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Impacts of Historical Land Cover Changes on the Climate of Australia
Reference
McAlpine, C.A., Syktus, J., Deo, R.C., Lawrence, P.J., McGowan, H.A., Watterson, I.G. and Phinn, S.R. 2007. Modeling the impact of historical land cover change on Australia's regional climate. Geophysical Research Letters 34: 10.1029/2007GL031524.

What was done
Using an uncoupled version of a climate model with ocean and sea ice components represented by observed seasonally-varying sea surface temperatures and sea ice data, the authors completed two sets of model simulations for the period 1949-2003, where the first experiment employed pre-European land cover characteristics of Australia and the second employed modern-day land cover characteristics of the continent, as derived from corresponding land cover maps.

What was learned
McAlpine et al. report, as indicated by the climate model, that "replacing the native woody vegetation with crops and grazing in southwest Western Australia and eastern Australia has resulted in significant changes in regional climate, with a shift to warmer and drier conditions, especially in southeast Australia, the nation's major agricultural region." More specifically, they report that the anthropogenic-induced land cover change resulted in "a statistically significant warming of the surface temperature, especially for summer in eastern Australia (0.4-2°C) and southwest Western Australia (0.4-0.8°C), a statistically significant decrease in summer rainfall in southeast Australia, and increased surface temperature during the 2002/2003 El Niņo drought event."

What it means
Noting that "simulated changes in Australia's regional climate suggest that land cover change is likely a contributing factor to the observed trends in surface temperature and rainfall at the regional scale," the seven scientists suggest that "trying to attribute historical changes in mean and seasonal surface temperature and rainfall using a single radiative forcing such as greenhouse gases is simplistic and needs to be re-evaluated." Their work, as they describe it, "suggests the importance of land cover change as a contributing factor to the observed changes in Australia's regional climate," and, we might add, it has likely been a major contributing factor. In addition, this phenomenon has probably played a large role in forcing historical climate change in other parts of the world as well, with the consequence that much of modern global warming that has been attributed to anthropogenic greenhouse gas emissions may instead have been caused by this more direct influence of humanity on nature.

Reviewed 2 April 2008