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.

Growing calls for regulation

Solar geoengineering encompasses a suite of hypothetical technologies and processes for reducing global warming by reflecting sunlight away from the Earth that are largely unregulated at the federal level. The two most researched approaches include releasing sulfate particles in the stratosphere or spraying saltwater aerosols over the ocean.

But critics of the technologies warn that they could also disrupt weather patterns — potentially affecting farm yields, wildlife and people. Even if they succeed in cooling the climate, temperatures could spike upward if the processes are abruptly shut down before countries have transitioned away from burning planet-warming fossil fuels, an outcome described by experts as “termination shock.”

As a result, even researching them is controversial — and conspiracy theories driven by weather tragedies have worsened the backlash.

Rep. Marjorie Taylor Greene (R-Ga.) has erroneously suggested that geoengineering is responsible for the deadly July 4 flood in Texas and introduced a bill to criminalize the technology. Retired Lt. Gen. Mike Flynn, a former national security adviser to President Donald Trump, has embraced similar untruths.

Meanwhile, more than 575 scientists have called for a ban on geoengineering development because it "cannot be governed globally in a fair, inclusive, and effective manner." And in Florida, Republican Gov. Ron DeSantis signed a law last month that bans the injection or release of chemicals into the atmosphere “for the express purpose of affecting the temperature, weather, climate, or intensity of sunlight.”

Conspiracy theories involving the weather have reached enough of a pitch that EPA Administrator Lee Zeldin released a tranche of information this month debunking the decades-old claim that jet planes intentionally release dangerous chemicals in their exhaust to alter the weather or control people’s minds.

The small Alameda experiment was one of several outdoor solar geoengineering studies that have been halted in recent years due to concerns that organizers had failed to consult with local communities. The city council voted to block the sprayer test in June 2024 after Mayor Marilyn Ezzy Ashcraft, a Democrat, complained that she had first learned about it by reading a New York Times article.

The Alameda officials’ sharp reaction echoed responses to past blunders by other geoengineering researchers. An experiment in Sweden’s Arctic region that sought to release reflective particles in the stratosphere was canceled in 2021 after Indigenous people and environmentalists accused Harvard University of sidelining them. The entire program, known as SCoPEx, was terminated last year.

"It's absolutely imperative to engage with both local communities and broader publics around not just the work that is being proposed or is being planned, but also the broader implications of that work," said Jinnah, the UC Santa Cruz professor, who served on the advisory board for SCoPEx.

That view isn't universally shared in the solar geoengineering research community. 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, such as the one in Alameda.

"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 think tank discussion last month. Keith previously helped lead the canceled Harvard experiment.

Team sought U.S. ships, planes and funding

The trove of documents shows that officials with the Marine Cloud Brightening Program were in contact with officials from the National Oceanic and Atmospheric Administration and the consulting firm Accenture as the researchers prepared for the much larger ocean test — even before the small field test had begun on the retired aircraft carrier USS Hornet. They had hoped to gain access to U.S. government ships, planes and research funding for the major experiment at sea. (NOAA did not respond to a request for comment.)

After local backlash doomed the Alameda test, the team acknowledged that those federal resources were likely out of reach. The prospect of U.S. backing became more distant with the reelection of Trump, who opposes federal support for measures to limit global warming. (The White House didn't respond to a request for comment.)

The program's donors include cryptocurrency billionaire Chris Larsen, the philanthropist Rachel Pritzker and Chris Sacca, a venture capitalist who has appeared on Shark Tank and other TV shows. (Pritzker and Sacca didn’t respond to requests for comment.)

Larsen said research of marine cloud brightening is needed due to questions about the effectiveness and impacts of the technology. "At a time when scientists are facing political attacks and drastic funding cuts, we need to complement a rapid energy transition with more research into a broad range of potential climate solutions," he wrote in an email to E&E News.

The 2023 research plan shows that the experiments in Alameda and at sea would have cost between $10 million and $20 million, with "large uncertainties" due to operational or government funding challenges and the potential to expand the "field studies to multiple geographic locations."

They would require "significant cash at the outset" and continued support over several years, the plan said. It was submitted as part of a funding request to the Quadrature Climate Foundation, a charity associated with the London-based hedge fund Quadrature Capital.

The Quadrature foundation told E&E News it had given nearly $11.9 million to SilverLining and $5 million to the University of Washington for research on solar geoengineering, which is also known as solar radiation management, or SRM.

"Public and philanthropic institutions have a role in developing the knowledge needed to assess approaches like SRM," Greg De Temmerman, the foundation's chief science officer, said in a statement. The goal is to ensure that decisions about the potential use of the technologies "are made responsibly, transparently, and in the public interest."

'Avoid scaring them’

For more than a dozen years, the University of Washington has been studying marine cloud brightening to see if the potential cooling effects are worth the risks, the research team told Quadrature.

"The MCB Program was formed in 2012 and operated as a largely unfunded collaboration until 2019, when modest philanthropic funding supported the commencement of dedicated effort," the plan said.

The source of the program's initial financial support isn't named in the document. But the timing coincides with the establishment of SilverLining, which is six years old.

SilverLining reported more than $3.6 million in revenues in 2023, the most recent year for which its tax filings are publicly available. The group does not disclose its full list of donors, although charities linked to former Democratic New York Gov. Eliot Spitzer and the late Gordon Moore, a co-founder of the chipmaker Intel, have reported six-figure contributions to the group. (The Bernard and Anne Spitzer Charitable Trust didn't respond to a request for comment.)

“The Moore Foundation is not involved in the Marine Cloud Brightening Program," said Holly Potter, a spokesperson for the charity, adding that “solar geoengineering research in not a focus of the foundation’s work.”

The program pitched Quadrature and other donors on the idea that its need for private philanthropy was only temporary. Public support would eventually arrive for solar geoengineering research, the team argued.

In a 2021 update for supporters, the team said it had received $1 million over two years from NOAA and the Department of Energy for modeling studies and had begun work on the modified snow-making machine that the researchers would later test in Alameda. That technology is also being used in a field trial along the Great Barrier Reef that's funded in part by the Australian government.

At the same time, the donor report acknowledged the potential for "public perception challenges" like those that would later short-circuit the Alameda field test. "The MCB Program is well-positioned both in terms of its government ties, scientific analogues and careful positioning to move forward successfully, but this remains a risk."

The plan for Alameda included elements to engage the public. The deck of the USS Hornet, which is now a naval museum, remained open to visitors.

But the team relied on museum staff to manage relations with Alameda leaders and carefully controlled the information it provided to the public, according to the documents provided by the University of Washington that included communications among the program leaders.

"We think it's safest to get air quality review help and are pursuing that in advance of engaging, but I'd avoid scaring them overly," said an Aug. 23, 2023, text message before a meeting with Hornet officials. "We want them to work largely on the assumption that things are a go." No names were attached to the messages.

Then in November 2023, a climate solutions reporter from National Public Radio was planning to visit the headquarters of SRI for a story about the importance of aerosols research. A communications strategist who worked for SilverLining at the time emailed the team a clear directive: "There will be no mention of the study taking place in Alameda," wrote Jesus Chavez, the founder of the public relations firm Singularity Media, in bold, underlined text. (Chavez didn’t respond to a request for comment.)

At the same time, the program was closely coordinating with government scientists, documents show.

The head of NOAA’s chemical sciences division was one of three "VIPs” who were scheduled to visit the headquarters of SRI for a demonstration of a cloud-making machine, according to a December 2023 email from Wanser of SilverLining. Other guests included a dean from the University of Washington and an official from the private investment office of billionaire philanthropist Bill Gates, a long-time supporter of geoengineering research. (Gates Ventures didn’t respond to a request for comment.)

“The focus of this event is on the spray technology and the science driving its requirements, validation and possible uses,” Wanser wrote to the team.

The same month, the program detailed its progress toward the Alameda experiment in another donor report.

“The science plan for the study has been shared with our colleagues at NOAA and DOE,” said a draft of the report.

A Department of Energy spokesperson acknowledged funding University of Washington “research on how ambient aerosols affect clouds,” but said the agency hadn’t supported "deliberate field deployment of aerosols into the environment.”

Mayor wondered 'where it's leading to'

On April 1, 2024, the day before the Alameda experiment was launched, the program and its consultants appeared to be laying the groundwork for additional geoengineering tests, which an adviser said would likely need the support of federal officials.

Leaders from SilverLining, SRI and Accenture were invited to attend the discussion “to kick off the next phase of our work together” in the consulting firm’s 33rd floor offices in Salesforce Tower, the tallest building in San Francisco, a calendar invitation shows. Officials from the University of Washington and NOAA were also given the option to join. That evening, the calendar notifications show, everyone was invited to a happy hour and dinner.

Accenture, SRI, the University of Washington and NOAA didn't directly respond to questions about the events. Wanser of SilverLining said in an email that the San Francisco meeting "was completely separate" from the cloud brightening program, even though it included many of the same researchers.

The following afternoon, team members and Accenture executives planned to give a sprayer demonstration to Pritzker, an heir to the Hyatt Hotels fortune and board chair of the think tanks Third Way and the Breakthrough Institute, and Michael Brune, a former executive director of the Sierra Club, according to another scheduling document.

It was an important moment for the team. The same technology that was being tested on the aircraft carrier’s deck would also be deployed in the much larger open-ocean experiment, the research plan shows.

"I was impressed with the team that was putting it together," Brune said in an interview. He attended the demo as an adviser to Larson, the crypto entrepreneur who has donated to SilverLining via the Silicon Valley Community Foundation.

Brune, who lives in Alameda, said he wasn’t aware of the larger experiment until E&E News contacted him. "The engagement with leaders here in Alameda was subpar, and the controversy was pretty predictable," he added.

In May 2024, city officials halted the experiment after complaining about the secrecy surrounding it. They also accused the organizers of violating the Hornet's lease, which was only intended to allow museum-related activities. (The Hornet didn’t respond to a request for comment.)

At a city council meeting the following month, Mayor Ashcraft said she wanted "a deeper understanding of the unintended consequences … not just of this small-scale experiment, but of the science, of this technology [and] where it's leading to." Then she and the other four council members voted unanimously to block the program from resuming its experiment.

Using federal aircraft 'isn't going to happen'

Between April 2024 and the city council's vote that June, the research team scrambled to limit public backlash against the test. By then, the controversy had attracted national and local media attention.

The information request from E&E News sought roughly 14 months of text messages from or to Doherty and Robert Wood, another University of Washington researcher, that included or mentioned their collaborators at SilverLining or SRI. Some of the text messages that were shared by the university did not specify the sender, and Doherty and Wood did not respond to questions about them.

In one text message chain on May 15, 2024, one person suggested SilverLining would pay to keep the Hornet museum closed when the tests were running "to give us some breathing space."

The sender added, "for risk management and the project [it's] an easy call, and we can cover it."

But an unidentified second person responded that "the community could actually find it additionally problematic that the project kept the Hornet shut down."

The team members sent each other letters from people who supported the program, including one from science fiction writer Kim Stanley Robinson, whose 2020 novel Ministry of the Future featured a rogue nation that unilaterally implemented planetary-scale solar geoengineering.

"The truth is that in the coming decades we are going to have to cope with climate change in many ways involving both technologies and social decisions," he wrote to the city council on May 29, 2024. The Alameda experiment "has the advantage of exploring a mitigation method that is potentially very significant, while also being localized, modular, and reversible. These are qualities that aren't often attributed to geoengineering."

After the council vote, SilverLining hired a new public relations firm, Berlin Rosen, to handle the media attention. It also discussed organizing local events to recruit potential allies, emails show.

Wanser, SilverLining's executive director, wrote in a June 6, 2024, email to the research team that the program was considering "another run at a proposal to the city post-election, with, hopefully, a build up of local support and education in the interim."

Ashcraft, the mayor, said in an email to E&E News that she is "not aware of any additional outreach with the community" by the researchers, adding that they hadn't engaged with her or city staff since the vote.

Meanwhile, even before Trump returned to office, the team had begun acknowledging that its mistakes in Alameda had decreased the likelihood of gaining government support for solar geoengineering research. Access to federal aircraft "isn't going to happen any time soon," Doherty, the program director, wrote to Wanser and other team members on June 14, 2024.

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.

That doesn't mean the team was wise to closely guard its plans, said Visioni, who last year helped author ethical guidelines for solar geoengineering research.

"There's a difference between what they should have been required to do and what it would have been smart for them to do, from a transparent perspective, to gain the public's trust," he said.