When the European Union decided to launch a comprehensive emissions trading scheme in 2005, observers commonly described it as a “grand policy experiment”. Three years later, we can look back on the first trading period (2005-2007) and safely affirm that this emissions trading scheme is far from being a mere experiment: instead, it has become an economic and political reality, as is evidenced by the multi-billion dollar carbon market it helped conceive. But how will this trading scheme evolve as we move into an uncertain future for the climate regime, and what lessons can we draw from its first phase of implementation? These are the questions that participants addressed during the 3rd international Summer Academy “Energy and the Environment”, and their conclusions are summarised in this timely volume. Authored by government officials, academics, legal advisers and policy analysts, this volume provides unique insights into the past, present and future of the European emissions trading scheme.