.ON APRIL 2ND a device resembling a snow equipment on the deck of the USS Hornet, an obsolete aircraft-carrier tied in San Francisco Gulf, began making a moisture of salty aerosol bits. The scientific partnership responsible for the task, the Marine Cloud Brightening (MCB) programme, led by the University of Washington, is investigating whether such aerosols could help to decrease temperature change with a form of "geoengineering". What performs this phrase mean-- as well as why is it thus controversial?