Ari Rabl obtained his PhD in physics at the University of California, Berkeley and worked for many years as research scientist for energy technologies at Argonne, NREL and Princeton University. He moved to the École des Mines de Paris as Senior Scientist at the Centre Energétique et Procédés until his retirement in 2007, and now continues to work as a consultant. For the last 20 years, his work has focused on environmental impacts and costs of pollution. He is one of the principal participants of the ExternE Project series (External Costs of Energy) of the European Commission DG Research, for which he has co-ordinated several research projects.