Hervé Le Treut is Director of the Dynamic Meteorology Laboratory (LMD) at the Pierre Simon Laplace Institute (IPSL)², and for him the PRISM project is about federating efforts being made across the scientific community of climatology. The idea took shape near the end of the 1990's as Europe began to take the lead from the United States in climate modeling. At that point European researchers felt it made more sense to pool existing models and data through common model interfaces rather than build one big new common model. In December 2001, the Fifth Framework Programme got PRISM started with a 4.8 million euro grant.

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© D.R

Steps in digital modeling, from discretization of equations to writing digital code and to simulation by computer calculation resulting in a simulated model.

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Defining the perimeter of a common model
Climate models, according to Jan Polcher – lead researcher for PRISM at the IPSL's modeling department – come in several categories according to their subfield: atmosphere, continental surfaces, oceans and chemical and carbon cycle models. PRISM brings together the actors who developed the models, like the IPSL, the Max-Planck Institute in Hamburg, or the UK's Hadley Center, as well as scientists who specialise in the various subfields. For Polcher, a common infrastructure will allow climatologists to get the most benefit out of these models. Once such an infrastructure is in place and can coordinate the rich variety of European models, it will be possible to reduce the uncertainties in climate change predictions, and thus bring more solid information to decision-makers.
The first task, as Polcher sees it, is define the perimeter and interfaces of the model for each component of the Earth system, that is, what information it can calculate itself and what things it would do better to get from another model. This is not as easy as it sounds, since such definitions go right to the heart of how these numerical models are developed.

Shared reflection
For Marie-Alice Foujols, co-leader of the PRISM project at IPSL, the important thing is to work together to develop a tool which allows multiple points of view. In her view the common infrastructure will make it possible to bring various modules together in the same model (for example the same atmosphere module could be successively associated with one of several different ocean models).
The computing innovations resulting from the PRISM project will be available in open source programming so that anyone may benefit from them whether they participated directly in the project or not. Hervé Le Treut points out that at the same time “there is a general move, in the context of the Sixth Framework Programme, towards setting up a Network of Excellence* entitled ENES, for European Network for Earth Modelling System. This should ensure that PRISM and the European climate research community become permanent features of the research landscape.”