.ON APRIL 2ND a contraption appearing like a snow device on the deck of the USS Hornet, a defunct aircraft-carrier tied in San Francisco Bay, began producing a mist of salty aerosol bits. The clinical cooperation responsible for the task, the Marine Cloud Whitening (MCB) programme, led by the Educational institution of Washington, is exploring whether such sprays may aid to slow down climate improvement via a type of "geoengineering". What performs this condition method-- and also why is it therefore disputable?