Pagani : CO2 level in atmosphere portends major changes . He says research on the past shows the dangers of high levels of greenhouse gases . 35 million years ago 's CO2 levels comparable to time when Mark Pagani had little ice , sea was 200 feet higher . Pagani : With more CNN , we hark back to when crocodiles and sub-tropical plants inhabited the poles .
Mark Pagani : CO2 level in atmosphere portends major changes . He says research on the past shows the dangers of high levels of greenhouse gases . Today 's CO2 levels comparable to time when Greenland had little ice , sea was 65 feet higher . Pagani : With more CO2 , we hark back to when crocodiles and sub-tropical plants inhabited the poles .