nytimes.com

Soumya Karlamangla

City officials decided to block testing of an experimental technology to fight global warming, even though experts hired by the city found that it posed no health risk to residents.

June 5, 2024 Updated 8:21 a.m. ET

The international debate over how much to interfere with nature to slow the planet’s warming was fought on a surprising stage this week: a City Council meeting in Alameda, on the eastern edge of San Francisco Bay.

Researchers had chosen Alameda, a city of about 75,000 residents built on a group of islands south of Oakland, as the first place to field test a device intended to brighten clouds, so that they would reflect more light back into space.

But concerns about the experiment led Alameda officials last month to ask the scientists to suspend the testing. And early Wednesday, at the end of a contentious meeting that dragged on past 1 a.m., the Alameda City Council voted unanimously to call it off entirely.

“I don’t have a huge desire to be on the cutting edge,” Mayor Marilyn Ezzy Ashcraft said.

Strong emotions are stirred by cloud brightening, and more broadly, by what is called solar geoengineering or climate intervention: attempts to temporarily cool the Earth at a time when global warming is accelerating. Scientists see these interventions as possible ways to buy time for the world to move away from the main driver of global warming, the use of fossil fuels. But the concepts tend to be divisive, because some people are uncomfortable with trying to intervene in the climate.

In Alameda, a team of researchers led by the University of Washington began conducting cloud brightening experiments in April, spraying tiny sea-salt particles into the air across the flight deck of a decommissioned aircraft carrier, the U.S.S. Hornet, that is moored in the city. The scientists wanted to see whether they could consistently spray the right size of particle.

If the device works, the idea is to eventually use it to change the composition of clouds above the ocean, boosting their reflectivity and bouncing more of the sun’s rays back into space before they can warm the Earth’s surface. The experiment in Alameda was the first outdoor test of such a device in the United States.

Alameda residents began expressing alarm about the technology being used in their backyard. Soon after the experiment began, the city asked the researchers to stop testing while they evaluated the risks.

“If there are issues, we want to understand it, and we want to put limits on what they’re doing,” Griff Neal, a chemical engineer who has lived in Alameda for 25 years, said this week. He said he was worried about the effects of inhaling the particles on older residents who work as volunteers on the Hornet, which is now a floating museum, and students at a nearby high school.

He questioned why scientists from Washington State were conducting the experiments in his community and not their own. “There are certainly neighbors of mine who have said, ‘Why aren’t they doing it in Puget Sound?’” he said.

The researchers said that the often foggy conditions in San Francisco Bay made it an ideal spot for the experiment, which they hoped to run for at least 20 weeks in various kinds of weather.

The deck of the Hornet offered conditions similar to the open ocean, and the ship’s role as a museum would allow the public to engage with the research, one of the primary goals of the program, according to Sarah Doherty, an atmospheric scientist and the program director of the Marine Cloud Brightening Program at the University of Washington.

Analysts hired by the City of Alameda to assess the experiment found that it posed no health risk. They said the salt water being sprayed by scientists was similar to natural sea spray from the ocean. The city manager recommended Tuesday evening that the Council approve the project. But the councilors ultimately decided that they still weren’t sure the experiments were harmless.

“I don’t think it’s appropriate for our community to be asked to bear that risk,” Trish Herrera Spencer, one of the five councilors, said at the meeting. “I don’t think this is the right place.”

It is unclear what will happen next. Alameda officials say that the project cannot continue on the Hornet without their approval. The University of Washington research team could not immediately be reached for comment.

During the meeting, the debate moved beyond the impact of the salt particles and got into whether climate interventions like cloud brightening should be attempted at all. Some environmentalists worry that the technology could distract people from addressing the causes of climate change, and could slow the momentum of efforts like switching to renewable energy and electric vehicles.

“While this is a local decision, it has far-reaching consequences,” Gary Hughes of the environmental group Hands Off Mother Earth Alliance said at the meeting. “There are global climate justice dynamics at stake.”

Another public commenter who was a youth climate leader in Honduras urged the Council to approve the project, saying that the University of Washington had expertise that could help countries like his that are most affected by climate change. He also called on the lawmakers to consider “the bigger implications that this has for countries like mine.”

Tony Daysog, the vice mayor of Alameda, said he and other elected officials had been inundated with emails from residents with strong opinions about the project. He said Alameda, a rare California city on an archipelago, was particularly susceptible to problems like sea-level rise.

“We do have to take climate change seriously, more so than many others,” Daysog said. “At the end of the day, you can’t make everybody happy. You just have to do what you think is right.”

For more:

• An in-depth look at marine cloud brightening by Christopher Flavelle, a New York Times reporter who covers climate issues.