The Dark Side of Summer

Turn off your air conditioners. Take a cue from a camel. Lay off the ice cream. And other advice for surviving a 'heat island'

Each year, New Yorkers suffer and quietly die on our beloved "heat island"— a special urban hell where average temperatures soar more than seven degrees higher than in the gas-guzzling suburbs. Last summer's 46 confirmed heat victims in New York City included Tyron Dugger, a 47-year-old mentally handicapped man who died along with his 82-year-old mother in their sealed and sweltering East New York apartment. Just blocks away, 69-year-old Edna McEachin also succumbed, as did 85-year-old Anne Cialeo, of Conduit Boulevard, who died sitting upright in her bed. City health officials can't be sure, but they think another 100 New Yorkers were killed by that particular blast of summer.

"Heat waves are invisible killers of invisible people," says NYU sociologist Eric Klinenberg, author of the landmark Heat Wave, an analysis of Chicago's apocalyptic summer of 1995. "More heat waves are on the way, and it's important to get a real sense of the danger posed."

While world leaders fret over the 20th century's one-degree Fahrenheit temperature climb, localized high temperatures in large North American cities have risen up to two degrees Fahrenheit each decade since 1950. Global warming could double that rate, warns E. Gregory McPherson, a research forester with the U.S. Department of Agriculture Forest Service, in the book The Ecological City.

photo: Ira McCrudden

The density of our cityscape—where we live and work stacked floor-upon-floor and commute in packed subways and buses—fosters energy efficiencies unheard of elsewhere in America. On a per capita basis, our gasoline consumption matches the national average of 1920 and our electricity usage is half of contemporary San Francisco's. Our per capita greenhouse gas emissions are a third of those seen nationally today.

Yet we roast our relatively virtuous skins on vast acres of concrete between asphalt and glass towers that convert nearly 45 percent of incoming sunlight into sensible heat. Dead-end or poorly oriented canyons interfere with air convection, trapping warm and dirty air. Meanwhile, our physiological vulnerability to heat has grown. Hypertension, diabetes, depression, obesity, and other modern ailments—and the treatments for them—compromise our ability to flush and sweat, the primary coping mechanisms.

By many measures, heat deaths have actually dropped, thanks to one of the least sustainable contraptions ever invented: the air conditioner. In 1970, 40 percent of NYC households had at least one. Last year, 80 percent did.

But switching on the AC starts a negative feedback loop.

"Anyone who has ever stood in the West 4th Street station in the middle of summer knows it feels like 120 degrees down there, and it's because of the air conditioners blowing out hot air from the subway cars," says Joyce Rosenthal, an urban planning doctoral student and research investigator with the Cool Cities Project at Columbia University.

Now imagine that phenomenon on a citywide scale. An Okayama University study found air conditioners raised ambient temperatures in Tokyo by almost three degrees Fahrenheit. The Heat Island Group at Lawrence Berkeley Laboratory, in California, calculated that the efforts to offset the phenomenon in Los Angeles cost more than $100 million annually. By comparison, New York City is denser and lacks the steady ocean breezes. "I would not be surprised if in New York the number was on the order of $150 million," says lead scientist Hashem Akbari.

Heat is also an issue of local environmental justice. Just look at Hunts Point in the South Bronx, where poverty is the handmaiden of heat death. Hunts Point is chockablock with low-slung warehouses, virtual ovens. Without adequate street trees, asphalt turns to goo. The exhaust of 60,000 weekly truck trips, power plants (to keep New York's air conditioners chugging), and sewage treatment plants is transmuted by heat into thick smog. The children there, mostly black and Latino, are afflicted with asthma so severe that they require hospitalization for it at a rate four times the national average.

photo: Ira McCrudden

Heat preys on the most vulnerable among us. Nearly half of all heat victims live alone. People older than 65 account for more than half of heat deaths. The city health department reports that 28 percent of the 2006 victims had known cognitive or psychiatric disorders. Pregnant women are also vulnerable, and lab mice have shown extreme deformities in fetuses where the mother experienced a six-degree body temperature rise for just 30 minutes. Children, like the elderly, overheat faster.

Lessons gleaned from nature's billions of years of evolution—and innovations from our preindustrial past—might help us survive on our urban heat islands, and even cool them a bit.

You can almost take comfort in the knowledge that humans remain one of the most astonishingly heat-tolerant mammals. Our simple ability to sweat—five times that of horses and double that of camels—is alone absolutely remarkable. And it makes no particular difference where your ancestors came from or what they looked like. "All humans appear to function as tropical animals," writes Dr. Sarah A. Nunneley, an editor with the journal Aviation, Space, and Environmental Medicine.

So why are we wilting and dying?

"We're born with a lot of sweat glands, and that will be true if you are Nordic, African, or Indian. You'll retain that ability, regardless of your ethnicity, if you're raised in a tropical environment," says Mark S. Blumberg, author of Body Heat: Temperature and Life on Earth. "But we lose some of that capacity through disuse, especially in the first few years of life." If you grow up under an AC, you risk losing the ability to function without one.

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