Scientists are taking a hard look at tweaking the planet's thermostat with geoengineering methods, which were once a taboo avenue for research, as a way to stave off some of the worst-case scenarios for the warming Earth.

Earlier this week, the National Research Council convened a committee to review approaches that could cool the world, with the goal of creating a scientific foundation that could help resolve political, ethical and legal issues surrounding these controversial techniques. Geoengineering refers to techniques that deliberately change the climate at scale, like dispersing aerosols and sucking greenhouse gases straight out of the air.

The researchers, gathered at the National Academies on a sweltering afternoon in Washington, D.C., laid out the immensity of the task before them. With the huge scale and threat of global climate change, many are now willing to consider ideas that once gathered dust on the fringes of acceptable science.

"We have no findings yet; we have no conclusions yet," said Marcia McNutt, a former director of the U.S. Geological Survey, who leads the committee. She emphasized that the discussion was an exploration and would not reflect on what makes it into the committee's final report.

"Geoengineering is not an easy subject to come to grips with," said Richard Rosen, a climate researcher at the National Oceanic and Atmospheric Administration, one of sponsors for the study. "Some are advocating for field experiments now, while others have called the idea of putting sulfate aerosols in the atmosphere 'barking mad.'"

Madness or a needed backstop?
The idea of meddling with the global climate through seeding clouds or absorbing carbon dioxide with giant machines is risky, but with two centuries of industrial emissions, humanity has engineered the climate already, albeit with looming disastrous consequences. In addition, while interest in geoengineering is growing, geoengineering data are lacking, creating a frustrating self-fulfilling cycle from risk-averse funding agencies that won't finance geoengineering projects without better information and more accountability.

Researchers are also concerned about how geoengineering could fit in within the broader climate change response framework, whether it should be integrated into existing emissions mitigation and adaptation initiatives or if should remain locked away behind an "In Case of Emergency" glass pane. Some are worried that making geoengineering viable would create complacency in mitigating climate change on other fronts, like cutting emissions or displacing fossil fuels.

"I believe NOAA can play a leadership role in geoengineering research, but we hesitated in large part because of what one of you has labeled the 'deadlock of governance' in geoengineering research," Rosen said, addressing the committee.

NASA, another sponsor for the study, is particularly interested in developing the science behind geoengineering and filling in its knowledge gaps, more so than in the techniques to implement it, according to David Considine, a researcher at the agency. "I think that NASA would be interested in knowing the answer to the question 'What don't we know?'" he said.

Robert Socolow, a professor at Princeton University and co-director of the school's Carbon Mitigation Initiative, concurred. "The scrimmage line is not deployment; it's research," he said.

He explained that geoengineering strategies tend to center on either solar radiation management or carbon dioxide removal. Radiation management encompasses reflecting the sun's energy into space with clouds and aerosols, while carbon removal includes industrial-scale capture devices, as well as planting trees and cultivating algae.

What should we know?
Carbon removal tends to be slower and more expensive but less risky than radiation management approaches. Consequently, Socolow suggested the committee should spend the bulk of its time investigating techniques that modulate the sun's light and heat.

"It would be wise for the [National] Academies to focus exclusively on solar radiation," said David Keith, a professor at Harvard University who holds appointments in the school's public policy and physics departments. "In particular, I believe there should be a U.S. government research program on solar radiation, how to manage it and eventually how to commercialize it."

Earlier this year, Keith called for federal guidelines on geoengineering research to rein in rogue experiments and to build up a body of potentially useful knowledge (ClimateWire, March 18).

However, many scientists are reluctant to step into this realm. "I spend a lot of time trying to convince a lot of people to start research," said Jane Long, co-chair of the Bipartisan Policy Center's Task Force on Geoengineering. "There is definitely more interest, but people are still uncomfortable for a whole lot of reasons."

Though concerns about how the world will respond to a deliberately driven climate are valid, Long noted that these approaches are still very far off and investigating them would yield information that benefits geophysical research. "It makes climate science more robust," she said. "We should not decide a priori we won't develop an idea."

As for the committee, Long said its report should call for further geoengineering studies. "I think the best thing they can do is highlight the fact that there could be more utility in these methods and that we don't know enough about them and we should do more research," she said.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500