Johannes J. Feddema and colleagues have a paper in Science today(Feddema et al. 2005) on the importance of land use in climate change. (And the suddenly ubiquitous Roger Pielke Sr. has an accompanying Perspective piece(Pielke Sr. 2005), and Roger also blogs it here.)
What Feddema and company did was run a global climate model with greenhouse gas changes alone and with land use changes as well. No surprise – the land use changes had a significant effect on the results – especially in terms of regional spatial variability.
The details of the changes here are less important, I think, than the underlying message – that land use changes matter a lot, especially at the regional scale, which is, after all, where we all live.
The details are, however, pretty interesting here in the southwest. Their simulation suggests a weakened Hadley circulation because of deforestation in the Amazon, which changes the circulation that contributes moisture to the North American Monsoon system, intensifying the summer monsoons that bring parts of New Mexico up to 40 percent of its annual precipitation.
I don’t think you should view this as a prediction, so much as a clear indication of the scope and significance of land use changes in climate change at the regional scale, and of the importance of seeing this question explored further.
Feddema, J.J., K.W. Oleson, G.B. Bonan, L.O. Mearns, L.E. Buja, G.A. Meehl, and W.M. Washington. 2005. “The Importance of Land-Cover Change in Simulating Future Climates.” Science 310(5754):1674-1678.
Pielke Sr., R.A. 2005. “ATMOSPHERIC SCIENCE: Land Use and Climate Change.” Science 310(5754):1625-1626.