Researchers have developed a new concept to explain the phenomenon known as Green Sahara. They demonstrate that a permanent vegetation cover in the Sahara was only possible under two overlapping rainy seasons. Dr. Enno Schefuß of MARUM—Center for Marine Environmental Sciences of the University of Bremen, Dr. Rachid Cheddadi of the University of Montpellier, and their colleagues have now published their study in the journal PNAS.