The Wall Street Journal
SCIENCE JOURNAL
By ROBERT LEE HOTZ
In Case We Can't Give Up the Cars -- Try 16 Trillion Mirrors
June 22, 2007; Page B1
What if we wait too long to act on global warming? What if nothing we do is enough? Already, scientists are working up plans of last resort: stratospheric sprays of sulfur, trillions of orbiting mirrors and thousands of huge off-shore saltwater fountains. Each is designed to counteract global warming by deliberately deflecting sunlight, rather than by retooling the world's economy to eliminate carbon-rich oil, coal and natural gas.
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One now under more serious scrutiny was inspired by volcanoes. Climate researcher Tom Wigley at the National Center for Atmospheric Research in Boulder, Colo., and Nobel Prize-winning chemist Paul Crutzen at the Max Planck Institute for Chemistry in Mainz, Germany, last year proposed that an overheated planet could be safely cooled by an artificial haze of sulfur particles, which would reflect solar radiation. The 1991 eruption of Mt. Pinatubo spewed enough sulfates to lower the average world temperature by almost one degree Fahrenheit for a year, with no apparent ill effects. A sulfate sunshade might cost $400 million a year.
Earlier this month, researchers at the Carnegie Institution of Washington, D.C., released the most precise computer studies yet evaluating the controversial sunshade idea. Their findings, reported in the journal Proceedings of the National Academy of Sciences, revealed that a last-ditch engineering effort to block sunlight could reverse global warming -- at least temporarily. Indeed, it could lower average temperatures to levels not seen since 1900. "Every study we do seems to indicate it would work," said Carnegie climate modeler Ken Caldeira.
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The computer scenarios also revealed the quandaries of climate control without emissions reductions. Even on a cooler planet, oceans still would become more acidic because excess carbon dioxide would continue to leach into sea water, endangering marine wildlife and commercial fisheries. Regional rainfall also would be disrupted, the researchers reported. The world would become much drier. All in all, geo-engineering is no substitute for reducing greenhouse gases because it can only suppress the symptoms of global warming, the scientists calculated. It might even make things worse. "If the system failed, for technical or political reasons, you would be compressing a century's worth of climate change into a decade or so," said Dr. Caldeira. Depending on the scenario they tested, the rebounding climate could heat up 10-to-20 times faster than today, or as much as 7 degrees Fahrenheit per decade.
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