The use of air conditioners to cool the inside of buildings can make cities hotter, said researchers who studied the summer temperatures of a Japanese city.
Yukitaka Ohashi of the Okayama University of Science and colleagues compared the summer temperatures in downtown Tokyo on weekends versus weekdays, reported ABC online (Australian Broadcasting Corporation).
The study showed that air conditioners dump enough heat into the streets to raise the temperature at least one to two degrees Celsius.
Air conditioners remove not only ambient heat from buildings, but they expel heat from their use of electricity. In other words, coolers don't just move heat from the inside to the outdoors, they also add new heat just by being machines that consume power, the report said, quoting Discovery News.
In fact, Tokyo sucks up about 1.6 giga-watts of electricity for every two degrees of warming on a hot summer day, the Japanese researchers say. That's equivalent to the output of one-and-a-half nuclear power plants.
To accurately predict the air temperature in any big city, meteorologists need to better understand exactly how big buildings are expelling heat, the study suggests.
US-based urban heat researcher Stuart Gaffin of the Center for Climate Systems Research at Columbia University in New York suspects the Japanese researchers are right about the significant contribution of air conditioning to hotter cities.