Influence of the blended ship log book and

station SLP data set on Mediterranean

temperature & precipitation back to 1750

June 23 2008

Jürg Luterbacher and collaboratorsOeschger Centre for Climate Change Research andInstitute of GeographyUniversity of Bern, Bern, SwitzerlandEmail: juerg@giub.unibe.ch

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Introduction, why is the Mediterranean of importance?

CCA between the blended SLP data and Mediterranean winter climate 1750-2006 main patterns, trends and crossvalidation

Future scenarios

Conclusions

Outline

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Küttel et al. 2008

Network, Winter SLP 1817 after Tambora (April 1815) and Verification statistics

L L

H

Very good quality

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European Winter temperature and SLP anomalies 1817

Luterbacher et al. 2007; Fischer et al. 2007; Küttel et al. 2008

-

+

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Tambora (April 1815), produced the “year without a summer 1816”

Luterbacher et al. 2007; Fischer et al. 2007; Küttel et al. 2008

+

-+

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> The area is a ‘Hot-Spot’ for which potential climate change impacts on the environment and other activity sectors are particularly pronounced

> Local/regional feedbacks (e.g. soil moisture-precipitation feedback), changes in atmospheric circulation and modes of natural variability are of importance

> Importance of hydrological cycle, winter precipitation is crucial Water resources & water quality Agriculture & environment Economics & social development & behaviour

Why is the Mediterranean of importance?

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Importance of winter precipitation compared tothe annual rainfall (in %)

Xoplaki 2002

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Data and Methods

Independent reconstructions> Gridded temperature 1750-2006, Mediterranean land areas

(Luterbacher et al. 2004, 1901-2006 Climatic Research Unit)

> Gridded precipitation 1750-2006, Mediterranean land areas(Pauling et al. 2006, 1901-2006 Climatic Research Unit)

> Gridded SLP 1750-2006, combined station pressure and CLIWOC/ICOADS data(Allan and Ansell, 2006; Küttel et al. 2008)

Method> Canonical Correlation Analysis (CCA)

selection of optimally correlated patterns between SLP and Mediterranean temperature & precipitation

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CCA1(SLP – temperature/precipitation 1750-2006)

dryer and warmer (North),wetter and cooler (South)

wetter and cooler (North),drier and warmer (South)

+warm

& dry

cool

& w

et

Xoplaki et al. 2008, work in progress

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CCA2(SLP – temperature/precipitation 1750-2006)

dry and warm, pos NAOI

wet and cool, neg NAOI

warm & dry

Xoplaki et al. 2008

+

_

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Mediterranean winter precipitation and temperature trends 1966-2006

GISS/NASA

Precipitation Temperature

Overall drying trend Overall warming trend

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Cross-validation; importance of SLP to explain Winter precipitation and temperature variability1750-2006

Xoplaki et al. 2008

Precipitation Temperature

Good skill: northern parts and Iberia Good skill: northern and eastern parts

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Impacts of recent climate change in the Mediterranean (deforestation, desertification, drought, fires …)

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A1B-Scenario for Winter 2021-2050(with respect to 1961-1990)

Giorgi and Lionello 2008

Sea Level Pressure

Temperature Precipitation

+ 2 hPa

+ 1–2°C - 10–30%

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Conclusions

> New dataset allows dynamical studies on the large scale influence on European climate back to AD 1750

> Crossvalidated results indicate good predictive skill in the north and west (precipitation) and north and east (temperature)

> Recent dry and warm winter conditions over the entire Mediterranean are not unique in the context of the past 250 years Regional differences

> Recent trend towards drier and wamer conditions seems to be exceptional

> The combined influence of two atmospheric patterns (NAO, East Atlantic / Western Russia) account significantly for the recent drier and warmer trend

> Scenarios indicate a trend towards more high pressure situations (similar patterns found through CCA) drier and warmer winter conditions Implications on environment, economy and society

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Thank you very much forThank you very much foryour attention!your attention!