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US should explore manipulation of sun rays to cool Earth: National Academies

05 April 2021 Karin Rives

Noting the growing urgency of climate change, the National Academies of Sciences, Engineering and Medicine (National Academies) are proposing that the US government spend up to $200 million over the next five years to coordinate research and explore policy options for manipulating cloud cover that would reflect solar rays away from Earth and help it cool.

In a March report titled "Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance," experts with the academies and from universities across the US emphasized that even just an inquiry into whether altering the sun's impact on the planet is technically and ethically feasible can be fraught with risk.

"For solar geoengineering, there are many unanswered scientific questions that address risks and unintended consequences, but equally important are the governance questions of who will decide and how long to deploy this intervention to mask global warming," Marcia McNutt, the president of the National Academy of Sciences, said in a 25 March statement. Her organization is part of the broader National Academies, which conducted the study.

"Given the urgency of the climate crisis, solar geoengineering needs to be studied further," McNutt said. "But just as with advances in fields such as artificial intelligence or gene editing, science needs to engage the public to ask not just can we, but should we?"

What is geoengineering?

Geoengineering has historically been sorted into two categories and is only now gaining traction as a last-resort tool for curbing climate change.

The first, direct air capture, is in its infancy with only one commercial project in operation thus far in Switzerland. It centers around massive fans that suck carbon out of the air, ton for ton, and then buries it underground.

In contrast, the other, lesser known category that is solar radiation management ignores carbon emissions and focuses instead on spraying material into the atmosphere to change the cloud cover. This, in turn, reflects a small portion of the sun's light and heat back into space rather than hitting Earth.

So far, nobody has tried to manipulate the sun's rays and the idea is considerably more complex than carbon removal. Last week, a first-ever Harvard University-led atmospheric test, known as the Stratospheric Controlled Perturbation Experiment (SCoPEx), was called off after running into resistance from environmental and indigenous groups in northern Sweden.

A cautious approach

For climate experts, the idea of shooting particles into the atmosphere to reduce global warming can be both counterintuitive and seem counterproductive if it distracts from actual reductions in greenhouse gas emissions.

"Lofting particles into the atmosphere as a last-ditch effort to cool the planet is a deeply unsettling concept," acknowledged Marissa Saenger, a research fellow with the Harvard University Solar Geoengineering Research Program, one of the academic institutions exploring the issue.

"Critically," she noted in a 2020 blog post, solar geoengineering "could ameliorate catastrophic climate damages while slower-acting mitigation takes effect." When weighed against catastrophic climate damage and so-called irreversible climate tipping points, the risks may be relatively small, she wrote.

The National Academies of Sciences report echoes those sentiments.

"Meeting the challenge of climate change requires a portfolio of options," it said. "The centerpiece of this portfolio should be reducing [GHG] emissions, removing and reliably sequestering carbon from the atmosphere, and pursuing adaptation to climate change impacts that have already occurred or will occur in the future."

But those strategies may not be sufficient to keep the global temperature rise below 1.5 degrees Celsius compared with pre-industrial levels, as recommended by the 2015 Paris climate treaty. This is why policymakers and nations will need to know what else works or doesn't — without getting steered in a particular direction, the researchers wrote.

"The program should focus on developing policy-relevant knowledge, rather than advancing a path for deployment; and the program should be subject to robust governance," their report said.

The US solar geoengineering research proposed by the National Academies would be housed in the US Global Change Research Program, but account for just a fraction of the program's climate research, the report said. The research program should proceed stepwise with regular peer reviews, prioritize international coordination to hedge against ethical pitfalls — and proceed cautiously.

To that effect, the Harvard study said, there should be built-in "exit ramps" with mechanisms for ending a research activity if it's found to post pose unacceptable physical, social, geopolitical, or environmental risks — or if research shows that a certain technique just doesn't work.

Citizen protests halted landmark test

Meanwhile, initial experiments to further the understanding of solar geoengineering have already encountered resistance.

Harvard researchers were hoping to launch a high-altitude balloon over northern Sweden in June that would carry up to 2 kg of calcium carbonate, a common mineral dust. The material would be released at about 2,000 meters to create a "perturbed air mass roughly one kilometer long and one hundred meters in diameter," their project description said.

This description also argues that the landmark SCoPEx test would pose no hazards to people or the environment, noting that the release would be a fraction of what airplanes and rockets routinely emit and that the material is harmless.

Even so, European environmental groups raised concerns about the SCoPEx study just as the National Academies was preparing a proposal to expand research into that area of interest. And on 2 March, the Saami Council representing indigenous reindeer herders in Finland, Russia, Norway, and Sweden sent a letter to the advisory council for the Harvard experiment, asking that the balloon launch be canceled.

"Stratospheric aerosol injection research and technology development have implications for the whole world and must not be advanced in the absence of full, global consensus on its acceptability," their letter said.

On 31 March, the Swedish space agency called off the test. Before moving forward with geoengineering, a broad conversation must be held with the scientific community as well as the general public, the agency said.

Lack of research, however, can also pose a risk to the world, the National Academy of Sciences as well as the Harvard researchers argue. If other climate change strategies fail to deliver adequate results, policymakers may come under pressure to deploy more dramatic technology options.

"If decision makers make poor decisions because of no research, can they be blamed?" Frank Keutsch, the Harvard professor leading the SCoPEx experiment, wrote in a recent opinion piece. "As a scientist, I have no say on the decisions that society ultimately takes. But I can help provide facts for those who do."


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