This absolutely must be reasoned about together with climate change projections. I don't see there's any chance in hell we can stop at a 2 degree world. That me

This absolutely must be reasoned about together with climate change projections. I don't see there's any chance in hell we can stop at a 2 degree world. That means though that large parts of the world will likely become inhospitable to human life as we know it. So, I'd expect either huge population transfers, wars, or both. The population decline will likely not be uniform then, as people will flock to the still hospitable parts of the planet. Provided 'native' populations don't go full lock-the-borders mode.