Today, North Africa is one of the largest exporters ... and Liu, Z. Response of the African monsoon to orbital forcing and ocean feedbacks in the middle Holocene. Science 278, 440-444 (1997).

The AHP began ~14,500 years ago. It was primarily caused by orbital changes in the Earth’s axial tilt, which strengthened the African monsoon system. Moist air was drawn further north into the Sahara, ...