Personally, i think that CO2 race is already lost.
The only way, i imagine is extending tarpaulins in space over critical points.
By critical points, I mean, cost effective to bring down the temperature with a minimum of canvas area.
Now that Elon is going to send his clusters of bells into space, that would be a way forward.
It is possible, but would be very expensive. It has been investigated.
Much cheaper would be sulphate aerosols - but maybe this would have nasty side effects.
And, still much cheaper, freezing the arctic would be an important help.