Page 1 Storminess in N Europe and E Canada Hans von Storch Institute for Coastal Research, GKSS Research Center, Germany and KlimaCampus Hamburg, Germany January IDAG Spring Meeting, Boulder, Colorado

Page 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, WASA, 1998: Changing waves and storms in the Northeast Atlantic? - Bull. Amer. Met. Soc. 79, Bärring, L. and H. von Storch, 2004: Northern European Storminess since about Geophys. Res. Letters 31, L20202, doi: /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, /s 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 /s y The BACC author team, 2008: Assessment of Climate Change in the Baltic Sea Basin, Springer Verlag Berlin - Heidelberg; ISBN , 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 submitted

Page 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.

Page 4 Example of inhomogeneities in wind records

Page 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 in recent 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.“

Page 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

Page 7 Other storm proxies 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.

Page 8 N Europe

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

Page 10 Local pressure stats since 1800 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 (N p980 ), annual number of absolute pressure differences exceeding 16 hPa/12 h (N Dp/Dt ), Intra-annual 95-percentile and 99-percentile of the pressure differences (P 95 and P 99 ) in units of hPa. From Bärring and von Storch, 2005: see also BACC Stockholm Lund

Page 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 /s y

Page 12 Geostrophic stats 21 year Gaussian filtered normalized

Page hr pressure change stats normalized

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

Page 15 E Canadian stations available more less

Page 16 Direct estimates Subarctic Arctic

Page 17 Regressing seasonal mean SLP on low pressure percentiles

Page 18 Reconstructing past low pressure percentiles Subarctic Arctic

Page 19 Conclusion 1.Monitoring extra-tropical storminess may be based on air pressure proxies. 2.This allows assessments for 100 and more years. 3.Decades long upward and downwards trends have been detected in recent years. 4.These trends are not sustained and have show recent reversals in all considered regions. 5.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. 6.In E Canada, there seems some phase reversal between the Arctic and Subarctic region. 7.In N Europe the present absence of a detectable signal is consistent with RCM simulations.

Page 20 Reserve

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

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

Page 23 Hamburg – Storm surges Inhomogeneity

Page 24 Inhomogeneity

Page 25 Regionale Entwicklung der Temperatur und Sturmtätigkeit Lund und Stockholm 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.