An "extreme heat belt" reaching as far north as Chicago is taking shape, a corridor that cuts through the middle of the country and would affect more than 107 million people over the next 30 years, according to new data on the country's heat risks.
The report, released Monday by the nonprofit research group First Street Foundation, found that within a column of America's heartland stretching from Texas and Louisiana north to the Great Lakes, residents could experience heat index temperatures above 125 degrees Fahrenheit by 2053 — conditions that are more commonly found in California's Death Valley or in parts of the Middle East.
The projections are part of First Street Foundation's new, peer-reviewed extreme heat model, which shows that most of the country will have upticks in the number of days with heat index temperatures above 100 degrees over the next 30 years as a result of climate change.
The heat index represents what a temperature feels like to the human body when humidity and air temperature are combined. It is commonly referred to as the “feels like” temperature.
"Everybody is affected by increasing heat, whether it be absolute increases in dangerous days or it’s just a local hot day," said First Street Foundation’s chief research officer, Jeremy Porter, a professor and the director of quantitative methods in social sciences at the City University of New York.
It has already been a sweltering summer for much of the U.S. and Europe. The National Oceanographic and Atmospheric Administration’s latest monthly climate report, published Aug. 8, found that last month was the country’s third-hottest July since record-keeping began nearly 130 years ago.
As humans continue to pump heat-trapping greenhouse gases into the atmosphere, temperatures around the world are rising, which increases both the frequency of extreme heat events and their severity.
Researchers at First Street used their model to create an online tool called Risk Factor to give people hyperlocal snapshots of how their property is affected by extreme temperatures and what could change over the next three decades. The organization previously created similar resources to evaluate specific addresses’ risks from wildfires and flooding.
The new model uses high-resolution measurements of land surface temperatures and incorporates the effects of canopy cover, proximity to water and other factors that determine local temperature variability. Future heat risk is then calculated using different forecast scenarios for greenhouse gas emissions in the decades to come.
The researchers looked at the seven hottest days expected for any property this year and calculated what the equivalent could be in 30 years. Across the country, they found that, on average, a community's seven hottest days are projected to become the location's 18 hottest days by 2053.
The most pronounced shift was found in Miami-Dade County, Porter said, where the area's seven hottest days, with heat index temperatures at 103 degrees, are projected to increase to 34 days at that temperature in 30 years.
But in addition to widespread increases in heat exposure, First Street's model also identified what Porter and his colleagues call an "extreme heat belt" that covers about one-quarter of the country's land area.
About 8.1 million U.S. residents in 50 counties are at risk of experiencing heat index temperatures over 125 degrees. But by 2053, the projection expands to more than 1,000 counties across an area that is home to more than 107 million people, according to First Street’s model.
The zone's geographic boundaries and its sheer size were surprising, Porter said.
"How far north it stretched — I think a lot of people just hearing southern Wisconsin, Chicago and those areas being part of the extreme heat belt is surprising," he added.
The agricultural impact of such a wide-ranging heat belt in the country's heartland is particularly worrisome, said Noboru Nakamura, a professor of geophysical sciences at the University of Chicago, who was not involved with First Street's research.
"If there are hot spots and dry spells in these places, farmers will have to shift their priorities and what types of crops they'll plant, and that will all have a lot of long-term consequences," Nakamura said.
There are also enormous public health and safety concerns with heat exposure, he added. Across the country, heat causes more deaths every year than any other weather event, according to the National Weather Service.
Sharp increases in extreme heat are likely to affect people's lives and livelihoods in certain places, Nakamura said, and they could even play a factor in where people choose to call home.
"If a certain fraction of days per year are over 100 degrees, then unless you have the resources and infrastructure to stay cool, then it makes certain places very difficult to survive," Nakamura said. "I can certainly envision that would shake up peoples' decisions about where to live."