Just finished Brian Fagan�s The Long Summer, whose subtitle �How Climate Changed Civilization� sums up the book�s premise. Specifically, Fagan describes the coincidence of the rise of human civilization in about the last 15,000 years with a period of unusual warmth and climactic stability in the millennia after the end of the last ice age. This period, in which we are currently living, is known as the Holocene. As Fagan notes when discussing the record of the Earth�s climate over the past 420,000 years preserved in the remarkable Vostok ice core extracted by the Russians at their Antarctic station:��the Vostok core shows us that the world�s climate has almost always been in a state of change over these 420 millennia. But until the Holocene it has always oscillated. The Holocene climate breaks through these boundaries. In duration, stability, degree of warming, and concentration of greenhouse gases, the warming of the past fifteen millennia exceeds any in the Vostok record. Civilization arose during a remarkably long summer. We still have no idea when, or how, that summer will end.�It’s chastening to realize that humanity may have attained its present state due to a freakish blip in the earth�s eons-long cycle of climate change. And as Fagan evocatively charts the rise and fall of civilizations�in Mesopotamia, Mesoamerica, Egypt, and even Europe�during this �Long Summer,� he again and again demonstrates that as soon as people forget that their standard of living (in fact, their very survival) is dependent on the vagaries of the weather, calamity (usually in the form of extended droughts) is surely not far off. It is interesting, particularly in his accounts of the civilizations that flourished along the banks of the Tigris and Euphrates, that when conditions became exceptionally harsh, the ancient cities actually expanded rather than shrank because of refugees fleeing the parched hinterland in search of rations. (And Fagan suggests that those keeping records in the precious granaries were the first bureaucrats.)For example, to stem the flow, the rulers of the legendary city of Ur built a 180-kilometer long wall, fantastically titled the �Repeller of the Armorites.� This state of �hyperurbanism� was in almost all cases the prelude to final collapse, during which the abandoned the benighted city, leaving it, like the statue of Ozymandias, to be consumed by the drifting sand.