Much of arid sub-Saharan Africa, notably in the Sahel (the region just south of the Sahara desert), has experienced a pronounced drop in rainfall over the past quarter-century. This decline coincided with a rise in the surface temperature of the neighboring Indian Ocean, a hint that the decline in rainfall is in fact part of the longer-term process of man-made global warming.
撒哈拉沙漠以南的大部分干旱地区，尤其是Sahel（该地区就在撒哈拉沙漠南面），过去25年的降雨量已经明显下滑。与此同时，离它不远的印度洋却水温上升，这一现象暗示着，降雨量的减少实际是人类一手造成的长期全球性气候变暖的一部分。