Drought return times in the Sahel: A question of attribution

Abstract

Recurrence times for extreme drought events in the African Sahel are estimated using a classical peaks-overthreshold model. Results, which are computed for both mean seasonal rainfall and fractional area in drought, suggest that the distribution of dry extremes after about 1970 is statistically distinct from that of preceding years. This finding throws into relief the critical role played by attribution of causes, and the necessity of improving our understanding of the physical processes driving precipitation variability in the Sahel. Copyright 2009 by the American Geophysical Union.