.ON APRIL 2ND a device resembling a snowfall maker on the deck of the USS Hornet, an invalid aircraft-carrier tied in San Francisco Bay, started creating a haze of salted spray bits. The medical partnership responsible for the job, the Marine Cloud Whitening (MCB) program, led due to the University of Washington, is actually looking into whether such sprays may assist to slow down environment change via a kind of "geoengineering". What performs this phrase mean-- as well as why is it therefore controversial?