The real answer to climate change is stop using fossil fuels, but that involves a collective action problem. The US emits an outsize amount of CO2 per capita but it is one of a number of large emitters. If the US, China, or Europe unilaterally ended CO2 emissions it would still be insufficient. As it is, each major bloc can be delinquent in it's own way such as the US being contemptuous of climate change under Trump, Germany closing nuclear power plants, etc. There is always the excuse that other blocs are not doing their share so whoever isn't the "problem child" can do nothing and not be noticed.

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.