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Phoenix glows even after 10 p.m. one April night in this image made with a camera sensitive to infrared light, which is generated by heat and invisible to the naked eye. Researchers call the city an “urban heat island.” (Brent C. Hedquist)

The Reality of a Hotter World is Already Here

As global warming makes sizzling temperatures more common, will human beings be able to keep their cool? New research suggests not

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(Continued from page 1)

Outside my hotel, in the heart of downtown, the streets illustrate why the noun “desert” is cognate with “deserted.” At mid-morning on an ordinary weekday, I can walk around the block twice without encountering another human being on foot. In late afternoon, I meet a radio reporter named Jude Joffe-Block. She arrives a few minutes late, apologetically; she says she was once two minutes late to meet a friend at a bar, which happened to be closed that day; he was gone, unable to bear 120 seconds on the sidewalk. Phoenicians defend their city with variations of the claim that “everyone has air conditioning,” but during a heat wave last June, whose average high temperature was 107, Joffe-Block interviewed people who were doing without it, usually because they couldn’t afford monthly electric bills of $400 or more. Sharon Harlan, a sociologist at Arizona State University, who has been studying how communities are affected by extreme heat, says that in some poor neighborhoods a third of the population says the high cost of electricity keeps them from using their air conditioning. Joffe-Block herself was living in a rented apartment with a device called a “swamp cooler,” a machine that blows air over a water-saturated pad, lowering the temperature by evaporation. On a recent 105-degree day, the swamp cooler chilled Joffe-Block’s apartment all the way down to 95. The machines are common in the small stucco and cinder-block houses that line the streets of south-central Phoenix, a low-income neighborhood a 15-minute walk from the skyscrapers of downtown, if anyone was around to walk it.

And by the iron law of real estate values, people too poor for air conditioning tend to live in the hottest parts of town, flat and shadeless under the relentless desert sun, far from the soothing balm of golf courses and parks. Wealthy neighborhoods receive the “microclimate ecosystem services” of trees and shrubs. Over the course of a summer, Harlan measured temperatures in the yards of houses in various neighborhoods and found differences up to 14 degrees. Plants provide shade, intercept sunlight and cool the surrounding environment as water evaporates from their leaves, whereas the built environment absorbs energy from the sun and radiates it back as heat. Driving by a golf course at night during summer, with the windows down, the change in air temperature can be “startling,” says Chris Martin, a professor of horticulture at Arizona State.

Unfortunately, the cooling effects of plants come at a cost, namely water, which is becoming increasingly a precious commodity in the Southwest as the climate warms and population increases. With the advent of air conditioning and high-insulation building materials, people felt less need to surround their houses with shade trees. Improvements in artificial turf have made it an acceptable alternative to grass in small patches, even in wealthy neighborhoods. Such a yard “can be 15 or 20 degrees warmer at night than the same yard if it were irrigated,” Martin says. “You can see very nice homes in a yard without a single living thing in it. It’s one hot place, but most people are inside so they don’t care.”

***

Phoenix, like most big cities, is what meteorologists call a “heat island,” hotter than the surrounding countryside, or than the land would be without the burden of civilization: of asphalt parking lots and tinted-glass skyscrapers, of the air conditioners, automobile engines, appliances and light bulbs of 1.5 million people. (Or, for that matter, the people themselves: The population of the Phoenix metropolitan area, over four million, generates as much energy in the form of body heat as a medium-size power plant.) The heat island effect creates a phenomenon that meteorologists and ordinary citizens find even more disturbing than the occasional 115-degree afternoon: the trend toward higher nighttime temperatures.

Citing National Weather Service data, Norman, the meteorologist, said the last record low in Phoenix was in December 1990. “Since then we have set 144 record [daytime] highs and 230 record-high [nighttime] lows. Back in the 1980s, even in the hottest part of the year, there were cool mornings, but this year there were nights it never got out of the 90s. I wonder if eventually we will never get below freezing, and that worries me because when it happens, the next summer we get hammered by the bugs—spiders, roaches, ants—even mice.”

Fifteen to 20 times a year, Ken Waters of the National Weather Service issues a heat warning for the region, based on predicted highs and, equally important, nighttime lows. “No question it has a major impact on people,” he says. “When it stays above 90 all night, it makes it very difficult to recover from daytime heating.” If you don’t have a home to go to, you are at the mercy of the elements, Harlan says, no less than someone sleeping on a subway grate in Manhattan to stay warm in December. In a study that looked at heat-related death by occupation, men in the category “unknown”—which usually means homeless—had a rate ten times that of men in known occupations.

For the rest of us—well, we will just have to get used to sweating more, and put up with what Anderson, of Iowa State, describes as the “crankiness” factor. “Being uncomfortable colors the way people see things,” he says. “Minor insults may be perceived as major ones, inviting, even demanding, retaliation.”

That was just what Richard Larrick of Duke University’s Fuqua School of Business, along with his co-authors, found when they examined the box scores of some 57,000 Major League Baseball games played since 1952—about 4.5 million plate appearances in all. They were looking into whether hot weather made pitchers more likely to throw at batters, and based on records of game-time temperatures, they found that it did, but in a specific and telling way. In theory, hot weather might increase the incidence of wild pitches by affecting pitchers’ control (distracting them, or making their palms sweaty), but that’s not what the study focused on. Instead, it found that after one or more batters were hit, intentionally or not, hot weather made it more likely that the opposing pitcher would retaliate later in the game. “What’s interesting is that the same act—your teammate being hit by a pitch—seems to mean something different in a hot temperature than a low one,” Larrick says. “An ambiguous act now seems more provocative when your own mind is in turmoil because of the heat.”

Of course, very cold weather makes people uncomfortable also, and in laboratory experiments cold has in fact been shown to increase aggression. But that doesn’t appear to translate into more crime during cold spells. There is some evidence from brain imaging that the perception and regulation of heat involves some of the same regions that process anger—the proverbial “hothead”—although the significance of those findings is unclear. Anderson speculates that in evolutionary history, extreme cold has generally posed a more immediate threat to personal survival than heat, and people are driven to escape it, with clothing, fire and shelter. “If I’m cold, I have to deal with that right away,” he muses. “I don’t have time to be irritable.”

And if you suffer from the heat, like Kenrick, the Arizona researcher, and you work on an academic schedule, you can head north for relief. “I go to Vancouver for a couple of weeks a year,” he says, “and I enjoy being able to go out for coffee without having to stop each time and think, is it worth it.” He should enjoy it while he can, because Vancouver recorded its two hottest days ever in 2009, and the city is considered at risk of flooding owing to climate change in the coming decades.

That honking sound you hear? It may be the climate apocalypse, right behind you.

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