Relatively little research has been conducted on the possible impact of climate change on deserts. Scientists have focused on a different question: Are deserts likely to expand?
Scientists at NASA have suggested that in the long run, a worldwide expansion of deserts is likely (Rind et al. 1990). Today, deserts tend to be found at latitudes between 20 and 32 degrees. Soils are extremely dry at these latitudes because the potential for evaporation and transpiration is generally greater than the average rainfall. If global temperatures were to rise by 4°C, the potential evapotranspiration (see glossary) would increase 30-40 percent, while precipitation would only increase 10-15 percent. As a result, the area with a deficiency of precipitation would expand poleward and toward the equator.
Studies that focus on what is likely to occur over the next century, however, do not indicate whether deserts are more likely to expand or contract. Studies using the biogeographic models have estimated that desert shrublands could increase by as much as 185 percent or decrease by as much as 56 percent.