California, United States (Enmaeya News) — Scientists are racing to find ways to cool the Earth amid rising global temperatures, even exploring methods to block sunlight over vast areas. Last year, University of Washington researchers made headlines when Alameda officials canceled an experiment testing a cloud-brightening machine, citing health and environmental concerns.

Documents obtained by Politico show the halted test was meant to pave the way for a much larger project, potentially covering an area larger than Puerto Rico.

The technique, known as marine cloud brightening, uses machines to spray seawater into the air. Salt particles form tiny reflective droplets in clouds, making them brighter and reflecting more sunlight away from the planet.

The Alameda test aimed to study cloud response and whether increasing cloud brightness could reduce warming. NASA notes some clouds reflect 30–60% of sunlight due to fine water or ice particles, helping cool the planet. Researchers believe the effect can be enhanced by boosting droplet numbers.

The idea dates to the 1990s, says Todd Laporte, a climate policy expert at George Mason University, who notes the method increases humidity and droplet formation.

While natural winds lift sea foam into the air, scientists say machines could intensify the cooling effect. Australia, the U.K., and NASA are exploring similar techniques, though experts warn altering clouds carries unknown risks.

Before the official halt, researchers secretly generated clouds over 3,900 square miles off coasts in North America, Chile, or South Africa. Lack of transparency sparked local concern, leading Alameda’s council to stop the project.

Marine cloud brightening is part of a broader field called solar geoengineering, including stratospheric aerosol injection, which releases reflective particles high in the atmosphere.

Proponents see it as a temporary climate solution, while critics warn of unknown environmental, health, and geopolitical risks. Effects could include ozone depletion, acid rain, disrupted rainfall, or “termination shock” if the process stops suddenly.

Despite uncertainties, some argue the worsening climate crisis justifies exploring unconventional interventions. Still, secrecy and controversy have fueled public distrust and heightened debate over whether such experiments are a temporary fix or a dangerous distraction from reducing greenhouse gas emissions.