Feb 21, 2017

The guilt of record warmth in Chicago — climate change?

Chicago, IL
USA
by
Patrick M. O'Connell, Kate Thayer
,
Chicago Tribune
Record-breaking temperatures draw Chicagoans outdoors. Photo: Chicago Tribune
Record-breaking temperatures draw Chicagoans outdoors. Photo: Chicago Tribune

Whether the record-breaking warmth is a sign of climate change, or of a harsh spring to come or just a burst of unseasonable weather is difficult for experts to discern. The warm spell is too short a time period to determine its true cause, climate scientists say. And meteorologists point out that there are natural variances in weather over time.

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"It's very extraordinary. I have to keep reminding myself this is February and not March or April. It's kind of weird," said Jim Angel, the Illinois state climatologist.

Angel said it's hard to draw a direct connection between stretches like the past few days and overall climate change because bursts of extreme temperatures are too short to allow for deeper conclusions. Illinois has always had great variability in its weather, he said.

A wider snapshot of the state's weather over the last century, however, shows that Illinois winters have warmed 1.8 degrees, Angel said. What's happening, he said, is harsh winters are being replaced with milder ones. The polar vortex winter of 2014, however, was a notable exception.

Climate scientist Katharine Hayhoe, a professor at Texas Tech University, agrees it's impossible to know if the recent warm spell is due to overall warming trends this past decade across the country — which points to climate change — or a natural, periodic shift in weather.

Still, "the reality is any conditions we have these days are different than they would've been 50 or 100 years ago because we've changed background conditions," she said, pointing to data that show there are now more than twice as many record-breaking high temperatures compared to a decade ago.

One theory, according to scientists, is that reduced ice cover at the North Pole and Arctic Ocean — some say due to climate change — creates more unstable conditions and leads to wild fluctuations in temperatures farther south, Angel said. The most recent balmy weather here has been the result of the jet stream staying to the north and the area experiencing a surge of warm, moist air from the Gulf of Mexico.

"When you get more mild winters, it's easier for the temperatures to shoot up because you don't have a snow cover and the ground is warm anyway," Angel said.

In recent days, the soil across the state has been in the 30s and 40s, not frozen, and that helps temperatures soar.

"It feeds on itself," Angel said.