18.104.22.168. Extreme Weather Events
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