The role of increasing temperature variability in European summer heat waves Christoph Schär, Pier Luigi Vidale, Daniel Lüthi, Christoph Frei, Christian.

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

Literaturseminar 30. April, 2004

Overview Luterbach et al: European

temperature trends and extremes since 1500

Summer 2003 data

Schär et al: Increasing temperature variability in European heat waves

Literaturseminar 30. April, 2004

Luterbacher et al: European mean temperature since 1500

- 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.

Winter

Literaturseminar 30. April, 2004

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

Luterbach et al: European mean temperature since 1500

Literaturseminar 30. April, 2004

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

Temperature anomalysummer 2003

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Deviation from the avg temp (1876-2000) in Karlsruhe

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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

Summary: 2003 data

Literaturseminar 30. April, 2004

Summary: 2003 dataComparison to 1876-2000 avg

Literaturseminar 30. April, 2004

Schär et al: European temperature anomaly

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Distribution of Swiss monthly temperatures 1864-2003

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Monthly Temp anomalies (J-D) 1864-1923 & 1941-2000

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Relative frequency change between the two periods

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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 uncertainty90% confidence interval: = 9000 yr.

Literaturseminar 30. April, 2004

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°CT(Meas) = 16.9°C , SD = 0.94°C

Literaturseminar 30. April, 2004

Modeling: Future scenario (SCEN) 2071-2100 summer

Statistical temperature distributions resulting from the RCM driven by a greenhouse-gas scenario

Literaturseminar 30. April, 2004

Temperature change and variability according to SCEN

Literaturseminar 30. April, 2004

Temperature and precipitation anomalies in n. Switzerland

Measurement data 1864-2003 CTRL & SCEN data

Literaturseminar 30. April, 2004

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