ENVIROMENTAL ISSUES - CLIMATE CHANGE
The main concern of climate change is global warming, which is based on a ‘greenhouse’ effect. The Earth has a natural temperature-control system in which certain atmospheric gases are critical. Water vapour, CO2, CH4, N2O, and ozone are known as greenhouse gases, because they trap some of the heat radiated by the Earth. They act like a blanket wrapped around the globe. On average, about one-third of the solar radiation that hits the Earth is reflected back to space. Of the remainder, the atmosphere absorbs some but the land and oceans absorb the most. The Earth's surface becomes warm and, as a result, emits infrared radiation. The greenhouse gases trap the infrared radiation, thereby warming the atmosphere. Human beings have, however, added to the quantity of naturally occurring greenhouse gases in the atmosphere. The concentration of CO2, for example, has increased by 32% from pre-industrial times to the present day, mainly because of fossil-fuel combustion and deforestation. In the same period, the atmospheric concentrations of CH4 increased by about 150% and the concentration of N2O by 16%. Higher concentrations of greenhouse gases in the atmosphere will raise temperatures (in the range 2–4.5 °C by the year 2100) and increase sea levels (in the range 38–55 cm over the next century). Both effects have potentially serious consequences. The developing world faces greater challenges than the developed world in terms of the impact of climate change and their capacity to respond to it. By far the greatest contributions to global climate change come from the wealthy developed countries of the northern hemisphere. Although there is debate about the way in which climate change will affect the Earth, it has been identified as a significant threat to human livelihoods and sustainable development. Changes in climate already affect various sectors of South African society and the economy as well as the biophysical environment, and the effects are predicted to be significant in future. The areas of highest vulnerability are the health sector, maize production, biodiversity, water resources, and rangelands.
If there is a doubling of CO2-equivalent concentrations, a summary of the integrated findings indicate the following potential climate changes for South Africa. •Most of the models indicate a net drying on the western two-thirds of the subcontinent, south of about 10 °S.•East coast regions, where topography plays a significant role in the formation of rainfall, are likely to become wetter. The extent to which this wetting will extend into the interior is uncertain. •The Western Cape is predicted to face a shorter rainfall season, with the eastern interior portions of the province likely to experience increased late summer rainfall.•Ambient air temperature is predicted to increase across the country, with the interior experiencing the greatest increases.Maximum warming for the interior is likely to be in the range 3–4 °C. •Other potential changes include more floods and droughts and stronger, more frequent temperature inversions, exacerbating air pollution problems.
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