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Robert Walker

Yes, our best predictions are that it will become uninhabitable between half a billion and a billion years from now. Not in the same way as Mars, instead of getting too cold, it gets too hot, like Venus. The oceans boil and the atmosphere eventually is lost. Finally as the sun goes red giant, maybe even the rocks will melt and boil. And is possible it will get absorbed by the expanding sun though general idea seems to be that it will probably escape that and end up rather as a hot rocky world like Mercury circling close to the massive red giant sun.

That is unless we - or rather our successors most likely half a billion years from now find a way to move it further out in the solar system. That shouldn't be ruled out as there are ideas for ways we could do that, even with current technology, given a huge investment and a project that lasts for millions of years.

Also - as Earth becomes uninhabitable, Mars becomes more habitable. In that distant future half a billion years from now, who knows, maybe humans - or whatever we evolve into or whatever comes after us - will live on Mars then. They won't need mega engineering with greenhouse gas factories or planet sized mirrors. Instead the planet will warm up by itself. But that's so far in the future we don't know what kind of creatures the future "us" would be. As an example, they could be creatures that live only in water - then they need to go to Europa probably.

Later on even Jupiter will get warm too. And then - even Saturn's Titan, and Triton, perhaps even Pluto will eventually end up in the habitable zone according to a paper by Alan Stern.

Outer Planets Could Warm Up as Sun Dies - Universe Today

So we might "leap frog" from planet to planet outwards in our solar system as the sun warms up.

See also End Of All Life On Earth - A Billion Years From Now - Can It Be Avoided - And Who Will Be Here Then?

And David Brin's Let's Lift The Earth!

It's not going to happen in the near future though. Even if humans were to burn all the fossil fuel in all the reservoirs on Earth - it would raise the temperature by a few degrees, but it would not end up with a runaway greenhouse effect. To do that would require ten times the amount of CO2 that would be released by burning all the fossil fuel on Earth. See: Will Earth's Ocean Boil Away?  Note, water vapour and clathrate methane release is included in those calculations.

Indeed, without the global warming we've had so far, we would probably have gone into the next ice age in the not so distant future - on scale of centuries, not years, but could have happened. When I was a child, scientists were wondering about whether this would happen, and science fiction writers wrote stories about e.g. ice encroaching on London. Our greenhouse warming so far may have averted that.

Geologically the whole Earth is in an "ice age" defined as a period when the Earth has ice at its poles. Much of the time, when there is no land at or near the poles, then Earth has no ice at all except on high mountains like the Himalays.

So Earth is unusually cold at present. Far colder than it was at the time of the dinosaurs. Global warming is an issue mainly because it is happening so quickly. Humans can adapt, we can live anywhere from tropical jungles to the Arctic and Siberia, with our technology - even before the industrial revolution we could do that. But many species can't.

In the case of tropical jungles, even a degree or two increase  in temperature could lead many species to become extinct. And plants especially can only move slowly. Trees could find themselves in a habitat they are not adapted to as the  Earth warms up by a few degrees. Coral reefs could disappear as the oceans become more acidic - this has happened many times in the geological history - there are periods of acid oceans with no coral reefs, then periods like ours with coral reefs - and interestingly, each time coral reefs return, it's a different group of creatures that form them. New species that develop the same adaptation as before. So over millions of years, coral reefs would certainly return if the acid oceans make them extinct - but not the same species as before.

So the reason there is so much concern about global warming is because it is so rapid and the reason for mass extinction predictions if we let the temperature get too high is because there isn't enough time for the Earth to adapt. But there isn't any worry that Earth could become uninhabitable as a result of global warming. That's a movie trope.

There are plenty enough reasons to do something about global warming :). But we don't need to have that extra worry that we can make Earth as uninhabitable as Mars or Venus.

Oh and people sometimes worry that by cutting down trees we could make our air unbreathable. But the residence time of oxygen in our atmosphere is 3,000 to 10,000 years (not easy to find a good figure for it but that's in the right ballpark). So there is no worry about that either. And though trees and plants also contribute, most of the oxygen comes from the green algae in the sea.

Even if humans cut down all the trees and removed all the vegetation on Earth and destroyed all the green algae - of course that would be disastrous for other reasons and not going to happen surely - but we would still be able to breathe even in that extreme scenario, and on the timescale of the oxygen residence time in the atmosphere, the plants and algae would soon return, from a few seeds or remaining algae. See also my answer to If the planet earth stopped producing oxygen, for how long could life exist?

About the Author

Robert Walker

Robert Walker

Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.
Studied at Wolfson College, Oxford
Lives in Isle of Mull
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