Aerosols aren’t gases in the classial sense and reflect sunlight. This works especially well high up in the atmosphere.

…nasa.gov/…/aerosols-small-particles-with-big-cli…

There are studies that collect data around volcano eruptions and coal power plants getting online and offline. Long story short: Climate is complicated; I’m not a climate scientist and not to be trusted; it would work great at cooling the planet; we definitely shouldn’t do it (yet?) because it masks the temperature problem and could lead to us not reducing CO2 because we “wouldn’t have to”, but it could be a tool if we might be on the edge of a catastrophic runaway effect that causes too much water to evaporate into the atmosphere.