The gases used to anaesthetise patients for surgery affect the climate up to 1,620 times more than carbon dioxide, Danish and American scientists claim.
And each year the gases used for anaesthetics have the same effect on the climate as one million cars.
The gases – isoflurane, desflurane and sevoflurane – are related to another gas, the refrigerant HFC-134a.
It is due to be banned across Europe from next month because it is 1,300 times more potent than CO2.
The focus of most efforts worldwide to fight climate change is to reduce carbon dioxide emissions.
It is the most important greenhouse gas because it has been emitted in such vast volumes through the burning of fossil fuels.
But other greenhouse gases, such as methane, account for up to 40 per cent of the greenhouse gas effect, trapping the Sun’s heat on Earth.
Dr Benny Peiser of the Global Warming Policy Foundation, which is sceptical about climate change, said yesterday: “Just as cheap fossil fuels will remain the life-blood of the world economy, stability and growth, we cannot give up on anaesthetic gases just because they are very potent greenhouse gases.
“The sooner people begin to accept the hard realities of what drives modern society and secures modern medical treatment, the better.”
In the new study Professor Ole John Nielsen of Copenhagen found that two of the main anaesthetic gases used, sevoflurane and desflurane, are respectively 210 and 510 times more powerful greenhouse gases than carbon dioxide.
A third, isoflurane, is 1,620 times more potent than CO2, according to analyses by Professor Nielsen and American colleagues at Nasa and the Ford Atmospheric laboratories. Professor Nielsen told the British Journal of Anaesthesia: “We studied three different gases in regular use for anaesthesia, and they’re not equally harmful.
“This ought to make anaesthesiologists sit up and take notice.
“If all three compounds have equal therapeutic worth, there is every reason to choose the one with the lowest global warming potential.”
Professor Nielsen said the relatively small amount of anaesthetic gases used means that a ban on the gases is not justified.
But he added: “The surprising properties of anaesthetic gases are an important reminder to anyone who is using any kind of gases.
“They really ought to examine the atmospheric fate of them, before releasing them into nature.”