1. IMPACT OF POSSIBLE FUTURE CLIMATE ON COASTAL WINDS, STORM SURGES AND WAVE CONDITIONS IN THE NORTH SEA Hans VON STORCH, Arnt PFIZENMAYER, Ralf WEISSE, Katja WOTH, Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany PACON, Kaoshiung, 2 December 2003 (OST-1: Climate Change)

2. Series of EU projects WASA (1995-97) STOWASUS (1998-2001) PRUDENCE (2001-2003)

3. Changing Scenarios Different emission scenarios, IS92a, SRES Different models, ECHAM, HADCM etc. Different regionalization: global T106 time slices, empirical downscaling, regional climate models; impact models (waves, storm surges) SIMILAR RESULTS

4. WASA: Mögliche Änderung der Windgeschwindigkeit der größten Stürme bei CO 2 Verdopplung STOWASUS: Ein ähnliches Szenario WASA, 1998. Institut für Küstenforschung I f K WASA results: 5 years of T106 „2 x CO 2 “ time slice experiment North Sea wind: increase of up to 0.5 m/s (10%ile)

5. Kauker and Langenberg, 2001 WASA results: 5 years of T106 „2 x CO 2 “ time slice experiment Mean water level: +10 cm Storm related sea level: + 5 cm

6. Langenberg et al., 1999 WASA results: 5 years of T106 „2 x CO 2 “ time slice experiment

7. Zukünftige Szenarien WASA: Mögliche Änderung der Höhen der größten Wellen bei CO 2 Verdopplung CDV-2075: Mögliche Änderung des Überspülens von Deichen bei CO 2 Zunahme Günther et a., 1998 Institut für Küstenforschung I f K WASA results: 5 years of T106 „2 x CO 2 “ time slice experiment North Sea waveheight: increase of up to 0.5 m (10%ile)

8. Andersen et al., 2001 STOWASUS results: 30 years of T106 „2 x CO 2 “ time slice experiment North Sea wind: increase of up to 2 m/s (0.1%ile)

9. STOWASUS results: 30 years of T106 „2 x CO 2 “ time slice experiment Flather and Wiliams, 2000 North Sea elevation: increase of up to 40 cm (estimated 50 yr return values) Kaas et al., 2001 North Sea elevation: increase of up to 20 cm (estimated 50 yr return values) RIKZ

10. STOWASUS results: 30 years of T106 „2 x CO 2 “ time slice experiment Kaas et al., 2001 North Sea waveheight: increase of up to 0.5 m (0.1%ile)

11. Mean and 99 percentile of wind speed obtained from CTL run and A2 Contour lines - mean percentiles of CTL Colour: Changes in wind speed in the scenario relative to the control run. Projections for the future / 10 m wind speed difference in percentiles (A2 - CTL) PRUDENCE results: RCM downscaling of HADCM3 A2 scenario, 2070-2100 HIRHAM RCA

12. Projections for the future / surge meteorological forcing: HIRHAM / RCA Differences in inter-annual percentiles of surge / A2 - CTL: HIRHAM Differences in inter-annual percentiles of surge / A2 - CTL: RCA Katja Woth, 2003 PRUDENCE results: RCM downscaling of HADCM3 A2 scenario, 2070-2100

13. Projections for the future : return values 50 year return value / CTL and A2 and 90 % confidence limits based on 1000 Monte Carlo simulations: HIRHAM RCA Cont. North Sea coast East coast of UK Katja Woth, 2003 PRUDENCE results: RCM downscaling of HADCM3 A2 scenario, 2070-2100

14. The scenarios indicate uniformly for the North Sea: A slight increase of higher wind percentiles of up to 0.5-2 m/s. A slight increase of storm surge levels, of up to 20-40 cm. A slight increase in significant wave height of up to 0.5 m. Conclusions