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China science

Climate change will lead to much more severe turbulence on flights, study suggests

Expect air travel to become more uncomfortable as the planet heats up

PUBLISHED : Thursday, 06 April, 2017, 7:00pm
UPDATED : Friday, 07 April, 2017, 10:12am

Air passengers are likely to experience nearly double the frequency of severe turbulence during flights in the coming decades because of the impact of climate change, according to a scientific study published on Thursday.

The research suggested that if the level of carbon dioxide in the atmosphere increases at projected levels by the middle of this century then severe air turbulence will increase by about 85 per cent compared with current levels.

Scientists said airlines may have to take more measures to avoid pockets of severe turbulence which can physically throw passengers around the cabin and cause structural damage to the aircraft.

“Today we are roughly halfway towards a doubling of CO2 [compared with pre-industrial levels], so arguably we have already seen roughly half the turbulence increases, with a further half to come in the future decades,” said Paul Williams, the author of the study and an associate professor in the meteorology department at the University of Reading in Britain.

The study suggests that turbulence will increase up to 188 per cent by mid century compared with pre-industrial levels.

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The research was published in the journal Advances in Atmospheric Sciences on Thursday and was based on supercomputer simulations of a busy flight route connecting London and New York.

But Dr Williams said the impact of increased levels of turbulence would be felt across the globe, including in Hong Kong and mainland China.

Temperature rises caused by greenhouse gas emissions stimulate the creation of wind shears in jet streams in the atmosphere - and with it a much higher chance of turbulence.

“The jet stream encircles the entire globe, not just the north Atlantic. The mechanism driving stronger turbulence applies throughout the jet stream, at all longitudes,” Williams said.

“Therefore, I fully expect severe turbulence to increase on other flight routes, too, such as trans-Eurasian and transpacific flights. We need further studies to put some numbers to this expectation,” he said.

The study examined several different turbulence strength levels at an altitude of about 12km.

It predicted the average amount of light turbulence in the atmosphere will increase by 59 per cent from pre-industrial levels, with light-to-moderate turbulence increasing by 75 per cent, moderate by 94 per cent, moderate-to-severe by 127 per cent, and severe by 149 per cent by the middle of the century.

“For most passengers, light turbulence is nothing more than an annoying inconvenience that reduces their comfort levels, but for nervous fliers even light turbulence can be distressing,” Williams said.

“However, even the most seasoned frequent fliers may be alarmed at the prospect of a 149 per cent increase in severe turbulence, which frequently hospitalises air travellers and flight attendants around the world,” he added.

Turbulence is one of the main causes of discomfort in air travel and can cause injuries and even deaths among passengers.

The average duration of turbulence is five minutes, but the unstable pocket of air is usually too thick to allow pilots to carry out evasive manoeuvres.

US airlines alone encountered about 5,000 severe or worse instances of turbulence annually, according to an estimate in 2006.

In one extreme case experienced by a plane over Colorado in December 1992, the turbulence tore off one engine as well as six metres of the plane’s left wing.

“The main advice to passengers is to keep their seat belts fastened at all times when seated, even when the seat belt sign is not illuminated,” said Williams.

“The pilots already do this. Most passenger injuries caused by turbulence occur to people who are not seat-belted,” he said.

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There are various technologies available to smoothen or avoid turbulence for commercial aircraft, but they are not implemented mainly due to airline concerns about cost.

The research suggested that aircraft could be fitted with an accelerometer in the nose cone. The motion sensor could register a sudden change in altitude indicative of turbulence, allowing a computer to adjust the wing flaps rapidly in an attempt to damp the jolts and reduce passengers’ discomfort.

Another solution is Lidar, or light detection and ranging radar. It emits a powerful laser which can tell the difference in air density ahead, something existing weather radar cannot detect, so pilots have time to take an evasive course.

Dr Liu Bo, a laser radar researcher at the Institute of Optics and Electronics in Chengdu in Sichuan province, said: “Lidar technology is mature after decades of development. It has already been used on many general aviation flights for remote sensing. I think it is time for major airlines and plane manufacturers to seriously consider implementing Lidar technology on civil aviation aircraft.”

The main obstacle, he said, was cost. Passenger injuries or plane damage caused by turbulence were still rare. For airlines, the jolts, albeit scary sometimes, simply do not justify the cost of retrofitting an entire fleet with the new technology.

But if William’s prediction of increasing levels of turbulence in the coming decades are correct, there might be good business reasons to make the change, said Liu.

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The economic cost of turbulence arising from injuries, accelerated aging of planes, flight delays, inspections, repairs and post-accident investigations will all add to airlines costs, the new research said.

“Airlines turning a blind eye to turbulence and ignoring the increasing demand for flight comfort may eventually lose passengers,” he said.