If 700 billion tons of co2 doesn't cause global warming, how much would it take to do so?

In case you didn't know, we (sub)humans have put 700 billion tons of co2 in the atmosphere so far. I hear all the time, "There is no global warning," or, "co2 does not cause global warming?"

Hmmmmm. For every action there is an equal and opposite reaction. 7000 billion tons? 7000000 billion? .007 billion?