This was fun last time, leggo again
I'll start with: libertarians have solid takes ~40-50% of the time and many of them just need to be pushed a step further in their thinking to turn against capitalist oppression along with state oppression. The libright-to-leftist pipeline is stronger than most seem to think it is.
Those fossil fuels we're burning now all used to be gases in the atmosphere. In the Cretaceous, the temperature was 10 degrees Celsius hotter than today. There was probably some snow in the winter, but there was no permanent ice anywhere on the planet, including the poles and mountain peaks. Take a look at the wiki page: https://en.wikipedia.org/wiki/Cretaceous#Climate
Human-induced climate change is going to be absolutely disastrous for the people of the world today. We need to be taking dramatic, global action and completely restructuring society. But it certainly won't make the planet uninhabitable and I very, very seriously doubt it will cause human extinction.