.ON APRIL 2ND a device resembling a snow equipment on the deck of the USS Hornet, an invalid aircraft-carrier anchored in San Francisco Bay, started creating a haze of salty aerosol particles. The medical collaboration behind the job, the Marine Cloud Whitening (MCB) programme, led by the Educational institution of Washington, is looking into whether such sprays might help to decrease temperature adjustment by means of a form of "geoengineering". What performs this term method-- and why is it therefore questionable?