Over the past half-century, American cities have taken on an unstable thermodynamic form, coming to resemble collections of boxes full of cool air crowded onto concrete heat islands. Turn off the AC, and office buildings would become uninhabitable, vehicles sitting in traffic would become torture chambers, apartment buildings would become death traps.
How did this happen? The technology was slow to take off: In 1960, 12 percent of U.S. households had air conditioning; by 1980, that had risen to just 55 percent; now it’s almost 90 percent . But once cooling technology became more efficient and affordable after World War II, it began transforming the architecture of cities and suburbs, as the historian Gail Cooper shows in her book “Air-Conditioning America.” It ushered in the glass office-block design with deep, cheap-to-build interior spaces that never could have been comfortable in the summer without artificial cooling. House and apartment builders could dispense with expensive warm-weather features such as porches, large eaves, high ceilings, cross-ventilated designs, transom windows, windows that open and attic fans. That made homes more widely affordable, but buyers usually ended up living in what Fortune magazine called a “TV-equipped hotbox” that was livable in the summer only with air conditioning.
With prosperity (and summer temperatures) increasing through the 1990s, builders and home buyers could have gone back to investing in warm-weather architectural features, but instead they opted to spend their money on more floor space. By 2006, the average new house had three times the square footage per occupant as it had in 1950, increasing from about 290 square feet per family member to nearly 900 square feet each. Cooling demand soared accordingly: Between 1993 and 2005, when the increase in house size was reaching its zenith, total consumption of electricity for residential air conditioning nearly doubled, from 134 billion kilowatt-hours to 261 billion, according to U.S. Energy Information Administration surveys. The Energy Department says air conditioners use about 5 percent of all the electricity produced in the country each year, costing homeowners more than $11 billion.
It’s not too late to reduce our dependence on air conditioning, especially in rural areas, small towns and leafy suburbs. Even in big cities, homeowners can plant shade trees and other vegetation, install whole-house fans, sleep in the basement. On the other hand, apartment dwellers have far fewer options: They can live with open windows, fans and cold showers up to a point, but when heat waves like this one arrive, it’s time to reach for the thermostat.
Economically distressed urban neighborhoods will face more than just discomfort this weekend. Decades of research demonstrates that heat-wave mortality is highest in concrete-and-asphalt urban disasterscapes, especially among elderly or ill people who are socially isolated, living behind closed windows for fear of crime (a factor in the 1995 Chicago heat wave, which killed 739 people) or unable to afford the electricity required to run an air conditioner or even a fan. There, community cooling centers become refuges of last resort.
Air conditioning has become a necessity but not a solution. It’s like an ice bath for a patient suffering an extreme fever, treating the symptom while leaving untouched the underlying cause — in this case, the one-two punch of climate change and the distorted physical and social structure of our cities. And by making our world temporarily cooler, air conditioning is making it permanently hotter, thanks to the increases in greenhouse gas emissions from power plants, vehicle fuel consumption and refrigerant production that keep the cool air flowing.
I calculate, based on figures from the Energy Information Administration and the Environmental Protection Agency, that the air conditioning of America has a climate impact equivalent to 500 million tons of carbon dioxide — more than all industrial processes combined. About three-fourths of the impact is from generating the electricity to cool buildings, and the rest is split evenly between excess fuel consumption by air-conditioned vehicles and leakage of refrigerants used by all air conditioners.
So as temperatures rise this weekend, it’s a good time to question the prevailing assumption that adapting to more frequent heat waves in the future will simply mean using even more air conditioning. That will be an exercise in tail-chasing. It will do nothing for the millions of people who work outdoors or in the many industrial plants that are well out of air conditioning’s reach. Global warming will take an especially harsh toll on them.
Climate adaptation can work only if it’s linked to stopping global climate disruption, and both require us to start digging up root causes. Acute problems should have priority. We must help the most distressed urban hot zones cool down again by jackhammering concrete, re-creating green space and improving the quality of housing. All that would help fight the “urban heat island” effect, which can make cities as much as 22 degrees Fahrenheit warmer than their surrounding areas.
Reducing air conditioning dependence in urban areas will require a serious overhaul: things like steadily shrinking parking and driving space, accompanied by improvements in public transportation; depaving and revegetating the rescued space; retrofitting large buildings with ventilation shafts to allow air in when weather permits; and mandating that all new construction be designed for non-air-conditioned comfort at times of the year when it’s achievable, with features such as windows that can open, better air-flow within buildings and building shapes that give everyone an external window. For significant parts of the year in much of the country, air conditioning systems are running to keep temperatures at 70 or 72 when the outside temperature is, say, 85. With better ventilation and building design and a tolerance for only slightly higher temperatures indoors, we wouldn’t need artificial cooling.
According to analysts at the Lawrence Berkeley National Laboratory, a crash program to maintain or establish three shade trees per building and make all roofs and pavement in U.S. cities reflective could decrease national cooling demand by a whopping 20 percent by driving temperatures lower. That would directly reduce electricity and vehicle fuel consumption, and it would also increase the number of days per year when air conditioning could safely be switched off by making buildings more comfortable without artificial climate control.
For U.S. households, cutting energy use for cooling will mean working with the weather, not against it. Rather than keeping homes tightly sealed year-round while switching the thermostat from “heat” to “cool” in April and back in October, we can open up, use fans and enjoy the fresh air on days when temperatures are warm but not extreme.
Initiatives to wean society away from the overuse of air conditioning will be self-reinforcing. Extensive exposure to air conditioning reduces the human body’s capacity to tolerate heat; conversely, the more we live with warm weather, the more we are able to tolerate it, according to Michal Horowitz of the Hebrew University of Jerusalem and many other heat researchers. That’s real adaptation.
Getting used to warmer temperatures won’t be as unpleasant as it sounds. Studies in countries around the world show that the more warmth we have experienced in recent days and weeks, the hotter the temperatures in which we feel comfortable. When we’ve been exposed to temperatures around 70, we’re most comfortable in the 70s when indoors. When we’ve been exposed to the low 90s, we prefer the 80s.
That said, I would not recommend this weekend as a good time to start adapting. Go ahead — run the AC. But unless we start transforming our society soon, indoors and out, summers will eventually spin out of the control of any thermostat.