In the United States, 145 natural disasters resulted in 14,536 deaths from 1945 to 1989. Of these events, 136 were weather disasters; these extreme weather events caused 95% of all disaster-related deaths. Floods are the most frequent type of disaster.
More frequent extreme weather events are predicted to accompany global warming
(see Figure 8-10), in part as a consequence of projected
increases in convective activity. More intense rainfall events accompanying
global warming would be expected to increase the occurrence of floods, and warmer
sea-surface temperatures could strengthen tropical cyclones (IPCC 1996, WG I).
|Figure 8-10: Average annual weather-related mortality for 1993, 2020, and 2050 climate (Kalkstein and Greene, 1997), based on 1980 population and the GFDL89 climate change scenario. Annual estimates were obtained by adding summer and winter mortality. The projections do not account for population growth, nor do they fully account for air-conditioning use; however, they do assume acclimation to changed climate.|
Climate models are unable to predict extreme events because they lack spatial and temporal resolution. In addition, there is no clear evidence that sustained or worldwide changes in extreme events have occurred in the past few decades. Nonetheless, such events cause loss of life and endanger health by increasing injuries, infectious diseases, stress-related disorders, and adverse health effects associated with social and environmental disruptions and environmentally enforced migration. Because each extreme weather event is unique in scale and location, and population vulnerability varies considerably, it is not possible to quantify the health impacts that would be associated with potential changes in extreme weather events.
Recent floods in the United States (e.g., Mississippi River flooding in 1993) were caused primarily by unusually high precipitation combined with soil saturation from earlier precipitation (Kunkel et al., 1994). In the United States, flash floods currently are the leading cause of weather-related mortality. In addition to causing deaths by drowning, flooding can lead to widespread destruction of food supplies and outbreaks of disease as a result of breakdowns in sanitation services. Flooding also may result in the release of dangerous chemicals from storage sites and waste disposal sites into floodwaters. Increased runoff from agricultural lands during periods of heavy precipitation also can threaten water supplies. The 1993 Mississippi River flooding, for example, caused wide dispersal of microorganisms and chemicals from agricultural lands and industrial sites (Changnon, 1996).
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