We can wait for private enterprise to build giant mirrors in orbit or, you know, lobby for subsidies for oil, coal and gas to end and become more sustainable, thus transitioning to a society that doesn't need giant mirrors in orbit to survive.

There's already a more practical way of accomplishing what you're suggesting:

https://news.harvard.edu/gazette/story/2019/09/harvard-group...

The problem is that it a) is tackling a symptom rather than the underlying problem,

b) may encourage "business as usual",

and c) may come with undesirable side effects.

I can't wait for a world where economic sanctions are based on sunlight restriction.

Is there any science fiction around this concept?

Also, regarding your questions. It is possible to adjust the earth's temperature with that method, but aerosols seem to be cheaper. Regarding solving global warming. Kind of. There are some trade-off with sunlight reduction. See https://youtu.be/dSu5sXmsur4 for more detailed information.

I did the math on this once out of curiosity. If we launch lots of bits of thin, reflective mylar film to the L2 Lagrange point with the sun, it will reflect incoming light and lower the Earth's insolation. About $200 billion worth of Falcon Heavy launches, all carrying mylar film to L2, would be sufficient to lower insolation by 1/20th of a percent, which would indeed halt global warming.

Obviously this would have tons of other consequences for the planet, and doesn't account for solar wind pushing the mylar out of position, etc.

I briefly looked at this a while ago. The short answer is no, space mirrors (or lenses which focus light away and need less fuel to maintain position) are not a viable solution launched from earth. We'd be better off reducing emissions.

If you want to do large scale construction in space you need to get material from outside of a gravity well.