NEW YORK • More frequent heat waves and rising temperatures because of climate change could ground up to a third of airplanes worldwide during hot days in decades to come, with some airports in New York and Dubai likely to be hard hit, a study showed yesterday.

Extreme heat affects a plane's ability to take off. Hot air is less dense than cold air, and the hotter the temperature, the more speed a plane needs to lift off.

A runway might not be long enough to allow a plane to achieve the necessary extra speed for a safe takeoff. That means weight must be dumped, or the flight is delayed or cancelled.

Airlines could be forced to cut their loads of passengers, cargo or fuel to take off safely, Reuters, quoting the study published in the journal Climate Change, reported.

Worldwide, average temperatures are expected to climb about 3 deg Celsius by 2100, the researchers said.

But it is more prevalent heat waves that pose a larger threat to the airline industry, they said.

Annual maximum daily temperatures at airports could rise by 4 to 8 deg C by 2080, they found, leading to more costly delays in take-offs or cancellations.

During the hottest parts of the day, between 10 and 30 per cent of fully loaded planes might have to dump weight to begin their journey.

The phenomenon could force the aviation industry to brace for thinner profit margins, the authors said.

A full 160-seat aircraft trying to safely take off in searing heat might, for instance, need to remove 13 passengers, said the study.

But the costs of delays or cancelllations could also disrupt other sectors of the economy as they trickle down, they said.

"Our results suggest that weight restriction may impose a non-trivial cost," said Mr Ethan Coffel, the study's lead author and a researcher at Columbia University in New York City, in a statement.

Airports likely to be most affected, according to the researchers' appraisal of 19 major airports, include New York's LaGuardia, due to short runways, and Dubai International Airport in the United Arab Emirates, because of scorching heat.

Projections found the least affected airports included New York's John F. Kennedy International Airport, London's Heathrow and Paris' Charles de Gaulle.

Last month, major airlines were forced to delay or cancel dozens of flights out of Las Vegas and Phoenix airports, citing difficulty in operating aircraft amid a heat wave.

Heat waves are not the only problem facing the aviation industry as the earth's climate changes rapidly.

Other scientists have calculated that severe turbulence could also be more prevalent.

Professor Paul Williams, an atmospheric scientist at the University of Reading who has studied the connection between climate change and turbulence this past year, believes the industry needs to start dealing with climate change more aggressively including developing new engines.

"I've yet to see a benefit of climate change to aviation," he was quoted as saying in Wired magazine.

"All the published studies have been about things getting worse," he said.