Global Wetland Methane Emissions From 2001 to 2020: Magnitude, Dynamics and Controls

Abstract The large uncertainties in estimating CH 4 emissions from wetland ecosystems, the leading natural source to the atmosphere, substantially hinder the quantification of the global CH 4 budget. This study used the IBIS‐CH 4 (Integrated BIosphere Simulator‐Methane) model, a process‐based model integrating microbial mechanisms associated with CH 4 production and oxidation processes, to simulate global wetland CH 4 emissions from 2001 to 2020. Initially, we employed the IBIS‐CH 4 model to evaluate its performance across 26 diverse wetland sites worldwide. The results showed that the magnitude and seasonality of observed CH 4 fluxes over various wetland sites were well reproduced. We then used this model to estimate the annual global wetland CH 4 emissions from 2001 to 2020, averaging 152.67 Tg CH 4 yr −1 , with a range of 135.72–167.57 Tg CH 4 yr −1 . The estimated global wetland CH 4 emissions are generally in agreement with the current bottom‐up estimates (117–256 Tg CH 4 yr −1 ) and closely overlap with independent top‐down estimates (139–183 Tg CH 4 yr −1 ). During 2001–2020, the estimated global wetland CH 4 emissions initially showed an increasing trend, followed by a decline. The peak of CH 4 emissions reached in 2010, coinciding with the peak of wetland area. The majority of global wetland CH 4 emissions were concentrated in tropical regions, which exhibited a clear seasonality and had a peak in July. The impact of meteorological factors on wetland CH 4 emissions was greater than that of leaf area index, indicating the importance of soil hydrothermal conditions on wetland CH 4 emissions.