Solar geoengineering is not a good idea as I explain on this site in this article:
In short, there is a role for geoengineering to play but this isn’t it simply because blocking sunlight is like the after effects of a big volcano eruption — it will reduce temperatures but also crop yields. It is an idea that has not been thought through that doesn’t attempt to solve the root cause problem of too much CO2 in the atmosphere.
Geoengineering that uses heat from earth’s crust to produce large amounts of electric power or geoengineering that encourages plankton growth to absorb carbon from the atmosphere are good ideas and should be supported.
But aerosols? No, bad idea, needs more thinking.