.ON APRIL 2ND a contraption being similar to a snowfall equipment on the deck of the USS Hornet, a defunct aircraft-carrier moored in San Francisco Gulf, began creating a mist of salty spray fragments. The scientific cooperation behind the job, the Marine Cloud Brightening (MCB) programme, led by the College of Washington, is looking into whether such aerosols could aid to slow down environment change with a type of "geoengineering". What does this phrase way-- and also why is it thus disputable?