.ON APRIL 2ND a gizmo resembling a snow machine on the deck of the USS Hornet, a defunct aircraft-carrier tied in San Francisco Bay, started making a haze of salted aerosol particles. The clinical partnership behind the project, the Marine Cloud Whitening (MCB) programme, led due to the Educational institution of Washington, is exploring whether such sprays could help to slow temperature adjustment via a form of "geoengineering". What performs this condition way-- as well as why is it thus debatable?