But there may be a way to cheat. Scientists have proposed various geo-engineering techniques that would artificially hold the temperature below +2 degrees even if we go through 450 ppm. They are only stop-gap measures, but if they worked they might win us enough extra time to get our emissions down without triggering the feedbacks.
This is the biggest crisis human beings have ever faced, and overcoming it will require an unprecedented level of global cooperation. But there may be a way through it.