CERFACS CERFACS Scientific Activity Report Jan. 2010 – Dec. 2011

1 Introduction
The Climate group conducts basic and applied research in the field of climate variability and predictability
and global environmental changes. Our main scientific objectives are the following :
– To improve the understanding and simulation of climate processes underlying the variability of the main
climate natural modes, such as the Northern and Southern Annular Modes (NAM and SAM), the Atlantic
Meridional Overturning Circulation (AMOC) and the El Nino Southern Oscillation (ENSO) (and its
decadal counterpart, the Pacific Decadal Oscillation (PDO) ) and of the response of the NAM/SAM,
AMOC, ENSO and PDO to anthropogenic climate change.
– To detect, attribute and describe anthropogenic climate change on global to regional scales using high
resolution climate models, statistical methods and long-term high quality observations.
– To assess the impacts of anthropogenic climate change at regional to local scale with specific interest
in the changes of the hydrological cycle and to provide reliable uncertainty bounds in future climate
projections.
– To study the potential of decadal predictability due to both external forcing (from both natural and
anthropogenic sources) and low frequency ocean fluctuations.
– To explore the influence of small-scale phenomena upon ocean-atmosphere coupling and their impact on
intra-seasonal to interannual predictability
The methodology relies upon a dual approach combining observations and simulations performed with
state-of-the-art general circulation models of the atmosphere, ocean, land surface, sea-ice and the coupled
climate system. As an example, we have recently achieved a very large ensemble of decadal hindcasts and
forecasts simulations in the framework of the Coupled Model Intercomparison Project version 5 (CMIP5)
exercise which will provide the modelling results for the next Intergovernmental Panel on Climate Change
(IPCC) assessment report planned in 2013. The climate model is the CNRM-CM5 model developed jointly
with the Centre National de Recherches Météorologiques (CNRM). More than 5000 years of simulated
climate have been performed requiring 200 000 CPU hours on the Météo-France NEC supercomputer and
generating 120 Terabytes of data. This first achievement is the first step of a 10-year program devoted to the
study of decadal variability and predictability and its impacts.
Most of our objectives are endorsed by national and/or international programs through coordinated projects
and collaborations with other partners mainly at the french and European levels (European Framework
Program 7, FP7 : COMBINE, IS-ENES ; Agence Nationale de la Recherche ANR : SCAMPEI, ASIV ;
Ministère de l’écologie, du Développement Durable, du Transport et du Logement (MEDDTL) : DRIAS,
EPIDOM ; Fondation BNP-Paribas : PRECLIDE.
CERFACS ACTIVITY REPORT 115