.ON APRIL 2ND a device appearing like a snow machine on the deck of the USS Hornet, an invalid aircraft-carrier anchored in San Francisco Gulf, began producing a mist of salty aerosol fragments. The clinical collaboration behind the job, the Marine Cloud Brightening (MCB) programme, led by the College of Washington, is actually exploring whether such aerosols may help to reduce environment change with a form of "geoengineering". What performs this term way-- and why is it thus questionable?