Satellite Methane and Ammonia Observations Consistently Show Substantial Increases in Pan-Tropical Livestock Emissions

The inverse analysis of atmospheric observations has become a critical tool for constraining methane (CH4) fluxes and detecting their temporal changes. However, attributing inferred CH4 fluxes to specific source sectors often relies heavily on prior information and assumptions, introducing uncertainties. Incorporating co-emitted species into top-down analyses can provide additional observational constraints for more accurate source attribution. In this study, we examine the 2010–2018 emission trends of CH4 and ammonia (NH3), both of which are emitted from the livestock sector, using satellite observations of these two gases. Our analysis reveals a strong positive correlation between CH4 and NH3 emission trends at the continental scale, mainly driven by increases in Pan-Tropical regions including South Asia, East and West Africa, North Latin America, and Brazil. This observation-derived correlation is generally consistent with changes in livestock populations. In contrast, widely used bottom-up emission inventories fail to capture this correlation, likely due to inconsistencies in the activity data used for compiling greenhouse gas and air pollutant emissions. These findings support the attribution of substantial increases in CH4 emissions to the livestock sector, identifying it as one of the major drivers for recent rises in tropical CH4 emissions.