There isn’t that much CO2 in the atmosphere. This is obviously a WAG, but I’d suppose that the planet-scale geoengineering required to maintain plant-friendly CO2 levels in that changed solar environment would be at least as feasible as developing a sustainable, coherent interstellar civilization.

See this great article of wikipedia[1] (warning: potentially depressing). The problem is that it's not just one problem, it's a whole bundle of them happening simultaneously. It's not just that CO2 is being taken out of the atmosphere and into rocks, it's that the oceans are evaporating entirely at the same time.

Though you are quite right that this is potentially solvable for us: lagrange point sunshields to manage solar incidence would buy us a lot of extra time. But it's still hundreds of millions of years - not billions.

500 million years from now, we're fighting a losing battle against the sun's death.

[1] https://en.wikipedia.org/wiki/Timeline_of_the_far_future

I'm not so sure that estimate makes sense. It's kind of hand wavy. The sun's output will increase 1 percent every 100 million years. So even at 108% of what it is today in 800m years that doesn't seem like it's enough to lock all the CO2 in the rocks. But let's say for the sake of argument that CO2 does start being sequestered.... well it's a greenhouse gas so as it is removed from the atmosphere... the atmosphere should actually cool down. Plus Earth has self cooling mechanisms that work against an increase in solar radiation. For example Volcanic eruptions and your basic water cycle. More energy would create more moisture in the atmosphere and in turn more cloud cover blocking out the sun. If the amount of CO2 in the atmosphere was way less even at 108% of the sun's output the atmosphere could remain cold so I think a new equilibrium will develop and be sustained for quite some time.

sorry, but in a millennium or two we will possess the technology to travel at an appreciable percentage of the speed of light

in the next million years (let alone hundreds) humans will have populated most of the galaxy

that is, if we survive climate change

There is an absolute certainty that climate change will not make human race extinct. If we die out, it'll be because of some other disaster.

The largest risk to humans of climate change is the stress it will put on civilizations and the potential for war from that. If that stress triggered an all out nuclear war, it could make humans extinct.

It seems likely we will remove most or more likely all the vertebrates. There won't be significant long term damage beyond that (e.g. the coral will suffer but will grow back probably in less than a My) and the planet will do just fine.

> or more likely all the vertebrates

Don't worry, it won't be all. Cats will be doing just fine.

Right.

Personally, barring nuclear or bio warfare, I'm quite confident we can figure out how to geoengineer the Earth AND settle into Mars within 500 million years, considering we've come from cavemen to today's technology in only 10000-50000 years.

What worries me is actually after about 3 or 4 billion, where no level of geoengineering can make any of the inner planets of the solar system habitable, and with the red giant sun spewing out chunks of burning crap all over, Jupiter's and Saturn's moons aren't particularly safe either.

Space megastructures are probably easier and faster to build than terraforming Mars. With the added benefit of not jumping into another gravity well.

Hmm how do you repair those megastructures without a planet that you can mine resources (metal, silicon, ...) from?

Asteroids.

If you are still sitting in just the Solar System in a milion years, let alone thousand, something went horribly wrong. Or we got some interesting neighbors. ;-)

> cavemen to today's technology in only 10000-50000 years.

Honestly more impressive is us shedding the 4 element theory of nature and the infallible ancient knowledge of Greece in the mid 1600’s (The Sceptical Chymist was published in 1661). We went from a fairly static view of knowledge to seriously considering colonizing mars in 400 or so years. Human growth isn’t linear and we are pretty far to the right on an exponential curve. The thing about sitting on an exponential curve as far to the right as we are is a few steps (a few 100 years) can easily eclipse the total sum of all human progress so far.

Eventually the oceans will boil, but wikipedia links to paper evaluating the atmosphere in “1 Gyr and 2.8 Gyr from present” or 1 to 2.8 billion years not 500. It’s suggesting that life should stick around on earth for ~2.8 billion years though the total number of living cells will noticeably start to decline at 1 billion years. https://arxiv.org/abs/1310.4841

In general it would take a very large change in the suns output to make a noticeable difference on earth. There are critical secondary effects and feedback loops etc, but black body radiation is T^4 so you take the square root of the square root of the increase in output. A 5% increase in output should be something like a 1.2% increase in temperature kelvin.

It's not that it happens at 500 million years, it's that it starts happening - i.e. it's not that the ocean's boil, it's that the rate of evaporation increases, which exposes more rock, which increases weathering etc.

It's a pile of problems related to a common cause (increase solar radiance) that steadily is on a single definite trend.

Put it another way: at 288 Kelvin the partial pressure of water vapor is ~1.7 kPa. At 294K it's ~2.5 kPa. That's a 47% increase (naively). And that line trends upwards only.

What matters is what happens to the water in the atmosphere not the oceans surface. Evaporation requires energy, it cools the surface of the oceans and needs to be driven by sunlight heating that surface, rain is the reverse it heats clouds which then radiate that energy to space.

To boil the oceans you would need the upper atmosphere to retain that moisture or you just get more weather not net evaporation. 1 inch of rainfall represents a shocking amount of energy flow.

We have emitted more than the original amount of CO2 in a bit more than a century. Since it would take tens or hundreds of thousands of years for it to be all absorbed by the ground, yes, I think whoever is here in 1.4G years will do just fine.

Of course, there are other disasters to come after that one.

1.4 Gy is enough time to make more fossil fuel, as it is a renewable resource on that time scale.