Even if CC, as it is occurring now, is happening exactly as fact as it did in the past there is one big problem. There weren't all those humans running around, living in low-lying areas, that will get flooded out. Agricultural areas will change, which means a country that fed itself 50 years ago now can't. And so on. A few million years ago it didn't matter that the whole of the central US was a shallow sea. Imaging that now.