We have the technology, but it wouldn't involve cranking up the CO2 level, that's just global warming hoaxter idiocy. We could mine frozen nitrogen and oxygen in the outer solar system, and deliver it in chunks just big enough to amount to something but not so big that we couldn't move it and steer it.
But it would take a lonnnng time, and a lot of cash..
No problem, just "tax the rich." That solves everything, right?