On Heat Action Day, a report shows the growing influence of climate change on temperatures

Phoenix residents don't need to be reminded it's hot in June. But it can be helpful to have a refresher on how to keep yourself, your loved ones and your community safe when summer temperatures arrive. And data-driven insights into how much a warming climate has influenced modern heat extremes and their impacts don't hurt, either.

That's the purpose of the International Federation of Red Cross and Red Crescent Societies' "Heat Action Day," scheduled for Sunday. The IFRC is the world’s largest humanitarian network and, as such, has put resources into tracking how climate change has exacerbated the human toll of rising temperatures.

This year, the Red Cross Red Crescent Climate Centre collaborated on a scientific report looking at how much climate change has escalated global extreme heat over the past 12 months. They partnered with Climate Central, a nonpartisan science communication organization based in the U.S., and World Weather Attribution, an international research collective exploring how extreme weather events are influenced by atmospheric greenhouse gas concentrations.

The report, released Tuesday, has not been peer-reviewed but was produced using scientifically peer-reviewed methodology in an effort to get results to the public faster.

The scientist authors concluded that between May 15, 2023 and May 15, 2024 more than six billion people globally were exposed to 31 days of extreme heat — defined as hotter than 90% of temperatures typical across a given country between 1991 and 2020 — that were made twice as likely by human-caused climate change. This type of research, known as climate attribution science, builds on the understanding that the combustion of fossil fuels for energy has resulted in generally higher temperatures and more intense weather. The advanced climate models allow researchers to now pinpoint the exact influence these pollutants have on specific weather events.

Arizonans, according to the report, suffered through an average of 37.9 more days of locally-extreme heat over the past 12 months than they would have were it not for climate change. Arizona ranked fourth out of U.S. states and territories in this measure, behind Puerto Rico (109 extra days of heat), Florida (54 days) and Hawaii (52 days).

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Out of 168 countries analyzed, the U.S. ranked 144th with an average of 19 additional climate-influenced days of extreme heat this past year. Ecuador experienced 169 more days of locally-extreme heat because of human-caused climate change, nearly half the days in the timeframe considered. In the Marshall Islands and Micronesia, the report concluded that a heat wave in March had been made 35 times more likely by climate change.

The results surprised even the scientists who have been crunching these numbers for decades.

"Since we started World Weather Attribution 10 years ago we always found that these heat waves have been made more intense (by climate change), but this last year, almost in every heat wave we looked at there were temperatures that were so high it would have been impossible without climate change," said Friederike Otto, a climate scientist based in the U.K. who in 2021 was named one of Time Magazine's 100 most influential people in the world and who helped author this report.

"So that was a really noticeable shift, that we don't just get hotter and more (frequent) heat waves, but that they've become so hot that it's completely out of (the realm of) anything you would have even deemed possible without climate change."

Heat hits different depending on where and who you are

While there are many ways to measure heat, the approach in this report highlights the impact of locally extreme heat on residents adapted to particular temperature ranges based on local historical norms. A 110-degree day in Flagstaff, for example, would likely send a larger percentage of that city's elderly and vulnerable population to the emergency room than a 110-degree day in Phoenix, where those conditions are more expected.

“Phoenix is a super special place because you guys get some of the hottest temperatures in the country and so you’re going to use different benchmarks," Andrew Pershing, a scientist with Climate Central and an author on this week's report, told The Republic in a November interview about a similar report. "What we wanted to do was to have a single way of defining what an extreme temperature would feel like for people anywhere on the planet."

Local leaders on heat response:Mayor Kate Gallego on Phoenix's 'hellscape' year and what's in store for 2024

How people experience heat also depends on their health, housing, work and social support situations. In 2023, a year when many heat records were broken in metro Phoenix, Maricopa County recorded 645 heat-related deaths, a staggering 52% increase over the previous year. Almost half of these were among people experiencing homelessness, half had an existing medical or mental health condition and nearly two out of three victims were over 50.

Outdoor workers, many of whom are lower-income or minority individuals, are also particularly vulnerable. Advocates on this issue celebrated some recent local progress when Phoenix officials voted in March to enact heat safety protections for contractors. But many feel the risk is still vastly under-acknowledged and under-regulated across the country, especially given intensifying heat.

"For those of us who work in air conditioned offices and can afford a nice car and have a nice house or apartment, 110 degrees is annoying but you can deal with it," Pershing told The Republic.

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The steadily skyrocketing heat death toll in Maricopa County is despite the efforts of Phoenix's Office of Heat Response and Mitigation, which launched in October 2021 and has been adding staff and programs ever since.

In a call Tuesday about the new climate attribution results, Michelle Litwin, Phoenix's Heat Response Program Manager, said Phoenix handed out 400,000 water bottles and provided 28,000 people with heat response supplies last year in an effort to manage escalating human health impacts. The city office also works on tree shade initiatives and has a "Cool Caller" program to check on vulnerable residents during especially hot days.

Phoenix's heat office, the first of its kind in the nation to be publicly funded, has become an international leader on urban heat interventions. Still, it has been difficult for them to keep pace with how climate change exacerbates the risks every year. Recognizing this growing challenge in Arizona, Gov. Katie Hobbs appointed the nation's first statewide chief heat officer in March.

Tips for weathering hot weather

The report released Tuesday ahead of "Heat Action Day" includes tips on how to avoid becoming a victim of high temperatures. It also emphasizes that "deaths from extreme heat are preventable."

At the individual level, the best options to reduce exposure to extreme heat include staying hydrated, spending less time outdoors during the hottest parts of the day and making home weatherization improvements to increase energy and air conditioning efficiency, the report recommends.

For people like outdoor workers who are unable to stay inside on hot days, "self-dousing" with water can help by encouraging evaporative cooling. Installing shade options and taking regular breaks can also make the difference between life and death during heat events.

As whole communities, possible actions to address heat impacts include improving access to water, cooling centers and emergency medical services. Building more reliability and efficiency into electricity grids, transportation infrastructure and early warning systems can help. And pushing for stricter worker safety laws, more cold food storage and heat-mindful urban planning would also minimize human and economic losses, the report suggests.

Hobbs recently proclaimed May 6-10, 2024 as "Arizona Heat Awareness Week," so residents may already be more prepared for the summer ahead than people living in regions less accustomed to extreme temperatures. The Phoenix heat office also makes a point of reminding people about heat safety tips in early May each year. But officials have found the need for heat education to be never-ending.

"A big crux that we've been finding issues with is those that are most vulnerable don't know about the resources that are available to them," said Litwin with the Phoenix heat office. "So a lot of what I am working on is actually being out there on a day to day basis, interacting with those most vulnerable communities and making sure they know that they can call 2-1-1 and get a free ride to one of the cooling or respite centers, and then once they get there, making sure they know about the other resources that are available to them, should they be ready to have those conversations."

Phoenix-specific tips from the Office of Heat Response and Mitigation echo the advice in the globally-focused climate report, but also include recommendations to follow @NWSPhoenix (the Phoenix branch of the National Weather Service) on social media to keep track of heat alerts, to know and watch for signs of heat exhaustion and heat stroke and to wear light-colored clothing and apply sunscreen when going outside.

The city also wants renters to know that landlords are required to maintain indoor temperatures at or below 82 degrees Fahrenheit for units with air conditioning, and 86 degrees or cooler for units with evaporative coolers. Residents can call 602-262-7210 to lodge complaints about this.

Read our climate series:The latest from Joan Meiners at azcentral, a column on climate change

In the bigger picture of the Heat Action Day climate report, an infographic illustrates how effects from more frequent extreme heat events permeate every aspect of society, from disrupting tourism and the economy, to affecting water levels and crop success, to elevating air pollution, aggression and mental health concerns.

Collaborators presenting the research Tuesday emphasized that responding to each of these consequences of heat retroactively will be much more expensive and challenging than addressing the root cause now by taking action to limit climate change. The way to do that, the authors said, is by insisting on a shift to cleaner and more efficient energy options and by reducing unnecessary consumption of plastic and other emissions-heavy products.

"Of course, the cause of the climate change that's making more and more people experience extreme heat is the fossil fuels that we've been putting into the atmosphere. That's driving the increased heat," said Roop Singh, a climate risk advisor with the Red Cross Red Crescent Climate Center. "So it's absolutely a day to focus on both mitigation and adaptation."

Joan Meiners is the climate news and storytelling reporter at The Arizona Republic and azcentral.com. Before becoming a journalist, she completed a doctorate in ecology. Follow Joan on Twitter at @beecycles or email her at joan.meiners@arizonarepublic.com. Read more of her coverage at environment.azcentral.com.

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