Monsoon-driven dry-wet seasonal contrast reveals mitigation opportunity for methane emissions in South Asia

South Asia is a global methane (CH 4 ) hotspot with strong monsoon-driven seasonality, yet wet-season emissions remain poorly constrained due to persistent cloudiness. Here we quantify dry- and wet-season methane emissions separately over South Asia during 2019–2024 using TROPOMI-constrained analytical inversions. By leveraging satellite observations from downwind regions, we are able to effectively constrain wet-season emissions despite sparse coverage. Anthropogenic sources dominate the regional total, accounting for 77.2% (28.8 Tg a −1 ; interannual range: 25.3–30.9 Tg a⁻¹), with major contributions from livestock (35.0% (32.9%–36.0%)), rice cultivation (21.8% (20.4%–23.1%)), and waste management (13.8% (12.4%–14.5%)). Six-year mean wet-season emissions (49.9(44.6–53.4) Tg a -1 ) are nearly twice dry season emissions (28.2(23.8–33.6) Tg a −1 ), driven by wetlands (5.5×), rice (2.6×), waste management (1.2×), and fossil fuels (1.2×); seasonality in waste and fossil fuels emissions is however missing from current inventories. Furthermore, latest national reports underestimate India’s methane emissions partly by neglecting seasonal variability. Despite much larger wet-season emissions, dry-season livestock and waste, unexpectedly, dominate interannual variability, likely indicating sensitivity to climate anomalies and potential implications for climate-resilient mitigation. South Asia contributed substantially to global methane surge in 2021, but not 2020. Our findings underpin previously-overlooked mitigation priorities that vary sharply by season.