International audienceA new physically based distributed surface mass-balance model is presented for Alpine glaciers. Based on the Crocus prognostic snow model, it resolves both the temporal (1 hour time-step) and spatial (200 m grid-step) variability of the energy and mass balance of glaciers. Mass-balance reconstructions for the period 1981-2004 are produced using meteorological reconstruction from the SAFRAN meteorological model for Glacier de Saint-Sorlin and Glacier d'Argentière, French Alps. Both glaciers lost mass at an accelerated rate in the last 23 years. The spatial distribution of precipitation within the model grid is adjusted using field mass-balance measurements. This is the only correction made to the SAFRAN meteorological input to the glacier model, which also includes surface atmospheric temperature, moisture, wind and all components of downward radiation. Independent data from satellite imagery and geodetic measurements are used for model validation. With this model, glacier sensitivity to climate change can be separately evaluated with respect to a full range of meteorological parameters, whereas simpler models, such as degree-day models, only account for temperature and precipitation. We provide results for both mass balance and equilibrium-line altitude (ELA) using a generic Alpine glacier. The sensitivity of the ELA to air temperature alone is found to be 125 m °C−1, or 160 m °C−1 if concurrent (Stefan-Boltzmann) longwave radiation change is taken into account

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International audienceA simple method is used to study the response of runoff in the Sahel to climate change. The statistical characteristics of rainfall are calculated over the western part of the Sahel for the period 1961–1990, using the BADOPLU network. Daily rainfall is simulated using a Markov process with Weibull distribution for rainfall depths. Runoff is modelled using a conceptual SCS model and the curve numbers are calculated for West Africa. Climate change is provided by simulations using the Arpège GCM (Scenario A1B), and a perturbation method is used on the parameters which describe the rainfall. Changes in rainfall are assumed to occur through increases in frequency, not intensity. Using Arpège, runoff is mainly found to increase, in depth and in number of events, by the end of the 21st century. Changes in evaporation and land use are not included in the analysis. The impact of this 21st century potential climate change (rainfall) on the runoff is found to be of the same magnitude as the impact of changes in land use

l'enneigement et disponibilité des ressources en eau pour la production de neige dans les domaines skiables du Département de l'Isère (France), en conditions climatiques actuelles et futures »,