with satelite photos you can see ice expanding and shrinking yearly, but do we see the sea level moving? no, that's because in "winter" time, the ice on the south pole shrinks but the one on the north expands, in "summer" it's vice-versa.
ok so..i totally made this up, but wouldn't be surprised if a "global warming scientist" would explain it like this, LOL.
i actually got interested in the sea level rising thing so much that i did the calculations. all though rough and all, but from being convinced 6m is waaay too much..it is possible. on the other hand, you have looney saying 50m.
BUT, warmer climate means that the atmosphere can and will carry whole lot much water.
i don't believe sea level will raise, because if it would, it would have been mentioned in historical writtings from the year-around 1000, when temperatures were much higher.
also, i do not know, how much of the the "permafrost" is located on shore and how much is already in the water, but jerry is right, a pound of ice displaces a pound of water, so there should be studies about how much of the glaciers and other icy stuff are actually on solid ground.