.ON APRIL 2ND a contraption resembling a snow equipment on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, began creating a mist of salty aerosol fragments. The clinical collaboration behind the job, the Marine Cloud Whitening (MCB) programme, led due to the University of Washington, is checking out whether such sprays might help to decrease environment modification by means of a type of “geoengineering”. What performs this term method– and why is it thus controversial?