Forecasting Killer Heat: UD Systems Predict Deadly Weather Worldwide

January 28, 1999

ROME, ITALY -- Heat kills, claiming thousands of lives each summer, but new University of Delaware technology gives health officials up to 60 hours' advance warning of such deadly weather, which could prove particularly important in the 21st century, if global warming predictions come to pass.

UD climate expert Laurence S. Kalkstein -- sponsored by the United Nations Environment Programme (UNEP) -- will meet Feb. 1-2 in Rome to plan a new heat-health watch/warning system, with Italy's Lazio Health Authority, the World Meteorological Organization (WMO), the World Health Organization (WHO) and the Italian Meteorological Service.

The life-saving UD technology, to be installed in Rome by summer 2000, already protects people from killer heat in Philadelphia, Pa., and Washington, D.C. If the Italian system proves equally effective, Kalkstein says, warning systems may be launched in Shanghai, China, and elsewhere.

"In my opinion, heat is a leading cause of weather-related mortality, which may directly cause more deaths each year than lightning, tornadoes or hurricanes," says Kalkstein, director of UD's Synoptic Climatology Laboratory and associate director of the University's Center for Climatic Research.

On especially steamy days, he notes, the death rate can triple in certain cities such as New York, where total mortality jumped from an average of 490 to an astounding 1,260 fatalities during a single 24-hour period in 1966. Every summer in the United States, health officials point to heat as the key cause of some 2,000 deaths. And, many more heart attacks, strokes and other fatal afflictions may be triggered by stifling heat, according to Kalkstein.

"Our system saves lives by identifying and then forecasting the specific type of oppressive air mass known to kill large numbers of people within a given city," says Kalkstein, lead author of a health chapter in the landmark final report of the Intergovernmental Panel on Climate Change (1996). "Health authorities can then reach out to children, senior citizens, anyone in poor health and those in high-risk neighborhoods, where heat-trapping homes make people more vulnerable to very hot weather conditions."

As fossil fuel burning and other human activities increase the amount of greenhouse gases in the atmosphere, Kalkstein says, temperatures are likely to rise worldwide. By the year 2050, hotter summer temperatures could boost the annual number of heat-related deaths by 70 to 100 percent, according to Kalkstein. Slightly lower winter death rates aren't likely to offset such a dramatic increase in summer fatalities, Kalkstein reported in the journal, Environmental Health Perspectives (vol. 105, no. 1, January 1997, pp. 84-93).

Whether or not global warming occurs, ongoing weather events such as El Niño--that notorious disruption of the ocean and atmosphere within the tropical Pacific--routinely produce unhealthy heat levels, notes WMO representative Tanja Cegnar, head of climatology at the Hydrometeorological Institute of Slovenia.

"The current variability of climate, and the intensity of heat in large, urbanized areas, point to the need for this heat-warning technology," says Cegnar, who will work with Kalkstein to implement the Italian system. "Heat waves increase mortality rates, and they have a tremendous impact on our quality of life, often affecting physical and mental performance, and sometimes worsening an existing illness."

UNEP representative Hiremagalur Gopalan notes that hot weather also promotes such diseases as malaria and dengue fever, and it can contribute to harmful ozone levels, which affect elderly people, children and those with asthma or cardiovascular ailments. "Many of the health effects of climate changes-and in particular, heat-related effects-could be avoided through strong public health programs to monitor and treat people," says Gopalan.

Kalkstein proposed additional "showcase" heat-warning systems for selected cities during a January 1997 meeting of climate and human health experts in Freiburg, Germany, says Gerd Jendritzky, lead WMO rapporteur for that event. Existing systems clearly demonstrate the value of routine heat warnings, says Jendritzky (Deutscher Wetterdienst). And, they provide fundamental insights into the factors affecting heat-related death rates.

Philadelphia System Saves Lives

When a particularly brutal heat wave struck in 1995, the newly installed Philadelphia Hot Weather -- Health Watch/Warning System -- developed at UD and run by the city's Department of Public Health-"undoubtedly saved many lives," Kalkstein says.

If conditions threaten human health, Philadelphia officials distribute media advisories, activate telephone hotlines, alert neighborhood volunteers, open air-conditioned shelters, expand outreach to the homeless, coordinate efforts with local utilities or take other actions, depending on the level of risk predicted by UD's warning system. In Washington, D.C., the Office of Emergency Preparedness operates a similar warning system, based on the computer-software program developed by Kalkstein's research team.

"Putting into place an emergency-response program involving a large number of agencies and individuals requires a rapid shift of personnel and resources," notes Lawrence Robinson, a deputy health commissioner for public health promotion, who oversees Philadelphia's emergency heat program. "The UD system allows us to launch these special services exactly when they are needed to save lives."

The UD program analyzes National Weather Service forecasts, in light of a city's historic mortality rates, as well as meteorological variables, including temperature, humidity and cloud conditions. "A clear, blue sky may be beautiful," Kalkstein points out, "but it can kill people if the temperature rises high enough to cook residential buildings, which stay shaded and cooler on cloudy days, even in heavy heat."

UD's heat warning system also takes into account the type and severity of a predicted hot air mass; the duration and timing of the heat wave; and the city's specific "threshold," or temperature known to boost the death rate.

Southerners Stay Cool

This heat threshold varies from city to city, Kalkstein says, because people living in warmer regions adapt to the environment, and buildings in Southern and Southwestern cities -- from Miami, Fla., to Houston, Tx. -- are designed for warm-weather comfort. Such "acclimatization" explains why heat kills fewer people in warmer U.S. cities, Kalkstein says.

In Philadelphia, for example, the total number of "excess" deaths for a given summer, over and above the city's average, is 129 -- compared to zero for Miami, Kalkstein says, thanks to acclimatization. Using the same formula, the heat-related death rate is 307 for New York City, but zero for Phoenix, Ariz., Kalkstein's EHP article shows.

"Other U.S. cities with high summer heat deaths include Detroit, Mich.; Chicago, Ill.; Newark, N.J.; and St. Louis, Mo.," he reports. "Urban structures in these cities often are designed to trap heat, and people aren't prepared for sudden or long-lasting heat waves."

Like the UD systems in Philadelphia and Washington, D.C., the Italian warning system will reflect that city's unique climate conditions, and how the population has historically responded to different hot-weather events.

Participating in the Feb. 1-2 meeting in Rome will be representatives from the Italian Meteorological Service; experts from the WMO; a WHO official who coordinates European weather/environment research; and numerous public health officials from Rome's city government. The meeting, to take place in Rome's Villa Torlonia Hotel, will be coordinated by Kalkstein and Cegnar.

The Italian warning system will be funded by an initial $50,000 grant from the United Nations Environment Programme. Kalkstein's work for the City of Philadelphia was sponsored by the U.S. Environmental Protection Agency. His research also receives support from the National Oceanic and Atmospheric Administration, Johns Hopkins University and the state of Delaware.
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