Storminess in N Europe and E Canada

1. Storminess in N Europe and E Canada Hans von StorchInstitute for Coastal Research, GKSS Research Center, Germany and KlimaCampus Hamburg, Germany 28-30 January 2008 - IDAG Spring Meeting, Boulder, Colorado

2. N Europe storminess Relevant publications Schmidt, H. and H. von Storch, 1993: German Bight storms analyzed. - Nature 365, 791 Alexandersson, H., T. Schmith, K. Iden and H. Tuomenvirta, 1998: Long-term trend variations of the storm climate over NW Europe. The Global Atmos. Oc. System 6, 97-120 WASA, 1998: Changing waves and storms in the Northeast Atlantic? - Bull. Amer. Met. Soc. 79, 741-760 Bärring, L. and H. von Storch, 2004: Northern European Storminess since about 1800. Geophys. Res. Letters 31, L20202, doi:10.1029/2004GL020441, 1-4 Rockel, B., and K. Woth, 2007: Future changes in near surface wind extremes over Europe from an ensemble of RCM simulations. Climate Change, 10.1007/s10584-006-9227-y Matulla, C., W. Schöner, H. Alexandersson, H. von Storch, and X.L. Wang, 2007: European Storminess: Late 19th Century to Present, Climate Dynamics DOI 10.1007/s00382-007-0333-y The BACC author team, 2008: Assessment of Climate Change in the Baltic Sea Basin, Springer Verlag Berlin - Heidelberg; ISBN 978-3-540-72785, 473 pp von Storch, H., and R. Weisse, 2008: Regional storm climate and related marine hazards in the Northeast Atlantic, In Diaz, H.F. and Murnane, R.J. (eds.), Climate Extremes and Society, Cambridge: Cambridge University Press (in press) Matulla, C., and H. von Storch, 2008: Changes in Eastern Canadian Storminess since 1880. submitted

3. Challenge • Storminess best represented by wind statistics, possibly derived quantities such as stream function, vorticity, but wind time series are almost always • inhomogeneous • too short • No robust link to level temperature, but to pattern of seasonally mean air pressure.

4. Example of inhomogeneities in wind records

5. Damages and storms • May 2006 meeting of scientists and re-insurances (Munich Re) • Consensus statement:„1. Climate change is real, and has a significant human component related to greenhouse gases.2. Direct economic losses of global disasters have increased inrecent decades with particularly large increases since the 1980s.8. Analyses of long-term records of disaster losses indicate that societal change and economic development are the principal factors responsible for the documented increasing losses to date.9. The vulnerability of communities to natural disasters is determined by their economic development and other social characteristics.10. There is evidence that changing patterns of extreme events are drivers for recent increases in global losses.13. In the near future the quantitative link (attribution) of trends in storm and flood losses to climate changes related to GHG emissions is unlikely to be answered unequivocally.“

6. Pressure based proxies Air pressure readings are usually homogenous Annual/seasonal percentiles of geostrophic wind derived from triangles of pressure readings (e.g., 95 or 99%iles); such percentiles of geostrophic wind and of “real” wind are linearly related. Annual frequency of events with geostrophic wind equal or larger than 25 m/s Annual frequency of 24 hourly local pressure change of 16 hPa in a year Annual frequency of pressure readings less than 980 hPa in a year

7. Variance of local water levels relative to annual mean (high tide) water level. Repair costs of dikes in historical times. Sailing times of ships on historical routes. Other storm proxies

8. N Europe

9. Geostropic wind stats N Europe 99%iles of annual geostrophic wind speeds for a series of station triangles in the North Sea regions and in the Baltic Sea region. Relevant publications Alexandersson et al., 2002

10. Local pressure stats since 1800 Stockholm Lund Relevant publications Time series of pressure-based storminess indices derived from pressure readings in Lund (blue) and Stockholm (red). From top to bottom: Annual number of pressure observations below 980 hPa (Np980), annual number of absolute pressure differences exceeding 16 hPa/12 h (NDp/Dt), Intra-annual 95-percentile and 99-percentile of the pressure differences (P95 and P99) in units of hPa. From Bärring and von Storch, 2005: see also BACC 2008.

11. N + C Europe Matulla, C., W. Schöner, H. Alexandersson, H. von Storch, and X.L. Wang, 2007: European Storminess: Late 19th Century to Present, Climate Dynamics DOI 10.1007/s00382-007-0333-y

12. Geostrophic stats normalized 21 year Gaussian filtered

13. 24 hr pressure change stats normalized

14. E Canada + Grønland Matulla, C., and H. von Storch, 2008: Changes in Eastern Canadian Storminess since 1880. submitted

15. E Canadian stations available more less

16. Direct estimates Subarctic Arctic

17. Regressing seasonal mean SLP on low pressure percentiles

18. Reconstructing pastlow pressure percentiles Arctic Subarctic

19. Monitoring extra-tropical storminess may be based on air pressure proxies. This allows assessments for 100 and more years. Decades long upward and downwards trends have been detected in recent years. These trends are not sustained and have show recent reversals in all considered regions. Recent trends are not beyond the range of natural variations, as given by the historical past, but are more of intermittent character. Regional temperatures rose significantly at the same time. In E Canada, there seems some phase reversal between the Arctic and Subarctic region. In N Europe the present absence of a detectable signal is consistent with RCM simulations. Conclusion

20. Reserve

21. Stormcount 1958-2001 Relevant publications t ≤ T t ≥ T Weisse et al., J. Climate, 2005 Change of # Bft 8/year

22. Warming and Storms in the N Atlantic (11-yr running means) Fischer-Bruns et al., 2005 NH Temp & NA storm count: No obvious correlation in simulated historical times

23. Hamburg – Storm surges Inhomogeneity

24. Inhomogeneity

25. Regionale Entwicklung der Temperatur und Sturmtätigkeit 11) Temperaturen in Norddeutschland sind in den letzten Jahrzehnten gestiegen. Sturmtätigkeit hat von Jahrzehnt zu Jahrzehnt geschwankt, aber auf längere Sicht fast unverändert seit 1800. Lund und Stockholm