Do NOT miss this graph: If the Earth just hit 400ppm for CO2 for the first time in millions of years, how do we explain all these readings over 400ppm from the 1800s and later?

I think skeptics should question any claims that CO2 was stable around 280ppm at any point in the last few hundred years.

Callendar, Jaworowski and Beck, who is believable? | Tallbloke's Talkshop



CO2: The Greatest Scientific Scandal of Our Time: Dr Zbigniew Jaworowski's criticism's of the assumed reliability of IPCC graphics merging pre-industrial CO2 data from ice cores with atmospheric measurements from 20C

...glaciological studies are not able to provide a reliable reconstruction of CO2 concentrations in the ancient atmosphere.
...Formation of CO2 clathrates starts in the ice sheets at about 200 meter depth, and that of O2 and N2 at 600 to 1000 meters. This leads to depletion of CO2 in the gas trapped in the ice sheets. This is why the records of CO2 concentration in the gas inclusions from deep polar ice show the values lower than in the contemporary atmosphere, even for the epochs when the global surface temperature was higher than now.
... An ad hoc assumption, not supported by any factual evidence[3, 9], solved the problem: the average age of air was arbitrary decreed to be exactly 83 years younger than the ice in which it was trapped...The notion of low pre-industrial CO2 atmospheric level, based on such poor knowledge, became a widely accepted Holy Grail of climate warming models.
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Improper manipulation of data, and arbitrary rejection of readings that do not fit the pre-conceived idea on man-made global warming is common in many glaciological studies of greenhouse gases.