> Sooner or later, climate change will end humanity.

What makes you think this? Even in the worst case scenarios, I can imagine a smaller global population surviving in what remains.

Depends what timeframe you're talking about. As stars burn they get hotter, and eventually bigger. So yes, climate change will eventually end humanity though this would be the later scale.

>smaller global population surviving

This is just an unfound assumption on your part. Passenger pigeons went from billions of birds to extinct in less than a century. There are hundreds of different scenarios around climate change and disease evolution alone that could wipe us pretty quickly and a rapidly falling population would make it worse quickly as things like new medicines could not be developed quickly enough, or more technology couldn't be created fast enough (unless we have full AGI working on itself, but then you have alignment being its own problem).

Passenger pigeons did not have the capacity to alter their environment.

I simply find it unlikely that any amount of climate change (beyond the eventual death of our sun) will result in the complete elimination of humanity.

Yes, there are many likely bad scenarios that would drastically reduce the population.

Forever? I mean we'll probably be long gone by the time this happens but eventually changes to the nature of the sun will strip us of our atmosphere. That too will be climate change.

What sort of non-climate-threat do you suppose will take us out?

2. A big change in the climate will end humanity one day. I am skeptical it will be human caused climate change. Much higher probability it comes from asteroid or another exogenous event. The climate has always been dynamic, and it has been much more dynamic in the distant past.