California researchers planned a multimillion-dollar test of salt water-spraying equipment that could one day be used to dim the sun's rays — over a 3,900-square mile are off the west coasts of North America, Chile or south-central Africa. [1]E&E News calls it part of a "secretive" initiative backed by " [2]wealthy philanthropists with ties to Wall Street and Silicon Valley " — and a piece of the "vast scope of research aimed at finding ways to counter the Earth's warming, work that has often occurred outside public view."

> "At such scales, meaningful changes in clouds will be readily detectable from space," said a 2023 [3]research plan from the [University of Washington's] Marine Cloud Brightening Program. The massive experiment would have been contingent upon the successful completion of the [4]thwarted pilot test on the carrier deck in Alameda , according to the plan.... 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.âIn 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....

>

> 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.

"More than 575 scientists have called for a ban on geoengineering development," according to the article, "because it 'cannot be governed globally in a fair, inclusive, and effective manner.'" But "Some scientists believe that the perils of climate change are too dire to not pursue the technology, which they say can be safely tested in well-designed experiments... "

> "If we really were serious about the idea that to do any controversial topic needs some kind of large-scale consensus before we can research the topic, I think that means we don't research topics," David Keith, a geophysical sciences professor at the University of Chicago, said at a [5]think tank discussion last month... "The studies that the program is pursuing are scientifically sound and would be unlikely to alter weather patterns — even for the Puerto Rico-sized test, said Daniele Visioni, a professor of atmospheric sciences at Cornell University. Nearly 30 percent of the planet is already covered by clouds, he noted.

Thanks to Slashdot reader [6]fjo3 for sharing the news.



[1] https://www.politico.com/news/2025/07/27/california-sunlight-dimming-experiment-collapse-00476983

[2] https://www.politico.com/news/2024/06/19/flubbed-climate-test-rich-donors-altering-sky-00164011

[3] https://www.documentcloud.org/documents/25933857-20651572-20651572/

[4] https://news.slashdot.org/story/24/05/15/2357259/bay-area-city-orders-scientists-to-stop-controversial-cloud-brightening-experiment

[5] https://www.youtube.com/live/54Nc89hp3U0

[6] https://www.slashdot.org/~fjo3