Every morning, the Keutsch Research Group gathers for a meeting. Eight engineers and chemists give updates on their preceding day’s work: ordering parts, transferring software, untangling an administrative snafu. The whole affair usually lasts less than 15 minutes.
Scheduling vacations and requisitioning supplies do not scream “high stakes,” but the group’s project could someday have major consequences for global climate change. It is controversial, however. Some even fear it could make things worse. Right now the group is waiting for approval to schedule a new experiment in the stratosphere.
Their idea? To shield the Earth with a mist of tiny particles. It sounds like the stuff of sci-fi movies, but since it was first proposed in the 1950s the idea has gained traction among scientists around the world to shield us not from extraterrestrials, as Hollywood might have it, but from the sun. Known as solar geoengineering, the concept is to send planes into the stratosphere — 6 to 31 miles above the Earth — to spray particles that can reflect sunlight back into space and cool the planet.
Working in collaboration with colleagues from the Keith Group — more than a dozen environmental scientists, engineers, economists, and political scientists under the leadership of David Keith, Gordon McKay Professor of Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and a professor of public policy at the Harvard Kennedy School — the Keutsch Group is hoping to uncover some answers about the possibilities of such a scheme with a project they call the Stratospheric Controlled Perturbation Experiment, or SCoPEx.
The need for a bold new plan seems clear.
Global carbon dioxide (CO2) emissions reached an all-time high in 2018. In October, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) announced that those emissions must drop drastically to limit global warming to acceptable levels. In 2017, according to the IPCC, global warming reached 1 degree Celsius above preindustrial levels. To keep it from going more than half a degree higher, the panel recommends cutting emissions by about 45 percent by 2030 and to “net zero” by 2050. The panel’s website concedes, however, that even these drastic changes would mean that “any remaining emissions would need to be balanced by removing CO2 from the air.”
In other words, Professor Frank Keutsch said, “if we do only emissions cuts to reach the panel’s goals, we would need to get them to zero by 2021 or ’22, and that’s clearly never going to happen. It’s a purely utopian idea. Because of this, they include in their models a negative-emissions technology that we don’t have yet. It doesn’t exist.” The amount of land this IPCC-imagined equipment would need if it did exist, he added, is a parcel about the size of India.
But as the deadline for reducing emissions approaches, scientists have become more open to engineering solutions. “One thing that we know can cool down the planet quickly is putting particles into the stratosphere,” Keutsch said. Natural events have taught us that: In 1991, the Philippines’ Mount Pinatubo erupted, releasing 20 million tons of sulfur dioxide into the stratosphere. Afterward, the entire globe cooled by half a degree Celsius for more than a year.
Mimicking that sort of impact could have any number of side effects, including changes in weather patterns. Keutsch doesn’t think the particles would cause haze but said they could give our sunrises more vivid reds. The problem is that it’s hard to judge the odds of what might happen without more data.
“If in 20 years climate impact suddenly becomes bad and the public starts demanding fast action,” he said, “my concern is that we could get to a situation where sudden decisions are made, and we don’t have enough information to make them. I see my role as providing information on the risks of various scenarios.”