A trial of cloud-brightening technology sparks controversy in a California city

Scientists surprised the leaders of a Northern California city last month, when they unveiled a project to study technology that could one day be used to brighten clouds and mitigate global warming.

The experiment involved spraying saltwater along the deck of the USS Hornet — an aircraft carrier docked in Alameda that serves as a museum — to test devices that can create and measure plumes of aerosols. The team planned three sprays per day, four days a week for 20 weeks.

The actions themselves were harmless — and, indeed, environmental consultants the city hired to assess the project found no safety concerns, according to a report published Thursday. But the work represents a first step toward understanding whether this type of technology, at scale, could be used to make clouds reflect more sunlight back to space and slow some global warming effects.

This possibility has thrust the city into the center of a larger debate over whether and how the exploration of geoengineering technologies to fight climate change ought to be explored — and who should have a say.

The project, led by a team from the University of Washington, represents one of the first attempts to test marine cloud-brightening technology in the United States.

City officials and constituents in Alameda said they only learned the full details of it after The New York Times published a story in April. The Times said the researchers knew their testing might be controversial to some, so they had “kept the details tightly held.”

Following the article’s publication, city leaders ordered the scientists to halt the project, saying it was in violation of the lease with the USS Hornet. The Alameda city council will decide the project’s fate in a June 4 meeting.

The idea behind cloud brightening concepts is to increase the number of water droplets within low-level ocean clouds to boost their reflectivity and potentially make the clouds last longer. That process could lead clouds to reflect more sunlight to space. It wouldn’t help with other climate problems, like ocean acidification, and some researchers are concerned that, at scale, it could shift atmospheric circulation with unintended consequences.

Scientists are far from even experimenting on that level. On the aircraft carrier’s deck, the researchers were simply using a machine that looks like a snowmaker to spray saltwater.

“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,” Rob Wood, a professor of atmospheric sciences at the University of Washington and project leader, said in a statement.

The researchers had planned to study how different-sized particles affect the plume.

Wood said the studies are “basic science research” and not “designed to alter clouds or any aspect of the local weather or climate.”

The safety assessment released Thursday identified no potential harms from the work.

“We do not see this operation as a health risk to the surrounding community,” consultant and engineer Andrew Romolo wrote in a letter to city leaders. In a separate letter, a biological consultant said the plumes of saltwater wouldn’t harm terns (a type of seabird) or any other sensitive species.

Laura Fies, the executive director of the USS Hornet Museum, said her initial conversations with the research team centered mostly on immediate plans for the work, rather than its long-term implications. So the resulting controversy was a surprise.

“We were like — we’re making some seafoam breeze, that’s cute, that’s fun,” Fies said. “And you know, I fully admit, that the exciting, controversial portion is like the most newsworthy. It’s also years away from what they’re doing right now.”

Fies said the aircraft carrier has hosted events with pyrotechnics and Jeeps driving around on deck.

“We do wilder things on the flight deck all the time,” Fies said. “What’s being sprayed across the deck is saltwater, very clean saltwater. It didn’t occur to us that the city would want to come inspect with a Hazmat team.”

Most geoengineering ideas are theoretical and untested. Atmospheric scientists say there is no evidence of any large-scale programs, but scientists are taking baby steps to understand the basic physics and feasibility of some possibilities.

The broad implications of this research frighten some people, since certain kinds of geoengineering concepts have the potential to disrupt weather patterns, cause pollution or change the appearance of the sky. Proponents argue that humanity is already geoengineering Earth’s atmosphere by pumping carbon emissions into the atmosphere, and that the risks of global warming could be worse.

When it comes to regulation, geoengineering is something of a Wild West. Tennessee became the first state to broadly ban the practice this year. But the lawmakers’ debates there were marked by outlandish conspiracy theories about so-called “chemtrails,” widespread confusion and inaccurate suggestions that large, federal geoengineering programs were already underway.

In Alameda, Sarah Henry, a city spokesperson, said, the city manager’s office had been notified that “the Hornet had a research partner doing work on the Hornet and what they described as misting down the flight deck.”

“We didn’t know the University of Washington was a partner and we didn’t know the details of the research being done and that’s why this has come to the point,” she said.

The research team also includes scientists with SRI International, a nonprofit research institute founded by Stanford University, and SilverLining, a Washington, D.C. nonprofit focused on climate interventions.

The scientists say they got an outside assessment of regulatory and permit requirements before launching the project.

Josh Horton, a senior fellow at the Harvard Kennedy School who studies solar geoengineering policy, said such projects tend to stir deeper concerns and force people to think about the darkest possibilities of climate change.

“The research that’s contemplated at the present is super small scale and involves zero physical environmental risk. It’s all about the political symbolism and the uncomfortable questions it raises,” he said.

Horton also questioned why the scientists chose to keep the project quiet until it was in action.

“It fuels conspiracy theories. It fuels concerns there’s a set of privileged actors doing this behind the scenes without public input,” he said.

Wood, however, said public outreach was part of the plan and that the project leaders had selected the Hornet in order “to support engagement with the community and a wide array of stakeholders in a tangible way, through direct access to the research.”

Fies said the museum had been working with the researchers on plans for live exhibits for students. She hopes the city council will approve that work.

“Who doesn’t want to be in the splash zone?” she said.