Climate Extremes: Observations, Modeling, and Impacts

One of the major concerns with a potential change in climate is that an increase in extreme events will occur. Results of observational studies suggest that in many areas that have been analyzed, changes in total precipitation are ampliÞed at the tails, and changes in some temperature extremes have been observed. Model output has been analyzed that shows changes in extreme events for future climates, such as increases in extreme high temperatures, decreases in extreme low temperatures, and increases in intense precipitation events. In addition, the societal infrastructure is becoming more sensitive to weather and climate extremes, which would be exacerbated by climate change. In wild plants and animals, climate-induced extinctions, distributional and phenological changes, and speciesÕ range shifts are being documented at an increasing rate. Several apparently gradual biological changes are linked to responses to extreme weather and climate events. T here is general agreement that changes inthe frequency or intensity of extremeweather and climate events would have profound impacts on both human society and the natural environment. Recent years have seen a number of weather events cause large losses of life as well as a tremendous increase in economic losses from weather hazards. In 1998 Hurricane Mitch caused over 10,000 deaths in Central America, and more recently major flooding events with large loss of life have occurred in both Venezuela and Mozambique. In the United States, since 1987 more than 360 weather events each produced losses in excess of $5 million with several record-setting catas-trophes. These include the midwest drought of 1988–1989 ($39 billion), Hurricane Andrew in South Florida in 1992 ($30 billion), and th