Thing is, if you're in subcontinental Asia, you won't stay there to die. You'll move North. Ditto North Africa and Europe - there will be lots of bodies moving around. The social upheaval doesn't fill me with giggles; most of the temperate countries are already twitchy about immigration and we've never seen a real mass movement. If the to-be-desert folks would just shut up and die quietly in place, that would be peachy, but they're not that dumb.