A 40-million-year history of atmospheric CO2 Zhang, Y. G. ; Pagani, M. ; Liu, Z. ; Bohaty, S. M. ; DeConto, R. Abstract Publication: Philosophical Transactions of the Royal Society of London Series A Pub Date: September 2013 DOI: 10.1098/rsta.2013.0096 Bibcode: 2013RSPTA.37130096Z