In the last couple of years I've been thinking more often about a Venus scenario where life does not survive. We are just hoping that life will find a new equilibrium in the next couple million years like it has in the past. But if temperatures rise too fast, the planet will just get cooked before enough CO2 will be sequestered. The great filter is still in front of us.
I mean, we have bacteria living off of the heat and gases of underwater volcanoes — it is absolutely not realistic to think that life itself will be in jeopardy. It has survived the release of a highly reactive gas that killed off the majority of things (oxygen), a huge meteor that introduced a huge cooldown overnight, etc.
Of course, it doesn’t mean that we should not try to stop the impending doom that will kill off an insane amount of species, and render many populous places unlivable for humans, causing famine and wars - but Life itself will never be in any danger.
The Venus is quite a lot closer to the Sun, though. A few degrees C change in the average temperature of the Earth indeed can cause absolute large changes, potentially killing of most more complex life forms, but even that would be very far off from the point where life is infeasible - especially that the bottom of the ocean won’t be reaching anywhere close to temperatures where proteins denaturate.
Venus gets roughly double the sunlight that earth does, also:
“Conditions possibly favourable for life on Venus have been identified at its cloud layers, with recent research having found indicative, but not convincing, evidence of life on the planet.” https://en.wikipedia.org/wiki/Venus
I've sometimes wondered if Venus' runaway greenhouse had been caused (presumably unintentionally) by intelligent Venusians in the distant past, how could we find out? What bio- or techno-signatures would we still be able to find? And what possible such signatures would be easiest to look for given the inhospitable conditions?
We have a long, long way to go before Earth could be considered hot by historical standards. The IPCC worst-case warming scenario, where we do absolutely nothing to curtail global warming, puts us back at the midpoint in 2100.
Our 4.54-billion-year-old planet probably experienced its hottest temperatures in its earliest days, when it was still colliding with other rocky debris (planetesimals) careening around the solar system. The heat of these collisions would have kept Earth molten, with top-of-the-atmosphere temperatures upward of 3,600° Fahrenheit.
The second source is a chart going back 500 million years.
How is that related to IPCC projections and climate change, which are about the environment humans evolved to survive and thrive in - physiologically over 7 million years (when we had the last common ancestor with chimps), culturally and technologically over 10 thousand years.
I’m responding to the comments about the extinction of life on Earth, not the extinction of humanity. As you can see on the graph, for most of the last 500 million years the Earth was hotter than it is now, and obviously there was life.
I was not referencing the first couple paragraphs of the linked article, since obviously the first few million years of Earth’s existence are irrelevant, and they’re the same source, which tells me you did not actually read the article; please read through next time and respond charitably rather than assuming I’m some kind of crank. I would appreciate it if you read to understand rather than to respond. It’s very frustrating when people replying to you assume you are saying something completely different rather than reading what you said within its context - a Venus scenario wiping out all life. HN commenters should do much better. This isn’t Reddit. Your entire comment is premised on me saying or thinking something I never suggested or implied.
It’s true that humanity has survived during hotter and colder periods, but certainly nothing like that depicted on the 500mil graph, and anyway industrial civilization is obviously much more fragile.
> In the last couple of years I've been thinking more often about a Venus scenario where life does not survive. We are just hoping that life will find a new equilibrium in the next couple million years like it has in the past. But if temperatures rise too fast, the planet will just get cooked before enough CO2 will be sequestered. The great filter is still in front of us.
Clearly, even a rapid return to the projected IPCCC 2100 worst-case numbers will not cause this scenario. Would it be deleterious for advanced industrial civilization? [1] Yes. Would it continue to be part of the mass extinctions we're causing? Yes. Will it "cook the earth" or "boil the oceans" as he suggests downthread? No.
[1] And so are a lot of other things. Whether people like it or not, advanced industrial civilization is unsustainable with or without climate change.
