.ON APRIL 2ND a contraption appearing like a snowfall machine on the deck of the USS Hornet, an inoperative aircraft-carrier anchored in San Francisco Gulf, began generating a haze of salted spray particles. The clinical collaboration responsible for the project, the Marine Cloud Brightening (MCB) program, led by the University of Washington, is actually checking out whether such aerosols might help to reduce temperature change via a form of "geoengineering". What performs this phrase mean-- and also why is it thus questionable?