The last time the climate warmed the Sahara was green and had a huge lake in the middle that left behind vast deposits of fine mineral-rich sediments. In these drier days the dust from that ancient lakebed now blows all the way across the Atlantic to nourish the Amazon with phosphorus and the ocean with iron.

It also shades the patch of the Atlantic where hurricanes form, lessening the strength and frequency of tropical storms that reach the North Country. The current trend back toward a warmer world might be good for the Sahara, but not so good for us. Curt Stager and Martha Foley explain.