email a friend iconprinter friendly iconThe Big Idea
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Photo by Alberto Garcia, Corbis
Mount Pinatubo’s cloud of ash and pumice was deadly, but the whole Earth was cooled by its sulfur.
Not so the idea suggested by Roger Angel, an eminent astronomer and telescope designer at the University of Arizona. Angel has proposed launching trillions of two-foot-wide, thinner-than- Kleenex disks of silicon nitride—each disk an autonomous robot weighing less than a gram— into space between Earth and the sun, where they could deflect sunlight. By Angel’s own reckoning, the scheme would take decades and cost trillions of dollars. With that much time and money, we could wean ourselves from fossil fuels and actually solve the climate problem—by far the better outcome, as Angel and most proponents of geoengineering would agree. Unfortunately, though the recession has temporarily slowed the rise in carbon dioxide emissions, we’ve made no real progress toward that goal. Some say we’re running out of time.

If we put up a sunshade without restraining emissions and the sunshade later fails, the climate accident would become a train wreck: The global warming we’d been masking would come rushing at us all at once. That might be the worst unintended consequence of geoengineering, but there could be others—damage to the ozone layer, perhaps, or an increase in drought. If CO2 keeps rising, though, we may face greater emergencies. And what once seemed insane hubris just might become reality. —Robert Kunzig

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