One is to inject sulfur dioxide or a similar aerosol into the stratosphere to help shade the Earth from more intense sunlight. It is patterned after a natural solution: volcanic eruptions, which have been found to cool the Earth by emitting huge clouds of sulfur dioxide.
The second approach would use an aerosol of sea salt particles to improve the ability of low-lying clouds over the ocean to act as shade.
This technique is borrowed from “ship tracks”—or long clouds left by the passage of ocean freighters that are seen by satellites as reflective pathways. They could be widened by injections of vapor from seawater by specialized ships to create shading effects.
Research in both techniques, Fahey emphasized, are recommended in a forthcoming study by the National Academies of Sciences, Engineering, and Medicine titled “Climate Intervention Strategies that Reflect Sunlight to Cool Earth.”
But in a sign of how controversial the topic is, Fahey recommended changing the nomenclature from geoengineering to “climate intervention,” which he described as a “more neutral word.”
Fahey also emphasized this is not an approval to move forward with geoengineering. Rather, it’s to prepare the U.S. government for a political decision if the world fails to adequately limit the rise of global warming.
“Geoengineering is this tangled ball of issues and science is only one of them,” he said.
“One of the things I’m interested in doing is let’s separate the science out,” he added. The idea is to give policymakers a clear view of how a hurry-up bid to save the planet would work.
Even then, the results likely wouldn’t be immediate. Fahey showed slides and graphics that noted that a Plan B might take until the next century to complete the cooling.
Still, better science might “buy time” to improve the efforts, he said.
There would be drawbacks, he noted, after being asked by a researcher whether injections of sulfur dioxide into the atmosphere might reduce seafood by acidifying the oceans.
“When you put aerosols up into the atmosphere, it does a lot of things,” Fahey, a physicist, responded. “That opens up this whole menu of things that you’d have to worry about.”
He said other aerosols such as calcite or titania “might have less impact, but nobody knows. We want to look at them in the laboratory.”
Several smaller nations have complained that the use of aircraft to inject aerosols into the atmosphere might alter the weather or destroy the ozone layer, which protects humans from some of the more harmful radiation from sunlight.
Fahey suggested that a scientific approach would require solving a list of unknowns, including tests to find out what’s in the stratosphere today and how to get aerosols to spread there homogeneously. Another likely area of research: unintended consequences.
“We have to use atmospheric observations to find out what we’re doing,” he added.
At the moment, the government has no planned experiments and NOAA’s authority does not extend into the stratosphere. But there is a bill in Congress called the “Climate Intervention Research Act” that would broaden its jurisdiction.
“There could be more than $100 million attached to this, I’m told,” he explained.
Until now, neither Congress nor the administration has ventured to tackle the Plan B issue. The closest thing to testing it is a Harvard University-sponsored project called the “Stratospheric Controlled Perturbation Experiment” (SCoPEx).
It proposes a small-scale test using a propeller-driven balloon. It would ascend to a height of 12 miles over New Mexico and then release less than 2.2 pounds of calcium carbonate.
The idea is to create a tubular area in the sky—about six-tenths of a mile long and 109 yards in diameter—through which the sensor-packed balloon could slowly move back and forth, mixing the air and monitoring the solar-reflecting abilities of the scattered materials. It also would track the impact of the treated area on the surrounding atmosphere.
When SCoPEx would happen remains unknown.
Harvard, sensitive to the question of how to govern such experiments, has appointed an outside advisory committee to help oversee and evaluate the test. According to David Keith, a Harvard physicist who is one of the leaders of the project, the outside committee would help determine if and when the experiment should move forward.
Funding for the experiment will come from Harvard research funds and a list of outside contributors to a fund controlled by Harvard’s Solar Geoengineering Research Program. Compared with U.S. space, defense and climate-related experiments, the cost of the effort would be minuscule.
Keith could not be reached for comment about Fahey’s announcement, but Fahey said NOAA supports the Harvard stratospheric test and has contributed an instrument to help it measure the dispersion of particles.
“We’re going to have to give up some things to go into Plan B. That’s why we would be motivated to try designer aerosols, but we may not have time,” Fahey explained.
“That’s what Harvard wants to do. It goes back to the question of which path you want to be on,” he added, noting the difference between a possible international decision to reduce greenhouse gas emissions or being late and forced to implement a Plan B to stop runaway climate change.
“I don’t want to be on the late path, but the question is which paths are going to be open to us,” he said. “I think nobody can play out all the chess moves on this issue. It is so complicated.”