Geoengineering of the only planet where humans live strikes me as a really, really bad idea. Processes on that scale can’t be stopped or reversed quickly when the (inevitable) unintended consequences happen.
Try it somewhere else first.
Indeed. This is just like "green" energy and EVs. We've got a hydrocarbon-based transportation system that has gradually evolved for 163 years since the four-stroke engine was first patented by Alphonse Beau de Rochas in 1861. They want to throw it all away and build a new government-mandated system from scratch in a decade or two.
These idiots have no clue how complex systems are created and how they evolve. Worse, they have no clue whatsoever of unintended consequences. When you do R&D, lab tests, pilot scale evolution, and demonstration projects, you can identify and correct course when you identify bad results and outcomes. They want to skip over all that and jump right to the end program without even thinking about unintended consequences.
The potential unintended consequences and inability to reverse course could easily wipe out mankind.