The global distribution of potential wetlands and their methane (CH4) emissions at the present‐day and the Last Glacial Maximum (LGM) are estimated using a GCM simulation of LGM climate, a vegetation model, and simple algorithms for determining wetland area based on topography and soil moisture, and CH4 emissions based on ecosystem carbon turnover in wet soils. LGM wetland area was 15% larger than present, but CH4 emissions were 24% less. Extensive wetlands were simulated on the exposed continental shelves. The soil CH4 sink was simulated as 14 Tg now but <0.5 Tg at the LGM. CH4 emissions at LGM were limited by substrate availability, in turn due to low atmospheric CO2. The glacial‐interglacial change in atmospheric CH4 concentration cannot be completely attributed to changes in the wetland source.