.ON APRIL 2ND a contraption looking like a snowfall maker on the deck of the USS Hornet, an invalid aircraft-carrier moored in San Francisco Bay, began generating a haze of salty spray fragments. The medical collaboration responsible for the venture, the Marine Cloud Brightening (MCB) programme, led by the Educational institution of Washington, is actually exploring whether such aerosols could assist to slow temperature change via a type of "geoengineering". What performs this phrase way-- as well as why is it therefore disputable?