Satellite and isotopic constraints on global methane source attribution

Methane (CH₄) is the second most important anthropogenic greenhouse gas, yet the drivers of recent increases in its atmospheric concentration remain insufficiently constrained, particularly regarding the relative contributions of different source sectors and sinks. Improving methane source attribution is therefore essential to support effective climate change mitigation strategies.Atmospheric methane isotopic measurements (δ¹³C–CH₄) provide valuable information to distangle between methane sources, but have so far relied primarily on sparse surface observations. Recent advances in satellite remote sensing, notably with the TROPOspheric Monitoring Instrument (TROPOMI) onboard Sentinel-5P, now offer near-global coverage of column-averaged methane mole fractions (XCH₄), opening new opportunities for integrated source attribution approaches.Within the ESA-funded SMART-CH4 project (2024–2026), we investigate how combining satellite methane observations with surface isotopic signature measurements can improve constraints on the global methane budget. We assimilate TROPOMI XCH₄ observations (2018–2024) together with updated δ¹³C–CH₄ datasets using inversion techniques implemented in the Community Inversion Framework (CIF), coupled to the LMDZ-SACS chemistry transport model.We explore the sensitivity of inferred methane emissions to the choice of observational data streams and inversion configurations, and assess the potential added value of isotopic information for separating methane source categories at the global scale. This work aims to contribute to improved estimates of the global methane budget and its uncertainties by integrating satellite and isotopic constraints, with implications for emission monitoring.