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With the planet facing potentially severe impacts from global warming in coming decades, a government-sponsored scientific panel on Tuesday called for more research on geoengineering — technologies to deliberately intervene in nature to counter climate change.
The panel said the research could include small-scale outdoor experiments, which many scientists say are necessary to better understand whether and how geoengineering would work.
Some environmental groups and others say that such projects could have unintended damaging effects, and could set society on an unstoppable path to full-scale deployment of the technologies.
But the National Academy of Sciences panel said that with proper governance, which it said needed to be developed, and other safeguards, such experiments should pose no significant risk.
In two widely anticipated reports, the panel — which was supported by NASA and other federal agencies, including what the reports described as the “U.S. intelligence community” — noted that drastically reducing emissions of carbon dioxide and other greenhouse gases was by far the best way to mitigate the effects of a warming planet.
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But the panel, in making the case for more research into geoengineering, said, “It may be prudent to examine additional options for limiting the risks from climate change.”
“The committee felt that the need for information at this point outweighs the need for shoving this topic under the rug,” Marcia K. McNutt, chairwoman of the panel and the editor in chief of the journal Science, said at a news conference in Washington.
Geoengineering options generally fall into two categories: capturing and storing some of the carbon dioxide that has already been emitted so that the atmosphere traps less heat, or reflecting more sunlight away from the earth so there is less heat to start with. The panel issued separate reports on each.
The panel said that while the first option, called carbon dioxide removal, was relatively low risk, it was expensive, and that even if it was pursued on a planetwide scale, it would take many decades to have a significant impact on the climate. But the group said research was needed to develop efficient and effective methods to both remove the gas and store it so it remains out of the atmosphere indefinitely.
The second option, called solar radiation management, is far more controversial. Most discussions of the concept focus on the idea of dispersing sulfates or other chemicals high in the atmosphere, where they would reflect sunlight, in some ways mimicking the effect of a large volcanic eruption.
The process would be relatively inexpensive and should quickly lower temperatures, but it would have to be repeated indefinitely and would do nothing about another carbon dioxide-related problem: the acidification of oceans.
This approach might also have unintended effects on weather patterns around the world — bringing drought to once-fertile regions, for example. Or it might be used unilaterally as a weapon by governments or even extremely wealthy individuals.
Opponents of geoengineering have long argued that even conducting research on the subject presents a moral hazard that could distract society from the necessary task of reducing the emissions that are causing warming in the first place.
“A geoengineering ‘technofix’ would take us in the wrong direction,” Lisa Archer, food and technology program director of the environmental group Friends of the Earth, said in a statement. “Real climate justice requires dealing with root causes of climate change, not launching risky, unproven and unjust schemes.”
But the panel said that society had “reached a point where the severity of the potential risks from climate change appears to outweigh the potential risks from the moral hazard” of conducting research.
Ken Caldeira, a geoengineering researcher at the Carnegie Institution for Science and a member of the committee, said that while the panel felt that it was premature to deploy any sunlight-reflecting technologies today, “it’s worth knowing more about them,” including any problems that might make them unworkable.
“If there’s a real showstopper, we should know about it now,” Dr. Caldeira said, rather than discovering it later when society might be facing a climate emergency and desperate for a solution.
Dr. Caldeira is part of a small community of scientists who have researched solar radiation management concepts. Almost all of the research has been done on computers, simulating the effects of the technique on the climate. One attempt in Britain in 2011 to conduct an outdoor test of some of the engineering concepts provoked a public outcry. The experiment was eventually canceled.
David Keith, a researcher at Harvard University who reviewed the reports before they were released, said in an interview, “I think it’s terrific that they made a stronger call than I expected for research, including field research.” Along with other researchers, Dr. Keith has proposed a field experiment to test the effect of sulfate chemicals on atmospheric ozone.
Unlike some European countries, the United States has never had a separate geoengineering research program. Dr. Caldeira said establishing a separate program was unlikely, especially given the dysfunction in Congress. But he said that because many geoengineering research proposals might also help in general understanding of the climate, agencies that fund climate research might start to look favorably upon them.
Dr. Keith agreed, adding that he hoped the new reports would “break the logjam” and “give program managers the confidence they need to begin funding.”
At the news conference, Waleed Abdalati, a member of the panel and a professor at the University of Colorado, said that geoengineering research would have to be subject to governance that took into account not just the science, “but the human ramifications, as well.”
Dr. Abdalati said that, in general, the governance needed to precede the research. “A framework that addresses what kinds of activities would require governance is a necessary first step,” he said.
Raymond Pierrehumbert, a geophysicist at the University of Chicago and a member of the panel, said in an interview that while he thought that a research program that allowed outdoor experiments was potentially dangerous, “the report allows for enough flexibility in the process to follow that it could be decided that we shouldn’t have a program that goes beyond modeling.”
Above all, he said, “it’s really necessary to have some kind of discussion among broader stakeholders, including the public, to set guidelines for an allowable zone for experimentation.”