There have been major changes in the heat content and ice cover of the Arctic Ocean since 1990. Year after year, this observational evidence underscores the likelihood that predictions of global climatic effects will turn out to be true. Changes in the freshwater flow from the Arctic Ocean may have very significant consequences for humanity, including those alive today. It is vital that we develop the capability to predict the magnitude of such effects with far greater certainty, as well as the probability of their occurrence within a giver time frame. To do so, we need the internationally organised commitment of scientific labour and funding. This book has been written by many of the world's most knowledgable polar oceanographers, meteorologists and hydrologists, takes full account of the latest results and discusses their significance. It draws together assessments by many specialists to present an integrated view of possible future changes in the climate of the Northern hemisphere.