I suppose anybody contemplating this summer's U.S. heat wave has hit on a scary number that somehow resonates with one's most pessimistic fantasies. My personal paranoid favorite, which I hit upon reading an issue of USA Today while driving up the parched banks of the Missouri River earlier this summer, was the temperature of Lake Superior, the biggest of the Great Lakes: In late June, its average water temperature was 68 degrees Fahrenheit (20 C), compared to 56 degrees (14 C) the same time the year before (and roughly the usual temperature for that time of year).
What scares Michael Sivak, a research professor in energy at the University of Michigan, is the number he calculated for the future air conditioning needs of Mumbai, India, based on its population—the country’s largest urban agglomeration—and its local climate. He found that its cooling needs may eventually be one quarter those of the whole United States at present. The United States has long consumed more energy for air conditioning than the rest of the world combined. Sivak considers that to be "one scary statistic."
Sivak's work is reported on and discussed in a commentary article that appeared in the Sunday New York Times, by Elisabeth Rosenthal, who ably summarizes the frightening dilemma facing the world:
"Fact 1: Nearly all of the world’s booming cities are in the tropics and will be home to an estimated one billion new consumers by 2025. As temperatures rise, they — and we — will use more air-conditioning.
Fact 2: Air-conditioners draw copious electricity, and deliver a double whammy in terms of climate change, since both the electricity they use and the coolants they contain result in planet-warming emissions.
Fact 3: Scientific studies increasingly show that health and productivity rise significantly if indoor temperature is cooled in hot weather. So cooling is not just about comfort.…
A companion table to the Rosenthal article lists the world's cities most in need of air conditioning, ranked in terms of "cooling degree days," a technical metric. Of the 13 hottest cities, 12 are in fast-growing Southeast Asia and 6 of them in India, a fact that also sobers the mind.
According to a similar article recently posted on Yale University's environment360 website, Stan Cox estimates that global air conditioning consumes about 1 trillion kilowatthours of electricity each year, and that automotive air conditioners in the United States alone account for 7-10 billion gallons (26 to 38 billion liters) of gasoline used. Cox, a senior scientist at the nonprofit Land Institute in Salina, Kansas, mentions a number of technical fixes, notably architectural design that emphasizes passive cooling and natural ventilation. Understandably, given the magnitude of the looming global problem, Cox feels we all ought to get accustomed to living and working under somewhat warmer summertime conditions.
One reason for his caution as to what we can expect from technical innovation: Between 1993 and 2005, when air conditioning efficiency improved almost 30 percent in the United States, total energy consumed by household cooling systems doubled.
In that spirit, Rosenthal left her air conditioning off one recent warm summer morning, while listening to a European official describe what the European Union is doing to mandate more energy-efficient buildings. She found it hard to concentrate.
Photo: A building with air conditioning units in Chennai (formerly Madras), the world's hottest major city.