Bottom-up estimation of regional methane budget in Asia

Abstract:

Methane is a potent greenhouse gas and important short-lived climate pollutant. Asia has a variety of methane sources such as paddy fields, fossil fuel mining sites, and mega cities, but its regional budget is still an open question. In this study, we adopt a bottom-up approach to evaluate the methane budget of Asia during a period from 1980 to 2015. Five natural sectors (wetland, soil oxidation, biomass burning, termite, and geological source) and five anthropogenic sectors (fossil fuel exploitation, industry and transportation, waste, agriculture, and livestock) are considered. Wetland emission and soil oxidation are estimated using a process-based terrestrial ecosystem model, Vegetation Integrative SImulator for Trace gases (VISIT). Biomass burning emission is derived from the GFED4s burnt organic matter and emission factors from the literature, after separating agricultural waste burning and wildfire. Termite emission is estimated on the basis of land-use types. Geological sources such as mud volcanoes are derived from a dataset of Etiope et al. (2019). Anthropogenic emissions are obtained mainly from EDGAR 5.0 dataset, which are compared with other emission inventories to estimate the range of uncertainty. We develop spatial maps for each sector with the same mesh size of quarter degree and evaluate the regional budget by aggregation. Also, we analyze spatial hot spots, interannual variability, decadal trend, and sectoral contributions. By relating with El Nino and Indian Dipole indices, we analyze the relationship between natural emissions and meteorological teleconnections. Finally, by relating with socioeconomic factors such as population and gross domestic product, we discuss the driving factors of anthropogenic emissions, carrying implications for climatic mitigation.