Existential risk due to astronomical or technological causes, as opposed to divine intervention, is pretty novel. No one thinks global warming will end humanity.
If you're well familiar with the idea of the world ending, the precise mechanism doesn't seem to be that important.
I think what's novel is the idea that humans can meaningfully affect that existential risk. However that's a lower bar / closer jump than the novelty of the whole idea of existential risk.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.