Role of atmospheric chemistry in monitoring changes in the CH4 budget
Gaubert, B., Mirrezaei, M. A., Arellano, A. F., Fernandez, R. P., Ortega, I., et al. (2025). Role of atmospheric chemistry in monitoring changes in the CH4 budget.
| Title | Role of atmospheric chemistry in monitoring changes in the CH4 budget |
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| Genre | Conference Material |
| Author(s) | Benjamin Gaubert, M. A. Mirrezaei, A. F. Arellano, R. P. Fernandez, Ivan Ortega, Louisa K. Emmons, Behrooz Roozitalab, L. Bruhwiler, Y. Oh, G. Petron, K. McKain, X. Lan, A. Saiz-Lopez, C. A. Cuevas, C. Feng, Y. Xu, Guy Brasseur |
| Abstract | Despite that interactive chemistry models provide a mechanistic understanding of hydroxyl radicals (OH) sources and sinks, their use is often limited in the estimation of the methane (CH4) budget, in particular for emission and atmospheric growth rate quantification. This is due to discrepancies between models and observation-based estimates, regarding the global OH abundance, its spatial distribution and its temporal trends. These biases have historically led chemistry-climate models to rely on prescribed surface CH4 concentrations instead of CH4-fluxes as inputs for simulations. Here, we employ emission- and concentration- driven methane simulations using the Community Atmosphere Model with chemistry (CAM-chem) of the Community Earth System Model Version 2.2 (CESM2.2). Our model setup includes the use of posterior carbon monoxide emissions, an improved short-lived halogen chemistry representation, the use of NOAA CarbonTracker CH4 version 2025 for CH4 global fluxes as well as an interactive soil uptake parameterization. We first evaluate 20-year simulations (2003-2022) with observations from the international Network for the Detection of Atmospheric Composition Change (NDACC), the Measurements of Pollution in the Troposphere (MOPITT), the Greenhouse gases Observing SATellite (GOSAT), airborne in-situ field campaigns, and the NOAA Greenhouse Gas Marine Boundary Layer Reference for CH4. We find that the model has skills in representing global and regional methane distribution using the flux approach, often outperforming the concentration-driven simulations, while estimating the methane budget, and reproducing the observationally-derived annual growth rate. Furthermore, we will present a detailed investigation on the chemical fluxes which indicates that the modelled OH is well buffered to multi decadal emission perturbations of both CH4 and trace gasses, showing a small interannual variability and trends, in line with observation-based estimates. Second, we perform a series of sensitivity simulations to assess the role of total methane emissions, anthropogenic and fire trace gas and aerosol emissions on the changes in OH sources and sinks, and how these may have impacted the methane loss over the period 2006-2022. |
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| Publication Date | Dec 15, 2025 |
| Publisher's Version of Record | |
| OpenSky Citable URL | https://n2t.net/ark:/85065/d7b280tq |
| OpenSky Listing | View on OpenSky |
| ACOM Affiliations | ACRESP, MODELING |