New Federal Report on Research Into Sun-Dimming Technologies Delivers More Questions Than Answers

While hundreds of scientists around the world are urgently advocating for a non-use agreement for atmospheric sun-dimming experiments, the White House Office of Science and Technology Policy may be looking in a different direction. A June 30 report from the OSTP outlines, among other things, how to develop scenarios for deploying solar radiation management technologies like deliberately polluting the stratosphere with reflective particles, or spraying salt into coastal clouds to make them brighter and longer-lasting.

Both aim to temporarily cool the Earth by reflecting a tiny percentage of the sun’s heat away from the planet, which would require extensive and repeated applications across huge swaths of the atmosphere and carry the risk of unwanted side effects like changing global rainfall patterns, as documented by a 2021 study. 

There are no studies showing that such drastic climate interventions can be carried out safely, even though millions of government and philanthropic dollars have already been spent on research. The new report is the second by the U.S. government in the last two years on the broader topic of geoengineering, which encompasses a wide range of deliberate climate interventions, ranging from adding fertilizer to the ocean to spur the growth of plankton that take up carbon dioxide, to grinding up massive quantities of rock and spreading the dust on fields to absorb CO2 from the atmosphere.

By contrast, several major climate think tanks and research institutions have issued sharply worded cautions on the dangers of tinkering with the climate system, including Climate Analytics, which released a missive in 2018 called Why Geoengineering is Not a Solution to the Climate Crisis. 

Fundamentally, geoengineering would conflict with the primary mission of the United Nations Framework Convention on Climate Change, which is to prevent dangerous disruption of the climate system, Fahad Saeed, Carl-Friedrich Schleussner and William Hare wrote.

“Solar radiation management does not address the drivers of human-induced climate change, nor does it address the full range of climate and other impacts of anthropogenic greenhouse gas and air pollutant emissions,” they wrote. “At best, SRM would mask warming temporarily … would alter the global hydrological cycle as well as fundamentally affect global circulation patterns such as monsoons.”

Solar radiation management also doesn’t address dangerous ocean acidification and does not counter other negative effects of growing CO2 concentrations on land and ocean ecosystems, nor does it seem likely to mitigate the effects of global warming on global agricultural production, they added.

And as long ago as 2011, leading scientists with the Potsdam Institute for Climate Impact Research classified geoengineering as another type of “end-of-chimney fix” for human-caused global warming. 

“This is a tale of two fairies: the rather wicked one conjures up solar radiation management, and the tolerably good one delivers CO2 removal through schemes like industrial air capture,” then-PIK director Hans Joachim Schellnhuber wrote in a comment published in the Proceedings of the National Academy of Sciences. 

For Schellnhuber, solar radiation management evokes the nightmare of the nuclear arms race, with countries competing with each other in a scenario leading to mutually assured destruction. 

“If the climate can be influenced rather inexpensively by sending aerosol rockets to the stratosphere, then who decides when and where the buttons are pushed,” he wrote.

Creeping Toward Normalization?

While the new report emphasizes a precautionary approach, the fact that it’s coming from the highest levels of the United States government could be another step down a slippery slope toward attempting such radical climate interventions before all the risks are well-understood, said climate scientist Raymond Pierrehumbert, a physicist and climate researcher at Oxford University.

“There is this unfortunate edging towards normalization, that geoengineering is just going to be another part of our response to climate change, when the case for whether it will ever be usable is still extremely weak,” said Pierrehumbert, who said he was asked to submit comments on the OSTP research plan, and who is part of the effort to establish a global agreement to prevent the normalization of solar geoengineering.

He said he’s concerned that “a lot of mainstream scientists” with little background studying solar radiation management have recently been signing on to petitions or letters promulgated by an active and vocal “pro-geoengineering camp.”  A recent policy statement update on geoengineering by the American Geophysical Union also could be construed as supporting a more active research program, potentially including atmospheric experiments, he said. 

“They used kind of a poorly worded blanket statement that doesn’t even state how you would decide what kind of experimentation would be allowed,” he said. “I’m actually a fellow of the AGU and I know I never voted on this. And so this decision was made in some mysterious council process.”

Building a constituency with a series of reports from governments and scientific institutions can make people more comfortable with the ideas, Pierrehumbert said. 

“If people get permission to do small-scale experimentation and then they admit that, well, this didn’t answer our questions, they will say they need something bigger,” he said. “You can see how there’s a slippery slope leading towards deployment.”

Other climate experts say the risks of unchecked global warming warrant more study of solar radiation management to head them off. A letter published in February 2023 calling for accelerated studies of technologies that could reflect sunlight away from the Earth has been signed by 110 scientists, including James Hansen, the former NASA scientist known for his groundbreaking Congressional testimony on warming, and other climate scientists who led recent Intergovernmental Panel on Climate Change assessments.

They wrote that spiraling climate impacts will increase the pressure to reduce the warming by any means, including solar geoengineering. A fuller understanding of the risks could enable scientists to issue even more clear warnings about using technological climate fixes, and could also help show what might result from a unilateral, unregulated deployment of aerosols to the stratosphere, or saline compounds to ocean clouds.

In fact, many countries are worried that rich developed countries in the Global North could use such interventions to try and protect their own territories, potentially presenting risks to countries in the Global South. A geoengineering monitoring website, for example, shows a number of geoengineering experiments conducted in Africa by scientists from developed countries, with very little, if any, involvement by local researchers.

The scientists who posted the February letter wrote: “We support a rigorous, rapid scientific assessment of the feasibility and impacts of SRM approaches specifically because such knowledge is a critical component of making effective and ethical decisions about SRM.”

The OSTP report was released quietly on the Friday before the Independence Day holiday, and was followed by a flurry of email pitches to journalists from geoengineering consulting and research companies citing the recent government reports and boosting their own solar geoengineering studies. One consulting firm called for a $13 billion increase in research funding over the next five years “to ensure a safe climate.”

“There’s been a lot of chatter, mostly celebratory, from the advocates of solar geoengineering,” said Prakash Kashwan, a Brandeis University climate justice and environmental governance researcher who has been tracking geoengineering discussions. He said the report suggests a thoughtful approach for geoengineering research, which is encouraging “within the context of the drumbeat that the geoengineering hawks have been building up.”

A Report Limited to the Sky

The new report focuses specifically on stratospheric aerosol injection and marine cloud brightening. It follows upon a 2021 report from the National Academies of Sciences, Engineering, and Medicine that helped mainstream geoengineering discussions. 

Multiple government agencies coordinated by the U.S. Global Change Research Program contributed to the report, which focused on atmospheric approaches because they could be implemented sooner than other methods and present greater governance challenges because their effects would cross the borders of many different nations.

Full consideration of the implications for society, in addition to the science of solar radiation management, “may reduce the risk that research is perceived as a step towards inevitable deployment,” the report states. Societal concerns include environmental justice, effects on geopolitical stability, implications for other aspects of climate policy like mitigation and adaptation, as well as risk tolerance and issues of public perception and acceptance. 

The scientific research program would include boosting satellite, aerial and ground observation systems, more modeling of solar radiation management approaches and scenarios as well as more experiments in labs and outdoors. Developing methods to detect unreported deployments would be key, the report states.

It also highlights the need for international collaboration on research and governance for solar radiation management, because any deployment of such an intervention large enough to affect the climate would, by definition, have impacts beyond the boundaries of any country that might launch a sun-dimming project on its own.

Kashwan said the report’s call for input from experts in everything from ecosystems, economics and public health to, history, ethics and political science shows that the federal science panel listened to some of the previous critiques of the U.S. government’s approach to geoengineering. 

“As we have argued, the report emphasizes the importance of genuine international cooperation,” said Kashwan, who also was co-author of a December 2022 paper warning of a trajectory Toward Dangerous U.S. Unilateralism on Solar Geoengineering. “All this notwithstanding, the OSTP report does not go far off in demanding effective global and democratic control under the watchful eyes of the United Nations.” 

The report should be seen as a form of course correction, he said, noting that the study identifies research gaps in how solar geoengineering could affect food and water systems, ecosystem services and environmental justice. 

“It is seeking to put brakes on an aggressive push by geoengineering advocates seeking to promote the preposterous idea that deployment of SRM is imminent.”

Who Got The Geoengineering Ball Rolling?

Pierrehumbert said that, even though the new report promotes transparency, it’s still not clear exactly who tasked 10 government agencies with advancing solar geoengineering research and why.

“The big mystery is, who in Congress actually mandated this report,” he said. “I bet most congressmen had no idea what they were really signing and it certainly had no public airing.”

A small number of ardent advocates have pushed to move ahead with geoengineering research, he said, with a team led by David Keith at Harvard the most vocal and visible. “But it is such a small group that some of us just call it the geo-clique. You tend to see the same names over and over again.”

Previous efforts to boost geoengineering research include House Resolution 5519, The Atmospheric Climate Intervention Research Act from the 2019-2020 legislative session, introduced by Congressman Jerry McNerney, who represented California’s 9th Congressional District from 2013 to 2023. 

That resolution didn’t make it out of the House, but shows the building political momentum for further geoengineering research, with language calling for improved measurement and assessment capabilities “for understanding proposed atmospheric interventions in Earth’s climate, including, as a priority, the effects of proposed interventions in the stratosphere and in cloud-aerosol processes.”

McNerney’s biggest contributor during the 2020-2021 political cycle, according to Open Secrets, was San Diego-based General Atomics, a military contractor making high tech drones that could play a key role in any actual deployment of solar radiation climate interventions. McNerney had previously introduced legislation directing the National Academy of Sciences to develop a geoengineering research agenda and oversight guidelines, which resulted in the 2021 Reflecting Sunlight report from the National Academy of Sciences.

Interest in climate interventions is linked with research on weather modification dating back to at least the 1950s, particularly chemical cloud-seeding to increase precipitation.That history is a cautionary tale, Pierrehumbert said, because cloud-seeding was quickly adopted and institutionalized by some governments before there was any solid evidence that it really works.

“It’s a great example of how science gets out of the hands of scientists and what government and politicians do with it,” he said. “Under political pressure, it becomes completely decoupled from the scientific facts.”

He said the recent framing of solar geoengineering as a response to global warming can be traced to a 2006 paper in the journal Climatic Change by Paul Crutzen, a Dutch meteorologist and atmospheric chemist who won the Nobel Prize for research on atmospheric ozone.

“Crutzen would toss out ideas randomly to see what would happen, and so this was one idea,” Pierrehumbert said. “He suggested in the editorial that, since we don’t seem to be making progress on decarbonisation, maybe we should start thinking of deliberately doing what volcanoes do naturally,” he added, referring to the slight climate cooling effect attributed to aerosol emissions from eruptions.

But geoengineering as a potential response to global warming has been discussed for more than 50 years and predates the idea of emissions reductions as a policy option, researchers have reported. In 1965, President Lyndon Johnson’s science advisory committee issued a report that raised the possibility of albedo geoengineering to offset CO2-induced climate change, but did not even consider cutting emissions. 

“The idea just sat there for quite a while. And then, after it became clear the world was really hotting up in a big way, it kind of got revived through a few people, maybe in the 1990s,” Pierrehumberthe said. “We talked about it, but it just seemed like it was too bizarre, with too many open-ended problems, to be worth pursuing.”