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The role of increasing temperature variability in European summer heat waves

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. Overview. Luterbach et al: European temperature trends and extremes since 1500

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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

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