Réf. Beniston 2009b - A

Référence bibliographique complète

BENISTON, M., 2009b: Trends in joint quantiles of temperature and precipitation in Europe since 1901 and projected for 2100. Geophysical Research Letters, Vol. 36(7), DOI: 10.1029/2008GL037119. Réf. Beniston 2009b [Etude en ligne]

Abstract: This study assesses the changes in the exceedances of joint extremes of temperature and precipitation quantiles for a number of sites in Europe. The combination of cool/dry, cool/wet, warm/dry and warm/wet modes reveals a systematic change at all locations investigated in the course of the 20th century, with significant declines in the frequency of occurrence of the “cold” modes and a sharp rise in that of the “warm” modes. The changing behavior of these four modes is also accompanied by changes in the particular conditions of temperature and precipitation associated with each mode; for example, the average amount of precipitation during cool/wet events decreases while that during warm/wet events increases, even though mean precipitation at most locations shows no significant trend. In a “greenhouse climate”, the “cool” modes are almost totally absent by 2100 whereas the warm/dry and warm/wet modes pursue the progression already observed in the 20th century.

Mots-clés

 

 

Organismes / Contact

• Chair for Climate Research, University of Geneva, Geneva, Switzerland (Martin.Beniston@unige.ch)

This work was conducted in the context of the Swiss NCCR-Climate network project, the EU/FP6 ENSEMBLES Project and the EU/FP7 ACQWA Project.

 

(1) - Paramètre(s) atmosphérique(s) modifié(s)

(2) - Elément(s) du milieu impacté(s)

(3) - Type(s) d'aléa impacté(s)

(3) - Sous-type(s) d'aléa

 Temperature, Precipitation

 

 

 

 

Pays / Zone

Massif / Secteur

Site(s) d'étude

Exposition

Altitude

Période(s) d'observation

 

 

 

 

 

 

 

(1) - Modifications des paramètres atmosphériques

Reconstitutions

 

Observations

The combination of cool/dry, cool/wet, warm/dry and warm/wet modes reveals a systematic change at all locations investigated in the course of the 20th century, with significant declines in the frequency of occurrence of the “cold” modes and a sharp rise in that of the “warm” modes. The changing behavior of these four modes is also accompanied by changes in the particular conditions of temperature and precipitation associated with each mode; for example, the average amount of precipitation during cool/wet events decreases while that during warm/wet events increases, even though mean precipitation at most locations shows no significant trend.

Modélisations

 In a “greenhouse climate”, the “cool” modes are almost totally absent by 2100 whereas the warm/dry and warm/wet modes pursue the progression already observed in the 20th century.

Hypothèses

 

 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

This paper reports on the trends of combined temperature and precipitation statistics in several European locations, using a concept that was described in a paper by Beniston and Goyette [2007] and more recently applied to Switzerland by Beniston [2009]. The use of joint PDFs, in this instance, those of temperature and precipitation, provides insight into the behavior of particular modes of heat and moisture that the analysis of the statistics of each variable taken individually does not. For example, while in some cases the precipitation record may show no particular trends, new insights on statistics that integrate mutual feedbacks between temperature and moisture are found when temperature and precipitation records are combined.

The paper makes use of 25% and 75% quantile thresholds in order to define particular modes of heat and moisture. Four modes are investigated here, defined by joint exceedances above or below these thresholds that serve to define “cool/dry”, “cool/wet”, “warm/dry” and “warm/wet” regimes. The paper shows that there have been substantial changes in these modes at all sites investigated and, interestingly, these changes are synchronous independently of whether the location is in a Mediterranean , continental or maritime climate regime. It is shown that even though the moist modes are less frequent than the dry modes, the quantities of precipitation also exhibit marked changes, signaling a probable feedback effect between surface processes, soil moisture and precipitation intensity.

Nine European sites have been selected for the statistical interpretation of temperature and precipitation data; they have been chosen as a function of the availability of data over long time scales and their distribution within different climatic zones. The stations fit into each of three climatic zones that can be broadly described as Mediterranean ( Lisbon , Portugal ; Lugano , Switzerland ; and Madrid , Spain ), maritime ( Copenhagen , Denmark ; Dublin , Eire; and Paris , France ), and continental ( Hannover , Germany ; Vienna , Austria ; and Zurich , Switzerland ). The data for the European stations is taken from the European Climate Assessment and Data website (http://eca.knmi.nl) and from the digital database of the Swiss Office for Meteorology and Climatology (MeteoSwiss). The data sets used have been quality-checked for homogeneity in the records [Begert et al., 2005; Klein Tank et al., 2002]. Data for six of the stations spans back to 1901; for Hannover, Lisbon and Madrid , the data is only available from 1951.

In a final section of the paper, an insight into possible changes of these four modes is conducted for the latter part of the 21st century, based on regional climate model projections for a “greenhouse” climate.

A suite of regional climate models (RCMs) was applied to simulate conditions in Europe for the last 30 years of the 21st century during the EU “PRUDENCE” project (http://prudence.dmi.dk). The inter-model variability and the quality of model simulations have been reported in a special issue of Climatic Change [PRUDENCE, 2007] and elsewhere. In the present investigation, the HIRHAM regional climate model (RCM) of the Danish Meteorological Institute has been used because of its skill in reproducing contemporary climate [Beniston et al., 2007]. The model has been applied to Europe at a 50-km resolution for both baseline climate (1961–1990), and a “greenhouse climate” for (2071–2100), using the IPCC SRES A2 scenario [Nakicenović et al., 2000] that leads to CO2 levels of about 800 ppmv by 2100. Climate response by 2100 to these emission levels is close to the upper range of possible global warming published by the Intergovernmental Panel on Climate Change (IPCC) [2007].

Quantile thresholds are calculated using the daily mean temperature and precipitation (24-hour precipitation totals) for each month of the 30-year baseline period 1961–1990. The thresholds calculated in this manner then serve to define the exceedances for all the time periods considered in the paper. The joint exceedance of the PDFs of mean temperature and precipitation is obtained by counting the frequency of exceedance, for each month, season or year, below or above the four combinations of heat and moisture quantiles, i.e., T25/ p25, T25/ p75, T75/ p25, and T75/ p75, that define respectively the cool/dry (CD), cool/wet (CW), warm/dry (WD), and warm/wet (WW) modes. Subscripts 25 and 75 refer to the respective quantile level for temperature and precipitation.

 

(2) - Effets du changement climatique sur le milieu naturel

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Sensibilité du milieu à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

(3) - Effets du changement climatique sur l'aléa

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Paramètre de l'aléa

Sensibilité des paramètres de l'aléa à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

 

(4) - Remarques générales

 

 

(5) - Syntèses et préconisations

This paper has used joint temperature-precipitation quantile exceedances to explore the behavior of four particular modes of climate extremes that have occurred in Europe, and their possible change in frequency by 2100 in a scenario climate. Beyond the very significant changes that have taken place in the course of the 20th century, and the redistribution of precipitation and temperature within each mode as a function of time, this type of study can provide an insight into the impacts associated particularly with the “warm” modes, that have already taken place in the past, but are projected to occur increasingly in the future.

The quasi-disappearance of the cold/dry and cold/wet modes by 2100 may have a number of beneficial consequences compared to today, in particular the reduction of damaging frosts for agriculture and the physiological consequences of cold and damp on humans, that often have a negative bearing on patients prone to cardio-vascular ailments. These positive impacts would, however, probably be largely offset by the projected increases in the warm/dry and warm/wet modes. These have in the past affected a number of key sectors such as human health (heat stress), agriculture (heat stress, droughts, floods, soil-moisture depletion), hydrological systems (droughts, floods, enhanced evaporation), infrastructure (floods), cryospheric systems (acceleration of glacier retreat and permafrost degradation), and slope instability events in mountain regions (associated with intense precipitation and, for higher elevations, the reduction in the cohesion of slope material by permafrost melting).

Without some form of economic or technological adaptation, the types of impacts associated with the WD and WW modes will become increasingly costly. Using the information of the type discussed in this paper can help in devising a number of precautionary measures that would help avert some of the more negative consequences of the projected changes in these extreme modes of climate.

Références citées :

Beniston and Goyette [2007]

Beniston [2009]

Begert et al., 2005; Klein Tank et al., 2002

PRUDENCE, 2007

Beniston et al., 2007

Nakicenović et al., 2000

Intergovernmental Panel on Climate Change (IPCC) [2007