Climate Science

Dry and Getting Drier

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Science  01 Aug 2008:
Vol. 321, Issue 5889, pp. 612
DOI: 10.1126/science.321.5889.612b

Global warming is expected to have a substantial impact on the amount and pattern of rainfall worldwide. Although projections indicate that the overall effect should be an increase in precipitation, at a regional scale there will be areas that receive less rainfall; many such areas are already arid and particularly vulnerable to further drying. One of these regions is northwestern Africa, which recently suffered a severe drought from 1999 to 2002. In order to establish a context for understanding drought frequency and severity in the region, Touchan et al. constructed a 547-year summer drought record by measuring and analyzing ring widths of cedar and pine trees across Algeria and Tunisia. They found that the multiyear drought of 1999 to 2002 was the longest in their entire record and that 2002 was the single driest year, a troubling set of statistics if the data do indeed reflect ongoing anthropogenic climate change. Climate models are unable to identify the physical causes of drought in this region, however, so a mechanistic understanding of rainfall dynamics there remains elusive. — HJS

Geophys. Res. Lett. 35, L13705 (2008).

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