The Development of Regional Climate Change Scenarios for Sub-Saharan Africa

Africa is one of the regions most vulnerable to climate change, is likely the most under-resourced continent for climate change research, and is a region where some aspects of the regional climate dynamics are still poorly understood. This project addresses these needs, primarily through the development of downscaled regional scenarios of climate change from GCM simulations. Analyses of observations and historical data are also presented and provide the necessary context for these scenarios. Further, important aspects of uncertainty are addressed and ongoing work to understand how land-use change may contribute to this uncertainty is presented. A primary component of this project was to extend existing capacity among African scientists in methods and regional scenario construction. The scenarios focus on spatial and temporal scales appropriate to the primary vulnerability sectors in Africa, and incorporate both computationally efficient empirical downscaling and more computationally demanding regional climate models (RCMs) -both of which have been identified in the IPCC 2001 TAR as having equal skill, with respective advantages in different impact sectors. Substantial capacity was developed at the host institution and through interactions with both partners and other stakeholders. Facilities for running RCMs (PC hardware and software) were installed at partner sites, enabling partners to investigate aspects of their local climate they considered important for realistic simulations. This capacity was supplemented by strong international links during all phases of scenario development. The project provides for the first time a comprehensive scenario base for IPCC and related impacts activities in Africa. Besides increasing the capacity to conduct fundamental climate research within Africa, the project produced important scientific results, including: i) the development of a new empirical downscaling technique which demonstrated convergence between projections from a suite of GCMs; ii) the detection of trends in the regional climate dynamics which are also projected in the GCM future projections; iii) the dependence of an RCM’s hydrological cycle on the choice of convection scheme and how this leads to RCM-dependent downscalings from one particular GCM, reinforcing the imperative that multiple RCMs be employed; iv) the impact of a changing land surface on the local climate and the importance of so far unquantified changes in land use. The resulting scenarios are continuing to be developed and analysed, however some consistent projected changes are apparent: i) a drying towards the west of southern Africa during summer, consistent with an increase in the frequency of extensive high pressure systems over the Atlantic; ii) an increase in rainfall over East Africa, iii) increases in rainfall over eastern southern Africa during late summer; iv) 1-5°C increases in temperature over much of southern Africa. It should be noted that these generalised projections are highly timeand space-dependent. Some of the projected changes are also more clearly apparent in the statistics of daily rainfall as opposed to changes in total rainfall e.g. changes in rainfall intensity and number of rain days may influence total rainfall in opposition to each other. This project has laid the foundations for future research, which given a continued impetus can further improve scenario development. Such an impetus will involve multiple research thrusts, including efforts to reduce model uncertainty whilst incorporating aspects of environmental change, e.g. land-use change and biogenic aerosols, not accounted for in current scenario development. Administering Institution: University of Cape Town, South Africa.