An experiment will study injecting aerosol into the stratosphere to see whether that can reduce global heating somewhat.

This is not the best way to try to do it. I would do nothing about the other big effect of CO₂: ocean acidification, which is likely to wipe out all coral and shellfish.

Another method of geoengineering that could address both problems is to strew minerals in the sea so as to stimulate growth of sea life. Giant icebergs do this to a substantial extent, but we don't need icebergs to dump minerals: ships can do it.