With all the nonsense that there is in the world why this particular nonsense? Lemme tell ya: friend of mine showed me a graph showing that we had historically low levels of CO₂. Took me a while to catch on but it didn’t have the Holocene individually marked, it was mostly concerning the epochs before mankind arrived. So the argument is totally irrelevant to the discussion of greenhouse gasses. Unless… unless you could convince yourself that there were lost civilisations that existed in distant pre-history. Of course there’s absolutely zero evidence for these… must be a cover-up.