An integrated analysis of contemporary methane emissions and trends over China using in-situ, satellite observations, and model results

Abstract:

Atmospheric methane plays an important role in both chemistry and climate as an essential precursor for tropospheric ozone and the second most important human-influenced greenhouse gas. A better understanding and quantification of the interannual variability of methane emissions and the drivers of trends over the recent decade is important to support its mitigation. Here we evaluate two gridded global anthropogenic emission inventories: the Emissions Database for Global Atmospheric Research (EDGAR v4.3.2) and the Community Emissions Data System (CEDS), using a global chemical transport model (GEOS-Chem) and an ensemble of in-situ, satellite and aircraft observations. The annual Chinese methane emissions in the EDGAR and CEDS anthropogenic inventories are, respectively, 68.03 and 72.07 Tg averaged over 2000-2018, and the trends are, respectively, 1.36 and 2.14 Tg yr^-1 during the period. Model simulated atmospheric methane concentrations with the CEDS inventory (also with interannual variations of OH concentrations) show a mean trend of 7.15 ppbv yr-1 over China in 2010-2017, higher than the model simulated trend of 4.16 ppbv yr-1 with EDGAR and also more consistent the observed trend of about 8.05 ppbv yr^-1. We find the simulated trends are sensitive to global OH concentrations. A 1% increase in global mean OH decreases the background methane trend in China by 2.13 ppbv yr^-1, being equivalent to a 4.08 Tg yr^-1 decrease in methane emissions. We have also applied a tagged methane simulation with CEDS, and find that increases in domestic methane sources (mainly from the energy sector) account for 68.3% of the total trend while the domestic methane sources contribute 11.4% of the column concentration in 2007-2018 over China.