Scientists surprised 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 salt water 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 aerosol plumes. The team planned three sprays a day, four days a week, for 20 weeks.
The actions themselves were harmless - and environmental consultants the city hired to review the project indeed found no safety concerns, according to a report released Thursday. But the work represents a first step toward understanding whether this kind of technology could be used widely to help clouds reflect more sunlight back to space and slow some of the effects of global warming.
This possibility has put the city at the center of a larger debate about whether and how to explore the exploration of geoengineering technologies to combat climate change - and who should have a say.
The project, led by a team from the University of Washington, represents one of the first efforts to test marine cloud-clearing technology in the United States.
City officials and voters in Alameda said they only learned the full details after The New York Times published a story in April. The Times said the researchers knew their tests could be controversial to some, so they had "kept a close eye on the details."
After the article's publication, city leaders ordered the scientists to halt the project because it violated the lease with the USS Hornet. The Alameda City Council will decide the fate of the project at a June 4 meeting.
The idea behind cloud brightening concepts is to increase the number of water droplets in low-level ocean clouds to increase their reflectivity and potentially make the clouds last longer. That process could cause clouds to reflect more sunlight into space. It wouldn't help with other climate problems, such as ocean acidification, and some researchers worry it could widely alter atmospheric circulation with unintended consequences.
Scientists are far from experimenting at that level. On the deck of the aircraft carrier, the researchers simply used a machine similar to a snow maker to spray salt water.
"The studies involve brief emissions of salt water evolving into a plume of tiny salt particles whose number, size and path are measured by instruments installed along the Hornet's flight deck," said Rob Wood, professor of atmospheric sciences at the university. of Washington and project leader, said in a statement.
The researchers planned to investigate how different sized particles affect the plume.
Wood said the studies are "basic scientific research" and not "designed to change clouds or any other aspect of local weather or climate."
The safety assessment released on Thursday shows that there is no potential damage as a result of the work.
"We do not consider this operation to pose 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 would not harm terns (a type of seabird) or other sensitive species.
Laura Fies, the executive director of the USS Hornet Museum, said her initial conversations with the research team focused on immediate plans for the work, rather than long-term implications. So the resulting controversy was a surprise.
"We were like, we're making a sea foam breeze, that's cute, that's fun," Fies said. "And you know, I fully agree, that the exciting, controversial part is the most newsworthy. It is also years away from what they are doing now."
Fies said the aircraft carrier has hosted events with fireworks and jeeps driving around on deck.
"We do wilder things in the cockpit all the time," Fies said. "What is sprayed over the deck is salt water, very clean salt water. It never occurred to us that the city would want to come and inspect with a Hazmat team."
Most geoengineering ideas are theoretical and untested. Atmospheric scientists say there is no evidence for large-scale programs, but scientists are taking small steps to understand the fundamental physics and feasibility of some possibilities.
The broad implications of this research scare some people, because certain types 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 geo-engineering the Earth's atmosphere by pumping carbon emissions into the atmosphere, and that the risks of global warming could be even greater.
When it comes to regulations, geoengineering is something of a Wild West. Tennessee became the first state to broadly ban the practice this year. But lawmakers' debates there were marked by bizarre conspiracy theories about so-called "chemtrails," widespread confusion and inaccurate suggestions that major, federal geoengineering programs were already underway.
In Alameda, city spokesperson Sarah Henry said the city manager's office had been notified that "the Hornet had a research partner working on the Hornet and what they described as fog in the cockpit."
"We didn't know that the University of Washington was a partner and we didn't know the details of the research that was being done and that's why this got to the point," she said.
The research team also includes scientists from SRI International, a nonprofit research institute founded by Stanford University, and SilverLining, a Washington, DC-based nonprofit focused on climate interventions.
The scientists say they received an external review of regulatory and licensing 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 climate change's darkest possibilities .
"The research currently being considered is super small-scale and does not pose any physical environmental risk. It's all about the political symbolism and the uncomfortable questions it raises," he said.
Horton also wondered why the scientists chose to keep the project quiet until it took action.
"It fuels conspiracy theories. It fuels concerns that a group of privileged actors are doing this behind the scenes without public input," he said.
However, Wood said that public outreach was part of the plan and that project leaders selected the Hornet to "support engagement with the community and a wide range of stakeholders in a tangible way, through direct access to the research."
Fies said the museum has been working with the researchers on plans for live exhibitions for students. She hopes the city council will approve this work.
"Who doesn't want to be in the splash zone?" she said.
This article was originally published on NBCNews.com