Atmospheric drivers of climate change over Romania with focus on CH4: sources and changes inferred from reanalysis, observations, and emission inventories

Atmospheric methane (CH4) is a key short-lived climate forcer whose concentration has increased rapidly over the last two decades, yet important uncertainties remain regarding its regional-scale evolution and its relationship to reported anthropogenic emissions. In particular, Eastern Europe remains comparatively underrepresented in regional methane assessments based on consistent long-term datasets. In this study, we investigate recent methane trends at global, European and national (Romania) scales by combining atmospheric reanalysis products, surface observations and emission inventories.Near-surface methane concentrations are analysed using the Copernicus Atmosphere Monitoring Service (CAMS) global greenhouse gas reanalysis for the period 2003–2022. Regional mean time series are derived for Europe and Romania and compared to the global mean methane evolution obtained from NOAA surface observations. To provide a bottom-up perspective, anthropogenic methane emissions are analysed using the EDGAR inventory, with a focus on national and sectoral contributions relevant for Romania. The consistency between atmospheric concentration trends and reported emission changes is assessed across spatial scales.The study provides new insight into the regional behaviour of atmospheric methane in Eastern Europe and contributes to the ongoing evaluation of methane mitigation efforts at European and national levels. The value of combining reanalysis products, observational datasets and emission inventories to characterise methane trends from global to national scales is also shown.