Vulnerabilities – The storm Gudrun

The storm Gudrun hit Scandinavia and the Baltic States on 7-9 January 2005. It was one of the worst storms in this region in the last 40 years. Detailed information on this storm is presented on the page on Estonia.

Gudrun and Energy production

In Denmark, that first experienced the effects of the storm, the struggle started towards the afternoon of January 8th. Main worry seems to have been the faith of the country’s wind energy production and whether the some 5400 wind turbines in Denmark would stand the storm (1).

As wind speed rose above 25 m/s on a broad front in whole of western Denmark, most of the circa 4000 turbines operated by the local electricity provider Eltra automatically shut down. This reduced the amount of energy produced locally to less than 1/20 of the full capacity of total 2380 MW. This power demand was filled with regulating power bought abroad – but not without difficulties, as the storm started to affect energy production on a wide area in Northern Europe (2).

The single most notable event was forced closing down of four nuclear reactors and considerable downscaling of fifth in Sweden (3). The Finnish nuclear units at Loviisa encountered problems as well. Although not really threatening events, the examples of Sweden, Finland and Denmark can be seen as signs of the problems of unilateral energy production. In a case of extreme weather event, as normal means of energy production fail, acquiring the capacity needed from abroad may be hard, as was seen in Denmark.

Gudrun and forest losses

In Denmark, the amount of felled forest of 1.5 – 2 mio m3 equals to 1.52 times the annual conifer harvest. The cost was some 300 mio DKK (almost 40 mio EUR) (4). Mainly conifers, presenting the main forest type in Denmark, were hit.

Vulnerabilities – Future storm frequency

It is not yet clear how climate change will influence the characteristics of extratropical cyclones. Climate physics tells us that a warming climate would have confounding effects on extratropical cyclones. However, while the body of evidence in this area gives a fairly clear picture that extratropical cyclones could become less frequent in both hemispheres, there could be a larger number of the most intense storms.

The most robust result is that there will be a poleward shift in the position of the storm tracks, and therefore, some regions can expect to experience a lower frequency of storms, while others a higher frequency of storms (5). In Europe, studies project an increase in storm track density (the number of storms) over Northwestern Europe, in particular, the UK and Scandinavia. There is also evidence that the intensity of storms will increase over Europe (6,7).

More hurricanes

Model simulations (based on a climate change scenario showing 1°C less global warming than the SRES A1B scenario) suggest that tropical hurricanes might become a serious threat for Western Europe in the future (8). An increase in severe storms of predominantly tropical origin reaching Western Europe is anticipated as part of 21st global warming. An eastward extension of the development region of tropical storms is projected. In the current climate, the main genesis region for hurricanes is confined to the western tropical Atlantic, where sea surface temperatures are above the threshold (27°C) required for tropical cyclones to develop. Future tropical storms that reach western European coasts (and cause hurricane-force storms) predominantly originate from the eastern part of the tropical Atlantic. This is because climate warming in the eastern tropical Atlantic causes sea surface temperatures to rise well above the 27°C threshold. In addition to an increase in the frequency of severe winds (Beaufort 11–12), a shift is projected of the season of highest occurrence from winter to autumn (8). Scientists stress that both natural variability and human influences (including climate change) play a role in determining the frequency, strength and trajectory of hurricanes on the Atlantic Ocean (10).

After their formation, tropical cyclones move in a north-westerly direction. When they reach the mid-latitudes they are caught by the predominant westerly winds, thereby veering their track in a north-easterly direction, with the possibility of reaching Western Europe. Geometrically, this likelihood increases if their genesis region in the tropical Atlantic is further to the east. In addition, the shorter travel distance in the mid-latitudes will enable the “tropical” characteristics of hurricanes to be better preserved along their journey to Western Europe. Hence, the likelihood of these storms maintaining their strength when reaching Western Europe will increase, because there is simply less time for them to dissipate (9).

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 Denmark.

1. Haanpää et al. (2007)
2. Andersen (2006), in: Haanpää et al. (2007)
3. WNA (2005), in: Haanpää et al. (2007)
4. MIM (2006), in: Haanpää et al. (2007)
5. Hallegatte et al. (2008)
6. Fenger et al. (2008)
7. Fischer-Bruns et al. (2005)
8. Haarsma et al. (2013)
9. Hart and Evans (2001), in: Haarsma et al. (2013)
10. Rosen (2017)