High humidity reduces the human body's ability to cool via perspiration. "When it is both very hot and humid outside, heat in the body cannot be expelled; this creates a condition called 'heat citotoxicity' that is damaging to many organs. "Think of it as a sunburn, but inside the body"
International team of 18 scientists identified 1,900 locations worldwide where heatwaves since 1980 had resulted in deaths."We collected climatic data for each location and time when there was a recorded heat-related death," explained co-author Iain Caldwell, also of the University of Hawaii.
By statistically comparing these heatwaves to "normal" periods, the researchers teased out the key factors contributing to excess mortality.
Temperature and humidity topped the list. How long a heatwave lasted also mattered, but -- surprisingly -- did not significantly improve predictive accuracy.
The researchers then plugged their findings into the averaged projections of 20 global climate models running until 2100.
