Wetlands at the Last Glacial Maximum: Distribution and methane emissions

The global distribution of potential wetlands and their methane (CH 4 ) 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 CH 4 emissions based on ecosystem carbon turnover in wet soils. LGM wetland area was 15% larger than present, but CH 4 emissions were 24% less. Extensive wetlands were simulated on the exposed continental shelves. The soil CH 4 sink was simulated as 14 Tg now but <0.5 Tg at the LGM. CH 4 emissions at LGM were limited by substrate availability, in turn due to low atmospheric CO 2 . The glacial‐interglacial change in atmospheric CH 4 concentration cannot be completely attributed to changes in the wetland source.