I did this once when they we claiming a 60’ rise. Calculate how many cubic miles of ice would need to met to raise sea level by 14’.
It takes a while, but basically figure out the square miles covered by water on the planet, and figure out the volume it would take to fill it up, then figure out the square miles of available land and how much ice would need to be sitting on land waiting to thaw.
I believe my answer was every square mile of available land needed to be under about 20 miles of ice. I know there is quite a bit of error in the math, but it is all on the side of the numbers being to low since quite a bit of ice is already in the ocean, and the earth is not a flat plane, so the volume goes up with altitude. What a bunch of F’n morons these people think we all are.