Using Climate Projections for Assessing Impacts at the City Scale


Local Governments for Sustainability recently launched a project entitled Sub-Saharan African Cities: A Five-City Network to Pioneer Climate Adaptation through Participatory Research and Local Action. One of the aims of this project was to establish a standardised approach for the collection and analyses of climatic base-line data, which will assist in the generation of future localised projections, which, in turn, will assist in planning and decision making.

As Global Climate Model (GCM) climate projections, and their associated downscaled data, are routinely used to infer impacts at a regional and sometimes local level, the question arises as to whether downscaling is useful, in terms of additional insights it may provide regarding the likely direction and magnitude of change, as well as the confidence in those changes.

This paper looks at the results from applying a downscaling methodology, developed at the University of Cape Town, to nine suitable GCMs (forced with the A2 emissions scenario) and the observed rainfall and temperature data from the Cape Town station. The downscaling relates daily weather systems to the observed rainfall and temperature at a particular location on each day. Taking the simulated changes in daily weather systems from each GCM, the expected changes in daily rainfall and temperature were then simulated for each location. The Priestly-Taylor method was used to calculate reference evapotranspiration (ET0) based on simulated temperatures, solar radiation and altitude.


Tadross, M.; Johnston, P. Using Climate Projections for Assessing Impacts at the City Scale. ICLEI – Local Governments for Sustainability - Africa, Cape Town, South Africa (2012) 18 pp. [Annex 51 from "Adaptation to Climate Change: Stakeholder engagement and understanding impacts - International Council for Local Environment Initiatives (ICLEI)]

Using Climate Projections for Assessing Impacts at the City Scale

Published 1 January 2012