Réf. Palmer and Räisänen 2002 - A

Référence bibliographique complète
PALMER, T. N. RÄISÄNEN, J. Quantifying the risk of extreme seasonal precipitation events in a changing climate. Nature, 2002, vol. 415.

Abstract: Increasing concentrations of atmospheric carbon dioxide will almost certainly lead to changes in global mean climate. But because -by definition- extreme events are rare, it is significantly more difficult to quantify the risk of extremes. Ensemblebased probabilistic predictions, as used in short- and mediumterm forecasts of weather and climate, are more useful than deterministic forecasts using a `best guess' scenario to address this sort of problem. Here we present a probabilistic analysis of 19 global climate model simulations with a generic binary decision model. We estimate that the probability of total boreal winter precipitation exceeding two standard deviations above normal will increase by a factor of five over parts of the UK over the next 100 years.We find similar increases in probability for the Asian monsoon region in boreal summer, with implications for flooding in Bangladesh. Further practical applications of our techniques would be helped by the use of larger ensembles (for a more complete sampling of model uncertainty) and a wider range of scenarios at a resolution adequate to analyse average-size river basins.

Mots-clés

Global climate model simulations, extreme precipitation envents, Europe


Organismes / Contact
European Centre for Medium-Range Weather Forecasts, UK
Rossby Centre, Sweden

(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
Precipitations      

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Europe Alpine region        

(1) - Modifications des paramètres atmosphériques
Reconstitutions  
Observations
 
Modélisations
The probability of occurrence of E2 over Europe from the control ensemble in boreal winter is approximately 2.5%. The probability of E2 at the time of CO2 doubling has increased to over 12% (associated with enhanced storm-track activity and “wetter” storms) for much of central and northern Europe.

For the alpine region, the probability of occurrence of E2 from the control ensemble is 2-4%, and 6-12% from the greenhouse ensemble. The probability of occurrence of a very wet winter over the alpine region is estimated to increase by a factor of 3-5 over the next 50-100 years, due to man's effect on climate.
Hypothèses
 

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

The dichotomous event En, defined to occur if the total seasonal precipitation at a specific location exceeds n standard deviations above the mean. The methodology, based on the risk of any dichotomous climate event E, is used to analyse the changing probability of the extreme events E2 and E3, as determined by an ensemble of climate projections.
80-year integrations from the CMIP2 multi-model ensemble of 19 global coupled ocean-atmosphere climate models were used. The first (control) ensemble was run with a constant twentieth-century CO2 concentration (about 330 p.p.m.v.), and the second (greenhouse) ensemble with a transient compound increase in CO2 of 1% per year. Then, the results of the 2 ensembles have been compared.


(2) - Impacts 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) - Impacts du changement climatique sur l'aléa
Reconstitutions  
Observations
 
Modélisations
 
Hypothèses
 

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 
 

(4) - Remarques générales

 


(5) - Syntèses et préconisations