When Mount Pinatubo erupted in the Philippines in 1991, the volcano shot 20 million tons of sulfur dioxide into the stratosphere. Those particles reflected enough sunlight to cool the earth by about one degree Fahrenheight—a temporary phenomenon, but one whose implications are still very much debated. Why not, some scientists have asked in the decades since, counter climate change by reproducing the effects of Mount Pinatubo—for example, by flying a plane into the stratosphere and spraying enough sulfate aerosols to turn down the sun?
That question was held up for scrutiny on Tuesday by the National Academy of Sciences, which released a study (funded, in part, by the CIA) of two ideas for staving off the worst effects of climate change via technological manipulation of the climate: to remove carbon-dioxide from the atmosphere and sequester it elsewhere, or to reflect sunlight away from the planet by what’s known as albedo modification, à la Mount Pinatubo. The unequivocal message from the committee was that the world cannot expect to geoengineer its way out of the climate crisis.
“There is no silver bullet here. We cannot continue to release carbon dioxide and hope to clean it up later,” said committee chair and Science Editor-in-Chief Marcia McNutt at a press briefing in Washington. The climate “doesn’t go backwards. It goes different. And we don’t even understand where that different state ends up,” said another member of the panel. In preparing and discussing the report, its authors declined to use the term “geoengineering,” opting instead for “climate intervention.” McNutt explained, “We…felt that ‘engineering’ implied a level of control that is illusory.”
Current carbon-capture and storage methods would take “decades to achieve moderate results and be cost-prohibitive,” according to the report. These carbon-removal strategies include land management and reforestation; ocean iron fertilization; and sucking carbon dioxide from the air, which is difficult to do because its much more diffuse in ambient air than, say, in a smokestack at a power plant. According to the committee, large-scale deployment of these techniques would cost just as much if not more than transitioning to clean-energy sources. Still, given the political barriers to emissions reductions, and the scale of reductions needed, the committee said it was “almost inevitable” that some carbon-capture technology would be required to avoid some of the worst effects of warming. As such, the concluded, more research and development is warranted.
Albedo modification presents a more troubling case. It would be “irrational and irresponsible” to pursue those techniques without reducing emissions, the committee wrote. Not only do they fail to address the root cause of climate change. They also pose a number of known risks, including ozone loss and changes to rainfall, and could disrupt the climate in other, less clear ways. “There is significant potential for unanticipated, unmanageable, and regrettable consequences in multiple human dimensions from albedo modification…including political, social, legal, economic, and ethical dimensions,” the report reads.