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Could we -- should we -- tinker with climate to stop global warming? MIRANDA: If by your art, my dearest father, you have Put the wild waters in this roar, allay them. ...Oh, I have suffered, With those that I saw suffer! A brave vessel, Who had no doubt some noble creature in her, Dashed all to pieces. - The Tempest, Act I, Scene II

STANFORD -- Not to worry, Shakespeare's Prospero reassures Miranda. Yes, it is true, he used magic to stir up a storm and shipwreck his enemies. But it was a precision storm, and strictly a non-lethal shipwreck.

Therein lies the rub for modern climate tinkerers, warns climatologist Stephen H. Schneider. Since Homer's Odysseus was blown out to sea by angry gods, humans have dreamed of controlling the weather. Prospero was only a tempest-maker in a teapot compared with Russian geographer Nikolai Rusin. In 1960, he pronounced as "already possible" such projects as diversion of the Gulf Stream to warm North America, or placement of a Saturn-like ring around Earth to scatter more sunlight toward the poles and warm up the planet's colder regions.

Nowadays, climate engineering projects nearly this ambitious are being given a serious hearing by scientists and policymakers as a hedge against large amounts of global warming. But it's a bad idea to count on a 21st-century engineering "fix" to save us from our 20th-century addiction to deforestation and fossil fuels, Schneider told a session of the American Association for the Advancement of Science on Sunday, Feb. 20, in San Francisco.

Unlike Prospero's magic, climate engineering is likely to be imprecise and could even be lethal for people or other species living in the wrong region. Like global warming itself, any human-induced global cooling mechanism will have unpredictable effects in different regions of the Earth. And in the litigious modern world, Schneider warned that anyone who tries to fiddle with the climate had better take out a good insurance policy against unwanted results - or results arguably perceived as unwanted.

Schneider is a professor of biological sciences and senior fellow at the Institute for International Studies at Stanford University, and a senior scientist at the National Center for Atmospheric Research.

The idea of global climate engineering was lent respectability by a 1992 National Academy of Sciences report, Policy Implications of Greenhouse Warming: Mitigation, Adaptation and the Science Base.

In a chapter on geoengineering to stop global warming, the NAS panel rejected several ideas to deflect the sun's excess heat, including a parasol of Earth-shading balloons to be floated in the stratosphere. But the report concluded that at least two ideas for reducing the greenhouse effect might be practical enough and of low enough cost to warrant further study. Both would reflect some of the sun's heat back into space, by seeding clouds to provide more cloud cover over the ocean; or by shooting dust into the stratosphere with naval guns, in a human-made imitation of the eruption of Mt. Pinatubo.

Schneider was a member of the panel that analyzed the geoengineering schemes. It was chaired by a former NASA administrator, then a vice president of General Motors, Robert Frosch.

Schneider has long been outspoken on the topic of climate change, saying that the massive use of fossil fuels and ozone-damaging chemicals constitute an experiment in human-induced, inadvertent climate modifications that have the potential to be disastrous. He said that environmentalists criticized him for contributing to the NAS study. "They asked how could I have gone over to the enemy. Naturally, representatives of some industries that pollute liked the study's conclusions: that geoengineering might be cheaper than controlling emissions, since that could hurt their industries."

Schneider said the best way to deal with the threat of global warming is to get people and nations to slowly replace fossil fuels with more sustainable energy sources. "But as a risk hedger," he said, "it would be immoral and unethical not to try to come up with a back door in case the worst happens and we can't get people to wise up in time."

In a worst-case scenario, if global warming began to rapidly accelerate and affordable fuel alternatives are not available, Schneider said, "we could find ourselves in 2047 with nine billion people hooked on soft coal in China, India and the U.S., facing social and economic collapse if we go cold-turkey off that carbon heroin. We may find ourselves throwing dust into the stratosphere whether we like it or not, while we do 50 years of crash deployment of alternative energy systems. So, unhappily, I agreed we should know what's possible and at what cost."

The cost, he suspects, is likely to be unpredictable disruption of international weather and climate.

For example, if geoengineers used naval guns to shoot 20 million tons of dust annually into the stratosphere, as suggested by the NAS panel, the effect as the dust spread around the Earth would be to reduce overall global heating by about 1 watt per square meter. This would be designed to offset about 1 watt per square meter of global warming from greenhouse gases emitted by humans over the past few decades.

But the temperature rise from the inadvertent climate change of global warming would not change evenly in all regions, as Schneider showed in a paper published recently in Science (21 January 1994). Moist tropical regions would be heated only slightly because persistent cloud cover would nullify most of the extra greenhouse effect from our pollution. Deserts and open plains would see temperatures rise much more. The Jet Stream and ocean currents would react in ways that present climate models are not sophisticated enough to predict credibly. The deliberate scheme to put dust in the stratosphere would reject sunlight more uniformly than the greenhouse gases would trap heat.

In the wake of such an experiment, if a flood occurred in the Midwest, or India was struck by drought, fingers from all over the world would point at the geoengineers.

"We'd have no clue whether we contributed to it or not," Schneider said. "Nature is so bouncy, a flood or drought might have happened anyway. The geoengineering project might have made it worse, or better - or neither.

"Thus, the only way you could do large-scale climate modification would be to start with a big superfund. My colleague Will Kellogg and I proposed this, tongue in cheek, in 1974: the 'no-fault climate disaster insurance fund.' Because if anything goes wrong, whoever's in charge of geoengineering had better pay off. They're never going to be able to prove beyond doubt that they didn't contribute to the problem."



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