Bay Area city presses pause on controversial sea-spray climate project

The East Bay Area city of Alameda, Calif., has temporarily halted a boat-based climate research project, as local officials work to determine whether spraying sea salt particles into the air poses any environmental or health risks to members of the public.

The University of Washington endeavor, called the Marine Cloud Brightening Program, is exploring how aerosol particles from both natural sources and human activities contribute to cooling the Earth’s climate, by causing clouds to brighten and reflecting more sunlight back into space.

To evaluate these effects, a team of interdisciplinary researchers have been spraying sea salt particles from ships in the ocean into low-lying clouds — specifically, aboard the U.S.S. Hornet in the San Francisco Bay.

But after word got out about the project in the local media, the City of Alameda — which houses the U.S.S. Hornet and its Sea, Air and Space Museum — decided to put the program on hold.

“Upon learning of the spraying experiment, the City instructed the U.S.S. Hornet and the University of Washington to halt the experiment on the grounds that it was in violation of the City’s lease with the U.S.S. Hornet,” a recent statement from Alameda said.

City officials described the on-deck facility as “a machine resembling a snow maker,” noting that the spraying was “taking place without the city’s knowledge on the deck of the U.S.S. Hornet.”

Alongside the project’s launch earlier this spring, a press release issued by the Marine Cloud Brightening Program touted the new facility’s ability to generate small sea salt plumes. The scientists stressed, however, that these plumes “are not large enough to have any effect on local weather conditions” and that natural spray from crashing waves puts more sea salt mass in the air.

After halting these activities, Alameda leaders said they were working with biological and hazardous materials consultants to assess any health and environmental safety issues associated with the experiment.

“In particular, the city is evaluating the chemical compounds in the spray to determine if they are a hazard either inhaled in aerosol form by humans and animals, or landing on the ground or in the bay,” the city’s statement added.

Noting that the findings would be available to the public and shared for City Council consideration in June, the officials stressed that there is currently “no indication that the spray from the previous experiments presented a threat to human health or the environment.” 

Addressing an Alameda Facebook post on the subject, the U.S.S. Hornet responded in a comment beneath the post that thanked the city for writing about the project.

“We believed that our existing permits and lease covered these activities when we started,” the museum stated, recognizing an apparent “gap in communication” regarding the project’s scope. “We are committed to working with the city to meet all of their needs regarding this effort.”

In response to Alameda’s order, program leaders Rob Wood and Sarah Doherty, released a statement Monday stressing that the research is “not designed to alter clouds or any aspect of the local weather or climate.” Rather, they explained, the work is part of a larger endeavor to understand how cloud-aerosol interactions could potentially reduce warming.

“The studies involve brief emissions of salt-water that evolves into a plume of tiny salt particles whose number, size and path are measured by instruments installed along the flight deck of the Hornet,” they said, noting that this occurs “well below established thresholds” for human health or environmental impact.

Also pointing out that the U.S.S. Hornet welcomed the program as part of its STEM education curriculum, the scientists emphasized that city officials were aware of the plans — but ultimately decided to conduct a more detailed review after the news articles surfaced.

Wood and Doherty said that they saw the review as “an integral part” of involving the public in the scientific process, while crediting city officials for its “highly constructive” action thus far.

“We continue to appreciate our engagement with the community on the nature of this type of research study, which is not designed to impact clouds, the environment or climate,” they added.