I'm more worried about taking intrusive measures (that probably have known or unknown yet disruptive side effects) to deal with symptoms instead of targeting the core problem. I don't know, like the solar shades of above or dumping iron in ocean instead of lowering extraction/burning oil/coal/gas or more or less harmless technologies of carbon capture.
It may be too late to avoid some of the incoming damage that will cause what we emitted so far, but there is always space for worsening things even more.
An asteroid like 24 Themis
https://en.wikipedia.org/wiki/24_Themis
is rich in volatiles (carbon, hydrogen, nitrogen) and also in stony minerals. You'd need to send a factory that builds a larger factory, it is a lot like building a ship inside a bottle except it's the other way around, you're in the bottle and have to build the ship outside.
What's funny about it is that you have to use the kind of chemistry that people use to capture carbon, make e-fuels, etc. on Earth. An asteroid like that has materials on it that are a lot like coal and you will have something that looks like a petrochemical plant that runs combustion processes but the carbon is too precious to vent into space so you will circularize as much as you can.
There is also a large sail yard that makes something like
https://en.wikipedia.org/wiki/IKAROS
basically large plastic films coated with layers of aluminum.
it doesn't have to be high performance compared to other solar sails, in fact a heavier and less reflective sail will sit closer to Earth near the L1 point and be more effective at blocking sunlight.
Some real headscratchers for me are: (1) Do you send people? If you don't you need to run the whole thing remotely and face a half hour latency when you're debugging problems. If you do then you have to build a habitat for the crew. (2) I think a good asteroid for this might be pretty gassy and if you start digging into it the gas will escape which is not only a precious resource but could be dangerous. You're going to have to do devolatilization at the very beginning when your stock of materials, storage tanks, and such are at the very lowest they'll ever be.
The big advantage of this is that it won't have effects on Earth other than reducing sunlight.
If I were going to write a science fiction story about this it might be a bit like Gundam in that the "Zeons" decide that sinful Earthers deserve to have their civilization fall and they send too many sunshades to L1 to drop sunlight and temperatures enough to crash agriculture. Maybe 1000 years later their descendants arrive on Earth...
(One thing about Gundam is the giant robots are more plausible than the O'Neill colonies with large airspaces... I sketched out a minimum size Bernal sphere to be a really flashy destination in LEO and it needs 15 Starship loads of ammonia to make the atmosphere. It drives me nuts that some article gets published about making oxygen on the moon for people to breathe, which isn't really useful unless you can get 4 parts of nitrogen, helium or SF6 to go with it... If you try breathing pure O2 that's a sure way to "burn out" as opposed to "fade away" https://en.wikipedia.org/wiki/Apollo_1)
video: https://www.youtube.com/watch?v=Mc_4Z1oiXhY
Transcription: https://spaswell.wordpress.com/2016/11/18/dr-gwynne-dyer-geo...
> I talked–actually, the head of the Bangladesh Institute of Strategic Studies about this (you didn’t even know that existed, did you?). Well, there is one, it’s quite serious–run by a General, bright guy. I said, “have you heard about geoengineering?” and he smiled–seraphically–and he said, “Mmm. Yes. Your question?”
> And I asked the question, “Do you think that this is something the Bangladesh government might want to do a little bit, before, let’s say, the US government or the Chinese government?”
> He said, “yes it has crossed our minds.”–and then he stopped talking.
Geoengineering will have side-effects. You can't just laser-cool the atmosphere. You have to accept trade-offs.
Imposing the side-effects of geoengineering, whether by carbonyl sulfide or metallic reflectors or something else, on unwilling countries is bound to have geopolitical ramifications. International agreements to permit geoengineering will face just as difficult of a political battle as agreements to prevent GHG emissions, if not even worse.
You have to block a lot of sunlight for a long time. The whole biosphere literally runs on sunlight. This is not easy.
Finding a technology is easy. COS, probably the crudest option, could probably stop global warming for less than a trillion dollars [1]. But the ecosystem damage could easily be extreme.
1: https://acp.copernicus.org/articles/22/5757/2022/acp-22-5757...
I would think that the arms industry would get behind that. Thus both of their political parties here in the US would vote to fund it - freedom! As long as there's profit for those companies there will be "political will."
On the other hand
https://en.wikipedia.org/wiki/Stratospheric_aerosol_injectio...
is cheap enough (a few billion a year) that it could be pursued by a single nation that is strongly affected by climate change, say India. Alternately it is something a billionaire could afford, like a James Bond villain in reverse. The main difficulty is that you'd need to develop a specialized airplane
https://iopscience.iop.org/article/10.1088/1748-9326/aae98d
but it wouldn't be particularly difficult because it would be no Concorde or SR-71.
The interesting thing about it is that it changes the politics dramatically. By taking reckless action one entity could change the discussion from making excuses for inaction to an attempt to stop the one entity that's doing something about it which could ultimately break the impasse.
This is roughly the premise of Neal Stephenson's new book Termination Shock, if anyone's looking for a (IMO pretty fun) fictional exploration of the idea.
https://www.aeronomie.be/en/news/2021/30-years-after-mt-pina...
Everything from COVID to guns demonstrates without a shard of doubt that society is happy with the "let people die as long as it doesn't impact me" option. So climate change ends in technological transformation or war.
We will end up with geoengineering if various cleantech companies fail or just develop too slowly. If the geoengineering fails, we get war.
I used to think so too, but I changed my mind. Two main reasons:
1. Our current systems are incredibly wasteful. If we just used our resources and technology efficiently we could reduce our environmental footprint drastically.
2. We can reconfigure our systems so that they work in harmony with Nature rather than against it. Ecology is a science, it's applications are technology, but it's very young and still not very influential. If we can reconfigure our systems in time we can easily support 9-12B people while improving the environment. (E.g. Gabe Brown in N. Dakota.)
Go prove you can make Venus or Mars livable before you poison the ocean or skies and unintentionally kill off all the fish or send our only planet into an ice age.