Unravelling a large methane emission discrepancy in Mexico using satellite observations

We use satellite observations from the Tropospheric Monitoring Instrument (TROPOMI) to map and quantify methane emissions from eastern Mexico using an atmospheric inverse analysis. Eastern Mexico covers the vast majority of the national oil and gas production. Using TROPOMI measurements from May 2018 to December 2019, our methane emission estimates for eastern Mexico are 5.0 ± 0.2 Tg a−1 for anthropogenic sources and 1.5 ± 0.1 Tg a−1 for natural sources, representing 45% and 34% higher annual methane fluxes respectively compared to the most recent estimates based on the Mexican national greenhouse gas inventory. Our results show that Mexico's oil and gas sector has the largest discrepancy, with oil and gas emissions (1.3 ± 0.2 Tg a−1) higher by a factor of two relative to bottom-up estimates—accounting for a quarter of total anthropogenic emissions. Our satellite-based inverse modeling estimates show that more than half of the oil/gas emissions in eastern Mexico are from the southern onshore basin (0.79 ± 0.13 Tg a−1), pointing at high emission sources which are not represented in current bottom-up inventories (e.g., venting of associated gas, high-emitting gathering/processing facilities related to the transport of associated gas from offshore). These findings suggest that stronger mitigation measures are critical to curbing the anthropogenic footprint of methane emissions in Mexico, especially the large contribution from the oil and gas sector.