A wobble of Earth’s axis causes the Sahara to cycle between desert and grassland every 23,000 years. The last cycle started 7,000 – 10,000 years ago and Sahara will turn back into vast grassland in around 16,000 years. These are known as Milankovitch cycles, which are caused by variation in orbit and tilt of the Earth. These cycles have a great effect on the earth’s climate and are a leading cause of periodic ice ages.
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