Millions of years ago, the Sahara was a green oasis covered in trees and grassland. So how did it become world's biggest hot desert, roughly the size of the entire U.S.?
In his book "When the Sahara Was Green," (Princeton University Press, 2021) Martin Williams explores the little-known history of this iconic landscape. In the extract from the book below, the author looks at how a vanishing ocean and global cooling set the stage for the birth of the Sahara desert.
