1. In a changing climate with uncertainties and impacts where journalists stand Dr, Ousmane Ndiaye International Institute for Climate and Society Earth Institute at Columbia University New York, USA

2. Bases of Climate Change Projections Modifications of atmospheric composition modifies the Energy balance of the Earth System Atmospheric composition Climate Information for Public Health Summer Institute, IRI, June 2009

3. Dealing with uncertainty Uncertainty in Observation (Initial Conditions)  Multiple forecasts made with slightly different IC Uncertainty in representation of processes (state of the science)  Use of different models Uncertainty in GHGs (Boundary Forcing)  Use of different scenarios Ensemble techniques (beyond a simple mean) Automatic Corrections Each model grid point is weight in function of the past performance Spatial smoothing applied to the weights Statistical correction and Regional modelling

4. SCALE OF THE FORECAST TYPE OF FORECAST ACCURACYFORCINGEXAMPLEVALIDITY WEATHERDeterministic Initial Condition (observation) Rainfall events, onset 1 to 10 days SEASONALProbabilistic Boundary condition (Sea surface temperature) Seasonal total, number of spells 1 to 3 months CLIMATE CHANGE Projection (scenario) Greenhouse gases : CO 2, aerosols, CFCs Mode of variability, shift of climatic zones 10 to 500 years

5. PROJETIONS : SCENARIOS

6. Health : Water related diseases Vector born diseases : malaria, dengue Heat wave frequency Forestry : Land use changes : agriculture, biodiversity Trapping CO2 (forest to savanna) Vulnerable/risk zones : stressed Forest fires due to CC desertification Agriculture (+ demand on food) Food security crises seawater chemistries Poor farmers more exposed ocean currents Change in Climate patterns diversities food chain