Engineering the atmosphere to forestall the worst results of global warming was once considered too hubristic to seriously contemplate. The grim prospects for passing an international climate-change treaty have changed that. Last year the National Academies of Science in the U.S. and the Royal Society in the U.K. both convened meetings on geoengineering. The schemes generally fall into two categories—CO2 capture (pulling carbon dioxide from the air) or solar-radiation management (reflecting sunlight)—but it’s a form of the latter, which involves using airplanes or long hoses to pour sulfate aerosols into the lower stratosphere, that’s the most audacious.
Once in the stratosphere, the theory goes, the aerosols would reflect
some solar radiation and prevent a devastating rise in the average
global temperature. The theory is not crazy. In 1991, after the eruption
of Mt. Pinatubo in the Philippines spewed 20 million tons of sulfur
dioxide into the stratosphere, the average global temperature dropped by
about 1° F from 1991 to 1993. But administering such a program well
would require an unprecedented degree of international coordination and
funding, and the odds of miscalculation are high.
And the potential negative consequences are, in the worst case, extreme.