Climate change in arid environments: revisiting the past to understand the future.

: Arid regions are expected to undergo significant changes under a scenario of climate warming, but there is considerable variability and uncertainty in these estimates between different scenarios. The complexities of precipitation changes, vegetation – climate feedbacks and direct physiological effects of CO₂ on vegetation present particular challenges for climate change modelling of arid regions. Great uncertainties exist in the prediction of arid ecosystem responses to elevated CO₂ and global warming. Palaeodata provide important information about the past frequency, intensity and subregional patterns of change in the world's deserts that cannot always be captured by the climatic models. However, it is important to bear in mind that the global mechanisms of Quaternary climatic variability were different from present-day trends, and any direct analogies between the past and present should be treated with great caution. Although palaeodata provide valuable information about possible past changes in the vegetation – climate system, it is unlikely that the history of the world's deserts is a key for their future. [ABSTRACT FROM AUTHOR]