A decent presentation on the subject:
I don’t know why no one ever references the data, but a global experiment was recently performed to test whether or not human emission of CO2 from the use of hydrocarbon energy was the cause of the increase in atmospheric carbon dioxide concentration.
The experiment was the global massive increase in oil prices which caused the massive decrease in global oil consumption which occurred about ten years ago. There are charts you can find out there which show the global consumption of oil taking a massive downturn as the price per barrel continued to rise and rise to quite absurd levels.
Separately, there are charts you can find out there which show that the CO2 concentration in the atmosphere continued rising perfectly along the trajectory it has been for the last several decades during this same time period.
You can simply visually look at these charts and conclude that the human contribution to the CO2 increase must be negligible, given that the massive reduction in human oil consumption during that period had no distinguishable effect upon the rise in CO2 concentration. If you were a mathematician and you had the required data, it would likewise be easy to statistically establish that, given these facts, and given the numbers involved and the requisite statistical tests, the likelihood that humans are the cause of the CO2 increase is quite small indeed.
In fact, I put forward that that was what the entire global oil price sky-rocket of ten-years ago was about. I do in fact believe that it was a test conducted on purpose, utilizing directed speculation in the markets to cause this effect on global oil consumption, so that the statistical test could be performed as an actual global empirical experiment.