April 2013 Climate Change Projections for African Urban Areas EGU General Assembly Ingo Simonis, Francois Engelbrecht, Edoardo Bucchignani, Paola Mercogliano, Mogesh Naidoo

Modelling Physical Processes

General Circulation Models On a global scale: Horizontal resolution: km Vertical: layers in atmosphere up to 30 layers in oceans

Uncertainties 1.Coarse resolution of models relative to the scale of exposure units 2.Many physical processes also occur on smaller scales and cannot be properly modelled  Properties must be averaged 3.Various feedback mechanisms, e.g. water vapour and warming, clouds and radiation, ocean circulation and ice and snow albedo…

Uncertainties 1.Coarse resolution of models relative to the scale of exposure units 2.Many physical processes also occur on smaller scales and cannot be properly modelled  Properties must be averaged 3.Various feedback mechanisms, e.g. water vapour and warming, clouds and radiation, ocean circulation and ice and snow albedo…  different GCMs simulate quite different responses to the same forcing

Downscaling

Ensemble Simulations Slide 6 Single Model perturbations of the initial conditions to account for the non-linear dynamics perturbations of the boundary conditions to account for the ‘imperfect’ characterization of the non- atmospheric components of the climate system and also – in case of a regional model – for the uncertainty of the driving global model perturbations of the model physics to account for the uncertainties inherent in the parameterizations Multi Model to account for the uncertainties inherent in the models themselves

Ensemble Simulations Slide 7 Single Model perturbations of the initial conditions to account for the non-linear dynamics perturbations of the boundary conditions to account for the ‘imperfect’ characterization of the non- atmospheric components of the climate system and also – in case of a regional model – for the uncertainty of the driving global model perturbations of the model physics to account for the uncertainties inherent in the parameterizations Multi Model to account for the uncertainties inherent in the models themselves CSIR: Six Models Ensemble for A2 Scenario CSIR: Six Models Ensemble for A2 Scenario CMCC: One Model multiple permutations for A1B Scenario

60-80km & 8km Resolution Data

60-80km & 8km Resolution Data

Projected change in annual rainfall and temperature 2040s vs 1960s Robust message across ensemble of an increases in rainfall in the north Moderate increase in temp: ~ 2 degrees C by the 2040s Dar es Salaam

© CSIR Projected change in rainfall across seasons s vs 1960s Median of ensemble projects relatively large increases in rainfall – all seasons except SON (spring) Dar es Salaam

© CSIR Time series of temp and rainfall: * climate as baseline – 1 ens member shown here * Temp increase reaches 2.5 degrees C by 2050 * Large shift projected in rainfall – increased variability Dar es Salaam

60-80km & 8km & 1km Resolution Data