.ON APRIL 2ND a gizmo being similar to a snow equipment on the deck of the USS Hornet, an invalid aircraft-carrier tied in San Francisco Bay, started creating a haze of salted spray fragments. The scientific partnership behind the task, the Marine Cloud Whitening (MCB) program, led by the College of Washington, is examining whether such sprays might assist to reduce climate adjustment by means of a kind of "geoengineering". What does this term method-- and why is it therefore disputable?