It would take nuclear war to require the rich to hide in bunkers. Climate change alone will not make the planet uninhabitable for humans. Of course, climate change is not the only factor contributing to the impending global ecological collapse, but even in a worst case collapse scenario, humans will survive. Life will be extremely unpleasant for most of us, but the billionaires would be just fine. That is, if we allow them to continue existing after their system of capitalism destroys everything. Hopefully it doesn’t take total collapse for us to gain class consciousness and achieve socialism though.