As you say it's been known about for a long time.

Species extinction? Of many other species for sure, biodiversity is under serious threat. Unlikely that there is a threat to the human species completely, although there may well be mass famine, drought, war etc caused by our food and water supplies dwindling. Which will affect many in first world countries although they don't want to admit it yet. Even if 9 in 10 humans die that's still quite a lot of humans remaining.

I changed my lifestyle years ago, I'm completely zero carbon except for the occasional rare outing on my motorcycle. My house is heated and cooled by heat pumps, my electricity supply comes exclusively from renewables and nuclear. I don't use jet airlines at all, the vast majority of my transport is by EV, electric train, and sailboat. I don't eat beef, which contributes an order of magnitude more towards methane emissions than any other meat, although I do eat fish and poultry which have little greenhouse gas effect.

For the moment I am still (obviously) on grid, but I am considering what it would take to go completely off grid. I have heard some positive stories about homesteading for women, but I think there are risks and dangers as well.