A technology that could one day cool the Earth cleared a key hurdle on Thursday.
In early April, scientists at the University of Washington began testing a device that sprays tiny particles of sea salt into the air. The initial tests, which took place on the deck of a decommissioned aircraft carrier in Alameda, California, were simply to see if the device could spray a decent-sized mist. But in the future, an improved version of the device could be used to spray clouds with particles that could reflect more sunlight back into space, temporarily mitigating global warming.
Two weeks later, Alameda city officials ordered the researchers to halt the experiment, citing health and environmental risks, and said they would commission an independent evaluation to determine whether the experiment posed any threat.
On Thursday evening, the city of Alameda released the results of its investigation. The city said the experiment poses no “measurable health risks to the surrounding area” and poses no danger to wildlife.
“The chemical components of the sprayed saline solution (similar to seawater) occur naturally in the environment,” the report said, noting that seawater is “one of the largest sources of natural aerosols in the atmosphere.”
Alameda City Council members are scheduled to meet June 4 to consider the report and decide whether to allow the experiment to resume. Researchers have been hoping to test the device in a variety of weather conditions for several months.
The report, submitted by Alameda's mayor, recommended that the city council “consider permitting” the program with additional safeguards, including installing air quality monitors at testing sites and limiting the time the devices can be used.
The agency also recommended that the City Council require researchers to document that the experiments meet “all local, state and federal regulations,” including written confirmation from the Bay Area Air Quality Management District and the Regional Water Quality Control Board.
Alameda spokeswoman Sarah Henry said the staff member who wrote the report was not authorized to comment on it.
Brightening clouds is one of several ideas for transmitting solar energy back into space, a concept sometimes called solar radiation modification, solar geoengineering, or climate intervention.
The idea is based on a scientific concept called the Twemy effect, which says that a large number of tiny water droplets reflect more sunlight than a few larger ones, so spraying huge amounts of tiny aerosols into the sky to form lots of tiny droplets can change the reflective properties of clouds.
Compared to other options, such as injecting aerosols into the stratosphere, the marine cloud brightening is localized and relatively harmless sea-salt aerosols are used instead of other chemicals.
The researchers say there are potential side effects that still need to be studied, such as negative effects on fisheries due to changes in ocean circulation patterns and water temperatures.
Environmentalists warn that the technology could stifle the fundamental changes needed to address climate change: If people are led to believe that global warming can be addressed by artificially cooling the planet, some say it could slow momentum for renewable energy, electric vehicles and other changes needed to reduce greenhouse gas emissions.
Marine cloud brightening researchers agree that the technique shouldn't be seen as a replacement for moving away from fossil fuels. Rather, they say, the work is important if the transition is slow and short-term efforts to cool the planet are needed. In other words, the technique might buy us some time.
The intense emotions that accompany solar geoengineering debates have been evident in the debate over the Alameda test. When the city announced on Facebook that it was canceling the test, commenters argued over the decision.
“Leave the sky alone. Natural sunlight is our birthright,” one person wrote. Another commenter wrote, “We can do it in Washington. No need to do it here.” (Researchers say the weather conditions in San Francisco Bay make it an ideal place for the experiment.)
But the announcement also drew comments in support of the experiment. “I hope this can be a tool to fight global warming,” said one commenter. “I just wish there were more clouds,” wrote another.
