Modeling methane emissions from irrigated rice cultivation in China from 1960 to 2050

Rice paddy is a major source of anthropogenic terrestrial methane (CH4). China has the second‐largest area of rice cultivation in the world, accounting for ca. 19% of the world's rice‐producing area. Recognizing the significance of China's rice cultivation in the global CH4 budget, we estimated the CH4 emissions resulting from irrigated rice cultivation in China from 1960 to 2050 using a CH4MOD model. The model estimates suggest that the annual CH4 emissions decreased from 5.62 Tg yr−1 in 1960 to 4.13 Tg yr−1 in 1970, and this decrease was attributed to changes in water management from continuous flooding to mid‐season drainage irrigation. Since the early 1970s, the amount of CH4 emissions gradually increased to 6.85 Tg yr−1 by 2009 because of significant improvements in crop production that led to high‐crop residue retention. Higher levels of CH4 emissions occurred in southern China, where double rice cropping systems are most common. For the A1B and B1 scenarios of the IPCC Special Report on Emissions Scenarios (SRES), the amount of CH4 emissions from 2010 to 2050 is predicted to increase at an average rate of 1.2 kg ha−1 yr−1 in response to global warming. Compared to 2009, the CH4 flux is predicted to increase by ca. 14% by the late 2040s, and the increase in these emissions in northeastern China is estimated to become more significant than in the other rice‐growing regions of the country. Under the assumptions that the rice‐producing land area will remain the same, decrease by 25% or increase by 38% by the late 2040s, the CH4 emissions are projected to be 7.8, 5.6 or 11.7 Tg yr−1, respectively.