Well I think it depends on how you define “extinction”. I think as long as some amount of life remains on earth some number of people will be around clinging on to scraps, humans are very resourceful. I think the 4C extinction means the vast majority of humans dying as a result of ecosystem collapse and being incapable of sustaining themselves

Part of the problem is how much of the pollution is concentrated at the top. As we continue to automate industries the people most likely to be harmed by climate change contribute the least, whereas the people with resources are actively hoarding them to be able to utilize for the rest of their lives. They seem to be fine if they’re the last humans