Preface -- 1 International agreements and Baltic Sea environmental management -- 2 HELCOM Baltic Sea Action Plan: An ecosystem approach to the management of human activities -- 3 Some aspects of the Baltic Sea marine system -- 4 A basic introduction to climate modeling and its uncertainties -- 5 Impacts of climate change, including acidification, on marine ecosystems and fisheries -- 6 Towards Integrated Ecosystem Assessments (IEAs) of the Baltic Sea - Investigating ecosystem state and historical development -- 7 Sustainable climate science. The Baltic Sea area is an old cultural landscape with a well developed international framework for monitoring, assessing and managing its marine ecosystems. It provides a good case study for other regions where such management is being set up. The chapters in this book are based on lectures given at a summer school on the Baltic Sea island of Bornholm in the summer of 2009. They cover a range of topics, spanning from detailed descriptions of political agreements that protect the marine environment, to basic modelling instructions, to an assessment of the possible impacts of climate change on the marine ecosystem, to a reflection on the role of climate scientists and their responsibility in society. This interdisciplinary book is primarily directed at students and lecturers of the environmental disciplines to provide an overview of the possible impacts of climate change on the Baltic Sea. It is also intended to serve as a background reference for scientists and policy makers, both for the Baltic Sea area and more generally. The book is a contribution to the BALTEX programme and to the BONUS+ projects ECOSUPPORT and Baltic-C.