They're not talking specifically about climate change. Doomsayers have always existed, warranted or not. Previously, it seemed inevitable that the cold war would end in a massive nuclear exchange and yet here we are. That was a very real threat, just like climate change, but it was avoided. We also have AI/Singularity doomsayers right now and, previously, Bird flu, SARS, Ebola, etc. and where the doom actually came, humanity has survived just fine.

Through all of that, everything has gotten better.