.ON APRIL 2ND a gizmo appearing like a snowfall device on the deck of the USS Hornet, an inoperative aircraft-carrier moored in San Francisco Gulf, started generating a mist of salty spray fragments. The medical collaboration responsible for the job, the Marine Cloud Whitening (MCB) programme, led by the University of Washington, is exploring whether such sprays could help to decrease climate adjustment through a form of "geoengineering". What performs this phrase mean-- as well as why is it so questionable?