High-resolution inversion of methane emissions over Europe using the Community Inversion Framework and FLEXPART

Abstract. Constraining methane (CH₄) emissions at high spatial and temporal resolution is critical for accurate European greenhouse gas budgets and mitigation policy. We use the Community Inversion Framework to estimate monthly CH₄ fluxes across Europe (2017–2022) at 0.2° × 0.2°, coupling the FLEXPART and assimilating observations from 46 in situ stations, including ICOS and non-ICOS sites. Prior emissions combine GAINS and EDGARv8 anthropogenic inventories with GFED biomass burning, JSBACH-HIMMELI wetland fluxes, and climatological natural sources. The inversion markedly improves agreement with atmospheric observations (r² = 0.87, RMSE = 24.35 ppb, mean bias = –2.14 ppb), performing best at northern European stations. Posterior EU27+3 CH₄ totals 23.28 ± 0.36 Tg CH₄ yr⁻¹, 6.6 % above the prior. Anthropogenic emissions average 17.6 ± 0.3 Tg CH₄ yr⁻¹, exceeding GAINS by 11 %, EDGARv8 by 4 %, and UNFCCC NGHGI (2023) by 3 %, consistent with recent studies. Country-level differences are substantial: emissions are higher in BENELUX (+54 %), Germany (+37 %), and France (+10 %), and lower in the UK (–11 %), Romania (–25 %), Poland (–16 %), and Italy (–11 %) compared to UNFCCC NGHGI (2023). Sectoral changes primarily reflect agricultural increases in western and central Europe, with reductions in northern wetlands and southern geological sources. Sensitivity tests highlight the influence of horizontal correlation length and the value of dense observational networks for refining regional CH₄ budgets.