One of the major themes in today’s report from the Intergovernmental Panel on Climate Change is the significance of oceans, which absorb 30 percent of the carbon dioxide we emit. This turns the water increasingly acidic, which threatens to dissolve many marine critters’ hard shells. I sat down with Monika Rhein, an oceanographer at Germany’s University of Bremen and a lead author of the IPCC report’s chapter on oceans, to talk about the state of the science on ocean acidification.