Sidebar: Can We Engineer Our Way Out of a Crisis?

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Mirrors in space, solar filters, stratospheric injections of sulfate aerosols meant to mimic volcanic ash, covering the Arctic with reflective materials—it all sounds a bit like science fiction. But these and other radical-sounding strategies to manipulate the global climate in our favor—known as geoengineering or climate engineering—have recently been gaining traction after years on the fringes of climate science. Some of the proposals seem more far-fetched—installing orbital mirrors to reflect solar radiation out of the atmosphere, for example, could be seen as too resource-intensive to compete seriously for funding with more thoroughly proven strategies like greenhouse gas mitigation. But others have prompted more serious debate: the idea to inject aerosols periodically into the atmosphere to block radiation, for example, is backed up by observations that the Earth cooled by 1ºF after Mt. Pinatubo launched sulfate aerosols into the atmosphere in 1991.

But such strategies come with their own unintended consequences—the Pinatubo eruption also preceded a worldwide drop in precipitation, according to a recent study in Science, and other studies have predicted damages to the ozone layer. And therein lies the central obstacle to tinkering with the climate: there may be further downsides to these proposals that research has yet to uncover, and still others that we cannot predict. The Obama administration has recently stated that geoengineering cannot be ruled out, though it still considers these strategies emergency measures to be used as a last resort. In a statement issued in July 2009, the American Meteorological Society cautioned: “Research to date has not determined whether there are large-scale geoengineering approaches that would produce significant benefits, or whether those benefits would substantially outweigh the detriments.”

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September 1, 2009