If it weren't collectively bullshit, I might care whether man is contributing or not. The atmosphere is opaque to infrared, in a matter of feet. The idea that we're all going to die from heat because it blocks 7% of the infrared half an inch sooner is just absurd. The atmosphere does, and always has contained enough carbon dioxide to completely block that narrow band of infrared coming in and leaving, multiple times over.
CO2 covers the scant area between 12 and 14 microns, a small fraction of the total Infrared coming in, and blocks it entirely a few percent of the way through the atmosphere. Mankind, in it's entire existence, has created less than resides in the atmosphere, and a scant fraction of what we create has potentially been added. Nearly all of it is reabsorbed by the increased health in the flora. Warmer climates lead to more life cycle production. The ocean itself stores and releases CO2 based on temperature. With the latest climbing temperature, we saw a correlating increase in CO2, the current falling trend is equally mirrored. CO2 levels have dropped off and shown reductions the last few years.
Venus? It's not hot because of CO2. They like to reference the black ball temperature, it just doesn't make sense for it to be that hot! Perhaps if it had a bit more vigorous rotation... The actual blackball surface temperature of Venus is nearly 700K, on one side. The center of the facing side would be far hotter, an area where solid rock combusts. Venus has massive volcanic activity, much like a newly formed planet would. It didn't get there because of a greenhouse effect. It started out on fire just like this one did, the difference is it stayed that way.
The final nail in the coffin? CO2 absorbs more infrared at higher pressure. Not only does it rise when heated, taking that trapped heat to a higher level just like any other gas, it also bounces more up than it does down. Just like any other gas. We panic over our contribution to a greenhouse gas that accounts for a few percent of a few percent of a few percent, and it actually cools the earth. CO2 accounts for the only wide band of infrared that doesn't make it past the stratosphere.
It's just a bogus theory pushed by politicians looking for an excuse to tax oil companies. They've been the devil for decades now, universal scapegoat and punching bag for dirt bags in office the world round.