Methane emissions in East Asia for 2000-2011 estimated using an atmospheric Bayesian inversion

We present methane (CH4) emissions for East Asia from a Bayesian inversion of CH4 mole fraction and stable isotope (C-13-CH4) measurements. Emissions were estimated at monthly resolution from 2000 to 2011. A posteriori, the total emission for East Asia increased from 434 to 594Tgyr(-1) between 2000 and 2011, owing largely to the increase in emissions from China, from 394 to 544Tgyr(-1), while emissions in other East Asian countries remained relatively stable. For China, South Korea, and Japan, the total emissions were smaller than the prior estimates (i.e., Emission Database for Global Atmospheric Research 4.2 FT2010 for anthropogenic emissions) by an average of 29%, 20%, and 23%, respectively. For Mongolia, Taiwan, and North Korea, the total emission was less than 2Tgyr(-1) and was not significantly different from the prior. The largest reductions in emissions, compared to the prior, occurred in summer in regions important for rice agriculture suggesting that this source is overestimated in the prior. Furthermore, an analysis of the isotope data suggests that the prior underestimates emissions from landfills and ruminant animals for winter 2010 to spring 2011 (no data available for other times). The inversion also found a lower average emission trend for China, 1.2Tgyr(-1) compared to 2.8Tgyr(-1) in the prior. This trend was not constant, however, and increased significantly after 2005, up to 2.0Tgyr(-1). Overall, the changes in emissions from China explain up to 40% of the increase in global emissions in the 2000s.