Hotter heat waves that last longer: What's happening here and in Europe

As heat waves sweep the globe this week, scientists say there's no question that climate change is playing a role in intensifying the weather events around the world — but the environmental drivers of extreme heat vary regionally.

One hundred-degree weather is bearing down on several European countries and a large swath of the U.S. in the coming days, while temperatures in the Chicago area will surpass 90 degrees through the weekend. These spikes of heat have been happening for a long time, but global warming is pushing temperatures higher.

“Because our overall background climate has warmed, it makes it more likely that we can get those extreme temperatures that even 30 to 50 years ago were very unlikely,” state climatologist Trent Ford said. “From that standpoint, climate change plays an important role.”

The mechanisms that typically drive heat waves are naturally occurring: heat gain at the surface establishes high pressure, slows the jet stream — the rivers of wind that circle the planet at high altitudes — and creates a mountain of atmospheric flow.

High pressure systems are stubborn, Ford said, and can deflect movement that would otherwise bring in rainfall, cool air and cloud cover. In Illinois, we also get air flow from the south and southwest, driving heat even higher.

Ford added that the kinds of atmospheric patterns we tend to run into in Illinois are different from what impacts extreme heat in Western Europe.

For us, the Pacific Ocean and the Gulf of Mexico play important roles in our atmospheric circulation, especially when it comes to humidity. In the U.K., the climate is more dependent on the North Atlantic, the Arctic and the subtropical Atlantic.

“The idea of global warming, or the increase in global average temperatures, results in climate change — the change in a regional climate,” Ford said. “Climate change itself means different things for different regions.”

Ford said Illinois has warmed over the last 100 years, and the magnitude of that increase has accelerated over the last 30 years.

“That is what we're seeing. Every single county, every single place in Illinois has warmed, and projections for models indicate that that warming is going to continue if not intensify over the next coming decades,” he said.

Over the last century, average daily temperatures have increased by 1-2 degrees statewide, a recent study found.

Donald Wuebbles, a climate scientist at the University of Illinois at Urbana-Champaign who co-led the report, said heat waves are not only getting hotter but lasting longer.

“When we talk about climate change, we don't talk about any particular year, but this year what we've been seeing is heat waves getting more frequent and intense,” he said.

Extreme heat is cause for varied concerns, particularly for human health, infrastructure, wildlife and crop production, Wuebbles said.

“The agricultural community is likely going to be affected by very dry soils. Extreme heat is not good for all these crops,” he said.

Ford added that while it is clear to scientists that global warming is causing more intense and hotter heat waves, he said scientists continue to study the extent to which global warming is generating longer heat waves more often.

“When it comes to the frequency, or the persistence of these sorts of weather patterns that cause heat waves, it's a lot harder to establish that evidence. It's something that scientists are working on, but it's not as well established and developed as, for example, the change in temperature.”

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work, click here to make a tax-deductible donation.

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work, <a href="https://checkout.fundjournalism.org/donateform?org_id=reportforamerica&campaign=701f40000003GaH&theme=The%20Daily%20Herald.">click here</a> to make a tax-deductible donation.