> What happens when 1.5B come knocking because if they stay they die?

Like let them build few of those sci-fi domes and let them keep buying disposable bottled oxygen? I don't get the pessimism. India makes its own rockets. Pakistan has nukes. Why are they supposed to be incapable of holding the nation together on Mars-like Earth?

Tokyo is already hitting 40C/100F at >90% RH during summers. It's already mildly unsurvivable. Nobody cares. Maybe in 10-20 years we'd be wearing spacesuits, but do anyone seriously think the equatorial regions will be uninhabitable and land prices on northern Europe is going to skyrocket???