>Large parts of humanity have always had a problem getting water or food and it had nothing to do with global warming, rather politics, governance, and culture.

Yes. But not relevant. One has to remove such constants in order to see what's new.

So, while "Large parts of humanity have always had a problem getting water or food and it had nothing to do with global warming", now it also HAS to do with global warming.

http://en.wikipedia.org/wiki/Desertification