A recent study in the journal Nature says the Greenland ice sheet is now melting seven times faster than in the ‘90s. Why should we care? Faster melt means faster sea level rise, and that puts an extra 400 million people at flood risk by 2100, according to the same study. It was a hot topic among attendees at last month's American Geophysical Union conference in San Francisco. Two of them, University of St. Thomas professor John Abraham and world-renowned climate scientist Kevin Trenberth sent Climate Cast an audio postcard with their thoughts. To hear it, click play on the audio player above.