'Killer' heatwaves could threaten U.S.

NEW YORK, May 30 (UPI) -- More than 150,000 Americans could die by the end of this century due to the excessive heat caused by climate change, a U.S. environmental advocacy group says.

The Natural Resources Defense Council said illnesses that are caused or made worse by extreme heat -- including heat exhaustion, heat stroke, cardiovascular disease and kidney disease -- currently lead to hundreds of deaths each year, and increased warming due to climate change could lead to a dramatic increase in the number of lives lost in the country's Top 40 cities.

Scientists predict average temperatures in North America will rise by another 4 degrees to 11 degrees Fahrenheit this century, an NRDC release said Wednesday.

The risks to public health are greatest when high temperatures mix with other weather conditions to cause what's known as an "Excessive Heat Event," when a location's temperature, dew point temperature, cloud cover, wind speed and surface atmospheric pressure throughout the day combine to cause or contribute to heat-related deaths in that location, the organization said.

The frequency of such events varies by region and location, the NRDC said, influenced by factors such as geography, green space, local warnings and preventive measures.