A San Francisco nonprofit has created a detailed plan for experiments and studies. This plan aims to help us make informed choices about using solar geoengineering.
Scientists have spent 50 years looking into how we could fight climate change. The idea is to release reflective particles into the stratosphere. This would mimic the cooling effect of volcanic eruptions.
This concept is called stratospheric aerosol injection (SAI). Hundreds of studies have been done, but we still don't fully understand how well it would work or what other effects it might have. There hasn't been a clear plan to fill these knowledge gaps.
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Start Your News DetoxReflective, a research group that funds solar geoengineering studies, has now released its SAI Research Roadmap to address this.
Dakota Gruener, Reflective's cofounder and CEO, said their goal is to give the world the data and tools needed for quick, informed decisions about sunlight reflection. She believes the world might need to make big decisions faster than our current research system is ready for.
The hope is that this plan will guide scientific efforts. It could also encourage charities and governments to fund important work and speed up research responsibly.
The report estimates that if this work is coordinated, it would take about 10 years and cost around $370 million. If not coordinated, it could take about 20 years and cost nearly $1.4 billion.
Gruener emphasized that Reflective does not support using solar geoengineering. However, the report does suggest doing outdoor experiments. These experiments would release increasing amounts of sulfur dioxide into the stratosphere to see what happens.
This idea is controversial. Since 2002, hundreds of academics have signed an open letter. They called for a ban on outdoor experiments and an "international non-use agreement." They argue that such a powerful technology could never be managed fairly worldwide. Some also believe that more studies won't answer the biggest question: Who gets to use it?
The main question is who would control a planet-changing technology like SAI. Who would develop and deploy it, and for what purpose? These are fundamental questions because this technology would create winners and losers.
Moving Research Forward
Reflective, founded in late 2023, has quickly become a key player in solar geoengineering research. It has raised over $20 million from charities and individuals. It has also given about $4 million to dozens of research groups. Reflective has also started its own projects, including an open-source simulator and an online hub for research collaboration.
Earlier this year, Reflective released its SAI Uncertainties database. This listed many scientific unknowns and engineering problems that need solving before even small-scale solar geoengineering can proceed.
Some major unknowns include which gas or particles to use and what happens when they are released into the dry stratosphere. For example, it's unclear if they would spread out to maximize reflectivity or clump together and fall quickly into the lower atmosphere. The new road map builds on this database, showing how to answer most of these questions.
The Research Road Map
The first phase of Reflective's road map is called "foundational knowledge." It involves more computer simulations and lab experiments. These would study potential impacts on different regions, ecosystems, and phenomena. This includes ocean currents, ice sheets, and crop yields.
The report also highlights the need to develop more tools for observation during this phase. This would improve our understanding of the stratosphere's natural conditions. This, in turn, would help us assess any effects from releasing materials later.
This first stage would last two to three years and cost $30 million to $75 million. Some analysis and observation would continue into later phases.
The next stage would involve using modified aircraft to release 10 metric tons of sulfur dioxide into the stratosphere. This would happen four times over two seasons. This research stage could take four to eight years and cost $70 million to $150 million. This work might reduce uncertainty about the "cooling efficacy" of solar geoengineering by about 25%. This means how much the planet would cool per ton of sulfur released.
The experiments in the following phase would increase these levels significantly. They would release 25,000 tons of sulfur dioxide over one season, possibly twice. This research stage, which includes other work, would last four to 11 years and cost $270 million to $1.1 billion. It would decrease efficacy uncertainty by about 66%.
The final phase would be ongoing monitoring of full-scale solar geoengineering, if it is deployed. The goal would be to collect real-world data, update models, and spot any "unexpected or undesired consequences."
Gruener said this road map is a "Version 1." It's meant to be clear enough for people to debate. Reflective plans to update the plan based on feedback from researchers and others.
She also noted that there are "stage gates" between the later stages. This means research should not move forward if experiments show the releases don't have the desired impact, have worrying downsides, or fail to resolve key uncertainties. Gruener stated that these gates are in place because there might be points where the answer is "You should stop."
Weighing the Risks and Solutions
Most experts agree that these studies could reduce uncertainty about solar geoengineering's effectiveness and our technical ability to carry it out. However, highlighting the scientific importance of outdoor experiments doesn't make them easier to implement. Past proposals for such experiments were stopped due to opposition from environmentalists or policymakers.
Not everyone agrees that these experiments will lead to an "informed decision." Wil Burns, a research professor and legal scholar, fears that scientists won't fully understand potential downsides. These include impacts on the ozone layer and changes to regional rainfall. He believes these effects won't be clear until full-scale solar geoengineering is deployed.
Burns said the research would provide some answers, but he doesn't think they would be very relevant. To get relevant answers, deployment at scale is needed, which he believes is not sustainable.
He argues that using the technology would violate principles of fairness for future generations. If greenhouse gas emissions continue, solar geoengineering would only hide the ongoing warming. This means future generations, who had no say in its use, couldn't stop it without causing a sudden surge of warming, known as "termination shock."
Burns believes this would put a "sword of Damocles" over future generations. Even if it "works," he doesn't think it would be fair from an intergenerational perspective. (Some researchers, however, argue that termination shock risks are lower than often assumed and that solar geoengineering could be gradually reduced.)
Ilan Gur, former CEO of ARIA, praised Reflective's road map. He believes that scientists, policymakers, and citizens should all want to quickly and efficiently answer the biggest scientific questions. This would tell us if this approach might work or never work. He fully supports Reflective's approach.
Sebastian Eastham, an associate professor at Imperial College London, agrees that outdoor experiments can't resolve all unknowns. However, he says the road map helps start a conversation about making decisions on a tool with potential benefits and risks, especially with increasing climate dangers.
Eastham noted that every difficult decision is made with some uncertainty. He added that it's crucial to move beyond computer simulations. He argues that well-designed outdoor experiments can teach us much more than millions of hours of computer processing. He believes it becomes almost irresponsible to say "there cannot be ever any experiment."
The risk, he says, is repeatedly running the same computer simulations. This could prevent researchers from learning essential things about SAI's effectiveness or dangers.
Gruener acknowledges that solar geoengineering could worsen inequality. However, she points out that unchecked warming also disproportionately harms developing regions. She also agrees that outdoor experiments won't answer all scientific unknowns but can answer many. She stresses they carry little environmental risk. For example, 10 tons of sulfur dioxide is less than 2% of what global aviation releases daily.
Gruener said some people will be uncomfortable with any outdoor experiment. But if we want decisions based on good science, then experiments are necessary to answer these questions.
She fears that rising climate change dangers will pressure nations to move forward with solar geoengineering. This could happen even if the necessary research to reduce scientific uncertainty and solve technical challenges hasn't been done. She believes the alternative is not that decisions won't happen, but that they will be made in a panic or without enough evidence.
