City Officials Halt Experiment to Hack Earth's Climate, Citing Health Concerns

Brightening Clouds

To cool our planet in the wake of climate change, some scientists have advocated for blocking sunlight by using clouds as giant reflectors.

But early forays into these feats of so-called marine cloud brightening have proved controversial. In Alameda, California, local officials have ordered scientists from the University of Washington to halt their experiments using a device that would inject cloud-brightening particles into the atmosphere, The New York Times reports, fearing that those particles could be hazardous.

"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," Alameda officials wrote on Facebook, as quoted by the NYT.

They note, however, that "there is no indication that the spray from the previous experiments presented a threat to human health or the environment."

The setback is emblematic of the resistance that sunlight-dimming efforts, or solar geoengineering, will have to face, even at this very nascent stage. As the NYT previously reported, the experiment was the first outdoor test of marine cloud brightening technology in the United States.

Particle Power

Airborne particles, or aerosols, play a crucial role in our climate. They serve as the medium for water molecules to clump around and become water droplets, seeding the formation of clouds.

Marine cloud brightening proposes taking advantage of this by injecting them with tiny sea salt aerosols to boost the formation of water droplets, thereby creating denser clouds that bounce back more sunlight.

In their experiment conducted last month, the researchers tested their snowmaker-like device for dispersing aerosols, the Cloud Aerosol Research Instrument (CARI), on the flight deck of the decommissioned aircraft carrier the USS Hornet.

The purpose of the test was to see if CARI could reliably spray small sea salt aerosols into the air. Size is the key concern; the aerosols need to be fine in order to create sufficiently dense clouds.

Salty Officials

If city officials have it their way, definitive answers will have to wait. But the researchers, for their part, have defended their handling of the experiments.

In a statement on Monday, UW's Marine Cloud Brightening Research Program argued that the sea salt aerosols "operate well below established thresholds for environmental or human health impact for emissions," as quoted by the NYT.

The program also claims that the city was already informed about the details of the experiment, and that officials only demanded another review after the study began gaining media attention.

Its fate lies in the hands of the City Council, which will meet on June 4 to discuss the study, according to an Alameda spokeswoman.

"They could decide it doesn't pose any risk, and they could allow it to move forward," she told the NYT.

More on climate change: Scientists Say New Material Can Suck Carbon Out of Atmosphere Faster Than Trees