Climate change isn’t really an existential threat. To be a filter it has to kill all humans and even the bleakest models don’t predict that.

Also for it to be a Great Filter it has to be something that ALL civilizations do to kill themselves. Seems unlikely that all civs wou ld even have analogs to gossil fuels in quantities sufficient to do this kind of damage. And the idea that zero of them actually course-correct when they notice it seems equally implausible