.ON APRIL 2ND a gizmo appearing like a snow device on the deck of the USS Hornet, an invalid aircraft-carrier anchored in San Francisco Bay, started generating a haze of salted spray fragments. The clinical collaboration responsible for the venture, the Marine Cloud Whitening (MCB) programme, led due to the University of Washington, is looking into whether such sprays could help to reduce climate adjustment through a kind of "geoengineering". What performs this phrase method-- as well as why is it so debatable?