"Increasing use of air conditioners to stay cool is having the vicious circle effect – especially at night – of worsening the problem of cities getting hotter as the climate changes, say US researchers"
"LONDON − Researchers in the United States have identified how city-dwellers inadvertently stoke the heat of the night: By installing air conditioners.
Because the cities are getting hotter as the climate changes, residents are increasingly investing in air conditioning systems − which discharge heat from offices and apartment blocks into the city air. The vicious circle effect is that cities get still warmer, making air conditioning all the more attractive.
According to scientists at Arizona State University, the air conditioning feedback loop is now having a measurable effect. During the days, the systems emit waste heat, but because the days are hot anyway, the difference is negligible. At night, heat from air conditioning systems now raises some urban temperatures by more than 1 degree Celsius, they report in the Journal of Geophysical Research Atmospheres."