Chicagoans were treated this past week to the warmest Christmas in nearly four decades.
While the rare December rays were cause for celebration for the thousands who ventured outside for holiday activities, the unseasonable warmth also raises a key question: Could such springlike yuletide weather be a gift that keeps on giving — with devastating effects for the Lake Michigan ecosystem?
Scientists are loath to attribute any single weather front to the worldwide pattern of climate change, but last week’s balmy late-season heat wave put a spotlight on the Great Lakes region, where temperatures have been rising for a century — and have climbed even more starkly in recent years.
Figures from the National Oceanic and Atmospheric Administration back up what numerous experts from across the Midwest say: Such weather extremes will become only more frequent if those temperatures keep going up.
“This kind of late-season extreme is indicative of the broader trend of climate change,” said Howard Learner, an attorney who serves as executive director of the Environmental Law and Policy Center, based in Chicago. “These are the kinds of things that scientists are telling us will become more frequent as temperatures and water levels continue to rise.”
That includes increasingly powerful hurricanes, more bone-rattling wind chills via polar vortices and, yes, late December days that feel more like mid-May, Learner said.
The Christmas high of 57 degrees was the warmest in Chicago since the mercury hit 64 degrees in 1982, making this year the second highest since the National Weather Service started recording temperatures in 1871. Wednesday was also the first time since 1954 that Christmas in Chicago was warmer than Halloween, forecasters said.
For Illinois, the average temperature of 52.5 degrees last year was up 0.9 degrees from the 21st century average of 51.6 degrees, according to NOAA figures. It also marked the fourth straight year the state’s temperature fluctuated upward from the average and the 16th year it did so in the last two decades.
Cook County, too, was up 0.4 degrees last year from the average of 48.9 degrees, NOAA figures show, with Chicago trending upward for a fourth straight year by 0.6 degrees.
Those follow the Great Lakes regional trends outlined by NOAA, which include an average air temperature increase of 2.3 degrees from 1951 to 2017.
The number of frost-free days increased by 16 days over that time frame, with a 14% increase in overall precipitation and a 35% increase in “heavy precipitation” events. The frost-free season could grow by an additional 50 days by the end of the century, the federal agency has noted.
Summer lake surface temperatures have increased even faster than the air temps, according to NOAA, with Lake Superior going up a whopping 4.5 degrees from 1979 to 2006.
Average temperatures are expected to increase by up to 6 degrees by 2050 and by up to 11 degrees by the end of the century.
It all spells trouble for the Midwest: increased flooding, decreased crop yields and reduced air quality. The Environmental Law and Policy Center published a comprehensive study earlier this year of the potential impact of Great Lakes climate change.
“By century’s end, the region will experience 30 to 60 additional days each year of these extremely warm temperatures,” the report concluded. “Areas within the Great Lakes Basin will see an increase of 17 to 40 extremely warm days as annual average temperatures continue to rise.”
The study, written pro bono by 18 experts from 14 universities in the region, also noted “unprecedented extreme changes in the timing of precipitation.”
So while the novelty of a temperate Christmas Day might make for a fun family game of holiday pigskin, it could point to stormier times ahead.
“This is an issue we need to address immediately, on multiple fronts,” Learner said, pointing to, among other things, investments in electric vehicles, solar energy and rail transit to cut down on carbon emissions.
Temperatures flirted with 60 degrees again Sunday, peaking in the high 50s, but were expected to fall to around 35 degrees Monday, according to National Weather Service in Chicago.