Fact-checking Casten’s overheated claim about extreme Chicago summers

A group of House Democrats and environmental group leaders held a news conference touting President Joe Biden’s infrastructure spending priorities, which include efforts to curb climate change.

Among them was U.S. Rep. Sean Casten, a former clean-energy entrepreneur who represents Illinois’ west suburban 6th Congressional District. To make his point, the second-term congressman gave a local example to emphasize the cost of a rapidly warming world.

"Chicago had a heat wave in 1995 that killed 739 people," Casten said Aug. 23. "Prior to 9/11 that was the largest single-day, non-war fatality in the United States. We are now expecting temperatures that hot in Chicago every summer."

The heat wave that struck Chicago that July more than 25 years ago was labeled the deadliest weather event in the city’s history. But it did not take those lives in a single day, making it impossible to compare the tragedy to more sudden disasters. Casten is on firmer ground when it comes to predictions about forecasts for more frequent extreme heat in Chicago, though he left out some important context there, too.

The lethal heat wave that July lasted three days and killed 739, according to one estimate from researchers, who also found elderly and Black Chicagoans were disproportionately affected.

While the event is considered among the nation’s deadliest climate disasters, it was not the deadliest domestic tragedy prior to the Sept. 11, 2001, terrorist attacks, nor the most fatal event in Chicago history. In 1915, for instance, a passenger boat called the SS Eastland capsized while tied to a dock in the Chicago River, killing 844.

Casten specified "single-day" fatalities, so we wondered why he chose to compare an estimated death toll for a heat wave that spanned multiple days to the number of fatalities from more sudden disasters like the SS Eastland sinking.

In response to our question, Casten spokesperson Emilia Rowland acknowledged the mistake. "I believe my boss misspoke," she wrote in an email.

As backup for the second part of Casten’s claim, Rowland sent us a 2010 research brief from the University of Illinois that explored what the Midwest’s climate may look like by mid-century.

During the deadly 1995 Chicago heat wave, the two-page publication notes, "temperatures soared as high as 106 degrees during the day and stayed above 80 degrees on many of the hottest nights. Such heat waves will be more commonplace in 2050. Under lower emissions scenarios, they could occur once per decade. Under higher emissions scenarios, they could happen once a year."

Those predictions were based on previous work from the climate scientists who authored the brief, Donald Wuebbles of the University of Illinois and Katharine Hayhoe of Texas Tech University. The future looks even more grim by the end of the century, when their research predicts Chicago could see 1995-like heat waves every other year even if emissions are lowered and up to three times per year if emissions are not significantly reduced soon.

More recent reports have also forecast unprecedented temperature increases in northern Illinois by the end of the century in line with those earlier findings, Wuebbles told us.

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stated on July 26, 2012 in a debate

After the 9/11 terrorist attacks grounded commercial air traffic, "there was a temperature drop while the airplanes weren't flying, for the week afterwards."

But the research doesn’t fully back up Casten’s claim that Chicago is "now expecting" temperatures as hot as the 1995 heat wave every summer.

"We are expecting temperatures as hot as the 1995 heat wave in Chicago to recur more frequently as a result of climate change: that is absolutely true," Hayhoe said. "The question is, ‘how often?’ — and that depends both on the time frame we’re talking about, and even more critically on our emission choices."

Casten said the 1995 Chicago heat wave that killed 739 people was "the largest single-day, non-war fatality in the United States" prior to 9/11 and "we are now expecting temperatures that hot in Chicago every summer."

That heat wave spanned multiple days, making it impossible to compare the event to more sudden tragedies, many of which also killed more people. Casten’s office told us the congressman was mistaken in this comparison.

Casten is correct that Chicago faces a future of increasingly frequent extreme heat. If significant actions are not taken to reduce emissions, the city could face 1995-like heat waves every year. But Chicago might still avoid this fate with lower emissions, researchers said, and even in the worst case such extreme heat events would not become so frequent until at least 2050.

We rate Casten’s claim Mostly False.

MOSTLY FALSE – The statement contains an element of truth but ignores critical facts that would give a different impression.

Click here for more on the six PolitiFact ratings and how we select facts to check.