April 2013

Climate Change Projections for African Urban Areas

EGU General Assembly 20013

Ingo Simonis, Francois Engelbrecht, Edoardo Bucchignani, Paola Mercogliano, Mogesh Naidoo

Modelling Physical Processes

General Circulation Models

On a global scale:• Horizontal resolution: 200-

600km • Vertical: 10-20 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 7

Sing

le M

odel • 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 Mul

ti M

odel • to account for the uncertainties

inherent in the models themselves

Ensemble Simulations

Slide 8

Sing

le M

odel • 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 Mul

ti M

odel • to account for the uncertainties

inherent in the models themselves

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

http://ict4eo.meraka.csir.co.za/anonftp/CLUVA/

60-80km & 8km Resolution Data

Projected change in annual rainfall and temperature 2040s vs 1960sRobust message across ensemble of an increases in rainfall in the northModerate increase in temp: ~ 2 degrees C by the 2040s

Dar es Salaam

© CSIR 2007 www.csir.co.za

Projected change in rainfall across seasons - 2040s vs 1960s

Median of ensemble projects relatively large increases in rainfall – all seasons except SON (spring)

Dar es Salaam

© CSIR 2007 www.csir.co.za

Time series of temp and rainfall: 1961-2050

* 1961-1970 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

http://ict4eo.meraka.csir.co.za/cluva/