Quote Originally Posted by drone View Post
Actually, it becomes a very difficult calculus problem. Since water does not stack, knowing the total volume of water released from the melt only gets you half way. The percentage of the earth's surface covered with water will change as the volume of water increases, in a very not-easily-computable way. How much coastline and brackish riverbank gets eaten with a 20 meter rise in water levels? 30 meters? They have computer models for it, it is not as easy as you make it out to be.
10%-20% margin error on quick calculations is usually close enough to be acceptable. If you're toying with really large numbers, a factor 100 is still a small error.
Yes, the good calculations takes that into consideration and as Nowake already displayed, is already considered in the given calculations.