You are mixing up CO2, CFCs and O3.
And weather has never been constant. It always changes. There are too many factors involved. Like Pboily says, where scientists don't agree, or don't know exactly, is how much is mankind to blame.
And since nobody knows exactly how big is the man's part in the global weather equation, or whether the "solutions" to the global warming issue are gonna be better or worse that the problem itself, then the issue gets contaminated with politics, and the contamination corrupts scientists and politicians on both sides.