Come to think of it: has there ever been any independently-verified inventory of the total amount of CO2 emitted by human sources, and a demonstration that it accounts for the increase in atmospheric CO2? I've never come across any; all I've ever seen is the assumption that it "had" to have come from human activity. One AGW loon I confronted on this point merely snarled back at me. No factual backup; not even an attempt at factual backup.
Word from the wised-up: "where else could it have come from?" = "I'm not willing to do my job."
(No wonder they try that ploy. Here I am, doing part of a peer-reviewer's job for free.)
The inventory comes from fossil fuel consumption, cement making and (to a smaller extent) forest clearing data. Those give a fairly precise figure for the amount of CO2 produced each year. Next those are compared to the natural increase for each year (the caveat being that the natural increase fluctuates with the NH growing season, so year to year growth has to be used).
It turns out that manmade CO2 is about double the rise observed in the atmosphere. That means nature is absorbing 1/2 of the "extra" which also means that there is and will be no such thing as a positive feedback from CO2 to warming to more CO2. It is all negative and will probably get more negative. Water vapor is another story, but it's a story about weather and has not been shown to produce large positive feedbacks.
These climate models are FUBAR, and a scientist with any integrity would divulge this up front. What they are left with is "we have no idea what the climate will be like ten years from now" - but it is likely to be much the same as it is now - yawn! As it was 50 years ago by my limited experience.