Approximately 50 million years ago, atmospheric CO₂ levels were above 1,000 ppm, and about 500 million years ago they are believed to have been above 5,000 ppm
factualpending
Evidence Quote
“about 50 million years ago they were above 1,000 PPM if you look back to about 500 million years they're believed to have been above 5,000 PPM”
Created: 8/11/2026, 1:16:05 AM
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