Is it possible that in the 3 billion years that it had liquid water, Venus evolved advanced life that managed to trigger runaway greenhouse warming?
Secondly, is Venus’s atmosphere a worst case scenario for global warming here or is there something that would prevent it happening?
(The worst we could do is still enough to destroy us, though.)
I doubt that runaway greenhouse warming could get so extreme for Earth. I recall reading that solar input is enough lower here. Also, at million-year scales, I gather that high CO2 levels increase weathering, and drive carbonate deposition in the oceans.
The only way that thought experiment could make sense is if they had the technology to do that, but not the technology to escape Venus and get to Earth.
Think about it; several hundred million years ago, Earth was habitable; maybe not for modern humans (but I bet we could do it - though uncomfortably), but definitely life existed in some form:
https://en.wikipedia.org/wiki/Age_of_the_Earth
So there was liquid water, and the Earth wasn't a Dante-esque hellscape of volcanos and lava, etc. It was probably much warmer and more humid, but overall not crazy to live on.
So if your situation was dire enough, and you had the technology to escape the planet (which you'd almost have to, if you had the energy resources to cause your own global warming and demise scenario) - wouldn't you at least try?
So either they tried and failed in some manner (never reaching Earth), or they succeeded (meaning?) or something in between.
Even if they didn't try, with the level of technology, wouldn't they at least have left something behind in the solar system that we'd recognised as created by intelligent life long ago? Some artifact somewhere?
Maybe they did, and we haven't found it (space is big - the solar system is a big place); but I'd almost expect there'd be something orbiting Venus that was artificial (though maybe again, we can't detect it from here - too small, likely inactive, etc). I guess a good question would be, if you were on Venus (or even in Venusian orbit) - could you detect Earth's satellites currently orbiting Earth? Could you detect a singular one (last of its kind) in a degraded, virtually inert state? Again, I don't know.
It's a bit fascinating to think about; part of me wants to say "we should be able/have found something by now" if such a scenario were real - but at the same time, I can think of reasons why we haven't or can't...
If you have the technology to do that, but don't have the civilization infrastructure to support it, then escape/colonization might well cease to be a viable option. A global warming catastrophe could well precipitate a collapse of global civilization, in precisely the initially slow, sneaking way which might catch a global civilization unprepared. The Romans knew things were breaking down, but the generation which was invaded by the Vandals didn't think it was quite that time yet. Global civilization might well kick the can down the road with building their sun-shield, then get caught with its pants down, when civilization starts crumbling, and it loses the industrial know-how to pull it off.
How about a downer Sci-fi story, where the closing scene is of a Flat-Venuser enclave surviving in a subvenusian tunnel, telling half understood mythological stories of the long dead Eloi and their plot to blot out the sun?
Maybe they DID get to Earth, and are currently busy transforming our atmosphere to generate cozier conditions for themselves?
It's not as if they would still be around ... unless they live at the sea bottom; then there is no reason we would know.
"Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn."
"In his house at R'lyeh dead Cthulhu waits dreaming."
But seriously, an invasion from Venus a billion years ago would leave no evidence we could reconstruct today. After they went extinct, less than a million years later, their microbes would remain. And eventually become us.
However, the Earth wasn't so hospitable, ~1000 Ma BP. There wasn't much free oxygen then. Not until 600-800 Ma BP, I gather. So if they were oxygen breathers, they would have been living in habitats. But maybe they made the move ~600 Ma BP. That would have been ~endgame on Venus.
I don't see how any of this is testable, however. Some have argued that Octopodidae aren't originally from Earth. But it's iffy.[0] Still, who knows? Maybe they did come from Venus ;)
Inverting it, we could probably not detect any artificial satellite on Venus here from Earth. But we've had launched satellites there, that should be able to detect other ones if they have a good camera (because satellites shine).
So, the question becomes, does any of the satellites there has a good enough camera?
A little while back two NASA scientists published a paper on how you would detect the existence of a previous advanced society on Earth. Apparently, over a long time scale it's actually fairly difficult.
Not at all my area, but it doesn't seem like we can actually answer that question you posed. It's fascinating. Carl Sagan's COSMOS might be the first time I'd ever heard about Global Warming, and he explained how it was through the study of Venus that we really began to understand it.
Now imagine detecting one, when the entire planet is covered in a 90 bar atmosphere with sulphuric acid clouds.
I'll update my downer Sci-fi novel premise. Humanity makes its first Alcubierre drive warp ship. On its test run, something goes wrong, and the ship is shifted by a vast amount in time-space. The ship arrives at an unfamiliar, abandoned star system, with a different sized Sun, vast amounts of orbital construction, but an eerily similar though slightly different configuration of planets. Over time, the test pilot crew realizes that they were merely in stasis and "arrived" back in the Solar System far in the future, and that the 2nd Venus-like planet is actually the Earth.
Depends on how you define advanced. Anything in geostationary orbit is basically there for the life of the solar system.
Also it's possible earth wasn't suitable for Venisian life back then.
It isn't particularly plausible that life destroyed Venus. It's especially not particularly plausible that it just so happens that life did it to Venus using exactly what happens to be a fashionable thing to talk about here on Earth at this exact time.
It's especially not particularly plausible that it just so happens that life did it to Venus using exactly what happens to be a fashionable thing to talk about here on Earth at this exact time.
But it could make for a timely, marketable, ripping good novel!
To use myself as a counterexample, I don't see the point, and wouldn't be inclined to help.
I think these things are path dependent. There's not a particularly good, short-term, economic reason to go to Mars and build it up enough to be self-sustaining. However long term, it probably does improve our civilization's and species' (and perhaps life's) chance at survival. Unfortunately, we're not terribly good at long-term decision making.
It could very well be that there was a window when the hypothetical Venusian civilization had the capacity to leave en masse to Earth but by the time the matter had become pressing enough, it was too late.
For instance, it could be that advanced geoengineering techniques were able to hold off the effects of warming for thousands or tens of thousands of years which reduced the urgency leaving Venus, but over time the cost to maintain such systems became much too expensive and then some crisis (global war?) destroyed the geoengineering scheme, quickly heating Venus and destroying the advanced technological civilization and/or putting it into terminal decline.
Point is you have to do such things when you have the chance, not necessarily when it seems most pressing.
As Randall Monroe has said, "The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision." https://xkcd.com/893/
We went to the Moon ~50 years ago and soon stopped. It was somewhat of a historical accident that we went at all. It's not obvious that we will return in the future (even those efforts to go to the Moon or Mars face voices calling on even private efforts to be stopped). The future has not been written, and we don't know that it'll end up in the positive direction. But we, today, have the power to try.