Does he have to be one? I'm not.
All I was looking for was a logical point, and Fox made one. And yes, you made the same point in your own way, and yes, it was obvious in hindsight. By the time the land hits ocean in Antarctica, you're already far north enough that sea ice isn't the same kind of issue.
I'd still like to see those charts run back another few hundred years somehow. Polar bears have been up there for tens of thousands of years...