I'm not sure how they argue that ice core CO2 is representative for the earth, but on the face of it I wouldn't compare Mauna Loa measurements (from near the eq

I'm not sure how they argue that ice core CO2 is representative for the earth, but on the face of it I wouldn't compare Mauna Loa measurements (from near the equator and at thousands of feet above sea level on the largest active volcano on the planet) with those directly above the Antarctic surface.