MEDSEA (Mediterranean Sea Acidification in a changing climate) is a Framework Program 7 (FP7) project that addresses ecologic and economic impacts from the combined influences of anthropogenic acidification and warming, while accounting for the unique characteristics of this key region. MedSeA forecasts chemical, climatic, ecological-biological, and socio-economical changes of the Mediterranean driven by increases in CO2 and other greenhouse gases, while focusing on the combined impacts of acidification and warmingon marine shell and skeletal building, productivity, and food webs. We use an interdisciplinary approach involving biologists, earth scientists, and economists, through observations, experiments, and modelling.