Cities globally face a growing, deadly threat: extreme heat. A product of climate change, heat waves are getting hotter, lasting longer, and killing more people.

No American city experiences extreme heat like Phoenix. Last year, the Arizona capital sweltered through a record 113 straight days with temperatures over 100 degrees Fahrenheit – the mercury even topped 110F (about 43C) for 70 days.

Phoenix did not begin the 2024 heat season unprepared, however. The city’s Office of Heat Response and Mitigation (HeatReadyPHX) works yearlong to plan adaptation measures (helping people cope with extreme heat in the moment) and mitigation (building shade and educating tenants that their landlords are legally required to provide AC).

And yet, excess deaths from the heat season are still being calculated.

The city’s 2024 heat emergency was the focus of a recent exercise at Harvard, where several dozen faculty from departments across the university simulated roles within Phoenix’s public agencies, health system, and non-profits to examine the causes, consequences and responses.

Many sides to a crisis

After Tess Wiskel, an emergency physician at Beth Israel Deaconess Medical Center, explained the physiological impacts of high temperatures, participants were divided into teams representing real Phoenix government agencies: the departments of Public Health and Public Works, the police, the Office of Homeless Solutions, and others. Hi-vis safety vests identified the different groups. These agencies each have responsibilities and jurisdictions that can intersect and overlap: where to place cooling centers, how to communicate the risks, when utilities are forbidden from cutting essential services. In real life, as in the simulation, strong collaboration is essential.

Next, each group was asked to discuss a breakout prompt for 10 minutes before presenting its strategy: “How can we prepare for 2024?” “What is the threshold for triggering the heat response plan?” “Who are most at risk and how do we reach them?”

Following each question, the organizers screened an interview with a Phoenix official or researcher addressing the issue and presented the latest peer-reviewed research.

Participants had only an afternoon to work through the long Phoenix summer. To mimic the advancing calendar, organizers aired local television news reports on the heat warnings and individual tragedies.

Exposure

With 100-degree days arriving by April, sim participants quickly discovered some of the hurdles to coordinating the needs of 1.6 million residents from all walks of life. For example, when should non-essential daytime work be stopped? Business groups, with an eye on the economic impact, want to set a higher bar than health officials, who measure an uptick in emergency room visits.

Such tradeoffs become the source of “constant negotiation,” said the lead organizer, Associate Professor of Emergency Medicine Satchit Balsari, who researches the use of digital tools to advance public health planning as co-investigator of the Salata Institute’s Climate and Adaptation in South Asia research cluster.

“Think about construction work. Common sense says, ‘Start early in the morning, before the day gets hot’. But most neighborhoods don’t want people banging tools at five or six in the morning, right?” said Balsari, who had discreetly turned up the thermostat in the classroom.

Another question: What exactly is a heatwave? Humidity plays a big role in the body’s ability to survive high temperatures. Wiskel distributed an 18-page handout outlining different criteria. After allowing participants to flip through the pages for few minutes, she noted, “That little package is the problem, right? It’s not obvious which of the various thresholds you should be using.”

One participant, an economics professor, aired a concern about “perverse effects.” Could the existence of public cooling centers – where people can enter an air-conditioned room to escape immediate danger – “encourage employers to feel they can make people work in the heat of the day because there are these designed places for safe breaks”?

Participants – who, at this point, were peeling off sweaters – also examined official communication strategies. Balsari highlighted the importance of actionable warnings. “Mild, moderate, severe – that doesn’t necessarily capture the intensity of the problem. The best warning systems should have actions attached: ‘stay home’, or ‘cool down’, or ‘this is air-conditioning weather’,” he said. “It should tell you what to do, not just tell you how bad the problem is.”

Identifying the people most at-risk can seem straightforward. The unhoused, those who struggle to afford air conditioning, older people, and those with heart trouble all face worse health outcomes during extreme heat. Officials can place cooling centers nearby, send medical teams to visit the unhoused, stockpile water bottles.

Yet even with these strategies, reaching the at-risk can be a challenge.

That’s why doctors and city officials in Phoenix collaborate with a variety of volunteer organizations providing unique services, said Robert Meade, a postdoctoral research fellow with the Salata Institute’s South Asia climate research cluster, and one of the organizers.

“We try to limit exposure as much as possible – with breaks, with shade. But once it gets hot, we must reach people at the greatest risk,” Meade said. “For example, people who don’t have loved ones, or are isolated, can sign up to be on Phoenix’s ‘cool callers’ list. When there’s a heat wave, they’ll call you every so often, check in, make sure you’re doing okay.”  

New normal

Toward the end of the sim, a participant playing team lead for the Emergency Management Department observed that his role should be assumed by a different government agency.

“At a strategic level, you can’t really respond your way out of the new normal,” he said. “Now that this [heat] is expected every summer, that’s not sustainable. We are discussing preventative approaches that don’t really fall under emergency management.”

Another feature of the new normal is the impact on the city’s bottom line. Extreme heat damages critical infrastructure such as roads and electrical transmission networks. Worker productivity declines. Without adaptation or mitigation, heatwaves will add $4 million to road maintenance needs per year in the Phoenix metro area for the next few decades, according to research by AECOM, a consultancy. The blow to labor productivity, even under a moderate warming scenario, will cost $850 million per year over the same period – only in the Phoenix metro area. 

Balsari believes it is no longer sufficient to prepare for the short timescales of extreme weather events; instead, emergency responders and government officials must examine how habitats, jobs, water, and power will be affected over longer time horizons.

“We are working on creating these new types of sims for a range of disasters on the rise – wildfires, hurricanes, and floods, all of which have increasingly resulted in sustained impacts on health and livelihoods, and even displacement. We hope to work closely with cities across the U.S. to change how we plan for our changing climate,” he said.

Simulating the changing times

The exercise grew out of the city-wide disaster drills that Balsari has run for first responders in India and Sri Lanka. But this experience was different, he reflected afterwards.

Though each academic participated because they recognize the growing hazard of urban heat, their different disciplines – there were chemists, architects, engineers, sociologists, and others – and varying levels of familiarity with disaster preparedness, made planning a pedagogical challenge.

“We needed to have something for everyone, and the bar was high – given the audience were our faculty members from across campus,” Balsari said, explaining how his team reviewed hundreds of hours of archival footage, conducted fresh interviews with doctors, city personnel and other response agencies, and designed a scripted, immersive three-hour multimedia experience.

For John Mulliken, a senior lecturer at Harvard Business School, the simulation was “eye opening” and has already influenced his teaching.  

“The real-time coordination and resource conflicts that cities, states, and countries are seeing can at times feel like an abstraction, but bringing the experience of mayors, city officials and other decisionmakers to life is a fascinating and concrete way to engage both researchers and people in similar roles,” Mulliken said. “I found it incredibly valuable, and I’ve discussed the learnings with a number of my students.”