Elected leaders in Alameda, Calif., voted early on Wednesday to stop scientists from testing a device that might one day be used to artificially cool the planet, overruling city staff members who had found the experiment posed no danger.
Despite assurances from experts that the experiment was safe for humans and the environment, residents in the small city of 76,000 voiced the kinds of fears that swirl around the idea of intervening with natural systems to temporarily ease global warming.
The test involved spraying tiny sea-salt particles across the flight deck of a decommissioned aircraft carrier, the U.S.S. Hornet, docked in Alameda in San Francisco Bay. Versions of that device could eventually be used to spray the material skyward, making clouds brighter so that they reflect more sunlight away from Earth. Scientists say that could help to cool the planet and to fight the effects of global warming.
As humans continue to burn fossil fuels and pump increasing amounts of carbon dioxide into the atmosphere, the goal of holding global warming to a relatively safe level, 1.5 degrees Celsius compared with preindustrial times, is slipping away. That has pushed the idea of deliberately intervening in climate systems closer to reality.
Universities, foundations, private investors and the federal government have started to fund a variety of efforts, from sucking carbon dioxide out of the atmosphere to adding iron to the ocean in an effort to store carbon dioxide on the sea floor.
The experiment in Alameda did not involve brightening clouds; it was only testing the way sea-salt particles emitted through a spraying device behave under different atmospheric conditions. It took researchers years to design and build the spraying device and the experiment was expected to last for months or even years at a cost of about $1 million a year.
But during a council meeting Tuesday that stretched past midnight, Alameda’s five elected councilors, none of whom are scientists, said they still weren’t sure the experiment off the deck of the U.S.S. Hornet was harmless.
“I don’t think it’s appropriate for our community to be asked to bear that risk,” councilor Trish Herrera Spencer said. “I don’t think this is the right place.”
Mayor Marilyn Ezzy Ashcraft echoed those thoughts. “I don’t have a huge desire to be on the cutting edge,” she said. “I just feel like this is not the right time.”
Testing, conducted by researchers from the University of Washington, began on April 2. It was temporarily halted by the city, after officials said they needed more time to assess its possible affect on human health or the environment. Two weeks ago, Alameda released a report from its city manager, which found no such risk.
“The chemical components of the saltwater solution (which is similar to seawater) being sprayed are naturally occurring in the environment,” the report said. Staff recommended that the City Council allow the experiment to continue, potentially with additional safeguards such as monitors to measure air quality at the test site.
Sarah J. Doherty, director of the Marine Cloud Brightening Program at the University of Washington, which is running the experiment, said in a statement that she and her team “are disappointed by the decision from the City of Alameda.”
Dr. Doherty said her team was “exploring alternate sites” for the research. But she noted that the city’s own findings showed no risk from the experiment, and urged the city to reconsider its decision.
The question of whether to allow the experiment to continue stretched beyond the local impact of the salt particles and got into whether climate interventions like cloud brightening should be attempted at all.
Some environmentalists oppose research aimed at so-called climate intervention, also known as solar geoengineering. They argue that such technology carries the risk of unintended consequences, and also takes money and attention away from efforts to reduce the use of fossil fuels, the burning of which is the underlying cause of climate change.
Opponents indicated concern that the testing in Alameda could move society closer to deploying such technology on a wide scale.
“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.”
In a statement after the vote, Mary Church, geoengineering campaign manager for the Center for International Environmental Law, an advocacy group based in Washington D.C., supported the city’s decision.
“The rejection rightfully reflects the gravity of what’s at stake for both local and global communities,” said Ms. Church, whose organization wants nations to pledge not to use climate interventions.
Not everyone who spoke at the meeting, which involved comments in person and online, opposed the research.
A youth climate leader in Honduras urged the council to approve the project, saying that the University of Washington had expertise that could help his country and others that are most affected by climate change.
