May/June 2002 The Science Pages Features

ARTICLE TOOLS

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First the bad news. "One of the most shocking scientific realizations of all time has slowly been dawning on us," William Calvin announces in the opening words of his new book: "the earth's climate does great flip-flops every few thousand years, and with breathtaking speed." For the last 8,000 years or so, we've enjoyed an unusually stable climate. But there's no reason to suppose that it will continue indefinitely—in fact, if geological history is any guide, we can be pretty sure it won't. Imagine the disruptions associated with the Little Ice Age (a.d. 1300-1850) but on a much larger scale and concentrated in a single decade. An episode of abrupt global cooling, such as has occurred many times in Earth's history, would create massive food shortages and could easily lead to worldwide conflict—"taking much of civilization with it."

Alarmist? Absurd? Wildly apocalyptic? Calvin isn't predicting such an outcome; rather, he's suggesting that it is a real possibility, worth pondering. He observes that the last episode of abrupt global cooling, the so-called Younger Dryas, "drastically altered Europe's climate as far east as Ukraine." Starting about 15,000 years ago, the Earth had been thawing out from the last major Ice Age. But about 12,900 years ago, "just in a matter of a decade or so, the climate flipped from warm-and-wet into the cool-and-dry mode, with temperatures plunging back to what they had been in the ice ages."

Today, Europe's population of more than 650 million is fed mostly by food grown in Europe. With a climate change like the Younger Dryas, Europe might be able to support a population comparable to Canada's. Lacking present-day Europe's "winter warmth and rainfall," Calvin notes, Canada is able to support a population ...