Ice at the top and bottom of the planet - on Greenland and Antarctica - is melting faster than scientists previously thought, thanks to warming temperatures. This freshwater ice will pour into the ocean, causing sea levels to rise as much as three feet by the end of the century, and 20 feet or more after that. These are the alarming conclusions of a group of top climate researchers, including Dr. Bette Otto-Bliesner, a climate change scientist at the National Center for Atmospheric Research, in Boulder, Colo.