My concern is we're changing the climate at geologically unprecedented rates, likely far too quickly for species to evolve and migrate, even if we hadn't locked up 50% of the world's landmass for our own use. That will play interesting havoc with food chains no matter what former permafrost and arctic is freed up for use (with its own emissions load on melting).
That leaves dramatic and expensive global scale action. We're not doing it. There's no sign we're thinking about doing it. Let the market resolve is the sole incredibly weak suggestion.
I don't think history is going to view citizens and politicians of the 21st century kindly. I can forgive and understand those contributing to the problem before say 1990, before the awareness was widespread. We've emitted more since 1990 than in the entire time before.
So a planetary scale game of chicken...
12C warmer would put vast amounts of the land area of the planet outside habitable conditions for humanity. We'd probably be restricted to former arctic regions, and not much else. So no, I don't think it's self evident at all. It won't take many degrees rise to rule us out of equatorial regions, then tropical...