Land use Changes and Northern Hemisphere Cooling

Recent reconstructions of Northern Hemisphere mean temperatures over the past millennium show a longterm cooling of about 0.25K between 1000 and 1900 AD, prior to the 20(th) 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 0.25K globally and 0.37K 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.