.ON APRIL 2ND a gizmo being similar to a snow maker on the deck of the USS Hornet, a defunct aircraft-carrier anchored in San Francisco Bay, began making a haze of salty aerosol fragments. The clinical partnership behind the venture, the Marine Cloud Brightening (MCB) programme, led due to the University of Washington, is actually looking into whether such sprays may aid to reduce climate improvement by means of a type of "geoengineering". What does this condition mean-- as well as why is it so disputable?