.ON APRIL 2ND a device resembling a snowfall equipment on the deck of the USS Hornet, an invalid aircraft-carrier moored in San Francisco Bay, started generating a haze of salted aerosol particles. The clinical cooperation responsible for the job, the Marine Cloud Brightening (MCB) programme, led by the College of Washington, is actually examining whether such aerosols may aid to slow down temperature improvement via a type of "geoengineering". What does this phrase way-- as well as why is it thus debatable?