There is still time to change course, however carbon sequestration is becoming a more important part of climate action. Doomerism just acts as an excuse to not take action.
I honestly hate this rhetoric (nothing personal). Thing is, it gets worse and worse, the less we do, it's not binary, and while the planet will not be able to support close as many people as of now, humanity will survive. But it's very dependent on the actions we do now, how many will...
Whether humanity will survive really is an open question. Despite all the rhetoric and protests and promises the annual CO2 emissions have continued to increase steadily. It's wishful thinking to imagine that we are going to do anything about this before the consequences of our choices force our collective hand. Any report or scientific paper that includes a phrase like 'there is still time' is just not accepting the reality of the situation. A year ago James Hansen published Global Warming in the Pipeline where he wrote "Equilibrium global warming for today’s GHG amount is 10°C". A 4–7 degree rise over 5000 years ended the last ice age, Ocean levels rose 400 feet. A 10 degree rise in a century or so would be way too fast for most species to adapt. It would inundate the majority of our most populated cities. I could go on, but I get depressed writing about this.
Yes it's absolutely depressing. Also just thinking about the idiocratic/authoritarian/right-wing movement that doesn't want to do against or even wants to accelerate climate-change.
Think about it, there are what > 8 billion people in a highly developed /technological advanced world, how realistic is it really that everyone of them will die for good? Evolution took all kinds of measures to avoid it. There will likely be humans (unfortunately likely those that mostly caused climate-change) that will survive. We can already create artifical climate, there's vertical farming that can be isolated from the outside. Even if we're approaching a hell like planet with > 10 C warming, it's not that we don't have very cold places that may be suitable for living then. Yes it will be a lot less people but I don't believe in a total collapse. We have all kinds of redundancy with data storage etc. know-how won't just be lost.
Also while all of this is happening rapidly on a geological timescale it's still slow for humanity and it's ability to adapt. We're still talking about centuries, for the hellish kind of development. It's getting uncomfortable the next decades, but likely so that humanity will finally grasp the fuck up, and takes effective counter-measures. Also the probability that we advance quick enough to sequester carbon so fast (and find safe geoengineering), to reverse at least some of the tipping points is still on the table.
If anything, society collapses and the very wealthy carve out fiefdoms for themselves and re-create medieval feudalism. They tell people they have a God-ordained to rule over the “small folk” and they continue on living like kings, albeit in a post-apocalyptic setting.