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Cities Are Becoming Climate Death Traps

A new era of heat waves is here. We aren’t ready.

Jessica Kourkounis/Getty Images
A man cools off in the spray of a fire hydrant during a heat wave in Philadelphia.

As the coronavirus pandemic continues throughout the United States, another deadly pandemic comes out to strike in the summer: extreme heat. Year after year, more people are dying because it’s simply too hot. As of right now, both this country and others lack even an accurate way of counting those deaths—let alone a comprehensive plan to reduce them. Thanks to climate change, it’s about to get much worse.

For the past week, the American South and Southwest have been experiencing record-breaking temperatures. The National Oceanic and Atmospheric Administration has predicted above-average heat for nearly the entire U.S. this summer. Unprecedented, early-summer heat waves roasted the Middle East in May and Siberia in June, setting the latter on fire. Arizona had its earliest-ever hundred-degree heat wave in April—and another 110 degree heat wave in May. Spain endured 105 degree heat this month.

When the heat index, a “feels-like” combination of temperature and humidity, reaches 104 degrees Fahrenheit indoors or out, human body temperature risks rising above the typical roughly 99 degrees Fahrenheit. When body temperature rises above 104 degrees, the consequences can be fatal within 30 to 60 minutes.

“Heat-related deaths are notoriously difficult to track because the role of heat isn’t always obvious. One 2017 study found that extreme heat can kill people in 27 different ways,” Juanita Constible, senior advocate, climate and health at the National Resources Defense Council, told me. “If someone dies of a heart attack during a heat wave, there’s a good chance that’s how their death will be recorded by officials, even if high temperatures were the trigger.”

Many scientists argue that official heat-death counts underestimate substantially. According to the World Health Organization, 166,000 people died due to heat waves between 1998 and 2017, but the true figure may be far higher. In the U.S., the Centers for Disease Control and Prevention only counts deaths where heat illness is explicitly noted, so the official CDC count of heat-triggered deaths sits at just around 600 per year. Epidemiologists estimate that the real figure may be closer to 12,000—20 times higher than the official count.

Climate change is making heat waves longer, hotter, and more deadly. Scientists estimate that 80 percent of record-breaking heat waves would not have occurred without human-caused warming due to greenhouse gas emissions. And urban areas, in particular, face special risk of heat deaths because of the heat island effect, in which dark pavement, roofs, and concrete absorb additional heat, making temperatures much hotter than the reported weather in any given city.

In the U.S., heat deaths have more than doubled in Arizona in the last 10 years. Last year, a dangerous heat wave hit while storms left residents in the D.C. and New York City metro areas without power. Power outages can be deadly in a heat wave because without air conditioning, many people can’t cool off. In two heat deaths in a 2018 Arizona heat wave, the deceased were found indoors with a broken air conditioning unit that they couldn’t afford to fix.

“Some people won’t use their air conditioning because they’re afraid of the bills,” Patricia Solís, executive director of the Knowledge Exchange for Resilience at Arizona State University, told National Geographic. “They think they’re OK without it, but that’s how people die.”

“There are huge policy gaps in the U.S. with respect to extreme heat protections,” Rachel Licker, a senior climate scientist at the Union of Concerned Scientists, told me. “We found that without real action on climate change, by midcentury more than 250 cities across the U.S. are projected to experience 30 or more days with a heat index above 100 degrees Fahrenheit. This includes many cities that historically haven’t experienced this level of extreme heat.”

Low-income communities are especially vulnerable. A 2020 study in Environmental Research Letters found that residents in low-income census tracts were less likely to use air conditioners when temperatures got hot. Heat wave exposure also disproportionately affects communities of color that have faced housing discrimination. Researchers at Portland State University and the Science Museum of Virginia found that urban neighborhoods denied municipal services during the mid-twentieth century are now the hottest areas in 94 percent of the 108 cities analyzed.

Extreme heat is a labor issue, as well. “One of the most urgent needs is an enforceable heat health standard for all workers from the [Occupational Safety and Health Administration],” said Constible. The current rule “has too much wiggle room for employers.” Licker pointed to the proposed Asuncion Valdivia Heat Illness and Fatality Prevention Act of 2019, which has yet to get out of the House Committee on Education and Labor, as a potential solution. The bill, sponsored by Democratic Representative Judy Chu of California, is named after Asuncion Valdivia, a California farmworker who died of a heat stroke in 2004 after picking grapes for 10 hours in 100 degree weather. The U.S. Postal Service has also received criticism for its role in workers’ heat deaths, for example in a troubling report from HuffPost this past week.

But killer heat is a worldwide phenomenon. In Europe, heat waves killed as many as 70,000 in 2003 and more than 1,500 last year. Good heat wave adaptation measures—such as handing out water at train stations, asking people to check on the elderly, and opening air-conditioned shelters for residents—likely contributed to the substantial reduction in deaths from 2003 to 2019. Accurate weather forecasting also allowed for greater preparedness. Still, just 5 percent of European households are air conditioned and scientists estimate that three degrees Celsius of warming could kill an additional 86,000 people each year in the EU.

While China and Japan are used to some sweltering-hot summers, record-breaking heat waves have nevertheless proved deadly. Consecutive heat waves in 2018 and 2019 in Japan hospitalized tens of thousands and killed hundreds. Japan doesn’t use excess mortality to calculate heat-related deaths like Europe does, which means that, as in the U.S., these numbers may be huge undercounts. In China, extreme heat combines with poor air quality to produce harmful ozone. Scientists estimate that three degrees of global warming could kill an additional 30,000 people each year in China.

Meanwhile, the impact of extreme heat on the global south remains underreported in Western media. Since developing countries tend to lack the cooling infrastructure present in North America and East Asia, regions in India, Bangladesh, and Pakistan could soon face regular summer heat waves that are impossible to survive. A recent Tokyo Institute of Technology study shows that heat-related deaths in Jakarta are expected to increase by 15 times by 2060. And while some regions of Africa are used to heat waves as a regular occurrence, the heat island slums of large cities such as Nairobi can create fatal conditions. A 2017 John Hopkins study found that temperatures in Kibera, one of the largest “slum” settlements in Nairobi, were typically 5 to 10 degrees higher than the official weather report.

The dual threat of extreme heat and the coronavirus makes for an especially challenging summer for policymakers and city-dwellers. Many cities this year and for each additional year that the pandemic persists will have to choose between opening public cooling centers and risking transmission of Covid-19 or keeping them closed and risking preventable heat-related deaths.

And the coronavirus also complicates the labor aspect of extreme heat. The current U.S. heat standard, for example, which is only a recommendation that employers take precautions when temperatures reach a certain threshold, was created in pre-Covid times. “A heat standard is especially important this summer because of the Covid-19 pandemic,” said Constible. “The masks and other protective gear needed to slow transmission of the virus have the potential to trap heat and increase heat-health risks to some workers.”

Faced with record temperatures, many cities in the U.S. have taken aggressive adaptation measures. “Dozens of cities and some counties and states have mandatory, incentivized or city-led initiatives using features such as cool roofs, cool pavements, and trees,” Laura Brush, resilience fellow at the Center for Climate and Energy Solutions, told me. “However, funding is a significant barrier for many communities, especially during the pandemic.”

“More diverse funding sources and innovative finance mechanisms are needed to invest in resilience projects. These could include a national infrastructure bank, loan programs, and tax incentives for companies and individuals,” Brush said. Brush points to Louisville, Kentucky’s regional climate and health assessments and cool roof rebate and installation programming as one effective example of a city taking action.

The tragedy of heat-related deaths is that they are almost always preventable. Distributing free air conditioners, paying residents’ summer cooling bills, and simply encouraging people to check in on vulnerable relatives or neighbors can save lives. All of these are extremely feasible policy measures. At the same time, nothing will slow the urban heat-death pandemic like climate mitigation and reducing greenhouse gas emissions. Limiting global temperature rise to 1.5 degrees Celsius (2.7 degrees Fahrenheit), for example, could save 2,700 lives per year in New York City alone, according to recent estimates. What’s known for sure is that ignoring either approach—the immediate or the long-term—will come with a body count.