the role of increasing temperature variability in european summer heat waves n.
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The role of increasing temperature variability in European summer heat waves

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  1. The role of increasing temperature variability in European summer heat waves Christoph Schär, Pier Luigi Vidale, Daniel Lüthi, Christoph Frei, Christian Häberli, Mark A. Liniger& Christof Appenzeller

  2. Overview • Luterbach et al: European temperature trends and extremes since 1500 • Summer 2003 data • Schär et al: Increasing temperature variability in European heatwaves Literaturseminar 30. April, 2004

  3. Luterbacher et al: European mean temperature since 1500 Winter • warmest winter: 1989/90 T = +2.4°C • warmest decade: 1989-98 T = +1.2°C • (second warmest 1733-42 T = +0.45°C) • linerar temperature trend for 20th century: • +0.08°C  0.07°C per dec. Literaturseminar 30. April, 2004

  4. Luterbacher et al: European mean temperature since 1500 Summer • warmest summer: 2003 T = +2.0°C • warmest decade: 1994-03 T  +1.2°C • conspicuous: warming trends of up to 0.7°C  0.20°C per decade can be observed 1731-57, 1923-47, and 1994-2003 Literaturseminar 30. April, 2004

  5. Luterbach et al: European mean temperature since 1500 Literaturseminar 30. April, 2004

  6. Summer 2003 Data • Warmest summer in the last 500 years in Europe (June, July, August) • Sub tropic high pressure belt shifted north over southwestern Europe  Warm air masses pushed north • Unusually small amounts of precipitation during spring and summer months Literaturseminar 30. April, 2004

  7. Temperature anomalysummer 2003 Literaturseminar 30. April, 2004

  8. Deviation from the avg temp (1876-2000) in Karlsruhe Literaturseminar 30. April, 2004

  9. Satellite views Satellitenbild, 8.8.2003, 12:09 UTC, NOAA 16, VISQuelle: Inst. f. Meteorologie, FU Berlin Satellitenbild, 8.8.2003, 18:00 UTC, MET 7, IR Quelle: Fak. f. Ingenieurwissenschaften, Univ. Ulm Literaturseminar 30. April, 2004

  10. Summary: 2003 data Literaturseminar 30. April, 2004

  11. Summary: 2003 data Comparison to 1876-2000 avg Literaturseminar 30. April, 2004

  12. Schär et al: European temperature anomaly Literaturseminar 30. April, 2004

  13. Distribution of Swiss monthly temperatures 1864-2003 Literaturseminar 30. April, 2004

  14. Monthly Temp anomalies (J-D) 1864-1923 & 1941-2000 Literaturseminar 30. April, 2004

  15. Relative frequency change between the two periods Literaturseminar 30. April, 2004

  16. Estimation of return period • Reference period = 1864-2000  return period  several million years • Accounting for warming: Reference period = 1990-2002  return period = 46000 yr. However: large uncertainty 90% confidence interval:  = 9000 yr. Literaturseminar 30. April, 2004

  17. Modeling • Regional climate model driven by two general circulation models at the lateral boundaries.  Fairly high resolution • Model control period (CRTL) 1961-90 shows good agreement with measured data for northern Switzerland: T(CRTL) = 16.1°C , SD = 0.96°C T(Meas) = 16.9°C , SD = 0.94°C Literaturseminar 30. April, 2004

  18. Modeling: Future scenario (SCEN) 2071-2100 summer Statistical temperature distributions resulting from the RCM driven by a greenhouse-gas scenario Literaturseminar 30. April, 2004

  19. Temperature change and variability according to SCEN Literaturseminar 30. April, 2004

  20. Temperature and precipitation anomalies in n. Switzerland Measurement data 1864-2003 CTRL & SCEN data Literaturseminar 30. April, 2004

  21. Schär et al: Conclusion • A shift of the statistical temperature distribution towards warmer temperatures fails to explain summer 2003 temperatures • Proposal: An increase in variability as well as mean temperature may account for summer 2003 conditions • RCM simulations seem to verify this hypothesis Literaturseminar 30. April, 2004