Let me get this out of the way, I realize the past snowball earths are not universally recognized as being fact. But for the sake of the hypothetical, let’s assume they were a thing.
Anyway, if the earth headed back into an icehouse climate would we be able stave it off? And if not, what would be a good survival strategy, going underground?
It depends - places with what I guess one would consider areas of high thermal activity due to deep underground conditions like Iceland, whichever of the Canary Islands has all the volcanic crap bubbling to the surface, basically hot spring areas like Yellowstone would probably be ‘safe havens’ for a small amount of the population. We now have the luxury of solar power, so we would be able to run a limited area of population in the safe haven areas. We might be able to actually pop up some sort of lunar settlement [would the minimal amount of gravity stave off the health issues that humans get in null g stations?]
In the theoretical sense, if we could salvage around 1 million people with minimal genetic issues we could potentially rebuild the population when the place warms up again. I believe the last population chokepoint was around 100 000 people.
I believe that one could salvage ‘useful’ animals in ‘greenhouse farms’ - we would have to freeze repopulation fetus sets and maintain womb hosting stock - it had been discussed in a few SF novels, one implants the unfrozen critters and implants them into host mothers that are reasonably compatible [cattle types like musk ox, buffalo, various breeds of cow, goaty sorts, sheep goats, not sure what else works, simians - chimps, orangs, gorillas. We would end up with a much less rich variety on earth when it thawed out though. I think the population would be on restricted food types during the glaciation, how long are we discussing, anyways?
It would be the almost perfect time for me to start my factory making cloned “surimi format” crab legs, shrimp, lobster tail. I am not certain if my idea would work for clams and oysters, would potentially work for scallops. [remember the old school sea legs that were a wrapped thin layer of crabish flavored whitefish rolled and a swipe of red dye along one side? Now imagine cloning a 4 cell layer of crab, and doing the sea leg roll - one would effectively have an actual crab meat ‘leg’ portion - one glues the layers together with transglutaminase, and call it good. The issue with cloning cells now is that you can only go so many layers of cells because of the need for nutrient circulation.]
Yeah, define “we”. The vast majority of the population would be toast… er, whatever the opposite of “toast” is. But some humans would survive, and in fact the number of humans that would survive would probably be greater than the current population of any other great ape.
Or we could release massive amounts (as in 50% of previously present ) in the atmosphere in less than two centuries, that could elevate global temperature to ideal levels…
Report On The Third Planet Of Star QR23/FZ7189/240119:
The Search Committee was correct; the repeated rapid temperature oscillations of the planet had indeed been caused by a semi-intelligent species trying desperately to correct for an originally accidentally caused temperature destabilization, and repeatedly overcorrecting. Unfortunately, by the time our Exploratory Committee was able to arrive, all members of the species, as well as nearly all their relatives, were extinct. We were only able to collect a few unicellular survivors. Perhaps these could be re-seeded on a planet recently cooled to life-supporting temperatures, and allowed to evolve again under supervision.
Rod Serling didn’t think so.