According to Isaac Asimov, polymath (and liberal):
If the 23 million cubic kilometers of ice in the world melted at the same time, the volume of the oceans would only increase 1.7%. This would be enough to raise the sea level by 180 ft.
The Empire State Building would be in water to nearly the 20th floor.
Like I said. What do I know. I really enjoyed the Foundation series when I was younger.