They're not making the point that "all civilizations will end because of this". The more interesting and credible point they're making is that 1,000 years of energy consumption growth rates at our speed must inevitably, even using 100% renewables, cook the planet. They're not saying "we can't beat climate change under any circumstances", they're saying (if I have understood them) that the way to do it is at least some amount of degrowth, which is quite reasonable.
You would think some alien species would figure out a way to make sure the worst individuals aren't put in charge of production and energy generation, as opposed to how us humans apparently have evolved to do.
If you take a long term view of things you could just not do the thing that cooks the planet until you figure out a technological solution for it, instead of going head first for it because that's the most profitable thing to do this quarter.
Maybe every time sapient life manages to evolve to dominate a planet, being selfish pricks like us is the only way their species was able to survive to get to that point, so they always end up destroying themselves. Would explain the Fermi paradox.
I feel this is a very anthropocentric view of things, projecting our own failings (some of which are coded in our genes) and assuming they're some kind of universal law of nature.
It's basically assuming that somehow every intelligent species would choose capitalism as their organising principle, something we've only 'decided' on 200 years ago.
There's also the possibility that a species managed to live more in harmony with nature and just never made it off the planet. The point is that nobody seems to have been able to create an interplanetary civilization in the observable universe.
It also seems to me that the circumstances implied don't seem the most likely? Like, we're working on space exploration and development right now, it's still early stages, but given another thousand years it would be strange for it to not go anywhere. It's not even like we'd need to stop building new energy using things in a few hundred years (which, given the current trends in population growth, we might I suppose), we literally just have to spread the things out rather than just piling more and more onto a single planet.
The literal scenario should be less emphasized than the subtler point that degrowth is a far more direct way to address climate change than any specific green (or greenwashed) technological advance, since consumption itself (merely using that amount of energy, regardless of its sources) is enough to destroy our habitat.
The issue there is the cause and timescale. Waste heat from energy use isn't what is causing our current climate change, it's the effect of greenhouse gas emissions on the energy absorbed from sunlight. They're related in that the greenhouse gas emissions are generally waste products too, but they're different physical problems that seem equivalent because they have same ultimate consequence, so they shouldn't be taken as having identical solutions. Not that degrowth wouldn't be a way to solve our current issues too, but it's not the only way to, and the point where it becomes such because we reach the physical limits of the planet is a long way off. In the meantime, it has a lot of downsides to consider vs the various other ways to deal with the current problem.
Okay, first thing to realize. All large power is steam power. It's just a matter of different ways to heat the water and propel the turbine inside the generator. Space is really bad at dispersing heat. To the point where the problem with space stations and ships hasn't been how to keep them warm, it's how to keep them cool. We also already know we can pump heat around with water. So I'm wondering if it's possible to off world the hottest parts of human development and then use the heat generated as a recycled energy source for the space stations we would house that infrastructure in.