Such warnings are supported by a study of US weather stations co-written by Anthony Watts, an American meteorologist and climate change sceptic.His study, which has not been peer reviewed, is illustrated with photographs of weather stations in locations where their readings are distorted by heat-generating equipment.
Some are next to air- conditioning units or are on waste treatment plants. One of the most infamous shows a weather station next to a waste incinerator.
Watts has also found examples overseas, such as the weather station at Rome airport, which catches the hot exhaust fumes emitted by taxiing jets.
In Britain, a weather station at Manchester airport was built when the surrounding land was mainly fields but is now surrounded by heat-generating buildings.