claim: The human fingerprint in global warming is evident in multiple lines of empirical evidence - in satellite measurements of outgoing infrared radiation, in surface measurements of downward infrared radiation, in the cooling stratosphere and other metrics.
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.