.ON APRIL 2ND a device appearing like a snow device on the deck of the USS Hornet, an invalid aircraft-carrier tied in San Francisco Gulf, started making a moisture of salted aerosol fragments. The scientific partnership behind the job, the Marine Cloud Whitening (MCB) programme, led by the College of Washington, is actually examining whether such sprays could help to slow down environment adjustment by means of a form of "geoengineering". What does this phrase mean-- as well as why is it so disputable?