.ON APRIL 2ND a contraption appearing like a snow device on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, started generating a moisture of salted aerosol bits. The scientific cooperation behind the venture, the Marine Cloud Brightening (MCB) programme, led by the Educational institution of Washington, is actually investigating whether such sprays could aid to decrease climate adjustment with a form of "geoengineering". What performs this term method-- and why is it therefore debatable?