[show abstract][hide abstract] ABSTRACT: We present the global general circulation model IPSL-CM5 developed to study the long-term response of the climate system to natural and anthropogenic forcings as part of the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). This model includes an interactive carbon cycle, a representation of tropospheric and stratospheric chemistry, and a comprehensive representation of aerosols. As it represents the principal dynamical, physical, and bio-geochemical processes relevant to the climate system, it may be referred to as an Earth System Model. However, the IPSL-CM5 model may be used in a multitude of configurations associated with different boundary conditions and with a range of complexities in terms of processes and interactions. This paper presents an overview of the different model components and explains how they were coupled and used to simulate historical climate changes over the past 150 years and different scenarios of future climate change. A single version of the IPSL-CM5 model (IPSL-CM5A-LR) was used to provide climate projections associated with different socio-economic scenarios, including the different Representative Concentration Pathways considered by CMIP5 and several scenarios from the Special Report on Emission Scenarios considered by CMIP3. Results suggest that the magnitude of global warming projections primarily depends on the socio-economic scenario considered, that there is potential for an aggressive mitigation policy to limit global warming to about two degrees, and that the behavior of some components of the climate system such as the Arctic sea ice and the Atlantic Meridional Overturning Circulation may change drastically by the end of the twenty-first century in the case of a no climate policy scenario. Although the magnitude of regional temperature and precipitation changes depends fairly linearly on the magnitude of the projected global warming (and thus on the scenario considered), the geographical pattern of these changes is strikingly similar for the different scenarios. The representation of atmospheric physical processes in the model is shown to strongly influence the simulated climate variability and both the magnitude and pattern of the projected climate changes.
[show abstract][hide abstract] ABSTRACT: The influences of physico-chemical and biological processes on dimethylsulfide (DMS) dynamics in the most oligotrophic subtropical
zones of the global ocean were investigated. As metrics for the dynamics of DMS and the so-called ‘summer DMS paradox’ of
elevated summer concentrations when surface chlorophyll a (Chl) and particulate organic carbon (POC) levels are lowest, we used the DMS-to-Chl and DMS-to-POC ratios in the context
of three independent and complementary approaches. Firstly, field observations of environmental variables (such as the solar
radiation dose, phosphorus limitation of phytoplankton and bacterial growth) were used alongside discrete DMS, Chl and POC
estimates extracted from global climatologies (i.e., a ‘station based’ approach). We then used monthly climatological data
for DMS, Chl, and POC averaged over the biogeographic province wherein a given oligotrophic subtropical zone resides (i.e.,
a ‘province based’ approach). Finally we employed sensitivity experiments with a new DMS module coupled to the ocean general
circulation and biogeochemistry model PISCES to examine the influence of various processes in governing DMS dynamics in oligotrophic
regions (i.e., a ‘model based’ approach). We find that the ‘station based’ and ‘province based’ approaches yield markedly
different results. Interestingly, the ‘province based’ approach suggests the presence of a ‘summer DMS paradox’ in most all
of the oligotrophic regions we studied. In contrast, the ‘station based’ approach suggests that the ‘summer DMS paradox’ is
only present in the Sargasso Sea and eastern Mediterranean. Overall, we found the regional differences in the absolute and
relative concentrations of DMS between 5 of the most oligotrophic regions of the world’s oceans were better accounted for
by their nutrient dynamics (specifically phosphorus limitation) than by physical factors often invoked, e.g., the solar radiation
dose. Our ‘model based’ experiments suggest that it is the limitation of phytoplankton/bacterial production and bacterial
consumption of DMS by pervasive phosphorus limitation that is responsible for the ‘summer DMS paradox’.
KeywordsDimethylsulfide (DMS)–Oligotrophy–Summer DMS paradox–Modelling–Field observations
[show abstract][hide abstract] ABSTRACT: The Pierre Simon Laplace Institute (IPSL), like many other climate modeling groups, is involved in the development of a comprehensive Earth System Model (ESM) to study the interactions between chemical, physical, and biological processes. This work entails the coupling of different components (land, ocean, atmosphere, chemistry...etc) and requires an execution environment platform that can tackle the entire range of interdependent model configurations. Furthermore, the ever-increasing number of simulations, executed against model configurations within scientific computing centres, is generating a huge volume of data and meta-data that must be made available to researchers, modelers, students and general users. Each user group has a different set of information demands related to climate simulation data and meta-data, and thus fulfilling the requirements of the entire community is highly challenging. This talk will focus upon the strategy adopted by IPSL to simultaneously fulfill the needs of the community and to lower the data distribution and data management burdens upon the climate modeling group due to the growing interest related to climate simulations data and information. To achieve these objectives we decided to integrate the efforts of international and European projects such as Earth System Grid, METAFOR and IS-ENES, within our execution environment platform. We will present the emerging workflow that will be in place to run CMIP5 simulations and that we will extend to manage the "every day" simulations that are intended not only for participation within a large model intercomparaison project such as CMIP5.
[show abstract][hide abstract] ABSTRACT: This paper presents the major characteristics of the Institut Pierre Simon Laplace (IPSL) coupled ocean-atmosphere general circulation model. The model components and the coupling methodology are described, as well as the main characteristics of the climatology and interannual variability. The model results of the standard version used for IPCC climate projections, and for intercomparison projects like the Paleoclimate Modeling Intercomparison Project (PMIP 2) are compared to those with a higher resolution in the atmosphere. A focus on the North Atlantic and on the tropics is used to address the impact of the atmosphere resolution on processes and feedbacks. In the North Atlantic, the resolution change leads to an improved representation of the storm-tracks and the North Atlantic oscillation. The better representation of the wind structure increases the northward salt transports, the deep-water formation and the Atlantic meridional overturning circulation. In the tropics, the ocean-atmosphere dynamical coupling, or Bjerknes feedback, improves with the resolution. The amplitude of ENSO (El Niño-Southern oscillation) consequently increases, as the damping processes are left unchanged.
[show abstract][hide abstract] ABSTRACT: Dans le cadre de la préparation du 4e rapport du Groupe intergouvernemental sur l'évolution du climat (Giec), qui doit paraître début 2007, les principales équipes de modélisation de par le monde ont réalisé un important exercice coordonné de simulation de l'évolution du climat au cours des XXe et XXIe siècles. Nous présentons ici les résultats obtenus par les modèles du CNRM et de l'IPSL, en évoquant les progrès réalisés depuis le précédent rapport du Giec. Nous replaçons également nos résultats par rapport à ceux des autres modèles, et indiquons les résultats qui sont communs à l'ensemble des modèles et ceux qui peuvent être différents. In support of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) that should appear in early 2007, modelling groups world-wide have performed a huge coordinated exercise of climate change runs for the 20th and 21st centuries. In this paper we present the results of the two French climate models, CNRM and IPSL. In particular we emphasise the progress made since the previous IPCC report and we identify which results are comparable among models and which strongly differ.
La Météorologie [ISSN 0026-1181], 2006, Série 8, N° 55 ; p. 45-59.
[show abstract][hide abstract] ABSTRACT: Résumé: Dans le cadre de la préparation du 4e rapport du Groupe Intergouvernemental sur l'Evolution du Climat (GIEC) qui doit paraître début 2007, les principales équipes de modélisation du climat de part le monde ont réalisé un important exercice coordonné de simulation de l'évolution du climat au cours du 20e et du 21e siècle. Nous présentons ici les résultats obtenus par les modèles du CNRM et de l'IPSL, en évoquant les progrès réalisés depuis le précédent rapport du GIEC. Nous replacerons également nos résultats par rapport à ceux des autres modèles, et indiquerons les résultats qui sont communs à l'ensemble des modèles et ceux qui peuvent être différents. Abstract: In support of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) that should appear in early 2007, modelling groups world-wide have performed a huge coordinated exercise of climate change runs for the 20th and 21st century. In this paper we present the results of the two french climate models, from CNRM and IPSL. In particular we emphasise the progress made since the previous IPCC report and we identify which results are comparable among models and which strongly differ.