Increasing Coal-Related Methane Emissions in Southeast Asia During 2010–2021: A Multi-Model Inverse Analysis

This study presents top-down estimates of coal-related methane emissions in Southeast Asia derived from a multi-model ensemble within the Methane Inversion Inter-Comparison for Asia (MICA) project. Using seven atmospheric inversion systems, we applied a standardized protocol featuring consistent prior emission inventories and a comprehensive suite of atmospheric constraints. These observations integrate GOSAT satellite retrievals, the NOAA ObsPack CH₄ dataset, and additional in situ measurements from Asian monitoring sites. Monthly sectoral emission fluxes from both in-situ-based and GOSAT-based inversion simulations were aggregated to characterize regional and national-level contributions and trends.

Total regional coal-related methane emissions are estimated at 7.90 Tg yr⁻¹ (range: 5.12–9.21 Tg yr⁻¹; median, min-max) for 2019-2021, with Indonesia identified as the dominant source, contributing 7.10 Tg yr⁻¹ (4.50–8.29 Tg yr⁻¹). Indonesia accounts for approximately 90 % of coal production in the region and remains a major global exporter, followed by Vietnam as the second-largest producer and consumer. In Indonesia, coal-related emissions exhibit a statistically significant increasing trend based on the Mann–Kendall trend test (p < 0.05), with mean posterior emissions rising nearly fourfold from 2.02 to 8.47 Tg yr⁻¹ between 2010 and 2021. Notably, Indonesia’s most recent National Greenhouse Gas Inventory (NGHGI) reports energy-sector (including coal) methane emissions of 0.784 Tg yr⁻¹ for 2019 , nearly an order of magnitude lower than our estimates. Emissions from Vietnam are estimated at 0.66 Tg yr⁻¹ (0.47–0.74 Tg yr⁻¹) for 2019-2021; while no significant trend was detected over the full study period, a statistically significant increase was observed during 2017–2021.

The rapid growth of coal-related methane emissions poses a critical challenge to Southeast Asia’s climate targets and decarbonization pathways. Our fingdings reveal a substantial discrepancy between top-down estimates and national inventories, identifying a vital opportunity for high-impact mitigation. Prioritizing the recovery of coal mine methane (CMM) is therefore essential; it transforms a significant environmental liability into a valuable energy resource while simultaneously enhancing operational safety. Given the nearly fourfold increase in emissions detected since 2010, aggressive mitigation of the coal sector is imperative if regional climate commitments are to be achieved.