Sustained methane emissions from China after 2012 despite declining coal production and rice-cultivated area

Abstract

China's anthropogenic methane emissions are the largest of any country in the world. A recent study using atmospheric observations suggested that recent policies aimed at reducing emissions of methane due to coal production in China after 2010 had been largely ineffective. Here, based on a longer observational record and an updated modelling approach, we find a statistically significant positive linear trend (0.36 ± 0.04 (±1 σ) Tg CH4 yr-2) in China's methane emissions for 2010-2017. This trend was slowing down at a statistically significant rate of -0.1 ± 0.04 Tg CH4 yr-3. We find that this decrease in growth rate can in part be attributed to a decline in China's coal production. However, coal mine methane emissions have not declined as rapidly as production, implying that there may be substantial fugitive emissions from abandoned coal mines that have previously been overlooked. We also find that emissions over rice-growing and aquaculture-farming regions show a positive trend (0.13 ± 0.05 Tg CH4 yr-2 for 2010-2017) despite reports of shrinking rice paddy areas, implying potentially significant emissions from new aquaculture activities, which are thought to be primarily located on converted rice paddies.