.ON APRIL 2ND a gizmo being similar to a snowfall maker on the deck of the USS Hornet, a defunct aircraft-carrier anchored in San Francisco Bay, started generating a moisture of salted spray particles. The clinical partnership behind the job, the Marine Cloud Whitening (MCB) programme, led by the University of Washington, is exploring whether such aerosols might help to reduce environment change with a type of "geoengineering". What does this condition way-- as well as why is it so debatable?