It might not seem like it this week as blizzard conditions are hitting the Midwest, but dangerous heat levels over the past few years have been breaking records. Graduate students at the University of Wisconsin-Madison are working with a climatologist to gather data to inform a public heat warning system that’s based on health outcomes.

Although extreme heat is one of the deadliest forms of extreme weather, it doesn’t garner the same immediate responses as other extreme weather events.

“We don’t necessarily prepare for it or respond to it with the same urgency as we do for things like hurricanes or tornadoes or other forms of extreme weather,” said Elizabeth Berg, UW-Madison graduate student. 

“The goal was to figure out a new way to forecast and communicate around heat events that trigger that same sort of response.”

Most heat warning systems solely consider meteorology. For example, a heat warning is issued if a city reaches a certain temperature, usually in the 90s, while also experiencing high humidity. 

But this project incorporates human health and mortality information into alerts, because people who live in different climates and living conditions respond differently to heat. The summer temperature variability is more important than just the absolute magnitude of the temperature, said Larry Kalkstein, a climatologist who is president of Applied Climatologists, Inc. and chief heat science advisor for the Adrienne Arsht-Rockefeller Foundation Resilience Center.

“In Wisconsin and in Chicago — in those places where it’s usually relatively comfortable in the summer, you have days when it’s 82 then suddenly it reaches 100 degrees — that’s what kills the people,” he said. “That doesn’t happen in the more southerly locations, like South Florida … where every day it’s hot, but everyone expects it and houses are built to accommodate that.”

Even heat waves that occur in the same location at different times during the summer can have different levels of deadliness. A heat wave occurring in Chicago in May, for example, could be more deadly because residents are less acclimated to hot temperatures than they would be during a heat wave in August.

Under the researchers’ health-dependent warning system, “you might call a warning for the one in May and not for the one in August,” Kalkstein said. “It looks at the weather 30 days prior to the heatwave, and if it’s been cool we deem it as more dangerous through this formula. If it’s been warm, it’s less dangerous.”

The project considers human health and morbidity holistically. Heat often becomes deadly when it exacerbates existing comorbidities or vulnerabilities, such as lung or heart conditions, rather than directly causing death on its own.

“This algorithm looks at overall heat effects and not just what you typically classify as heat effects,” said Sara Pabich, UW-Madison graduate student. “How does heat overall affect the human body, and do we see an increase in people going to the hospital for other diseases or impacts?”

Forging a partnership

Kalkstein, who now lives in Florida, began collaborating with UW-Madison for this project after he was contacted by Gavin Luter, director of UW-Madison’s UniverCity Alliance. The alliance’s core mission is to bring more exposure to the university’s research as it contributes to communities. Essentially, they foster partnerships to apply the research in cities where it could offer real-world benefits.

“We’re interested in embedding equity, sustainability, and democracy into how they operate in cities,” Luter said.

“We have a pretty big program where any local government across the state of Wisconsin can apply and ask us for help with a variety of projects.”

Luter organized a group of stakeholders, including Kalkstein, who are interested in networking and collaborating on the topics of heat and health. They formed the Wisconsin Heat Health Network. The group’s primary project is the heat health warning system that is under development.

“We’ve also been able to look at how the urban heat island effect has been disproportionately affecting lower-income communities in Milwaukee,” Luter said.

Testing the tool

The research team initially collected and analyzed heat and mortality data from six cities, including Madison and Milwaukee. 

They developed an algorithm for each city that considers weather data and mortality data from the last 30+ years. The formulas determine when more people are likely to die from heat based on historical precedent. 

“It started with a look at how mortality numbers historically have been impacted during periods of extreme heat,” Berg said. “From there, we were able to produce algorithms, or equations, to link the two and predict how future conditions that might look similar to some of these past events might impact health in the future in similar ways.”

Each city has its own algorithm because the conditions — weather, urban structures, demographics — vary, even if the cities are relatively close in proximity, such as Madison and Milwaukee. For instance, having a higher elderly population influences cities’ outcomes, as does having a high population of people living close together in high rises as opposed to spread out in single-family homes.

The researchers began a pilot program this summer that put the heat warning tool into action. They worked with the National Weather Service to evaluate how closely their data aligns with NWS heat advisories.

The pilot involved “monitoring in real time what kind of calls are being made [by weather agencies], from heat warnings being non-existent to mild to incredibly life-threatening,” said Becky Rose, UW-Madison graduate student. “Now, this is turning into a retrospective analysis, and this fall we were seeing how they’ve done. … This warning system incorporates a lot of things that are demonstrated through the training and learning of these algorithms for what actually affects human health.”

What’s next

The graduate students say an important finding from the initial pilot is that the data itself is only the first step; applying the data so it creates value and drives beneficial change is the larger task. The project aims to empower cities to use such tools to improve residents’ health outcomes amid climate change.

The researchers are centrally running the pilot program with the first six participating cities. “After a couple of years of being run centrally, the idea is that now the city has the tools to do these forecasts and use them how they want,” Berg said.

“It is likely that if this tool becomes public it would be more site-specific or more state-specific because regionality really matters,” Pabich said.

A key goal is to eventually prompt the National Weather Service and other organizations that issue heat advisories to reconsider the language in public heat warnings and to incorporate human health.

“The tool has already been created; the question is how much political will can we get across the United States to start to incorporate historical health-related data into the messaging and even a decision whether or not to issue a heat advisory,” Luter said. 

“We’re trying to ultimately make the conversation about what some real practices are that cities can use — especially Madison and Milwaukee — to slow the urban heat island effect.”

Advancing the tool and health-dependent heat warnings is a balancing act that has political considerations. The researchers also have to balance fine-tuning the tool so it adequately sends alerts during all concerning heat events without sending too many as climate change intensifies to prevent “warning fatigue” when the public tunes out the alerts.

“We don’t want to dismantle anybody’s credibility. It’s already hard enough, the climate of science and politics,” Rose said. “There’s a lot of pieces to figure out, and it’s really neat to be involved in this process.”

Photo: From left to right, graduate students Sara Pabich, Elizabeth Berg, and Becky Rose. (Credit: Althea Dotzour)