Researchers Quietly Planned Test to Dim Sunlight

A team of researchers in California drew notoriety last year with an aborted experiment on a retired aircraft carrier that sought to test a machine for creating clouds.

But behind the scenes, they were planning a much larger and potentially riskier study of salt water-spraying equipment that could eventually be used to dim the sun’s rays — a multimillion-dollar project aimed at producing clouds over a stretch of ocean larger than Puerto Rico.

The details outlined in funding requests, emails, texts and other records obtained by POLITICO’s E&E News raise new questions about a secretive billionaire-backed initiative that oversaw last year’s brief solar geoengineering experiment on the San Francisco Bay.

They also offer a rare glimpse into the vast scope of research aimed at finding ways to counter the Earth’s warming, work that has often occurred outside public view. Such research is drawing increased interest at a time when efforts to address the root cause of climate change — burning fossil fuels — are facing setbacks in the U.S. and Europe. But the notion of human tinkering with the weather and climate has drawn a political backlash and generated conspiracy theories, adding to the challenges of mounting even small-scale tests.

Last year’s experiment, led by the University of Washington and intended to run for months, lasted about 20 minutes before being shut down by Alameda city officials who objected that nobody had told them about it beforehand.

That initial test was only meant to be a prequel. Even before it began, the researchers were talking with donors and consultants about conducting a 3,900-square mile cloud-creation test off the west coasts of North America, Chile or south-central Africa, according to more than 400 internal documents obtained by E&E News through an open records request to the University of Washington.

"At such scales, meaningful changes in clouds will be readily detectable from space," said a 2023 research plan from the university's Marine Cloud Brightening Program. The massive experiment would have been contingent upon the successful completion of the thwarted pilot test on the carrier deck in Alameda, according to the plan. The records offer no indication of whether the researchers or their billionaire backers have since abandoned the larger project.

Before the setback in Alameda, the team had received some federal funding and hoped to gain access to government ships and planes, the documents show.

The university and its partners — a solar geoengineering research advocacy group called SilverLining and the scientific nonprofit SRI International — didn't respond to detailed questions about the status of the larger cloud experiment. But SilverLining’s executive director, Kelly Wanser, said in an email that the Marine Cloud Brightening Program aimed to "fill gaps in the information" needed to determine if the technologies are safe and effective.

In the initial experiment, the researchers appeared to have disregarded past lessons about building community support for studies related to altering the climate, and instead kept their plans from the public and lawmakers until the testing was underway, some solar geoengineering experts told E&E News. The experts also expressed surprise at the size of the planned second experiment.

"Alameda was a stepping stone to something much larger, and there wasn't any engagement with local communities," said Sikina Jinnah, an environmental studies professor at the University of California in Santa Cruz. "That's a serious misstep."

In response to questions, University of Washington officials downplayed the magnitude of the proposed experiment and its potential to change weather patterns. Instead, they focused on the program’s goal of showing that the instruments for making clouds could work in a real-world setting. They also pushed back on critics’ assertions that they were operating secretively, noting that team members had previously disclosed the potential for open-ocean testing in scientific papers.

The program does not "recommend, support or develop plans for the use of marine cloud brightening to alter weather or climate," Sarah Doherty, an atmospheric and climate science professor at the university who leads the program, said in a statement to E&E News. She emphasized that the program remains focused on researching the technology, not deploying it. There are no "plans for conducting large-scale studies that would alter weather or climate," she added.

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