The United States and many other countries face a severe and prolonged drought by 2040, according to Aiguo Dai's model for the US National Center for Atmospheric Research (NCAR). By the end of the 21st century it predicts climate disruption that has seldom or even been seen. Other scientists such as Richard Seager of Columbia University warn the changes will probably hit water supply harder than general climate.
Dai cautions that his findings are based on the best current projections of greenhouse gas emissions. What actually happens in coming decades will depend on many factors, including actual future emissions of greenhouse gases as well as natural climate cycles such as El Niño.
Combining 22 computer climate models and a comprehensive index of drought conditions, as well as data from previously published studies, he finds most of the Western Hemisphere, along with large parts of Eurasia, Africa, and Australia, under threat of extreme drought in this century. In contrast, Alaska, Scandinavia and Siberia may suffer heavier precipitation: floods and snowfall. Click on maps to see details.
Maps courtesy of Wiley Interdisciplinary Reviews, redrawn by UCAR: University Corporation for Atmospheric Research illustrate the potential for future drought if current trends continue. These maps are not intended as forecasts, since the actual course of projected greenhouse gas emissions as well as natural climate variations could alter the drought patterns. The maps use a common measure, the Palmer Drought Severity Index. Regions in blue or green have lower probability of drought, regions in red and purple could face extreme drought.