As a common basis for the entire Baltic Sea region, the dynamic, high-resolution regional model CLM (Climate Local Model) is used, together with the A1B and B1 scenarios. Modelling for the Baltic Sea itself is carried out with the biogeochemical 3D model ERGOM (IOW).

Dissolved ammonia, nitrates, phosphates and phytoplankton (diatoms, dinoflagellates and blue-green algae (cyanobacteria)).

1960-2100

Due to the proximity to the sea and the relatively balanced and temperate coastal climate, the air temperature on the German Baltic coast will increase only moderately.

Nevertheless, by the year 2100 the ice and frost days will continue to decline, while the summer days and tropical nights will increase. The bathing season, which currently lasts about 100 days, could be extended by around 25 days by 2050 and 60 days by 2100, due to higher water temperatures. A general decline in precipitation is expected in the summer, even as far as causing water scarcity in individual sections of the coast, and an increase in the winter. On the Baltic Sea coast of Mecklenburg-Western Pomerania, a relative increase of the sea level of the Baltic of between 20 and 30cms is expected by 2100, for the foreign as the bodden coasts as well as the outer coastline. This would mean that beach areas, protective structures and the land areas they shield, particularly the Baltic Sea resorts, would be at risk, as would the safety of tourists and the resident population.

For the Hamburg metropolitan area in particular, an increased flood risk in the area of the Elbe river is expected (sea-level rise, precipitation change, wind set-ups). Already today, 140,000 workplaces are located in flood-prone areas of the city, 180,000 inhabitants live there, and goods worth some 10 billion Euros are stored there. At the same time, low-lying areas such as the HafenCity or the Elbe Island are to be newly developed.

The inevitable consequence of a rise in the sea level would be the acceleration of the average coastal erosion rate for both cliffed and alluvial coasts, even with unchanged gale patterns (currently 35 cms/year in Mecklenburg-Western Pomerania). Large break-offs will occur more frequently on the cliffed coasts, while whole sections of the flat or alluvial coasts will be subjected to an increased level of erosion. More frequent occurrences of heavy storm surges would further increase the coastal erosion rate. At the flat shores of the bodden, the drainage requirements of the polders would rise, increasing the risk of ground water salinisation. In estuaries, longer flooding durations and permanent water collections could be expected, due to a decreased gradient.

Nitrogen limitation during the summer months, which could occur more frequently as a result of the climate change, can also be accompanied by an increase in the proportion of blue-green algae and, thus, a decline in water quality. Blue-green algae can cause skin, stomach and intestinal irritation. The already advanced degradation of the Baltic Sea (depletion of fish stocks, loss of filter/buffer function of coastal areas) also has an augmentative effect. Also the higher occurrence of jellyfish is partly linked to climate change.

Due to the climatic changes, the demand for holiday destinations on the Baltic Sea coast could increase. The German Baltic Sea coast would have to come to terms with more tourists in the summer and off-season and adapt accordingly. Perhaps, however, the extension of the summer season might serve the equalization and better utilization of existing infrastructures, averaged out over the year.

Last but not least, climate change is accompanied by costs for private and public stakeholders alike. BaltCICA will therefore also investigate the costs inherent in the climate change in case studies and at a pan-Baltic level.

For the case studies in Hamburg and Mecklenburg-Western Pomerania, vulnerability assessments will be performed for the above-mentioned sectors to obtain detailed knowledge of the most vulnerable elements within the sectors and regions.

As part of the vulnerability analysis, the sensitivity of society and the natural systems will be assessed - the sectors concerned often exhibit a low resilience. The capacity and institutional readiness to deal with the climate change and its consequences are part of the vulnerability studies.

There is an urgent need for action and investigation here, as there is a risk of damage to the economy and human health.

In the course of the project, BaltCICA will develop and, in part, also implement, proposals for different adaptation measures. In the two German case studies in Hamburg and Mecklenburg-Western Pomerania, the developed adaptation strategies and measures include:

• Urban development (e.g. communication strategies, governance concepts)

• Coastal protection

• Coastal tourism

• Beach management

• Water quality

As far as the available time frame allows, these will also be tested and implemented.

Great importance will be placed on the development of adaptation measures together with stakeholders, on the one hand to develop sustainable and locally adapted solutions, and, on the other, to sharpen risk awareness and impart knowledge and skills. In this manner, governance processes and decision-making processes will be examined and recommendations made for their further development. At the same time, the formation of stakeholder networks will be supported (e.g., a pan-Baltic tourism network).

Objectives:

• Assessment of relevant climate change impacts at the regional level
• Transfer of knowledge and risk awareness
•  Further development of governance processes
•  Development and implementation of concrete adaptation measures in close cooperation with and between regions and local authorities

Depending on the nature of the two case studies (Hamburg, Mecklenburg-Western Pomerania) and each of the assessed sectors, very different conflicts can arise from climate change impacts with different anthropogenic uses, conflicts between these uses can be exacerbated, and/or stakeholder interests can be interfered with. The BaltCICA project aims at sustainable solutions.