.ON APRIL 2ND a device looking like a snowfall device on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, started making a moisture of salty spray bits. The clinical collaboration behind the project, the Marine Cloud Whitening (MCB) programme, led by the College of Washington, is checking out whether such aerosols might aid to reduce temperature improvement via a form of "geoengineering". What performs this term mean-- and why is it thus debatable?