Because nuclear war balances itself: more nuclear bombings = less nuclear weapons, less people to send them. It will naturally stop at some fraction of humanity left which is incapable of making and launching more nukes

The general idea of a nuclear apocalypse is that all the nukes that matter are launched in a matter of hours, and anyone being targeted gets their launches out before they're hit. The feedback loop that slows things down is too late to matter.

Humans need food. Food does not just appear in supermarkets.

While true, the impact from global warming is likely to be less crops rather than no crops.

In the exact same way major sudden changes in the climate have lead to the extinction of the majority of plants an animals over this planets history. We are not special.

We are special in many ways, we have technology, we are everywhere, and we can think and plan (although considering global warming that is debatable). Global warming would have to create dramatic conditions everywhere on the planet, not leaving any small pocket of survivability to make humans extinct.

Possible? Theoretically yes, but pretty unlikely. But obviously extreme global warming would be a catastrophe even if some of humanity survive.

Technology depends on a lot of people cooperating around the globe. Disrupt a few critical chains (power generation, fertilizers, computers), add a bit of good old war and you'll soon be in the era before Haber process and a lot of people die. And then the remaining people will have trouble keeping that level of technology with how sudden the change would be.

Well yes that's what I said, it could destroy civilisations and their technology. It seems much harder to kill every isolated tribe in the whole world, and every survivors of the destroyed civilisations.

There's little evidence that humans are able or willing to cooperate at this scale. See: the past century of climate change.

Runaway greenhouse effects on other planets have resulted in surface temps of 400C+

Yes, but Venus has 93 times the atmospheric pressure of Earth, and it's overwhelmingly CO2.

Earth isn't likely to get a true runaway like that until the sun gets another billion or so years on the clock, and when it does it will be water vapour as the oceans are promoted to atmosphere.

What we're doing to ourselves is still bad, of course, but it's nowhere near that bad.

Is there a possible scenario for that on earth, that results in every place on earth having a temperature non survivable by humans?

For temperatures not survivable by humans we're talking about a sustained wet bulb of >=36C

On whether it's probable, I'd lean towards no but I'm not qualified. The certainty that I read in the parent comment was mainly what I was pushing back against. On a re-read though it's much less certain (either edited or perhaps I massively misinterpreted it the first time around). Runaway implies positive feedback which is hard to gauge, was all I intended to say

We have a massive survival range and we're on every continent. That kind of sudden climate change is not nearly enough to wipe us out. Some other climate scenarios might. Nuclear war definitely could.

The thing that would end our species due to nuclear war is the exact same thing that would end us from climate change - a collapse of the modern systems of society that we depend on for survival. A nuclear exchange won't set every human on fire, but it's the collapse of food production, healthcare, logistics chains, security, and eventual disease that follows. And because of the size of our population and how depended the majority of us are on these systems, it would likely happen extremely quickly before plateauing out to very small, scattered population groups that would struggle in a hostile environment.

Outside of extreme feedback loop scenarios, there is no way for climate change to disrupt food anywhere near the level of nuclear winter, and there would be no mass destruction of supply chains either.

Welp extreme feedback loops are indeed on the menu.

Okay.

Now look back at the post you originally responded to.

"That kind of sudden climate change is not nearly enough to wipe us out. Some other climate scenarios might."

Since ahistorical feedback loops fall under "some other", why are you telling me something I already included?

So you agree they would survive

Functionally extinct. I would wager that isolated tribes clinging for survival in a post-climate-disaster world may not progress very far, but that's kind of a moot point to argue over.