As far as I'm aware, until we get carbon emissions to zero (or net zero), temperatures will continue to rise.
The contrarian throwaway said: "A significant, geologically fast rise in global temperatures would kill millions/billions of people, inundate coastal areas, result in major migrations and resource wars, etc."
-- this sounds close enough to what I said, simply "We all die." I didn't say the oceans would evaporate. But with that amount of damage, global civilization and culture would probably not survive. Going carbon-neutral is not a "meh, let's do it later, or not" type of thing.
This is not just arguing over semantics. There is a huge difference between what I wrote and "we all die". The global population is 8.3 billion. Climate change would be most catastrophic to poor populations in heat prone areas like Southeast Asia, parts of Africa, parts of Mexico, etc. where the wet bulb temp would exceed human survivability. Also, coastal cities would have to build defenses or move.
But we could lose one or two billion people and there is nothing that makes me believe that "global civilization and culture would probably not survive". I just done see how you make that leap. There would be huge change but plenty of places would be perfect for human habitation, some moreso than today.
I, for one, don't believe civilization could handle perpetual catastrophe, the loss of billions of people while retaining a grow-or-die economic model, our largest cities needing to "move" inland/uphill, and migrating populations escaping ininhabitable areas, etc. etc., without altogether collapsing.
Look how fragile it is - blocking the Strait of Hormuz alone caused economic near-calamity in some markets. It's like we are all on a fast-moving treadmill, and once tripped, there's no getting back up. This isn't the world of 1933.