A report co-written by Anthony Watts, an American meteorologist, shows photographs of weather stations near heat-generating equipment which could be distorting the readings.

Some are next to air-conditioning units or next to waste-treatment plants, while one sits alongside a waste incinerator. A weather station at Rome airport was found to catch the hot exhaust fumes emitted by taxiing jets.

Rising temperatures around the stations, which have been in use for 150 years, could also have been caused by urbanization, the study claimed. One weather station at Manchester airport, which was built when the surrounding land was mainly fields, is now surrounded by heated buildings.

The IPCC used data from these weather stations to back up claims that greenhouse gases had already caused a 0.7C rise in temperature, and gave warnings that further warming of up to 6C by 2100 could have devastating effects on civilization and wildlife.

The IPCC did not find it necessary to assure that the data gathering equipment was properly used and monitored.