The potential for wetland emissions to feedback on climate change has been previously hypothesised <Houghton et al., 2001>. We assess this hypothesis using an interactive wetlands scheme radiatively coupled to an integrated climate change effects model. The scheme predicts wetland area and methane (CH4) emissions from soil temperature and water table depth, and is constrained by optimising its ability to reproduce the observed inter-annual variability in atmospheric CH4. In transient climate change simulations the wetland response amplifies the total anthropogenic radiative forcing at 2100 by about 3.5--5%. The modelled increase in global CH4 flux from wetland is comparable to the projected increase in anthropogenic CH4 emissions over the 21st century under the IS92a scenario.