Novel climate proxy reveals CO2 content of Earth’s atmosphere, of the past 400 million years

The study New constraints on atmospheric CO2 concentration for the Phanerozoic (DOI: 10.1002/2014GL060457), by Peter J. Franks, Dana L. Royer, David J. Beerling , Peter K. Van de Water, David J. Cantrill, Margaret M. Barbour, and Joseph A. Berry, estimates CO2 in Earth history based on a new climate proxy. Estimates are in particular based…