Satellite-based inversion of global methane fluxes: Capabilities and implications of GOSAT-2 measurements

Abstract. Methane (CH4) is a key greenhouse gas with a strong climate impact and a relatively short atmospheric lifetime, making accurate monitoring essential for mitigation strategies. Satellite observations provide global coverage and independent constraints on CH4 emission estimates, and GOSAT-2, launched in 2018 as the successor to GOSAT, was designed to improve retrieval accuracy and enhance flux estimation. This study presents an evaluation of the GOSAT-2 Level 4 (G2L4) CH4 flux product, supported by analysis of the underlying Level 2 (L2) XCH4 retrievals, and summarizes key findings on global and regional CH4 budgets. Using an atmospheric inversion framework, we generated G2L4 posterior CH4 fluxes and assessed their consistency by comparing them with inversions constrained by alternative observational datasets, including GOSAT L2 retrievals and ground-based and aircraft measurements. GOSAT-2 achieved substantial improvements in observational coverage and data density compared to its predecessor, particularly in tropical and high-latitude regions. Posterior flux estimates derived from G2L4 are broadly consistent with global CH4 budgets reported in synthesis studies, while prior-to-posterior differences reveal positive corrections in tropical regions and negative adjustments in several mid-latitude industrial areas. A preliminary sector-focused assessment further demonstrates the potential of GOSAT-2 to inform anthropogenic CH4 emission evaluations in regions where such sources dominate. These findings highlight the capability of GOSAT-2 to refine regional and global CH4 emission estimates and underscore priorities for future improvements in retrieval algorithms, observation strategies, and integration with complementary datasets.