The warming of the global climate is expected to continue in the 21st century, although the magnitude of change depends on future anthropogenic greenhouse gas emissions and the sensitivity of climate to them. The regional characteristics and impacts of future climate change in the Baltic Sea countries have been explored since at least the 1990s. Later research has supported many findings from the early studies, but advances in understanding and improved modeling tools have made the picture gradually more comprehensive and more detailed. Nevertheless, many uncertainties still remain. In the Baltic Sea region, warming is likely to exceed its global average, particularly in winter and in the northern parts of the area. The warming will be accompanied by a general increase in winter precipitation, but in summer, precipitation may either increase or decrease, with a larger chance of drying in the southern than in the northern parts of the region. Despite the increase in winter precipitation, the amount of snow is generally expected to decrease, as a smaller fraction of the precipitation falls as snow and midwinter snowmelt episodes become more common. Changes in windiness are very uncertain, although most projections suggest a slight increase in average wind speed over the Baltic Sea. Climatic extremes are also projected to change, but some of the changes will differ from the corresponding change in mean climate. For example, the lowest winter temperatures are expected to warm even more than the winter mean temperature, and short-term summer precipitation extremes are likely to become more severe, even in the areas where the mean summer precipitation does not increase. The projected atmospheric changes will be accompanied by an increase in Baltic Sea water temperature, reduced ice cover, and, according to most studies, reduced salinity due to increased precipitation and river runoff. The seasonal cycle of runoff will be modified by changes in precipitation and earlier snowmelt. Global-scale sea level rise also will affect the Baltic Sea, but will be counteracted by glacial isostatic adjustment. According to most projections, in the northern parts of the Baltic Sea, the latter will still dominate, leading to a continued, although decelerated, decrease in relative sea level. The changes in the physical environment and climate will have a number of environmental impacts on, for example, atmospheric chemistry, freshwater and marine biogeochemistry, ecosystems, and coastal erosion. However, future environmental change in the region will be affected by several interrelated factors. Climate change is only one of them, and in many cases its effects may be exceeded by other anthropogenic changes.
Future Climate Change in the Baltic Sea Region and Environmental Impacts
Climate Change Impacts on Cities in the Baltic Sea Region
While not all projected climate change impacts are affecting especially and directly at all the cities of the Baltic Sea region (bsr), including its basin, those cities expect very different direct as well as indirect impacts of climate change. The impacts are also a matter of location, if the city with its built structures and concentration of population is located in the northern or southern part of this basin, or more inland or directly at the coast. As there are many different definitions in use trying to determine what a city is, also in the different national contexts of the bsr, here it is cities in the sense of being human-dominated densely populated areas, which are also characterized by higher concentrations of built-up areas, infrastructure, and soil-sealing as well as socioeconomic roles than rural settlements are. Those characteristics render cities also especially vulnerable to climate change impacts while there are some opportunities arising too. There are many studies on climate change impacts on the Baltic Sea itself as well as on the various ecosystems, but the studies on the observed as well as potential future impacts of climate change on cities are disperse, many are also of a national character or concentrating on a small number of cases, leaving some cities not well studied at all. This renders an all-encompassing picture on the cities within the bsr difficult and even more complicated as every city provides a mix of built-up and open structures, of socioeconomic structure and role in a region, nation-state, or even on an international level, and further characteristics. Their urban development is dependent on manifold various interdependencies as well as climatic and nonclimatic drivers, such as, to name just a few diverse examples, urban to international governance processes, or topography and location, or also different socioeconomic vulnerabilities within the Baltic Sea basin. Accordingly every urban society and structure provides specific exposure, vulnerabilities, and adaptive capacity. Generally, the cities of the bsr have to deal with the impacts of temperature rise, natural hazards, and extreme events, and, depending on location and topography, with sea-level rise. With reference to temperature rise and the increase of heat waves, it is important to consider that cities of a certain size within the Baltic Sea basin contribute to their own urban climatic conditions and provide already urban heat islands. Also, urban planning and building facilitated by local political decisions contribute to the extent of urban floods as well as their damage, as these are regulating, for example, the sealing of soils or new built-up areas in flood-prone zones.