.ON APRIL 2ND a gizmo looking like a snowfall maker on the deck of the USS Hornet, a nonexistent aircraft-carrier tied in San Francisco Bay, began making a haze of salty spray particles. The medical partnership responsible for the task, the Marine Cloud Whitening (MCB) programme, led due to the College of Washington, is actually checking out whether such aerosols may help to slow environment improvement with a type of "geoengineering". What does this phrase method-- as well as why is it thus disputable?