Tuesday, April 15, 2008

A Global Warning?

By David Luhrssen
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Searching for evidence of the Ice Age in Death Valley may sound paradoxical, but to find that evidence is proof that the world’s climate was once vastly different than it has been since humans have kept records. The documentary “A Global Warning?” reminds us of what science has long known: the Earth has undergone not just one Ice Age but several significant climate shifts whose effects were etched into the geology of our planet.

But the History Channel program, out now on DVD, provides no aid or comfort to the knucklehead brigade that continues to deny the human hand behind the current cycle of freak weather or to minimize its consequences. In earlier eons greenhouse gasses released into the atmosphere through natural causes such as massive volcanic eruptions had a cataclysmic impact on the world’s climate. Nowadays as scientists interviewed for “A Global Warning?” rightly insist, human agency is pushing natural forces at unnatural speed.

Catastrophic climate change may be measured out in centuries or in a single generation. Some scientists point to a shift circa 11,500 BC that quickly wiped out many species of “mega-mammals,” including the wooly mammoth, and spurred the rise of civilization. The scattered bands of hunters and collectors that roamed the Earth began settling down as the glaciers receded. They learned to farm and build towns, enslave their neighbors and engage in commerce. Although the theory is controversial, some scientists have accepted the possibility that the global warming that advanced civilization and wiped out the great prehistoric beasts was caused by a single catastrophe, perhaps a comet striking the Earth.

Nowadays, with world population topping six billion, there is less for humanity to gain from global warming and much to lose. If the ice caps melt and sea level rises, New York City, most of Florida and the Netherlands and coastal areas the world over will be under water. Climate change may trigger new Katrinas, more killer tornadoes, great tsunamis, killing winds and the extinction of many species. Will humanity be among them?

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