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In this Aug. 9, 2017 file photo tourists refresh themselves at a fountain in Rome. Photo: Gregorio Borgia, AP File

Record-setting heat waves have swept the Pacific Coast, the U.S. Midwest, southern Europe, and elsewhere intermittently this summer. Weather records are set virtually every year, and every season, someplace on Earth.

But Chicago and the surrounding region are experiencing an unprecedented phenomenon: a summer-style heat wave lasting more than a week at the end of September. While that 92-plus degree week has been seen before in the Windy City, that was at the absolute peak of the summer of 1988.

“There has never been a heat wave of this duration and magnitude this late in the season in Chicago,” according to a National Weather Service public information statement issued Tuesday. “Chicago has never recorded seven consecutive days with high temperatures 92 degrees Fahrenheit this late in the year.”

The heat wave calendar could be expanding beyond the summer into the spring and autumn, according to a study published Monday in the journal Scientific Reports.

The Australian researchers found that more heat waves, of increasing duration and intensity, will arrive as the global temperature climbs.

“Global warming beyond 2 degrees Celsius (will) likely infer devastating impacts if anthropogenic climate change is not constrained as soon as possible,” write the authors, from the University of New South Wales in Australia.

The data is based on the CMIP5 (Coupled Model Intercomparison Project), a weather archive incorporating 27 models and long-term climate predictions at a global and regional level. The data inputs involve daily information from 1861 to 2005.

They found that between four and 34 extra heat-wave days are added per season, for each increased degree Celsius of global temperature.

The heatwaves will last up to an additional 10 days for each of those Celsius degrees, they report.

For some regions, “a perpetual heatwave state will emerge each summer once 2 degrees Celsius global warming is reached and exceeded,” they write.

According to those scenarios, an additional 60 to 120 extra days of heat wave will be achieved by the end of the century (though that is compared to the pre-industrial climate, not current levels).

Sarah Perkins-Kirkpatrick, the lead author from the Climate Change Research Centre, told Laboratory Equipment magazine in an email that the Chicago scenario can't be explicitly linked to climate change - but the likelihood of such events will continue to grow with higher temperatures.

"Extreme and prolonged heat events that were extremely rare, or had never occurred before, will occur much more frequently," she wrote. "It’s extremely difficult to attribute a single event to climate change (e.g., did climate change cause this heatwave in Chicago?), but higher temperatures, more frequently, is certainly what we expect with a warming climate."

Although some regions experienced a relatively cool summer this year, including the U.S. Northeast, NOAA announced that the relative heat continues. The year to date is the second warmest on record to date through August – and August itself was the third hottest on record.

The hottest year was last year – which represented the third annual record set in a row.

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