How seasonal forecast could help a decision maker: an example of climate service for water resource management

The FP7 project EUPORIAS was a great opportunity for the climate community to co-design with stakeholders some original and innovative climate services at seasonal time scales. In this framework, Météo-France proposed a prototype that aimed to provide to water resource managers some tailored information to better anticipate the coming season. It is based on a forecasting system, built on a refined hydrological suite, forced by a coupled seasonal forecast model. It particularly delivers probabilistic river flow prediction on river basins all over the French territory. This paper presents the work we have done with "EPTB Seine Grands Lacs" (EPTB SGL), an institutional stakeholder in charge of the management of 4 great reservoirs on the upper Seine Basin. First, we present the co-design phase, which means the translation of classical climate outputs into several indices, relevant to influence the stakeholder's decision making process (DMP). And second, we detail the evaluation of the impact of the forecast on the DMP. This evaluation is based on an experiment realised in collaboration with the stakeholder. Concretely EPTB SGL has replayed some past decisions, in three different contexts: without any forecast, with a forecast A and with a forecast B. One of forecast A and B really contained seasonal forecast, the other only contained random forecasts taken from past climate. This placebo experiment, realised in a blind test, allowed us to calculate promising skill scores of the DMP based on seasonal forecast in comparison to a classical approach based on climatology, and to EPTG SGL current practice

Projet Cyprim, partie II : Impact du changement climatique sur les événements de pluie intense du bassin méditerranéen

Un deuxième thème abordé dans le cadre du projet Cyprim vise à caractériser, dans le contexte du changement climatique, l'évolution des phénomènes de pluie intense en région méditerranéenne. À cette fin, une simulation climatique de 1960 à 2099 a été réalisée à l'aide d'un modèle régional couplé océan-atmosphère sous le scénario d'émissions A2 du Giec. Différentes méthodes de descente d'échelle (jusqu'à une échelle très fine de 2km) et de détection d'environnements synoptiques favorables aux précipitation sintenses sont ensuite proposées pour estimer l'impact du changement climatique sur les précipitations et l'hydrologie du sud-est de la France, tant du point de vue saisonnier que lors des épisodes de pluies intenses.A second topic covered by the CYPRIM project(1) aims to characterize the evolution of heavy precipitation events in Mediterranean in the context of climate change. To this end, a continuous climate simulation from 1960 to 2099 has been run using a regional ocean-atmosphere coupled model under IPCC A2 emission scenario. Various techniques of downscaling, down to the very fine 2 km scale, and methods to highlight synoptic environments favourable to heavy rain, have been used to estimate the impact of climate change on precipitation and hydrology over South-East France, both for the whole autumn season and the heavy rain events

Endoplasmic reticulum-mitochondria miscommunication is an early and causal trigger of hepatic insulin resistance and steatosis

International audienceBACKGROUND & AIMS: Hepatic insulin resistance in obesity and type 2 diabetes was recently associated with endoplasmic reticulum (ER)-mitochondria miscommunication. These contact sites (mitochondria-associated membranes: MAMs) are highly dynamic and involved in many functions. Up to now, it is not clear if MAM miscommunication could have a causal role in hepatic insulin resistance and steatosis. We therefore aimed to determine whether and how organelle miscommunication plays a role in the onset and progression of hepatic metabolic impairment. METHODS: We analyzed hepatic ER-mitochondria interactions and calcium exchange in diet-induced obese mice in a time-dependent and reversible manner, and investigated causality in hepatic metabolic alterations by expressing a specific organelle spacer or linker in mouse liver, using adenovirus. RESULTS: Disruption of ER-mitochondria interactions and calcium exchange is an early event preceding hepatic insulin resistance and steatosis in diet-induced obese mice. Interestingly, an 8-week reversal diet concomitantly reversed hepatic organelle miscommunication and insulin resistance in obese mice. Mechanistically, disrupting structural and functional ER-mitochondria interactions through the hepatic overexpression of the organelle spacer FATE1 was sufficient to impair hepatic insulin action and glucose homeostasis. In addition, FATE1-mediated organelle miscommunication disrupted lipid-related mitochondrial oxidative metabolism and induced hepatic steatosis. Conversely, reinforcement of ER-mitochondria interactions through hepatic expression of a synthetic linker prevented diet-induced glucose intolerance after 4 weeks' overnutrition. Importantly, ER-mitochondria miscommunication was confirmed in the liver of obese patients with type-2 diabetes, and correlated with glycemia, HbA1c and HOMA-IR index. CONCLUSIONS: ER-mitochondria miscommunication is an early causal trigger of hepatic insulin resistance and steatosis, and can be reversed by switching to a healthy diet. Thus, targeting MAMs could contribute to restoring metabolic homeostasis. LAY SUMMARY: The literature suggests that interactions between endoplasmic reticulum (ER) and mitochondria could play a dual role in hepatic insulin resistance and steatosis during chronic obesity. The present study reappraised time-dependent regulation of hepatic ER-mitochondria interactions and calcium exchange in diet-induced obese mice and their causal role in hepatic insulin resistance and steatosis. We show that organelle miscommunication is an early causal trigger of hepatic insulin resistance and steatosis, and can be improved by nutritional strategies