claim: CO2 limits won't cool the planet, but they can make the difference between continued accelerating global warming to catastrophic levels vs. slowing and eventually stopping the warming at hopefully safe levels.
evidence: The scientists raise the possibility that even if greenhouse gas emissions are substantially reduced to limit warming to 2 degrees, that might be the "threshold" at which self-reinforcing climate feedbacks add additional warming until the climate system stabilizes in a hothouse climate state.
category: Planetary boundaries