« on: 01/07/2021 11:43:23 »
What we know is that the Carbon Dioxide levels haven't been constant over time.There must have been an awful lot of it around in the past!But not all in the air at the same time.
I'm seeing notes that the CO2 was as high as 8,000 PPM (or about 20x today's levels) 500 to 600 million years ago. But, it would have been even higher a few billion years ago before the "Great Oxidation Event".
Stalactites and stalagmites are still forming indicating we continue to get calcium deposits.