White House cautiously opens the door to study blocking sun’s rays to slow global warming

The White House offered measured support for the idea of studying how to block sunlight from hitting Earth’s surface as a way to limit global warming, in a congressionally mandated report that could help bring efforts once confined to science fiction into the realm of legitimate debate.

The controversial concept known as solar radiation modification is a potentially effective response to fighting climate change, but one that could have unknown side effects stemming from altering the chemical makeup of the atmosphere, some scientists say.

The White House report released late Friday indicates that the Biden administration is open to studying the possibility that altering sunlight might quickly cool the planet. But it added a degree of skepticism by noting that Congress has ordered the review, and the administration said it does not signal any new policy decisions related to a process that is sometimes referred to — or derided as — geoengineering.

"A program of research into the scientific and societal implications of solar radiation modification (SRM) would enable better-informed decisions about the potential risks and benefits of SRM as a component of climate policy, alongside the foundational elements of greenhouse gas emissions mitigation and adaptation," the White House report said. "SRM offers the possibility of cooling the planet significantly on a timescale of a few years."

Still, the White House said in a statement accompanying the report, "there are no plans underway to establish a comprehensive research program focused on solar radiation modification."

Skeptically or not, that the White House weighed in on solar experimentation at all is remarkable. The concept has created divisions among experts, with some saying it could be a last line of defense against runaway warming if nations fail to reduce their greenhouse gas emissions, while others warn that it could result in an atmospheric substance dependency that, if stopped, could lead to abrupt increases in temperatures.

"The fact that this report even exists is probably the most consequential component of this release," said Shuchi Talati, the executive director of the Alliance for Just Deliberation on Solar Geoengineering, a nonprofit that seeks to include developing countries in the debate over solar modification. "This report also signals that the U.S. government is supportive of well-governed research, including outdoor experimentation, which I think is quite significant."

The report, which was required by Congress in a policy report accompanying the 2022 appropriations bill, was released the same week that European Union leaders opened the door to international discussions of solar radiation modification. It also followed a call by more than 60 leading scientists to increase research on the topic.

The 44-page document considers a few plausible ways to limit the amount of sunlight that hits Earth, all of which could have significant drawbacks. One method is to multiply the amount of aerosols in the stratosphere to reflect the sun's rays away from the planet — a process that can occur naturally after a major volcanic eruption. Others include either increasing cloud cover over the oceans or reducing the amount of high-flying cirrus clouds, which reflect solar radiation back to Earth.

There are risks associated with each form of solar radiation modification, the report said, that can affect human health, biodiversity and geopolitics. That’s because modifying sunlight could alter global weather patterns, disrupt food supplies and lead to abrupt warming if the practice was widely deployed and then halted. It also wouldn't address air pollution from fossil fuels or ocean acidification, a major threat to coral reefs' ecosystems driven by the overabundance of carbon in the air and seas.

At the same time, the White House emphasized that it was important to compare those uncertainties with the present dangers associated with a hotter planet.

"Climate change is already having profound effects on the physical and natural world, and on human well-being, and these effects will only grow as greenhouse gas concentrations increase and warming continues," the report said. "Understanding these impacts is crucial to enable informed decisions around a possible role for SRM in addressing human hardships associated with climate change."

The White House said that any potential research on solar radiation modification should be undertaken with "appropriate international cooperation."

Policymakers in the European Union have signaled a willingness to begin international discussions of whether and how humanity could limit heating from the sun.

"Guided by the precautionary principle, the EU will support international efforts to assess comprehensively the risks and uncertainties of climate interventions, including solar radiation modification and promote discussions on a potential international framework for its governance, including research related aspects," the European Parliament and European Council said in a joint communication Wednesday.

The White House didn't immediately respond to questions about the timing of the new report or its potential political significance.

Given the polarized political climate in the United States, the Biden administration is right to proceed with caution, said Talati, a political veteran of Capitol Hill and the White House who most recently served in President Joe Biden’s Energy Department.

"Politicization around climate change has obviously been the huge driver" of policy gridlock on reducing carbon emissions, she said. "And so I think trying to avoid politicization around geoengineering is also important."