I believe that we should be genuinely worried about the possible collapse of the West Antarctic Ice Sheet.
A one meter rise in ocean levels would put nearly a hundred million people out of their homes in Bangladesh alone. The Maldive Islands would be gone and high tides and storm surges could be up by far more than one meter!
http://www.sciencedaily.com/releases...0205142132.htm
Collapse Of Antarctic Ice Sheet Would Likely Put Washington, D.C. Largely Underwater