AGU: Geophysical Research Letters

 

Editors' Highlight

Recent drought in northwestern Africa heralds drier conditions to come

Human-induced climate change is projected to cause drier conditions in the midlatitudes. To assess whether the onset of drier conditions has already begun, Touchan et al. (2008) studied newly developed multicentury tree ring records from Tunisia and Algeria for a longer-term perspective on drought in northwestern Africa. Using a new set of 13 chronologies from Atlas cedars (Cedrus atlantica) and Aleppo pines (Pinus halepensis), the authors analyzed the widths of individual tree rings, following the basic principle that thinner bands indicate years when water was relatively scarce. Through this, they reconstructed the region's Palmer Drought Severity Index, an index of dryness based on precipitation and temperature, for the years between 1456 and 2002. The reconstruction revealed the magnitude of droughts from the historic record, despite there having been no instruments to record these droughts. Interestingly, the most recent drought (1999–2002) appears to be the worst since at least the middle of the fifteenth century. This drought is consistent with early signatures of a transition to more arid midlatitude conditions, as projected by several climate models.

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