We have included climate-sensitive methane emissions from wetlands within the GISS climate model using a linear parameterization derived from a detailed process model. The geographic distribution of wetlands is also climate--dependent. Doubled CO2 simulations using this model show an increase in annual average wetland methane emissions from 156 to 277 Tg/yr, a rise of 78%. The bulk of this increase is due to enhanced emissions from existing tropical wetlands. Additionally, high northern latitude wetland areas expand and emissions nearly triple during Northern summer. The global increase represents ~20% of present-day inventories. These large values indicate that the potential response of natural emissions to climate change merit greater study, and should be included in projections of future global warming and tropospheric pollution.