[nomel]

But that's not realistic engineering. Every proposal for a solar shade that I've seen includes a way to remove it. Some are ephemeral, by design.

[pabs3]

I got the impression the Snowpiercer situation was chemical, but a solar shade does seem like a better option indeed.

Edit: they used atmospheric aerosol injection:

https://en.wikipedia.org/wiki/Snow_Piercer#Plot