The U.S. National Weather Service is predicting higher-than-normal temperatures this summer up and down the East Coast, through the Southeast, and across the entire West. Sales of air-conditioning equipment have now rebounded from the housing crash as well as from the unusually cool summer that much of the country enjoyed in 2009. And the global market for indoor climate control is expected to grow strongly in coming years thanks to stimulus provided by a warming outdoor climate.
But we are paying a high price for cooled air. The portion of output from the nation's electric utilities that goes to power air-conditioning has grown steadily in recent years. The resulting emissions will contribute to more intense summer heat, which is expected to make the outdoor climate harsher in coming decades. More hot weather would create even greater demand for air-conditioning, resulting in the combustion of even more fossil fuels and further rounds of warming.
The U.S. Global Change Research Program and the Environmental Protection Agency expect the death rate from summer heat waves to rise steeply between now and 2050. Accordingly, air-conditioning is being viewed less and less as an amenity and more as a life-support system. But even though air-conditioning has helped reduce death rates during heat waves over the past half-century, it has not eliminated them. Heat remains the nation's leading cause of weather-related mortality.
Many who die from heat stress don't have air-conditioning or cannot afford to run it, but that's only part of the story. Just as important are the generally harsh conditions under which heat-wave victims often live. They typically suffer and die in economically forgotten, concrete-rich, vegetation-free stretches of large, mostly northern cities. The nature of the surrounding community can be a matter of life and death in a heat wave. A study by the Midwestern Climate Center found that "features of neighborhoods on a relatively small geographic scale (e.g., amount of pedestrian traffic, small shops, public meeting places) affect survival rates [positively]." The researchers also suggested that in such areas, fear of crime makes already vulnerable people, especially older people, reluctant to leave doors and windows open or go outdoors in the cooler evening hours.
Christian Warren, an associate professor at Brooklyn College, specializing in the history of U.S. public health and medicine, told me he is troubled by our reliance on climate control as a remedy for ills that run much deeper:
"Now you see air-conditioning pitched in the medical literature as an environmental justice issue, because it can save lives during heat waves. But they aren't asking what really kills people. What about isolation, economic stress, crime, and paranoia about crime? You can easily imagine a couple staying shut away in their air-conditioned apartment during a hot spell, uninterested in checking on their elderly next-door neighbor, who could be dying of heat stroke."
Give Me a Little Fresh Air
Air-conditioning, once a mere economic product, is now an integral component of the economy itself. Today, in much of the country, it's hard to imagine life before air-conditioning. The idea that our society should become less dependent on climate control can seem radical, even absurd. But the post-air-conditioned world need not be one of malaise, poor health, social turmoil, and economic collapse; besides, hazards like those have become a bit too familiar already. In fact, several lines of research indicate that turning down or even turning off the flow of chilled air could improve our quality of life.
Research in human physiology suggests that artificial cooling of the indoor environment undermines our natural heat-adaptation mechanisms. I asked Michal Horowitz, professor at the Hebrew University of Jerusalem, about her pioneering research on the biology of heat stress and acclimatization and its implications for how we live. She responded that "those who live exclusively in an air-conditioned environment endanger their ability to cope with severe heat load."
It's not only the body's heat tolerance that suffers. Studies in California, Brazil, France, the United Kingdom, Denmark, and elsewhere have shown that people employed in air-conditioned workplaces have poorer health and visit doctors and hospitals more frequently than do those who work without air-conditioning. The specific causes of these health problems are not fully understood. But a study published in 2003 in the Lancet suggested that one of the several mechanisms at work could be the growth of bacteria and fungi in air-conditioning systems of office buildings. Such contamination has resulted in outbreaks of rhinitis, humidifier fever, asthma, pneumonitis, and Pontiac fever.
By attracting children to the great indoors, air-conditioning shields them from seasonal allergens and disease-bearing mosquitoes. But by living mostly indoors, children also receive less exposure to friendly soil bacteria and nematodes — organisms that appear to be required for the "training" of immune systems. And that, say a growing number of scientists, may be contributing to the dramatic rise in the incidence of asthma and allergy.
Medical researchers have speculated that air-conditioning may even contribute to rising obesity rates. There are at least three mechanisms: the human body burns calories more slowly when it doesn't have to work to shed heat; we eat more when we're in a cool environment; and people, especially children, are less physically active indoors than out. Thanks partly to air-conditioning, we just aren't getting outdoors as much. In my own Kansas neighborhood, a shady street on a pleasant 80° summer evening can be as free of human life as it would be on Super Bowl Sunday in the middle of a sleet storm.
Even our mental and emotional development (and especially that of our children) may be shaped by air-conditioning. Recent studies suggest that time spent in outdoor green spaces pumps up children's creativity and their ability to focus attention, whereas indoor activities tend to increase the symptoms of attention-deficit disorders. Air-conditioning has also helped pave the way for the widespread elimination of outdoor school recess, despite research showing that recess improves attentiveness and behavior in the classroom.
Make Yourself Comfortable
Air-conditioning is undermining the planet's health as well. It now accounts for almost 20 percent of year-round electricity consumption by American homes and an equivalent share of the resulting greenhouse emissions. Consumption has doubled just since the mid-1990s. Air-conditioning of U.S. homes, businesses, and public buildings consumes as much electricity as is available for all purposes across the entire continent of Africa — home to almost one billion people.
Residential air-conditioning units in service in 2005 were an impressive 28 percent more energy-efficient on average than they were in 1993. But that did not reduce energy consumption; instead, as square footage of residences expanded and summers grew hotter, the number of kilowatts of electricity used for cooling the average household increased by 37 percent. Federal standards have since tightened, requiring that new equipment be another 30 percent more efficient. Should we expect energy consumption to take another leap as a result?
The U.S. Energy Information Administration reported last year that improvements in overall energy efficiency of the nation's residential lighting and appliances during the past decade had been wiped out by the increased load imposed by air-conditioning. As a result, total residential electricity consumption shot up 23 percent. Most of that electricity is supplied by power plants burning coal and natural gas. Output from geothermal, biomass, solar, and wind sources could expand 400 percent and still not be sufficient even to run America's air conditioners, let alone serve other uses.
Low-energy cooling projects — for example, wind towers in India and solar absorption air-conditioning in Arizona — provide real-life examples of how a home or office can be kept comfortable without burning fossil fuels. Traditional hot-climate features such as heavy eaves, high ceilings, cross-ventilated designs, awnings, shade trees, screen porches, fans, whole-house exhaust fans, evaporative coolers, reflective or planted roofs, and even the creative use of basements can improve summer comfort without heating the great outdoors.
Those technologies can't always deliver the calm, uniform, predictable environment that conventional air-conditioning does — but that's not necessarily bad. In recent years, industry experts have incorporated into their natural-ventilation standards the "adaptive model of comfort," which says that the range of temperatures we find comfortable is not fixed but depends largely on the temperatures we've been experiencing over the past few weeks. In other words, we adapt mentally as well as physically to heat and cold. And once we're exposed to thermal variation, science shows, we begin once again to prefer thermal variation. In her book Thermal Delight in Architecture, Lisa Heschong went so far as to argue that the thermal sense should be assigned a status equal to that of the other five senses. Without thermal variety, she concluded, enjoyment of our environment withers.
By reducing our dependence on air-conditioning, we can not only save energy but also become more resilient human beings. And we'll need that resilience. The coming decades will test our ability to adapt and create, and we can't leave it to technology to bail us out this time.