Global sea level rise

Observations

For the latest results: see Europe Coastal floods

Projections

For the latest results: see Europe Coastal floods

Extreme water levels - Global trends

More recent studies provide additional evidence that trends in extreme coastal high water across the globe reflect the increases in mean sea level (7), suggesting that mean sea level rise rather than changes in storminess are largely contributing to this increase (although data are sparse in many regions and this lowers the confidence in this assessment). It is therefore considered likely that sea level rise has led to a change in extreme coastal high water levels. It is likely that there has been an anthropogenic influence on increasing extreme coastal high water levels via mean sea level contributions. While changes in storminess may contribute to changes in sea level extremes, the limited geographical coverage of studies to date and the uncertainties associated with storminess changes overall mean that a general assessment of the effects of storminess changes on storm surge is not possible at this time.

On the basis of studies of observed trends in extreme coastal high water levels it is very likely that mean sea level rise will contribute to upward trends in the future.

Extreme waves - Future trends along the western European coast

Recent regional studies provide evidence for positive projected future trends in significant wave height and extreme waves along the western European coast (8). However, considerable variation in projections can arise from the different climate models and scenarios used to force wave models, which lowers the confidence in the projections (9).

Sea level rise in Sweden in the future

The global rise in sea level of 88 cm gives a rise in average water level of about 80 cm in southern Sweden (up to Östergötland) at the end of the century, 50 cm in the central region (up to Uppland) and 20 cm in the northern region, taking into account subsidence. In northern Sweden, land elevation and any rise in sea levels essentially counter each other.

Vulnerabilities

Land uplift is taking place in most of Sweden as a result of the melting of the massive land ice of the last ice age, but in the southernmost part of the country uplift has come to a halt. The ongoing rise in sea level is therefore leading to substantial coastal erosion along Sweden’s southern coast where the land consists of easily eroded soils. Climate change as a consequence of future increased atmospheric temperature will strengthen this erosion (1). The stretches of coast at greatest risk are in Skåne and Blekinge and on the islands of Öland and Gotland (2).

Waterside housing has become increasingly sought-after. An increasingly large proportion of construction is taking place in the coastal zone (5 km from the coast), in southern Sweden almost half. Just over 30 per cent of buildings in the country are located in the coastal zone. The proportion of buildings constructed within 100 m of the shoreline more than doubled between the 1970s and the end of the 1990s, according to a report from the National Board of Housing, Building and Planning. This shoreline building development occupies around 30 per cent of the total coastline of Sweden (2).

According to the Swedish Commission on Climate and Vulnerability (2) the compensation system for preventative measures in the event of natural disasters should also include beach erosion. Erosion has thus far been interpreted as a natural disaster with a slow course of events, even though it can eventually lead to rapid events with major losses of land or development. Climate change with rising sea levels, higher winds and possibly changed currents can lead to the risk of threatened values increasing.

According to calculations of the Swedish Commission on Climate and Vulnerability (2), around 150,000 buildings are located in an area susceptible to erosion in the case of a rise in sea level of 88 cm.The value of these properties amounts to approximately SEK 220 billion.

A rough estimate of the cost of protecting against beach erosion (protection and beach nourishment) along these 220 km is SEK 2.7–5.4 billion. In addition to this, the annual maintenance cost amounts to SEK 3,000–4,000 per metre of coast (3).

In Ystad, around 20 percent of the buildings that are below the 5-metre curve will end up under the hundred-year water level in the event of a global rise in sea level of 88 cm. For Sundsvall, the corresponding figure is 6 percent. If we assume that the proportion of the floor space below the 5-metre curve that is threatened with flooding is 20 percent in Skåne and Blekinge, 10 percent in the rest of Götaland and Svealand, and 5 percent in Norrland, the restoration costs will amount to approximately SEK 25 billion for the whole country (2).

Economic impacts of sea level rise for Europe

The direct and indirect costs of sea level rise for Europe have been modelled for a range of sea level rise scenarios for the 2020s and 2080s (10). The results show:

1. First, sea-level rise has negative economic effects but these effects are not particularly dramatic. In absolute terms, optimal coastal defence can be extremely costly. However, on an annual basis, and compared to national GDP, these costs are quite small. On a relative basis, the highest value is represented by the 0.2% of GDP in Estonia in 2085.
2. Second, the impact of sea-level rise is not confined to the coastal zone and sea-level rise indeed affects landlocked countries as well. Because of international trade, countries that have relatively small direct impacts of sea-level rise, and even landlocked countries such as Austria, gain in competitiveness.
3. Third, adaptation is crucial to keep the negative impacts of sea-level rise at an acceptable level. This may well imply that some European countries will need to adopt a coastal zone management policy that is more integrated and more forward looking than is currently the case.

Adaptation strategies – Spatial planning

As in the other Scandinavian countries, coastal protection policy in Sweden is mainly focused on spatial planning. The Nature Conservation Act of 1974 states that the first 100 - 300 m of the coast needs to be free of exploitation. Spatial plans of the different municipalities need to comply with this Act. In addition, new development projects must incorporate a certain safety margin to protect against future erosion or higher water levels. Areas of the coastal zones without private or public interests should not be protected but given back to the sea (managed retreat) (19).

The Swedish Commission on Climate and Vulnerability (2) states that the planning basis and basis of knowledge underlying the municipalities’ comprehensive land-use and detailed development planning are often too deficient and inaccessible for the municipalities to be able to take account of the risks of natural disasters in the present-day climate, as well as in a future climate. The municipal planners and technical administrations state that they are unsure about what levels to plan for.

Difficulty is also seen in arguing against wishes for attractive waterside construction, even though the risks of flooding are known about in the municipalities. The municipalities today have to plan not just for the present-day climate but also take account of the increased risks and uncertainties a future changed climate will entail (2).

There is a need to give clear conditions in the detailed development plan concerning protection and safety measures to ensure the suitability of land. Measures may also be required on property other than that which is under consideration for construction, to ensure that the land is suitable for its purpose, for example geotechnical reinforcement measures and flood defences (2).

Adaptation strategies - The costs of adaptation

Both the risk of sea-level rise and the costs of adaptation to sea-level rise in the European Union have been estimated for 2100 compared with 2000 (11). Model calculations have been made based on the IPCC SRES A2 and B1 scenarios. In these projections both flooding due to sea-level rise near the coast and the backwater effect of sea level rise on the rivers have been included. Salinity intrusion into coastal aquifers has not been included, only salt water intrusion into the rivers. Changes in storm frequency and intensity have not been considered; the present storm surge characteristics are simply displaced upwards with the rising sea level following 20th century observations. The assessment is based on national estimates of GDP.

The projections show that without adaptation (no further raising of the dikes and no beach nourishments), the number of people affected annually by coastal flooding would be 20 (B1 scenario) to 70 (A2 scenario) times higher in 2100 than in 2000. This is about 0.05 - 0.13% of the population of the 27 EU countries in 2010 (11).

Without adaptation, damage costs would increase roughly by a factor of 5 during the century under both scenarios, up to US$ 17×109 in 2100. Total damage costs would amount to roughly 0.04% of GDP of the 27 EU countries in 2100 under both scenarios. Damage costs relative to national GDP would be highest in the Netherlands (0.3% in 2100 under A2). For all other countries relative damage costs do not exceed 0.1% of GDP under both scenarios (11).

Adaptation (raising dikes and beach nourishments in response to sea level rise) would strongly reduce the number of people flooded by factors of 110 to 288 and total damage costs by factors of 7 to 9. In 2100 adaptation costs are projected to be US$ 3.5×109 under A2 and 2.6×109 under B1. Relative to GDP, annual adaptation costs constitute 0.005 % of GDP under B1 and 0.009% under A2 in 2100. Adaptation costs relative to GDP are highest for Estonia (0.16% under A2) and Ireland (0.05% under A2). These results suggest that adaptation measures to sea-level rise are beneficial and affordable, and will be widely applied throughout the European Union (11).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Sweden.

1. Ministry of the Environment of Sweden (2009)
2. Swedish Commission on Climate and Vulnerability (2007)
3. Rydell (2007), in: Swedish Commission on Climate and Vulnerability (2007)
4. Bindoff et al. (2007), in: IPCC (2012)
5. Church and White (2011), in: IPCC (2012)
6. Velicogna (2009); Rignot et al. (2011); Sørensen et al. (2011), all in: IPCC (2012)
7. Marcos et al. (2009); Haigh et al. (2010); Menendez and Woodworth (2010), all in: IPCC (2012)
8. Debernard and Roed (2008); Grabemann and Weisse (2008), both in: IPCC (2012)
9. IPCC (2012)
10. Bosello et al. (2012)
11. Hinkel et al. (2010)
12. Cazenave et al. (2014)
13. IPCC (2014)
14. Watson et al. (2015)
15. Yi et al. (2015)
16. Church et al. (2013), in: Watson et al. (2015)
17. Shepherd et al. (2012), in: Watson et al. (2015)
18. Church et al. (2013), in: Watson et al. (2015)
19. Dronkers and Stojanovic (2016)