Interesting fact about geoengineering, the idea of large-scale climate intervention. It has a longer history than you might think. As far back as 1965, President Johnson’s scientific advisers were considering whitening the oceans to deflect sunlight back to the atmosphere. As Ken Caldeira, a Stanford climate scientist, told an audience at NYU: "The idea of geoengineering precedes the idea of emissions reductions."
Many people have since dismissed geoengineering as unworkable, unpredictable, or unnecessary. Or crazy. But that hasn’t stopped serious research into the topic over the last few years. Scientists have written papers modeling different methods, and convened conferences to discuss the effects. Caldeira has come up with what is widely thought to be the most feasible idea: the "Pinatubo Option."
Mount Pinatubo is a volcano in the Philippines that erupted in 1991, spreading 10 million tons of sulfur into the atmosphere. The impact on the local environment was horrific. But scientists later noticed that the acrid cloud deflected 2% of normal sunlight, and reduced worldwide temperatures by 0.5 degrees Celsius (0.9 degrees Fahrenheit). The thinking behind the "Pinatubo Option" is basically to re-enact this natural event: to put thousands of tons of particles into the atmosphere to deflect sunlight, and cool the Earth’s surface.
Caldeira says it would be possible to stop most of the global warming each year by releasing tens of kilograms a second into the air. The cost would be low, probably in the few millions of dollars. And the operation could be carried out by an airline-sized fleet of aircraft.
According to his models, it would be possible to offset 90% of the warming change from increased CO2 concentrations, and 70% of the precipitation change, even if emissions doubled. "The basic story is that climate models indicate that the deflection of sunlight will offset most climate change in most of the places, most of the time," Caldeira says.
Caldeira doesn’t actually endorse the Pinatubo Option, saying it is more like chemotherapy for a cancer patient than a painless cure. But he said it should be considered in an emergency, and that research should continue so that we’re ready if we need it.
The reasons not to mess with the atmospheric system are numerous. There would probably be lots of unforeseen consequences. There would likely be arguments between countries about when to employ the solution. Releasing large amounts of sulfur could further deplete the ozone, as happened with the 1991 eruption. And, it could be used as an excuse by emitters to carry on as usual.
Still, the advantage of geoengineering is that it gets round the "collective action" problem of other climate solutions, and it’s a lot less expensive than redesigning the whole energy system. It also potentially gets temperatures down faster than switching away from fossil fuels. Every model produced by the UN IPCC shows global temperatures rising—the question is just by how much.
The big unknown is whether the Pinatubo Option, or something like it, would work as the scientists say. Caldeira admits: "Where I am right now is that there is certain potential for risk reduction. But whether these things are going to reduce risks in the real world? I don’t think we really have any idea."