Land Use Changes and Northern Hemisphere Cooling
G. Bala, P.B. Duffy, & K. Caldeira
Before current global warming, the Northern Hemisphere experienced a long term cooling trend from 1000 - 1900 AD. Several possible explanations have been posed, including large scale changes in land use. This is an investigation of land use change as a cause of cooling.
Recent reconstructions of Northern Hemisphere mean temperatures over the past millennium show a long-term cooling of about 0.25K 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 0.25K 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.