Monday, June 05, 2006

Climate change in the prehistoric Sahara
This article summarizes and includes extracts from a book about the impacts of climate change - The Last Generation by Fred Pearce, published by Transworld . The write-up also offers a brief overview of what the Sahara was like following the end of the last ice age, after 13,000 years ago, when the desert could sustain human and animal life, and sites like Nabta Playa were occupied: "Jon Foley of the University of Wisconsin found that a reduction in Holocene summer sun sufficient to reduce temperatures by just 0.4C would have cut rainfall across the Sahara by a quarter, and by much more in the furthest interior. He says that once a region such as the Sahara becomes dry and brown it requires exceptional rains to trigger a regreening. Beyond a certain point - such as that reached 5,500 years ago - virtually no amount of extra rain is likely to be enough. Lack of vegetation "acts to lock in and reinforce the drought.
The people of the Sahara couldn't have known if the droughts were permanent. But as the desert asserted control, and waterways dried up, they had to leave. Lakeside settlements near the Sudanese border in Egypt were all abandoned at about the same time."
See the above page for the full review".

No comments: