Ensemble estimates of global wetland methane emissions over 2000–2020

Abstract. Due to ongoing climate change, methane (CH₄) emissions from vegetated wetlands are projected to increase during the 21^st century, challenging climate mitigation efforts aimed at limiting global warming. However, despite reports of rising emission trends, a comprehensive evaluation and attribution of recent changes is still lacking. Here we assessed global wetland CH₄ emissions from 2000 to 2020 based on an ensemble of sixteen process-based wetland models. Our results estimated global average wetland CH₄ emissions at 158±24 (mean ± 1σ) Tg CH₄ yr^-1 for the period 2010–2020, with an average decadal increase of 6–7 Tg CH₄ yr^-1 compared to the decade of 2000–2009. The increases in the four latitudinal bands of 90° S–30° S, 30° S–30° N, 30° N–60° N, and 60° N–90° N were 0.1–0.2 Tg CH₄ yr^-1, 3.6–3.7 Tg CH₄ yr^-1, 1.8–2.4 Tg CH₄ yr^-1, and 0.6–0.8 Tg CH₄ yr^-1, respectively, over the two decades. The modeled CH₄ sensitivities to temperature show reasonable consistency with eddy covariance-based measurements from 34 sites.  Rising temperature was the primary driver of the increase, while precipitation and rising atmospheric CO₂ concentrations played secondary roles with high levels of uncertainty. These modeled results suggest climate change is driving increased wetland CH₄ emissions and that direct and sustained measurements are needed to monitor developments.