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Heat-related Mortality and Heat Watch-warning Systems in the United States: Recent Developments

Sheridan, Scott1; Kalkstein, Laurence2; Kalkstein, Adam3; Greene, Scott4

doi: 10.1097/EDE.0b013e3181fa5ca1
Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Climate Change and Environmental Health

1Kent State University, Kent, OH; 2University of Miami, Coral Gables, FL; 3United States Military Academy, West Point, NY; and 4University of Oklahoma, Norman, OK.

Abstracts published in Epidemiology have been reviewed by the societies at whose meetings the abstracts have been accepted for presentation. These abstracts have not undergone review by the Editorial Board of Epidemiology.


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Heat watch-warning systems have increased in coverage, and in some US locales, have now been operational for over 15 years. Heat-related mortality has decreased over the last few decades, partially as a result of increased awareness, but it is still statistically significant in many locations. We present recent research results on several projects that assess these changes as well as projected future changes, and the spatiotemporal variability in heat-related mortality across the United States.

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Trends are assessed using both the synoptic climatological methodology, utilized in the authors' heat watch-warning systems, and the Heat Stress Index, a numerical quantifier of the severity of heat relative to location. Estimates of heat-related mortality are developed for 40 large US cities, using climate models for 3 decades over the next hundred years and various emissions scenarios.

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Over the past 30 years, the heat-mortality relationship has tended to converge across the United States, with areas in the warmer climates experiencing generally slight increases in mortality response, and areas in colder locations, which were historically more sensitive, experiencing more significant decreases. On a seasonal level, there is an asymmetry in heat-related mortality, with most cities exhibiting the largest increases before the summer solstice; in some cases in the southern United States, the hottest days in late summer exhibit a mortality decrease. Heat-mortality relationships are much more consistent across larger cities than smaller cities.

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The impacts of an anticipated climate change will vary among urban areas. The results show an increase in excessive heat event days and increased heat-attributable mortality across the cities with the most pronounced increase in the Southeast and Northeast. An evaluation to determine how various intervention activities would ameliorate this rise shows that public health responses and a nationalization of heat warning systems can dramatically lessen the increase posed by a climate change.

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