Erin O’Donnell profiles David Keith, a leading expert on carbon removal and solar geoengineering technologies, in Harvard Magazine:
The massive scale of the CO2 problem means that carbon removal “will always be relatively slow and expensive,” [Keith] added. It carries some local risks, but has no chance of harming the entire planet. Solar geoengineering, in contrast, could work quickly—and at surprisingly low cost. (By recent estimates, spreading sulfur in the atmosphere to reduce global temperatures could cost a few billion dollars annually, a fraction of the projected cost of reducing greenhouse gas emissions. One 2006 review by the British government estimated that cutting emissions by 25 percent by 2050 would cost about 1 percent of annual global GDP, or about $1 trillion in 2050.) Keith argues that costs for solar geoengineering are so low that “cost will not be a decisive issue.” Instead, he says, scientists and policymakers will have to weigh risks: “the risk of doing it against the risk of not doing it.”
Solar geoengineering, even if it works as intended, won’t solve all of our climate woes. For example, rising CO2 emissions will continue to contribute to the acidification of the oceans, which poses a danger to marine life. But the case for small-scale field tests of solar geoengineering technologies is extremely strong, as they have the potential to greatly reduce the cost of climate damages.