Death Rates Rise due to Global Warming

Global warming will cause more deaths in summer because of higher temperatures, but these will not be offset by fewer deaths in milder winters, claims a new analysis.

Researchers from the Harvard School of Public Health (Boston, MA, USA) analyzed city-specific weather data related to the deaths of more than 6.5 million people in 50 cities in the United States between 1989 and 2000. The researchers found that during two-day cold snaps there was a 1.59% increase in deaths because of the extreme temperatures. However, during similar periods of extremely hot weather death rates went up by 5.74%. Heart attacks and cardiac arrests were found more likely when it was very cold. Deaths did not rise as steeply when temperature fluctuations were less extreme.

The effect of extreme cold was homogeneous across cities with different climates, suggesting that only the unusualness of the cold temperature (and not its absolute value) had a substantial impact on mortality. Conversely, heat effects were quite heterogeneous, with the largest effects observed in cities with milder summers, less air conditioning and higher population density. Adjustment for ozone levels led to similar results, but some residual anomalies could be present due to other uncontrolled pollutants. The study was published online on June 28, 2007, in the journal Occupational and Environment Medicine.

"Central heating, which constitutes an important adaptive mechanism against cold, is almost universal in the U.S. and this may explain why the U.S. population seemed fully acclimatized to cold,” said lead author Mercedes Medina-Ramon, Ph.D., and colleagues. "Making air conditioning universally available may reduce heat-related mortality but would, on the other hand, have a perverse effect by enhancing global warming through carbon dioxide emissions from electricity consumption.”


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