According to the authors—who argued in their previous book, Rare Earth, that the complex life found on earth is probably unique in the vast expanses of the universe—our planet has a pretty bleak future ahead of it, one that is a mirror image of its past. Ward and Brownlee, a geologist and an astronomer respectively, claim that human civilization has flowered during an 11,000-year warm interlude in a recurring cycle of ice ages. In their view, "global warming," while possibly harmful in the short term, may help postpone the return of the ice. But not too many thousand years from now, skyscraper-high glaciers will again grind across North America as far south as New York City, and civilization will be driven toward the equator to survive, if not into space. Further into the future, the authors argue, the complex give and take between carbon trapped in rocks, water and oxygen in the sea, and carbon dioxide in the atmosphere—the latter playing the most important role in climatic change—will eventually turn earth into a barren sibling of Mars. While the authors don't make an airtight case for their claims about how our planet's climate and geology will begin to rewind, they do deftly bring together findings from many disparate areas of science in a book that science buffs will find hard to put down. 15 b&w illus. (Jan.)
