Recent reconstructions of Northern Hemisphere mean temperatures over the past millennium show a long-term cooling of about 0.25 K between 1000 and 1900 AD, prior to the 20th century's warming. In this paper, we present the results of equilibrium climate model simulations that indicate that the land-use change occurring over this period may largely explain this observed cooling, although other factors also could have played a significant role. The simulated annual mean cooling due to land-use change is 0.25 K globally and 0.37 K for the Northern Hemisphere, suggesting that the cooling of the prior centuries could have been largely the result of anthropogenic interference in the climate system. ¿ 2001 American Geophysical Union