Recent Change—River Run-off and Ice Cover

Abstract

Climate change and its impact on our life, our en- vironment and ecosystems in general, are in these days at the forefront of public concern and polit- ical attention. The Intergovernmental Panel on Climate Change (IPCC) reports have amply doc- umented that anthropogenic climate change is an ongoing trend, which will continue into the future and may be associated with grave implications. Thus, one conclusion to be drawn is clear – the driver for this climate change should be curtailed to the extent socially responsible and sustainable. We need to strongly reduce the emissions of radia- tively active gases into the atmosphere. However, even the most optimistic emission re- duction scenarios envision only a limited success in thwarting climate change. What is possible is to limit this change, but it can no longer be avoided altogether. Even if the challenging goal of a sta- bilization of global mean temperature at an upper limit of 2˚C above pre-industrial levels at the end of this century will be met, significant pressures on societies and ecosystems for adaptation will be the result. Thus, adaptation to recent, ongoing and possible future climate change is unavoidable. The BACC initiative has dealt with these pres- sures for the region of the Baltic Sea Basin, which includes the Baltic Sea and its entire water catch- ment, covering almost 20% of the European conti- nent. BACC has collected, reviewed and summa- rized the existing knowledge about recent, ongoing and possible futures regional climate change and its impact on marine and terrestrial ecosystems in this region. The acronym BACC stands for BALTEX Assessment of Climate Change for the Baltic Sea Basin and denotes an initiative within BALTEX (Baltic Sea Experiment), which is a Regional Hydrometeorology Project within the Global Energy and Water Cycle Experiment (GEWEX) of the World Climate Research Pro- gram (WCRP). The first chapter of the book places the initia- tive in context, clarifies a few key concepts and summarizes the key results; Chapters 2 to 5 doc- ument the knowledge about recent and ongoing changes in meteorological, oceanographical, hy- drological and cryospherical variables, about sce- narios of possible future climatic conditions, about changes in terrestrial and freshwater ecosystems, and about changes in marine ecosystems. A series of appendices provide background material rele- vant in this context. Two remarkable aspects of the BACC initia- tive should be mentioned. The first is the accep- tance of this report by the Helsinki Commission (HELCOM) as a basis for its intergovernmental management of the Baltic Sea environment. Based on this BACC report, HELCOM has compiled its own conclusions “Climate Change in the Baltic Sea Area – HELCOM Thematic Assessment in 2007”. The second aspect is the fact that the BACC re- port was made possible by the voluntary effort of many individuals and institutions – without ded- icated payment from scientific agencies, govern- ments, NGOs, industries or other possibly vested interests. We think this adds significantly to the credibility of this effort, which we expect will be used as a blueprint for assessments of other regions in the world. The success of BACC has convinced BALTEX that it would be worth to redo the effort in about five years time – assuming that significantly more knowledge has been generated, and that climate change has emerged even more clearly from the “sea of noise” of natural climate variability