system models that include interactive chemistry provide a mechanistic understanding of the hydroxyl radical (OH) sources and sinks. However, their use is often limited in the estimation of the global methane (CH4) budget. We conduct 20-year emission-driven methane simulations (2003–2022) with the Community Earth System Model Version 2.2 (CESM2.2) nudged to different meteorological datasets and input various chemical emissions, including the Seventh Coupled Model Intercomparison Project (CMIP7). Our evaluation includes in-situ observations from the NOAA Marine Boundary Layer Reference and airborne field studies, as well as ground-based and satellite remote sensing observations of carbon monoxide (CO) and CH4. We find that the model configurations with a lower OH bias have improved skill in reproducing both CO and CH4 spatial and temporal variations, including the CH4 annual growth rate. We quantify the OH impacts on the CH4 growth rate and derive a comprehensive attribution of OH changes to Earth System chemical processes. Despite an interannual variability lower than 4 %, changes in OH explains around 30 % of the interannual variability of the CH4 growth throughout the 2003–2022 period. The OH changes arise from both internal variability —via biogenic and lightning emission responses— and prescribed surface emissions, with remaining uncertainties. We find that OH is well buffered against chemistry perturbations, as increased chemical complexity raises the OH recycling probability. Consequently, studies relying on simplified and prescribed OH representations may neglect these complex chemical feedbacks and overestimate the role of OH changes in driving the CH4 growth rate.

Atmospheric chemistry and physicsVol. 26(21)
NSF National Center for Atmospheric Research (US), Centre National de la Recherche Scientifique (FR), National Oceanic and Atmospheric Administration (US), Consejo Superior de Investigaciones Científicas (ES), University of Arizona (US), Consejo Nacional de Investigaciones Científicas y Técnicas (AR), Universidad Nacional de Cuyo (AR), Cooperative Institute for Research in Environmental Sciences (US), University of Colorado Boulder (US), Purdue University West Lafayette (US), Instituto Interdisciplinario de Ciencias Básicas (AR), Laboratoire d'Aérologie (FR), Observatoire Midi-Pyrénées (FR), NOAA Chemical Sciences Laboratory (US), Instituto de Química Física Blas Cabrera (ES), Centro Científico Tecnológico - Mendoza (AR), Max Planck Institute for Meteorology (DE), NSF NCAR Atmospheric Chemistry Observations & Modeling (US), NOAA Global Monitoring Laboratory (US), Université de Toulouse (FR), Texas A&M University (US)
NOAA Research
Climate action
Openalex Percentile: Top 24%
Atmospheric and Environmental Gas Dynamics
1.71
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