The grassy prehistoric Sahara turned into Earth's largest hot desert more slowly than previously thought, a new report says—and some say global warming may turn the desert green once again.
The new research is based on deposits from a unique desert lake in remote northern Chad.
Lake Yoa, sustained by prehistoric groundwater, has survived for millennia despite constant drought and searing heat.
The body of water contains an unbroken climate record going back at least 6,000 years, said study lead author Stefan Kröpelin of the Institute of Prehistoric Archaeology at the University of Cologne in Germany.
James Owen, National Geographic News
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