There have been at least twenty such balmy intermissions like our own sprinkled throughout the past few million years of our ice age. But unlike the many previous warm interglacials, civilization—and all of recorded human history—happened to arise during this one. Our few millennia in the sunshine are up, and if it weren’t for us, we might be just about ready to leave this agreeable little interregnum and jump back into the ongoing deep freeze of the Pleistocene for 100,000 bitterly cold years.
