The Greenland Ice Sheet is the second largest ice sheet in the world and it's melting rapidly, likely driving almost a third of global sea level rise.A new study shows clouds are playing a larger role in that process than scientists previously believed."Over the next 80 years, we could be dealing with another foot of sea level rise around the world," says Tristan L'Ecuyer, professor in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison and co-author of the study. "Parts of Miami and New York City are less than two feet above sea level; another foot of sea level rise and suddenly you have water in the city."