So I went down the rabbit hole on wiki’s Timeline of the Far Future
Hey, it’s fun.
OK, then.
So look at 800 million years from now.
So I’m thinking…what prevents life from adapting, over those many millions of years, to those conditions and multicellular life from continuing to exist under the new conditions? Is there something inherently counter to life in these changes that wouldn’t allow for the evolution of macrocellular organisms to take advantage?
Difficult to say, without knowing what’s causing this purported drop in carbon dioxide levels. It seems a chicken-and-egg problem to me, since the only way I can see such a precipitous drop is for the consumers to already be vastly diminished.
I think the sink turns out to be carbonate rocks that never get recycled because plate tectonics slows down.
IIRC the problem is the opposite…
Way back in past eons, there was the episode of “snowball earth” where glaciation covered most of the earth, and life recovered afterwards only because of growing levels of CO2 in the atmosphere cause greenhouse effect and frozen life forms (including photosynthesis life) restarted the whole cycle. CO2 was a result of volcanic activity.
I am guessing (not a geologist) that volcanic activity - brought on by plate tectonics - would burn/melt carbonate rocks (subducted?) and liberate the CO2?
800 million years from now seems pretty soon in the life of a 3.5billion year old planet.
An autotroph that can make food out of carbonate rocks would need to evolve. Without plants, UV would be the least of our worries.
Thanks for this link. I never knew about it.
I wonder if the people who came up with that fact about carbon dioxide levels falling so much allowed for the fact that some of the CO[sub]2[/sub] we’re emitting today (and will be for the forseeable future) is released from carbonate rocks. It’s not all from fossil fuels.
The manufacture of lime is done by heating up limestone (calcium carbonate CO[sub]3[/sub]) so much that it breaks down into lime (calcium oxide, CO) and carbon dioxide. Not all of it stays in the atmosphere, though. Concrete, of which lime is a major ingredient, reabsorbs some CO[sub]2[/sub] as it cures. But only the surface layers do that, so there’s some net carbon dioxide released. And there will be even if we completely stop using coal, oil, and natural gas.
Oops. That chemical formula should be CaO.
If there are still intelligent inhabitants of the Earth 800 million years from now, they might be able to replace the missing CO2 with carbon liberated from carbonate rocks.
But, failing that, unless some non-intelligent lifeform develops this skill at some point over the next half-a-gigayear or so, there won’t be enough CO2 in the atmosphere to support photosynthesis and all plant life will cease.
But isn’t that exactly my point? There will be tremendous evolutionary pressure that will reward a life form that CAN take advantage of what carbon - and what form of carbon - is available.
Sometime between half a billion and a billion years, the Sun is going to get hot enough that the Earth’s seas will boil. If nothing is done about that (for example, moving the Earth away from the Sun), this loss of carbon dioxide will be irrelevant. But unless there’s some war or other severe ecological catastrophe that wipes out 99% of all life on Earth, I expect there’ll be some intelligent life here indefinitely. And yes I expect somewhere along the way, some civilization will do the move-away-from-the-Sun thing.
Note it doesn’t really take a very advanced tech to release CO[sub]2[/sub] from rocks. Somewhere I read that they used lime at Çatalhöyük, which was 8 or 9,000 years ago. That could be wrong, but lime production was one of the first industrial processes.
Such evolutionary pressure is no guarantee it’ll take place. Breaking down carbonate rocks biologically to get its carbon will probably take a whole new suite of enzymes and other specific chemicals not currently in any life form. There’s probably no evolutionary path that life can take to get there. One could probably be gengineered, but that would require better gene tech than we currently have.
In 800 million years I’d be willing to bet we might have developed the necessary technology. Heck, we might actually be only a couple of decades away from that level.
While we may be able to do it some time soon, it would not be a good idea. The reason is that as long as intelligent life is around on Earth, one of the things they’re going to have to do is manage the composition of the atmosphere. We’re already trying to do that, although with limited success so far. And as I pointed out, one of the basic industrial processes already releases carbon dioxide from carbonate rocks and it’s not an easy process to avoid. So future civilizations are going to have to manage the CO[sub]2[/sub] content of the atmosphere to keep it around 300 ppm, even if they don’t use any fossil fuels. So I think you’re trying to solve a problem that doesn’t exist and will probably never exist.
I agree that it would not be a good idea at the present time.
I’m just suggesting that if reclaiming CO2 from rocks becomes desirable at some in the far distant future, humans, or whatever intelligent, technologically proficient species inhabits Earth at that point in time, will likely be capable of doing so
This hypothetical far-future civilisation could probably cool the Earth by using a Lagrange sunshade, as suggested by James Early.
Hopefully, by that time we would have already tried the technology out around Venus. And around an arbitrary number of similar extrasolar planets. But sometimes my hopes and dreams are too ambitious, or perhaps too conservative (800 million years from now, our mind-children may not need to live on Earth-like planets at all).
Another possibility is that we could develop industrial-level artificial photosynthesis, extracting carbon from the atmosphere to use as a resource. We could be manufacturing organic materials such as plastic and fuel, and using carbon allotropes as hyperstrong building materials. If we manage to do this too efficiently (which I expect one day we will) then we may need to burn lime deliberately to maintain a usable level of CO[sub]2[/sub] in the atmosphere.
Atmospheric management is likely to be a very important activity in the long-term, but not necessarily just as a way of controlling global warming.