Large scale use of wind power can alter local and global climate by extracting kinetic energy and by modifying turbulent transport in the atmospheric boundary layer. We explored the climatic impacts of extracting 3-20 TW of electricity with a suite of numerical experiments using two independent atmospheric GCMs and to parameterizations of the wind-turbine arrays. Wind power has a negligible effect on global-mean surface temperature, but at continental scales, the average magnitude of climatic change due to wind power can be significant in comparison to the reduction in climatic change achieved by the substitution of wind or fossil-fuels.