Climate change won't cut it, neither would total nuclear war.
Even if you had something like an impact big enough to superheat the entire atmosphere, enough humans might survive inside buildings, basements, subways, etc to carry on.
Modern civilization though is a lot more fragile. It's possible to blast us back to pre-industrial times and the easy to access resources are mostly gone. It's not clear that we could bootstrap a second industrial revolution easily.
There would be some increase in mortality among remote tribes as radioactive fallout from a large scale nuclear war drifted down globally, but that wouldn't be enough to cause human extinction.
Good luck getting them to adopt your useless ass in the post-apocalypse.
https://en.wikipedia.org/wiki/Permian–Triassic_extinction_ev...
This is a good point, but the event wouldn't need to be more volcanic so much as that volcanism would need to ignite more carbon-containing materials - naively I would expect there to me more "fuel" in the Earth than there was 300m years ago.
Minoans went from the thriving trading center of the Mediterranean with written language as old as Egyptian Hieroglyphics to seemingly irrelevant for a while during the Bronze Age because volcanic eruptions seemed to have turned the air they breathed to poison. Not to mention places allegedly hit by the fall of volcanic ash whose remains are so far deep we only speculate they lived there.
I’m really hoping this is a ironic literary reference to “How I learned to stop worrying and love the bomb”
https://en.wikipedia.org/wiki/IUCN_Red_List_of_extinct_speci...
And homo cyberneticus will do it to us.
Those were pre-human ancestors, but humans aren't special, we are just animals that are more destructive than any species that came before us.
Hubris will likely play a large role in any possible future human extinction event. E.g., doing nothing to curb climate change because we are "smart" and invincible and/or god(s) wouldn't allow things to get that bad, a deadly pathogen develops resistance to all antibiotics because of free-feeding antibiotics in factory farming animal flesh, we use nuclear weapons in conflict X believing it will not escalate (George "Baby" Bush, "I want nuclear weapons I can use" [actual quote]), a pathogen intentionally developed to both spread quickly and be extremely deadly (because we can), that somehow... "no one could ever foresee the possibility..." escaped the lab-- or maybe it will be a large meteor impact wiping out humans (and other large animals) across the globe like a kid stomping on an ant hill.
[1] https://www.scientificamerican.com/article/human-ancestors-n...
The linked article talks about the human bottle neck 900,000 years ago, that's almost a million years, but well short of 900 million.