The world just eats the climate costs and keeps going.
There's no global catastrophe. No single moment when the magnitude of your folly is revealed to you a blinding flash. Just a slow trickle of "2% worse".
Nuclear superpowers are among the least likely countries to actually collapse from climate damage.
US isn't Syria, and it's Syria that's at risk.
First world countries like France can absorb a +30% spike to food prices. Countries where the same food price spike would come with a major death toll don't have the tools to kick off WW3.
Not the only reason, no. But their nuclear ambitions certainly did contribute to their current predicament.
Nuclear weapons take time, expertize, resources and sustained political will to develop and deploy. If you have all of that, you might be able to put all of that towards climate adaptation instead. Or: go for the nukes and bet hard that you aren't going to get bombed to shit for it. Worked out for NK, but doesn't seem to have worked for Iran.
I think the level of tolerance US has for marginally stable autocracies with nuclear weapons has receded permanently.
Not to mention that merely having a nuclear bomb doesn't automatically allow one to cause WW3. Nuclear weapons were used in a world war already, and that didn't even destroy a single country - let alone the world. It takes a lot of nukes, and a lot of delivery mechanisms, to actually move the needle on the matter of human civilization existing.
Invade? No. Bomb? Probably. Same if for India if e.g. Sri Lanka decides it wants nuclear weapons.
Global warming will unfortunately disproportionately hit poor, equatorial countries. (Also, starving countries can’t afford a nuclear programme. There is no breakout risk in Sudan.)
And you think a second, much larger Syrian refugee migration will have 0 impact on France?
Nothing happens in a vacuum. Everything and everyone is connected.
There are many mechanisms of positive feedback that can accelerate global warming instead of just reaching an equilibrium at a higher average temperature than now.
If some of those mechanisms of positive feedback would be triggered, a global catastrophe would be possible, due to the excessive speed of the climate change, which does not give enough time for the biosphere to adapt to it.
Instead of hoping that we will be lucky, it would have been much better to avoid such risks and prevent further increases in CO2 concentration and average temperature.
I am old enough to have seen a dramatic change in climate from the time when I was a child, when the seasons were still exactly as they had been described for centuries and millennia at that location in Europe, to the present time, when winters are no colder than autumns were before and I have never used again my winter clothes and boots for about 15 years.
I find such a radical change during my lifetime quite scary and I see no evidence for claims that "the world will keep going". The truth is that nobody knows whether this will be true and hoping that this will happen without doing anything to guarantee such an outcome is reckless.
Plenty of feedback mechanisms were proposed, investigated, and found lacking. It's a "makes climate change 10% worse than it would otherwise have been" kind of thing, not a "makes climate change 1000% worse than it would otherwise have been" kind of thing.
Severe enough to be noticeable, but not severe enough to warrant radical climate action. Not an extinction threat. A "slow trickle of economic damage, some amount otherwise preventable death and suffering, diffused across the entire world, applied unevenly, and spread thin across many decades" threat.
And stopping the GHG emissions demands radical, coordinated global action. Major emitters would have to pay local costs now - for the sake of global benefits many decades down the line. And those emitters are not the countries that face the worst climate risks. Global superpowers can tolerate climate change - it's countries that already struggle as it is, that don't have the resources to adapt or mitigate damage, that can face a significant uptick in death and suffering rather than damage in the realm of economics.
That makes climate action a very hard sell for the politicians. Thus the tepid response.
By now, I'm convinced that the only viable approaches to climate change lie in the realm of geoengineering. Which does not require multilateral coordinated action against a "tragedy of commons" scenario, and are cheaper than forcing local GHG emissions into negatives. Even non-permanent geoengineering solutions offset impacts here and now - thus buying time for fossil fuel energy to succumb to economics.