.ON APRIL 2ND a gizmo appearing like a snowfall equipment on the deck of the USS Hornet, an invalid aircraft-carrier anchored in San Francisco Bay, began creating a mist of salted spray fragments. The clinical partnership responsible for the project, the Marine Cloud Whitening (MCB) programme, led by the Educational institution of Washington, is actually looking into whether such sprays could assist to slow temperature improvement by means of a form of “geoengineering”. What does this condition method– and why is it so controversial?