Thanks for info. Quote from the paper.

 Levels of CO2 at around 250 parts per million (ppm) were said to be lower than often assumed with just a 20 ppm movement recorded for the following near three million-year period.

I understood CO2 levels in the atmosphere were around 6,000 ppm when the dinosaurs roamed the earth. 

From Google AI

Dinosaurs first appeared roughly 245 million years ago and roamed the Earth for approximately 165 to 180 million years before going extinct 66 million years ago. 

OK so the stable 250 ppm levels of CO2 reported in this paper only apply to the last 3 million years, during which surface temperatures changed with ice ages, indicating that temperature independent of carbon dioxide levels.  Is that the argument?