.ON APRIL 2ND a device looking like a snow maker on the deck of the USS Hornet, an invalid aircraft-carrier tied in San Francisco Gulf, began making a haze of salty aerosol particles. The scientific partnership behind the project, the Marine Cloud Brightening (MCB) programme, led by the Educational institution of Washington, is investigating whether such sprays may aid to slow down environment modification through a form of "geoengineering". What performs this condition method-- and also why is it therefore questionable?