Regional climate change and hydrological impacts in Mediterranean river basins

1. Regional climate change and hydrological impacts in Mediterranean river basins P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)

2. Regional climate change and hydrological impacts in Mediterranean river basins • Contents: • Introduction • Present trends • Regional climate change • Water balance for selected river basins

4. Rhone Danube Po Ebro 1700km 3700km Nile

5. Precipitation climatology 1961-1990 mm/month Wet season (ONDJFM) Dry season (AMJJAS) Graphics based on CRU climatology, interpolated from station data to 0.5 degree lat/lon grid ( New, M., M. Hulme and P. Jones, 1999: Representing twentieth-century space-time climate variability. Part I: Development of a 1961-90 mean monthly terrestrial climatology. J. Climate, 12, 829-856.

6. Wet season precipitation trend (1950-1999) Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004 mm/(season · 50years)

7. Winter (DJF) precipitation trend (1951-2000) Acknowledgement: Jacobeit, J., A. Dünkeloh & E. Hertig (2005): Mediterranean rainfall changes and their causes. In: Warnsignal Klima: Genug Wasser für alle? (ed. by J. Losan et al.), Hamburg.

8. LINK to NAO Correlation between the NAO index and precipitation (left) and air-temperature (right) in the cold season (DJF), derived from CRU NAO index and the NCEP reanalysis Courtesy of E.Zorita

9. WINTER NAO (DJFM) Index (1820-2005) Downloaded from: ”Tim Osborn: North Atlantic Oscillation index data” http://www.cru.uea.ac.uk/~timo/projpages/nao_update.htm

10. Winter (DJF) Mediterranean precipitation anomalies with reference to the period 1961-1990 from 1500 to 2002 Figure from Luterbacher et al., 2005, in “Mediterranean Climate Variability”, Lionello, Malanotte-Rizzoli, Boscolo eds, published by Elsevier, Amsterdam)

11. Dry season precipitation trend (1950-1999) Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004 mm/(season · 50years)

12. Summer (JJA) precipitation trend (1951-2000) Acknowledgement: Jacobeit, J., A. Dünkeloh & E. Hertig (2005): Mediterranean rainfall changes and their causes. In: Warnsignal Klima: Genug Wasser für alle? (ed. by J. Losan et al.), Hamburg.

13. Change in Summer Precipitation CRU Observations (1976-2000) minus (1951-1975) (% change)

14. Italy: Trends in precipitation regimes D1,D2 peaks in El-Nino years: 1953,65,82/3,86/7 (Alpert et al. GRL, Vol. 29,June 2002)

15. Summary: Present trends of precipitation Large negative trend in winter precipitation, linked to the positive phase of NAO, but somehow larger than what suggested by the positive NAO trend No clear evidence of a trend in summer precipitation for the entire Mediterranean if the whole second half of the 20th century is considered… but there are suggestions of a drier summer season during the last two decades Change of statistical distribution of precipitation events: percent-wise reduction/increase of the frequency of intense/weak precipitation events in Italy

16. REA Reliability Ensemble Average precipitation changes for the 21st century (bars: A1B scenario; spread: A2 and B1 Scenarios) From Giorgi and Bi, GRL, 2005

17. NEU NEE GRL ALA NAS WNA CAS TIB ENA MED EAS SAH CNA CAM WAF EAF EQF SEA AMZ SQF NAU WS >10% CSA WS 0-10% SAU SAF DS >10% SSA DS 0-10% WS < -10% DS 0- -10% Change in precipitation interannual variability (CV, 2080-2099 minus 1960-1979, A1B-A2-B1)

18. Summary: regional analysis of global simulations for the Mediterranean region Increasingly drier conditions both in the wet and in the dry season (~20%) Increasingly irregular precipitation in both seasons(~40% in the dry season)

19. RegCM experiment design Giorgi, F., X. Bi and J.S. Pal , 2004 a and b • Global Model: Hadley Centre HadAMH • Dx = 1.25 lat x 1.875 lon • SST from HadCM3 run • Coupled sulfur model • Regional model: ICTP RegCM • Dx = 50 km • SST, GHG and sulfate from HadAMH • aerosol effects • Simulation periods • 1961-1990 : Reference run • 2071-2100 : Scenario run • Scenarios: A2, B2

20. CTR RegCM model CRU Observed climatology S E A S O N D R Y S E A S O N W E T

21. Precipitation A2-CTR Jan Apr Jul Oct Aug Feb May Nov Mar Jun Sep Dec mm

22. Mediterranean River basins Rhone Po Croatian rivers Greek rivers Ebro Turkish rivers

23. PO and Croatian rivers - Evaporation Precipitation Water balance (P-E) =

24. Ebro - Evaporation Precipitation Water balance (P-E) =

25. Greece and Turkey - Evaporation Precipitation Water balance (P-E) =

26. Summary: water balance and river basins in future climate scenario • Reduced precipitation over most of the Mediterranean, but in the North-West area in winter • Much drier summer season in the Ebro, Po and Croatian river basins • Drier autumn for Greek and Turkish rivers • Larger climate change signal for higher GHG concentration

27. The Mediterranean appears to be particularly responsive to global change We cannot ignore this problem Climate change Hot-Spots From Giorgi, GRL, 2006

28. Regional climate change and hydrological impacts in Mediterranean river basins P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy) Thanks for your attention email: piero.lionello@unile.it Special acknowledgements to: Dr. E. Xoplaki and Prof. J.Jacobeit, for the figures that they provided and to Mrs.G.Vicentini for the graphics