Background

Human activities (emissions of greenhouse gases and other pollutants, change in land use, deforestation, etc.) modify the climate through a large number of physical, chemical and biogeochemical phenomena. In turn, this variation in climate affects ecosystems and human activities. Currently, research issues are to observe, model, understand and quantify these climate changes and the phenomena that govern them, at both global and regional scales.

IPSL has chosen to take an integrated multidisciplinary approach to the Earth System and to study past, recent and future climate changes in a coherent way. This approach is based on the climate modelling activities carried out in the various IPSL laboratories and is coordinated by the IPSL Climate Modelling Centre (CMC).

Currently, the main activities of the modelling centre are:

• To develop an integrated model of the Earth system from components developed in the laboratories of IPSL and partners and a software environment to support it,
• To carry out climate change simulations and analyse them,
• To develop an infrastructure that optimises the use of the simulations, in particular, their distribution,
• To conduct studies to improve our understanding of climate, its variability and climate change,
• To share skills, particularly between disciplines,
• To establish scientific expertise on climate change issues.

The activities of the climate modelling centre involve around 90 researchers and engineers from IPSL. In addition, a larger circle of people uses the results of the reference simulations carried out with different configurations of the models developed (over 200 in France, and even more abroad).

Developing an integrated climate model

IPSL's climate modelling centre is developing an integrated model of the climate system through a multidisciplinary approach covering the different parts of the climate system and the different processes that govern it. It constantly develops and improves its model and the various parts that constitute it:

• the LMDZ atmospheric model,
• the NEMO ocean, sea ice and marine biogeochemistry model,
• the ORCHIDEE continental surface model,
• the INCA tropospheric and REPROBUS stratospheric chemistry models.

Coupling between the atmospheric and oceanic models is carried out using the OASIS coupler developed at CERFACS, the inputs-outputs are managed by the XIOS model.

The modelling centre also constantly develops and improves the software tools which allow different configurations of the climate model to be run on available supercomputers, to analyse the results of the simulations carried out and make them available. This involves an ongoing  monitoring of developments in intensive computing and data processing. IPSL-CMC relies on GENCI for high performance computing located at TGCC and at IDRIS.

Climate simulations, analysis of results and dissemination

IPSL's climate modelling centre carries out and disseminates numerous climate simulations, many of them within the framework of national or international programmes. Analysis of the results of simulations carried out by different models is important to test the robustness of the results, as well as to identify and understand the origin of the differences between models. This is particularly the case for the simulations carried out within the framework of the international CMIP project which makes an important contribution to the various IPCC reports. These simulations are managed and distributed by ESPRI-MOD, the modelling part of the ESPRI service of IPSL. All of this contributes to the Climeri-France research infrastructure.