.ON APRIL 2ND a gizmo looking like a snowfall machine on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, began making a mist of salty spray particles. The medical cooperation responsible for the job, the Marine Cloud Brightening (MCB) programme, led due to the Educational institution of Washington, is looking into whether such sprays might help to slow environment adjustment by means of a form of "geoengineering". What does this phrase method-- as well as why is it thus debatable?