Global warming could increase U.S. death rate

By Amy Norton

NEW YORK (Reuters Health) - An increase in summertime heat waves from global warming could mean more deaths among Americans each year, a study by Harvard researchers suggests.

It's well known that extreme temperatures, whether in the form of heat waves or cold snaps, can be deadly. However, the new findings suggest that any increase in heat-related deaths from global warming would not be offset by a drop in cold-related deaths.

Using weather data and death rates for 50 U.S. cities between 1989 and 2000, researchers found that, on average, a two-day cold snap increased death rates by 1.6 percent. Heat waves, on the other hand, triggered a 5.7 percent increase.

"We saw that the effects of cold temperatures are not as big as the effects of hot temperatures," said lead study author Dr. Mercedes Medina-Ramon, of the Harvard School of Public Health in Boston.

This means that relatively milder winters attributable to global warming are unlikely to make up for the health effects of summertime extremes, she told Reuters Health.

Medina-Ramon and colleague Joel Schwartz report their findings in the journal Occupational and Environmental Medicine.

Deaths related to extreme cold are often from heart attacks or cardiac arrest. Extreme heat, along with causing deaths from heatstroke, can contribute to deaths from other causes, like heart attacks.

The elderly and people with known heart disease are among those most at risk during temperature extremes.