California city votes to block solar geoengineering experiment

A Northern California city council voted early Wednesday morning to cancel the nation’s first outdoor experiment into the potential to limit global warming by altering cloud behavior.

The five-member Alameda City Council voted unanimously to reject University of Washington researchers' aerial spraying of liquefied salt from the deck of a retired aircraft carrier in San Francisco Bay, two months after the experiment began.

City officials said they were put off by the project's lack of transparency. While researchers maintained they didn't need any federal, state or local permits to begin the experiment, officials faulted them for announcing the project in the New York Times rather than notifying the city first.

"You didn't start out on the right foot," Alameda Mayor Marilyn Ezzy Ashcraft told the researchers. "I'm not thrilled when I open the paper ... and read about this controversial experiment taking place in the Bay Area. I thought, 'Oh, I wonder where that is. Alameda? What?'"

It's one of the first votes on solar geoengineering research in the U.S. and could be a bellwether of public sentiment as investor interest in the technology grows and global temperatures continue to rise.

It’s also the second solar geoengineering experiment to run into opposition in recent months as the technology comes under increased scrutiny.

Harvard researchers seeking to inject the stratosphere with sunlight-blocking aerosols in northern Sweden ended their project in March after facing pushback from environmentalists and Indigenous communities concerned about the potential for negative impacts on weather patterns.

The University of Washington's Coastal Atmospheric Aerosol Research and Engagement (CAARE) project drew international attention when it began in April. Launched in partnership with the nonprofit research groups SilverLining and SRI International, it was a relatively small experiment: It planned to spray sea salt particles for 5- to 30-minute periods a few times a day for at least four months to study how they move through the air. The next phase of the study would aim for the clouds to increase their density and reflectiveness.

Consulting firm Farallon Strategies, which the researchers hired to evaluate regulatory challenges for the project, concluded in March that the ship's existing permit sufficed given the limited scope.

But Alameda officials, who were caught off guard when news stories about the experiment emerged, said it was in violation of the USS Hornet’s lease. They ordered the university to halt the experiment last month while they commissioned independent safety studies. The city's consultants found the tests would not harm the environment, sensitive species or the surrounding community.

Researchers apologized at Tuesday's hearing. "We thought the proper thing to do was to work through the Hornet and their permitting process and their communication and relationship with you," said Sarah Doherty, director of the University of Washington's marine cloud brightening program. "We now know that that was an error and we deeply apologize for that."

The project operated for about 20 minutes over the last week of March and first week of April until it was halted, Doherty said.

Researchers also maintained at Tuesday's hearing that the concentrations of salt were far too low to cause any health issues. But council members said they still had concerns about impacts on city residents.

"We are keenly interested in dealing with climate change," said Vice Mayor Tony Daysog. "But for me, I just feel that a lot of the information has just been far too thin."

Councilmembers weighed having the proposal come back after seeking permission from other regulating agencies but ultimately voted to simply stop the project.

"I'm not saying, you know, 'Never darken our doorstep again,'" Ezzy Ashcraft said. "But I just feel like this is not the right time."