The sea level rise is one of those things I find is over blown by advocates of the anthropogenic hypothesis and under rated by advocates of either the natural variation hypothesis or the non-variance hypothesis.

Given that 75% (to a first approximation) of the surface of the planet is ocean, and that ice that is currently in the ocean is already displacing its mass (so not contributory to sea level rise when it melts), lets do a little math.

Using a nominal radius of 4,000 miles for the planet (yes its an ellipsoid I know), and only 75% of the surface area is water, we can compute the surface area of the ocean (approximately) as

  (4/3*pi*4000^3) * .75 = 201,056,640,000 sq miles.

Call is 200 billion square miles. And we can convert 200' of sea level rise into miles by using 200 ft / 5280 ft/mi to get .0378 miles. So the volume of water that would have to flow into the ocean is then:

  201,056,640,000 * .0378 = 7,599,940,992 miles^3 of water

We know ice is 92% the density of water, so its going to take up 8.7% more volume so 7.6x10^9 miles^3 * 1.0869 is a bit more than 8.25 billion cubic miles of ice.

Now Wolfram Alpha [2] puts the area of the North American Continent at 9.461 million mi^2, so this ice we're melting, if it were on the north American continent, would cover it to a depth of 8.25 billion / 9.461 million, yes 873 miles. Way out into orbit. I've looked around on Google Earth and can find no ice structures which poke out of the atmosphere :-).

But there is an even simpler way to 'check the facts' here. For every foot of sea level rise, we need to melt 1.0869' * (.75/.25) = 3.4' of ice over all of the land in the world. That doesn't sound too bad until you try to figure out how much of the existing land today supports 100% ice holding (which is to say, water which is, but for temperature, permanently locked into ice so glaciers and the poles and the peaks over 12,000') That number is closer to 1% of the total land mass, and that is only .25% of the earths surface area, yes 300' thick ice in those areas for each foot of sea level rise.

Bottom line, given what we know of the ice on our planet, if we melt all of it, we'll be lucky to get 20' of sea rise. 200' is completely out of the question unless a comet hits us that is 100 miles in diameter, at which point all bets are off.

[1] http://www.wolframalpha.com/input/?i=area+of+USA

[2] http://www.wolframalpha.com/input/?i=area+of+north+america