According to UCLA professor Aradhna Tripati, the lead author on that paper, "The last time carbon dioxide levels were apparently as high as they are today ...global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland."

http://www.huffingtonpost.com/diane-husic/preparing-for-cop20_b_6214020.html?utm_hp_ref=climate-change