In 1900, Arvid Hgbom calculated the amount of CO2 emitted by industrial sources and, surprisingly, found that man was adding CO2 to the atmosphere at roughly the same rate as volcanoes. No one thought much of it as, at that rate, it would take centuries for the amount of CO2 to increase significantly. However, after a protracted heat wave during the 1930′s, Guy Callendar re-examined previous temperature and CO2 measurements and found not only that the Earth was getting warmer, but also that atmospheric CO2 concentrations were increasing rapidly. Callendar’s work was mostly ignored, but a few scientists began monitoring the concentration of CO2 more closely. Their results were sporadic but, by 1958, Charles Keeling had established accurate procedures for measuring atmospheric CO2. His lab was eventually moved to the Mauna Loa observatory, far away from most CO2 sources. His graph showing how CO2 varies with time, now called the Keeling curve, proved to be an important piece of evidence.I've bolded the significant portions. Same paragraph admits that volcanoes are a significant source of atmospheric CO2, then says moving a lab to an active volcano moved it away from "most CO2 sources."
Look folks, this is what we call "cognitive dissonance." I've calculated out in this blog before that anthropogenic CO2 only accounts for about a quarter of the increase in CO2 that we are currently seeing (PLEASE check my math on that one) and no one really knows where the rest is coming from. But sticking the observatory on top of an active CO2 emitter and saying it is "far away from most CO2 sources" is outright chicanery.