[hn_throwaway_99]

This idea that climate change would lead to "ending humanity" just shows to me how a lot of the popular messaging outran the actual science on the issue.

Again, a "runaway Venus" was never really in the cards. As far as I am aware, basically all the carbon that is now locked in the ground in fossil fuels was once in the environment, and Earth still supported copious life at that time. E.g. at one point when dinosaurs roamed the Earth, there were no polar ice caps (Antarctica, even when it was near its current position over the South Pole, had lush green forests and lots of dinosaurs, even with many months of darkness), sea level was many meters higher, but life still flourished.

I'm not downplaying climate change. 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. But "ending humanity" by making the entire planet unlivable was never supported by the science.

[CalRobert]

As far as I'm aware, until we get carbon emissions to zero (or net zero), temperatures will continue to rise.

[ndrh]

For another 50 years after we do stabilize them, yes.

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.

[hn_throwaway_99]

> this sounds close enough to what I said, simply "We all die."

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.

[fallingfrog]

Yes, all this is my understanding also. I would add to that that think it's good to keep as a goal that we want to have the political ability to make prudent changes to avoid disasters even if those disasters are not totally world ending but merely catastrophic levels of suffering for a hundred years or so.

[ndrh]

That is bad enough to prioritize avoiding at all costs (mainly costs to the upper crust of the economy, the part most resistant to meaningful change).

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.

[hn_throwaway_99]

But there is not unlimited carbon to burn. All that carbon in the ground was in the air/water at one point in Earth's past, when Earth was teeming with life.