In memorium. Bob Hoover died 25 Oct 2016 at 94. In WWII he was shot down in a Spitfire and stole an FW-190 to escape. He spent decades at air shows flying Ole Yeller, shown
Please contact me about board gaming in Orange County.
I'm pretty sure that calibrating CO2 monitors was not perfected until the late Bronze Age.
Atmosphere captured in glaciers (and maybe amber?) plus plants react to CO2 concentrations, so tree rings etc. are an indication.