.ON APRIL 2ND a device resembling a snowfall maker on the deck of the USS Hornet, a nonexistent aircraft-carrier anchored in San Francisco Gulf, started making a mist of salted aerosol bits. The clinical collaboration responsible for the task, the Marine Cloud Brightening (MCB) programme, led by the College of Washington, is looking into whether such aerosols could help to reduce climate adjustment by means of a kind of "geoengineering". What does this phrase method-- as well as why is it thus questionable?