.ON APRIL 2ND a gizmo looking like a snow equipment on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, began creating a haze of salty spray fragments. The medical cooperation behind the venture, the Marine Cloud Whitening (MCB) programme, led due to the College of Washington, is checking out whether such aerosols may aid to slow temperature modification by means of a kind of "geoengineering". What does this condition way-- as well as why is it therefore debatable?