Just because you can do something, does not mean it is a good idea.
Without such intervention, the Earth has maintained temperatures within a fairly close range.
Putting a finger on that scale might well tip it in a direction far more hostile to life than its present course, and may well be irreversible within the time it would take for humans (not to mention other species) to survive that recovery. Continuing to abdicate the energy forms which might enable humans to survive, and possibly reverse overdoing such a 'cooling' remedy,virtually guarantees extinction.
Of course, some of the people advocating such 'remedies' for the effects of natural cycles think humans are a virus on the planet that should be eliminated. Others apparently just want fewer humans so they can live it up. I don't think they can keep their little lifeboats going by themselves.