What is actually geoengineering?

.ON APRIL 2ND a device looking like a snow device on the deck of the USS Hornet, a nonexistent aircraft-carrier tied in San Francisco Bay, began producing a haze of salty aerosol bits. The scientific collaboration behind the job, the Marine Cloud Whitening (MCB) program, led by the Educational institution of Washington, is actually looking into whether such aerosols may assist to decrease temperature modification by means of a type of “geoengineering”. What does this phrase way– as well as why is it thus controversial?