We (governments) knew in the 70s. But the fossil fuel industry bought them off. Yes, our way of life is ending, and that’s good. We won’t all die at once for sure, it’ll be over hundreds of years if we go extinct. But don’t kid yourself thinking there won’t be massive levels of death. Brutal amounts and means of death.
It’s not like there’s not been environmental collapse before so we know what it looks like. Those were more isolated instances though. This time, it’s global. There’s nowhere to flee, escape will be temporary at best. Maybe people survive long term, but none of our societies will. Maybe we get a do over, maybe not. If we do, we’re starting from scratch.