Cloud seeding is a real thing, that the US government (and probably a few others) uses as a weapon, and does not like to talk about.

'Chemtrails' aren't real, the idea of ... basically all contrails (natural condensation trails) are laced with zany chemicals that make the frogs gay or whatever...

But cloud seeding has been a thing since Vietnam, you move moisture around at ... well small scales in terms of the global weather system, but roughly regional / area of operations scales... cause floods or landslides in one area, droughts in others.

But uh yeah... yeah, geoengineering is ... not a great plan, generally speaking.

At this point, the only thing that I can think of that might make some sense would be throwing up a stupendous amount of solar arrays at the L1 Lagrange point between the Sun and Earth.

Theoretically you could gather and store solar energy, use it as a kind of gas station in space.

And it could block out some radiance from the sun, and if you had a managed cluster sitting there, you could theoretically manage it over time.

... But this would require an utterly stupendous level of orbital engineering, that we are currently no where near.