.ON APRIL 2ND a contraption resembling a snow machine on the deck of the USS Hornet, an inoperative aircraft-carrier tied in San Francisco Gulf, began generating a mist of salted aerosol particles. The medical partnership behind the job, the Marine Cloud Whitening (MCB) program, led due to the College of Washington, is actually examining whether such sprays might help to decrease environment change via a kind of "geoengineering". What performs this condition method-- as well as why is it therefore controversial?