Exploring the effects of extreme weather events on methane emissions from croplands: A study combining site and global modeling

Abstract

Croplands, especially rice paddies, are important anthropogenic sources of methane (CH4) emission. Currently, the effects of extreme weather events, which are occurring more frequently with climate warming, on CH4 emissions from croplands still remain uncertain. In this study, we calibrated the CLM5BGCCrop model and implemented it to nine cropland sites and global simulations, in order to a) analyze the spatial and temporal variations of CH4 emissions from different crop and climate types, b) identify corresponding environmental controlling factors, and c) investigate the effects of extreme weather events on CH4 emissions. The results show that parameterized CLM5BGCCrop could simulate CH4 emissions from croplands well at both site and global scales. The simulated CH4 emissions from rice paddies (44.35 Tg CH4 yr−1) are 1–2 orders of magnitude higher than those from corn (0.38 Tg CH4 yr−1) and wheat (2.57 Tg CH4 yr−1) fields. Soil water content is the key factor affecting global CH4 emissions from croplands under present and future climate. Extreme high-temperature events occurring during the rice booting-flowering stage could reduce the CH4 emissions by 28%, while the CH4 emissions could be increased by 12–16% when extreme high-temperature events occurred during the rice milky-maturity stage. Extreme precipitation events increased CH4 emissions by 7% at the rice paddy site. At the global scale, extreme high temperature increased CH4 emissions from rice paddies by 8% at middle latitudes, in contrast, extreme high temperature reduced corresponding emissions by 12% at low latitudes, but the decrease in CH4 emissions from rice paddies at low latitudes will be reversed to a 9% increase in 2081–2100. Overall, the increasing frequency and intensity of extreme weather events in future may lead to increased global CH4 emissions from croplands.