Abstract:
The climate varies naturally on all time-scales. Variations may occur due to forces such as volcanic eruptions or changes in the Sun's output of energy. They may also be generated by interactions among the different components of the global climate system: the atmosphere, oceans, biosphere, ice cover, and land surface. These internal interactions may cause fairly regular fluctuations, such as the El Nitio phenomenon, or apparently random changes in climate. Since the human settlements and the economical activities on the earth are largely concentrated in mid-latitudinal regions, the impacts of floods and droughts are more apparent in these regions (Ponce, 1995a; Karl, 1983). Natural variability often produces climate extremes and disasters. On time-scales of days, months, and years, variability in weather and climate can produce heat waves, frosts, flooding, droughts, severe storms, and other extremes. An important question which scientists are trying to answer is whether mankind's interference with the climate system through the enhancement of the natural greenhouse effect will increase the frequency or magnitude of extreme weather events. Given the large natural variability and the obvious rarity of extreme weather events it is hard to ascribe the observed phenomena to the enhanced greenhouse effect or even discern a definite trend in extreme event throughout this century. What can be said with certainty, however, is that any change in climate will affect society mainly through extreme weather events.
