I think we're on the wrong issue or non-issue. I think water will be the problem. Especially in the southwest. And for many other countries for that matter. Where will the water come from, Seattle?
Canada no doubt. Look at the map. Canada has by far the largest supply of fresh water of any country in the world. In fifty years Canadians will be super-rich from selling their water to dry American snowbirds who found "paradise" but not much water in the Southwest.