.ON APRIL 2ND a contraption being similar to a snow maker on the deck of the USS Hornet, a defunct aircraft-carrier anchored in San Francisco Gulf, started making a haze of salted spray particles. The scientific collaboration responsible for the task, the Marine Cloud Brightening (MCB) programme, led due to the University of Washington, is looking into whether such aerosols could assist to decrease environment improvement with a type of "geoengineering". What does this phrase way-- and why is it therefore questionable?