DETROIT (WWJ/AP) A new report says the number of heat waves doubled in Detroit over the past 50 years.

University of Miami professor Larry Kalkstein, who co-authored the report, said Detroit averaged two heat waves per summer in 1959. Today we average four.

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Kalkstein said it’s a dangerous trend.

“More people die of heat then all of the other disasters combined — but it’s kind of a silent killer because you don’t see any damage associated with heat-related deaths like you do with tornado and hurricanes,” Kalkstein said.

The report, issued by the Union of Concerned Scientists, also said that while Detroit used to have 15 dry, comfortable summer days  the city now averages only five, with the first half of the year the hottest since 1895.

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Kalkstein said Detroit’s average night-time temperature has risen an average of 4-point-3 degrees during heat waves over the past five decades.

Read a summary of the findings for Detroit (.pdf format) 

Jeff Masters, co-founder of Weather Underground in Ann Arbor, said the new research doesn’t surprise him.

“We’ve had already 24 days in excess of 90 degrees; our average for an entire summer is usually just 11,” Masters said. “June was the ninth warmest June in Detroit history, but the year-to-date period is the warmest in Detroit history, going back to 1895.”

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