SOUTHERN-HEMISPHERE CLIMATE SCENARIOS

There is little doubt that between now and 2050 Earth faces global warming and other changes in climate unprecedented in magnitude since the end of the last glaciation some 10 000 years ago. Predicting the exact nature of that change is, however, difficult. Arguments from palaeoclimatic analogues, comparisons of recent warm versus cool years, physical reasoning and computer simulations are all subject to error and uncertainty. This is more so in the relatively less well understood climate system of the Southern Hemisphere, and at the local and regional scale, than in the Northern Hemisphere and at a zonally averaged scale. Nevertheless some broad features can be described with some confidence, and we can at least identify some of the major uncertainties and processes which we need to understand better. Increased poleward penetration of the subtropical monsoonal regimes is likely, and tropical cyclones may also occur at higher latitudes than at present. The role of the oceans, especially at high southern latitudes and in the tropics, and effects which may change with time as greenhouse gas concentrations gradually increase ('transient' effects) are particularly important and uncertain in the Southern Hemisphere. We know enough to declare the urgency of slowing down and eventually limiting the greenhouse effect. However, more research is needed to guide decision makers and planners at the local and regional level as they try to cope with those climatic changes which are unavoidable. Regional cooperation is essential to make the best use of the research and planning facilities available.