"He certainly did categorically state that and so far i've been unable to find any confirmation of that amazing figure.
I could be wrong. It just sounds insane based on the current level and no life as we know it could have existed in that brew. "
Correct, he did state that!!
"So when was the atmosphere composed of 40% CO2?"
If you hadnt turned it off you wouldnt be asking that question!
Good luck
