Simulating CH4 Lifetime and Abundance using the Global Carbon Project CH4 flux estimates

The quantification of the global methane (CH₄) budget holds significant importance in evaluating feasible approaches for mitigating climate change. The current lack of precise knowledge regarding decadal trends and yearly variations in the hydroxyl radical (OH) and significant uncertainties in the estimations of methane (CH₄) fluxes poses a significant challenge in understanding the observations of changes in atmospheric methane (CH₄) levels. Chemical transport models are considered a primary means of defining the connection between greenhouse gas fluxes and their atmospheric concentrations. However, these models often exhibit an error in estimating the lifetime of CH₄, mostly due to the uncertainty associated with its sources and sinks. Here, we conduct an ensemble simulations of the chemistry-climate model CESM/CAM-Chem using 12 CH₄ flux estimates from the Global Carbon Project. The simulated CH₄ and CO are compared with ground-based solar infrared FTS from the Total Carbon Column Observing Network (TCCON) and the Network for Detection of Atmospheric Composition Change (NDACC) alongside GOSAT-2 and TROPOMI CO and CH₄total column observations during 2019–2020. In addition, we evaluate the abundance of CH₄, CO and OH from the CAM-Chem simulations with the Atmospheric Tomography Mission (ATom) during 2016–2018 over the Pacific, Atlantic, Southern and Arctic oceans. The results of this study could provide an evaluation of the precision of the existing top-down estimations of CH₄ flux.