Reports last week of a new paper from researchers at Yale and Harvard proposing “sun-dimming” to mitigate climate change sure sounded alarming. Trouble is, those reports misconstrued the cited research, which made no suggestion that we actually engage in so-called solar geoengineering.
Instead, Wake Smith, a lecturer at Yale, and co-author Gernot Wagner, a research associate and lecturer at Harvard, attempted to calculate the cost of one of the most oft-discussed solar geoengineering methods—Stratospheric Aerosol Injection (SAI)—which basically involves dumping a bunch of sunlight-reflecting particles into the upper atmosphere. The authors confirmed such a strategy could be a “remarkably inexpensive” way of staving off some global warming. The research was published Friday in Environmental Research Letters
“The focus of the paper is very different from most of what news reports are saying,” Wagner, a co-director of Harvard’s Solar Geoengineering Research Program, told Earther. One of the biggest differences between how the report has been covered and what the authors wrote is the assumption that they are presenting the research as a viable solution to climate change.
“Solar geoengineering is not a solution to climate change,” Wagner said. “This does not address CO2 directly. It has indirect benefits, but frankly, that’s a sideshow. It simply does not address the root cause.”
The best way to think about the new research is as a sort of fact-check of one proposed method—an extremely controversial and potentially catastrophic one—by which climate change could be partly addressed. The researchers reviewed proposed methods for lofting sulfate particles into the lower stratosphere to lower temperatures on Earth and determined that a specialized high-altitude aircraft—one they dubbed SAI Lofter (SAIL), and which doesn’t even exist—would be the most cost-effective way to do that. They estimate that such a program would cost a little more than $2 billion annually over the first 15 years of deployment, and it would aim to “cut in half the rate of temperature change from the first year of the program onward.”
“It is a very focused paper that tries to cost out this one possible solar geoengineering deployment scenario. That’s all we’re doing,” Wagner told Earther. “We’re doing, I’d like to think, a better job in actually coming to real numbers, mostly because we’ve talked directly to aerospace companies and industry folks in this highly hypothetical scenario trying to cost out what a semi-realistic deployment scenario like this would in fact cost. That’s it.”
As the study authors note in their analysis, “solar geoengineering is often described as ‘fast, cheap, and imperfect.” They acknowledge the first point and present evidence for the second, however—and this appears to be what’s lost in translation in reports around this research by CNN, the Daily Mail and others—the authors write that they “make no judgment about the desirability of SAI.”
“We simply show that a hypothetical deployment program commencing 15 years hence, while both highly uncertain and ambitious, would indeed be technically possible from an engineering perspective,” they write. “It would also be remarkably inexpensive.”
Another focus of the paper was whether any such technology could be deployed in secret, which its authors note is unlikely “given the need for thousands of flights annually by airliner-sized aircraft operating from an international array of bases.”
Wagner said that the research is an important advance for a very narrow question about solar geoengineering, but as other experts in the field have noted, further research on the topic is paramount. If the effects of solar geoengineering are not fully understood, such a method could be adopted without a clear grasp of its potential consequences.
“The genie’s out of the bottle,” Andy Parker of the Institute for Advanced Sustainability Studies in Potsdam, Germany, who has also published research on solar geoengineering, told Earther in March. “And I don’t believe not talking about it is gonna make the idea go away.”