Yeah, arguably the war in Ukraine is teaching everyone who is listening that nobody is willing to be the first to use nukes and destroy the planet, which means that nuclear powers can actually fight wars--which is incredibly dangerous, of course.
https://www.atomicarchive.com/almanac/test-sites/testing-chr...
Ecosystem resilience is based in the so called natural buffers. They are a product of the interactions between life beings. Imagine the life bar in a videogame. A natural buffer is like a 4-D life bar, where each character actualize their life bars at the same time. You lose some life and your friends will change their energy automatically to fix your health bar, Is paid with energy but also needs some "time currency".
With healthy buffers, even big impacts in an ecosystem are absorbed and the system returns to the initial situation again and again. But it has a coast in the buffer. The life bar gets shorter.
When the buffer is spent, the system is not 'elastic' anymore. At this moment the danger is extreme, but the warnings are subtle or none. Just further impacts, even tiny impacts, on the ecosystem cause a total, devastating and irrevocable collapse that may extend over several years and can't be stopped.
Is unclear if we had crossed this line yet.
The life has recovered from huge collapses at a planetary level five times yet, but it needed millions of years for that.
Just because we had luck before, does not mean that we will have luck forever.
And of those nuclear tests, 528 were above ground, and only 200-300 of them were probably true airbursts. And all of them were in areas like atolls, deserts, and Arctic tundra where nothing burns. Their climate impact was near zero because they caused no fires and no dust, and they were spread out over 35 years.
That is different from thousands of detonations in an afternoon causing raging fires all over the globe. Estimates are that it would generate around 150 billion kg of stratospheric soot. For comparison, yearly generation is around 7-8 billion kg of soot, generally confined to the troposphere and therefore rains out fairly quickly. A nuclear exchange would produce 20 years of soot and dump it into the stratosphere, above the rain.
The largest pulses of soot that we've ever observed are the 2019 Australian megafires and the Canadian 2023 fires. These were roughly less than or equal to 1 billion kg and produced measurable climate effects that lasted months.
A full nuclear exchange would likely produce -10C of global cooling in its immediate aftermath, which would be catastrophic to agriculture and civilization. It would stabilize on the order of decades, but there would be a lot fewer humans in the world.
I don't believe Russia really cares about the rest of the planet. At the same time, China doesn't care if Russia gets a bloody nose on Putin's little vanity project and realizes a nuclear war is bad for their mercantile economy.
[1] https://www.politico.eu/article/volodymyr-zelenskyy-china-ur...
So Russia is only able to prosecute their war with China's permission. When your foreign policy is decided by another power, that's the textbook definition of a vassal.
And I disagree that USSR and PRC were just "rival peers". Rival peers would be UK/US (at least until Suez), or UK/FR until the 90s. USSR and PRC actively fought each other and almost started a nuclear war; that's way beyond "peer rivalry", that's actual direct competition.