The future methane (CH₄) emissions from natural wetlands are predicted to amplify due to global warming, thereby accelerating climate change. However, the magnitude of this predicted increase remains highly uncertain. Here we conducted a first-ever ensemble simulation of state-of-the-art terrestrial biosphere models to estimate wetland CH₄ emissions during the 21st century. We identified an emergent relationship between CH₄ temperature sensitivity and projected wetland CH₄ emissions. Our estimates indicate that warming will release an average of 22±8 Tg CH₄ yr^-1 K^-1 for every 1-K increase in global land temperature. Combined with contemporary observations from eddy covariance measurements, our analysis suggests that wetland emissions will increase markedly from the 2000s level at 190±59 Tg CH₄ yr^-1 to 308±102 Tg CH₄ yr^-1 in 2090s under the severe climate scenario RCP8.5. The constrained projection under RCP8.5 suggests a 2% probability in 2030s that the predicted increase in wetland CH₄ could completely offset the amount Global Methane Pledge committed to reduce, with this chance increasing to over 50% in 2050s. Our findings help reduce the uncertainty in predicting wetland methane emissions and imply greater certainty regarding the impact of natural feedback on future methane mitigating actions.