Southern Africa is considered here as the region of Africa south of 10°S and east of 20°E. The selected models for the analysis of 21st century projections in rainfall patterns under the A1B scenario forcing generally show a tendency for an increase in mean precipitation in much of eastern South Africa and Lesotho. Over the remainder of the region, there are projections for a drying trend. The models also show less severe dry extremes (i.e. the driest events that occur once every 10-years on average) in central South Africa and Lesotho. Two of the selected models project more severe dry events along the eastward edge of the Kalahari Desert in Botswana, and in Zimbabwe and southern Mozambique. Wet extremes are projected to increase in eastern South Africa and Lesotho. Tropical cyclones can not be simulated in these climate models. As these cause most flooding events along the eastern parts of the region we cannot assess the expected changes in the frequency of wet extremes from the model results. In southern Africa there are large differences in mean rainfall. The south-western parts bordering the Atlantic Ocean are driest and rainfall amounts increase eastward and northward. Over and above the influence of contrasting ocean currents to the west and east of the subcontinent (the cold Benguela system in the eastern Atlantic and the warm Agulhas system along the Indian Ocean coast), hills and mountains play a major role in inducing smaller-scale spatial variations in precipitation. Locations which experience coherent rainfall anomalies in a given season have been identified using cluster analysis. Projected rainfall trends in the 21st century in each of these regions as well as possible shifts in the rainy season (austral summer) are shown in these pages in the right-hand menu. Due to lack of reliable rainfall records over the western parts, the analyses have been confined to east of 20° E.

Much of southern Africa experiences one major rainfall season centred around December, January and February, when the ITCZ is in its southernmost position. The southern tip of South Africa (region 1) is an exception with rainfall all year round.

From the simulated climate changes in response to increased greenhouse gases, there seem to be a clear tendency towards increased intensity of high rainfall events in the Northern Cape, Eastern Cape, Free State and North-west provinces of South Africa, and Lesotho. Over these areas the 100-year wettest events are predicted to increase by up to 50%. Over the eastern parts of the region, there is no clear evidence for changes in wet extremes. This is probably because the models do not simulate south-west Indian Ocean tropical cyclones, which are one of the major sources of torrential rainfall in southern Africa (e.g. Domonia in January 1984 and Eline in March 2000). The climate models do not simulate these cyclones, so the results can not be trusted for this region. Simulated changes in extremely dry events show that in future climate such events are likely to be less severe in the Eastern Cape, Northern Cape, Free State, and Northwest provinces of South Africa, and Lesotho where the models show a high degree of agreement. Noteworthy is that over the same areas, the wet extremes are predicted to increase.

As seen in the mean map, most models are projecting a drying trend in the Kalahari Desert and its neighbourhood. This is accompanied by dry extremes becoming more severe in Botswana, Zimbabwe and central Mozambique. Such conditions would be favourable for an eastward encroachment of the Kalahari desert. The CCCMA and IPSL models simulate an increase in the 10-year driest rain seasons in contrast to other projections.