A trial of cloud clearing technology is sparking controversy in a California city

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 ...