NO CLEAR LINK BETWEEN CO2 AND WARMING IN LAST 425 MILLION YEARS SAYS STUDY

Here is the article. In a linked article other researchers document 8-16°C climate warmings in Greenland that extended to both hemispheres between about 80 and 15 thousand years ago. (Though global in scope, temperature changes were less pronounced outside Greenland.)

These abrupt warmings occurred within decades (or less), and they occurred without any CO2 fluctuation before or after the change. CO2 hovered around 190 ppm to 200 ppm throughout each warming and cooling event.