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African Rainfall
Nicholson, S.E.  2001.  Climatic and environmental change in Africa during the last two centuries.  Climate Research 17: 123-144.

What was done
The author reviews what is known about climatic changes in Africa over the past two centuries, much of which work she herself was instrumental in conducting.

What was learned
"The most significant climatic change that has occurred," in the words of the author, "has been a long-term reduction in rainfall in the semi-arid regions of West Africa," which has been "on the order of 20 to 40% in parts of the Sahel."  There have been, she says, "three decades of protracted aridity," and "nearly all of Africa has been affected ... particularly since the 1980s."  HOWEVER, she goes on to note that "the rainfall conditions over Africa during the last 2 to 3 decades are not unprecedented," and that "a similar dry episode prevailed during most of the first half [our italics] of the 19th century."

What it means
The author herself says it best: "the 3 decades of dry conditions evidenced in the Sahel are not in themselves evidence of irreversible global change."  And especially, we would add, are they not evidence of global warming-induced change.  Why not (to both points)?  Because a longer historical perspective of the type we are constantly striving to obtain clearly indicates, in the first instance, that an even longer period of similar dry conditions occurred between 1800 and 1850.  And in the second instance, this remarkable dry period occurred when the earth was still in the clutches of the Little Ice Age, a period of cold that is without precedent in at least the last 6500 years ... even in Africa [see our Journal Review of the work of Lee-Thorp et al. (2001)].  Hence, there is no reason to think that the past two- to three-decade Sahelian drought is in any way unusual or that it was caused by the putative higher temperatures of that period.  Simply put, like many other things, droughts happen.

Lee-Thorp, J.A., Holmgren, K., Lauritzen, S.-E., Linge, H., Moberg, A., Partridge, T.C., Stevenson, C. and Tyson, P.D.  2001.  Rapid climate shifts in the southern African interior throughout the mid to late Holocene.  Geophysical Research Letters 28: 4507-4510.

Reviewed 16 January 2002