Global Warming May Hike U.S. Deaths

June 27, 2007 -- Global warming might raise the U.S. death rate, Harvard researchers warn in a new study.

Mercedes Medina-Ramon, PhD, and Joel Schwartz, PhD, conducted the study. They work in the environmental health department at the Harvard School of Public Health.

The researchers reviewed death rates and temperatures in 50 U.S. cities from 1989 to 2000.

They found that death rates rose when those cities had two consecutive days of extremely hot or extremely cold days, based on each city's typical temperature range.

During two-day heat waves, death rates rose by 5.74%, compared with a 1.59% increase in death rates during two-day cold snaps.

The researchers note that global warming is expected to increase overall temperatures over time, as well as making extremely hot days more common and extremely cold days rarer.

Since the death rate jumped higher on extremely hot days, the drop in extremely cold days may not fully offset heat-related deaths, the researchers note.

Why did the death rate soar more on very hot days than very cold days? That may be because central heating is "almost universal in the U.S.," but air-conditioning is less common, especially in traditionally mild cities, note the researchers.

What if everyone got air-conditioning? That may not be an option for people with low incomes, and even if it was possible, more air-conditioning would mean more electricity consumption, more carbon dioxide emissions, and more global warming, according to Medina-Ramon and Schwartz.

Their study appears in the journal Environmental and Occupational Medicine's advance online edition.