This study evaluates the climatic impact of possible future changes in high-latitude inland water surface (IWS) area. We carried out a set of climate-change experiments with an atmospheric general circulation model in which different scenarios of future changes of IWS extent were prescribed. The simulations are based on the SRES-A1B greenhouse gas emission scenario and represent the transient climatic state at the end of the 21st century. Our results indicate that the impact of a reduction in IWS extent depends on the season considered: the total disappearance of IWS would lead to cooling during cold seasons and to warming in summer. In the annual mean, the cooling effect would be dominant. In an experiment in which the future change of prescribed IWS extent is prescribed as a function of the simulated changes of permafrost extent, we find that these changes are self-consistent in the sense that their effects on the simulated temperature and precipitation patterns would not be contradictory to the underlying scenario of changes in IWS extent. In this best guess simulation, the projected changes in IWS extent would reduce future near-surface warming over large parts of northern Eurasia by about 20% during the cold season, while the impact in North America and during summer is less clear. As a whole, the direct climatic impact of future IWS changes is likely to be moderate. © 2010.