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It's capable of self repair up to a certain point. A fully fledged runaway greenhouse effect is well past that point. The atmosphere would begin to be actively hostile to carbon/water based life. I mean just look at Venus, it experienced a similar runaway greenhouse effect and while we don't know if it ever supported life, it certainly never will now.
I give Earth more credit than that. The Asteroid that killed the dinosaurs cut the earth off from photosynthetic solar radiation for 15 years and filled our atmosphere with toxic dust and ash, life suffered greatly, but it was nowhere close to the end for Earth life. There's literally bacteria that makes it's habitat in pools of acid. Humans are a weak, fragile species defended only by our ability to discern and invent the tools to do so, but Earth life in general is Amazingly robust, it grows in just about any crevice you show it. I just recently saw a story about worms that have adapted to shrug off the radiation of Chernobyl. Have you seen what a fucking tardigrade can be exposed to without dying?
Even our mother will eventually die, most likely from changes in our sun's life cycle, and the universe will eventually suffer heat death, but our species will take itself out in fairly short order. Just smart enough to be dangerous to itself, and too stupid to know better.
Nothing can survive sulphuric acid rain and 500° air temperatures. The 15 years of darkness don't even come remotely close to the level of changes a runaway greenhouse effect would bring.
These single celled organisms literally take in elemental sulfur gas and excretes sulfuric acid.
I think it's the height of arrogance to believe that an ever evolving, ever changing chain of complex life that has existed for we estimate 3,700,000,000 years can be truly done in by one of those creatures that has only been here for about 200,000 years, and has only developed the technology to play recklessly with the environment at scale for about 200 years. As I said before, we aren't even the first macro-cancer to evolve from it that then dares to threaten the whole organism.
There have been catastrophic events in that time from within and mostly without that make our hydrogen bombs we're so proud of seem relatively cute. Maybe you're right. Maybe there is a specific pedal we're pushing on that is a secret kill move that no massive asteroid collision or geological event could ever trigger in its wake, but I also think you have to look at the record of what life on Earth has endured. This bowl has hosted a lot of fragile little species of dependent little fish like us that came and went, but the bowl is as of yet undefeated if winning means life goes on.
They still require things like oxygen and liquid water, neither of which will exist in appreciable amounts under a venus-like runaway greenhouse scenario. The earth, since life existed, has not ever experienced anything close to that.
It's a scary concept to be sure. It does make me wonder, however how it wasnt triggered when the Earth was still highly geologically active with volcanoes constantly spewing the Earth's contents into the atmosphere.
If that didn't make it occur, what prevented it? If it did occur, then it was clearly a temporary state that Earth has some mechanism to mitigate to return to something resembling its current state on a massive enough timeframe. Interesting stuff.
The earth was still a primarily molten ball and hadn't cooled yet. Much of the gases that contribute to the effect are trapped in permafrost and ice at the poles. There's also, of course, the matter of all the previously trapped carbon being pulled out from underground that otherwise wouldn't ever have a chance to reenter the atmosphere. The atmosphere of the early and geologically overactive earth was also much less dense as much of the water and gases came after that period on comets.
oh yeah peer at the biodiversity we observe in venus.