Origin = see the first paragraph of the following:
To wit, the "zero" point. It is not shown in the graph I commented on, hence it is suppressed. As my further comment pointed out. Which leads to a distortion of the perceived significance of the slope of the curve. Learn some basics before trying to piss on my leg.
The zero point of CO2 in the atmosphere would have been sometime during the planet’s formation. You really won’t accept a graph unless it goes back 4.5 billion years?