No. They didn’t guess. They measured it.so they guessed,,,From present to 1966 it was measured directly. From 1966 to 1000 AD measured from Law Dome ice cores. From 1000 AD to ~400,000 years ago measured from Vostok ice cores. Prior to that CO2 levels were determined from proxies; boron 11 isotopes and alkenoid carbon isotopes.I just wonder who made the gauge that tested that level and how it lasted 55 million yrs so we can read it now??Not sure but 55 million years ago it was about 3500 ppm.What were the CO2 levels?
lets face it its all an assumption that doesnt take into account that things didnt always happen the same way they do now,,,
the problem is they claim it to be fact
look at this account,,they claim to be able to give a day to day accounting 66 million yrs later,,,
I call bullshit
No one said it was day to day. The time resolution is like 2000 years or so.