Ellen Thomas, research professor of earth and environmental sciences, is the author of a paper titled "Rapid and sustained surface ocean acidification during the Paleocene-Eocene Thermal Maximum," published in Paleoceanography, May 2014. In this paper Thomas and her colleagues document that ocean acidification of the surface ocean not only occurred during past times of global warming and high CO2 levels, but also by how much — about 0.3 pH units. The group studied planktic foraminifers from a drill site in the North Pacific. Thomas' study has been highlighted in a press release from Columbia University and also on Phys.org.