Estimate of methane release from temperate natural wetlands using ENVISAT/SCIAMACHY data in China

Abstract Since wetlands are the largest natural sources of atmospheric CH 4 , it is important to estimate the CH 4 emissions from natural wetlands at regional scale and over a long time period. The annual CH 4 efflux from temperate natural wetlands excluding water surface in China was estimated, based on atmospheric CH 4 concentrations from SCIAMACHY/ENVISAT. The atmospheric CH 4 concentrations showed obvious seasonal cycles, and CH 4 emission from natural wetlands dominated the temporal variations of CH 4 concentrations in north China, accounting for about 67.94% of the variations of CH 4 concentrations. The chemical transport model, MOZART-4 (Model for Ozone and Related Chemical Tracers, version 4), was used to simulate the space-borne CH 4 column concentrations to the surface level, and then the relationship between surface concentrations and emissions of CH 4 from natural wetlands was simulated by a linear regression model. The results showed that the estimated annual budget of CH 4 emission from natural wetlands in the temperate zone of China was about 4.76 Tg CH 4 , which was within the range of 2.38–4.91 Tg CH 4 estimated by spatial distribution of wetland and the published CH 4 release fluxes during the 1990s–2000s. This demonstrated that the method of using space-borne CH 4 column concentrations to estimate CH 4 emissions from natural wetlands was reliable.