Air-conditioning units are being blamed for increasing the temeperature in US cities during the night, according to a new report.
Climate change has been to blame for the increase as city residents are turning increasingly to AC systems to stay cool due to higher temperatures. The result is that the heat discharged from units in offices and flats goes straight into the atmosphere, further warming the city.
According to scientists at Arizona State University, the air conditioning system 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 1C, they report in the Journal of Geophysical Research Atmospheres.
The team focused on the role of air conditioning systems in the metropolitan area of the city of Phoenix, which is in the Sonora desert in Arizona, and conditions in the summertime are harsh there anyway.
Fuethermore, according to the report, normally warm countries are experiencing increasing extremes of heat, and conditions in cities have become critical.
This situation is compunded by traffic, building heating and lighting, tarmac, tiles, bricks and people, which can rasie the temperature up to 5 C higher in the city than the surrounding area.