Changes in high-altitude winds resulting from a doubling of carbon dioxide in the atmosphere will add an average of just over one minute to a round trip from London Heathrow to New York, according to a UK researcher. Due to a stronger jet stream, plane trips back to the UK from the US will be quicker but outward trips slower – overall the changes will increase journey times.

"Transatlantic aircraft may be in the air for an extra 2,000 hours each year, adding $22 million to airline fuel costs, and increasing carbon dioxide emissions by the equivalent of 7,100 British homes," said Paul Williams of the University of Reading, UK. "Apart from potentially raising ticket prices, passengers will have a significantly increased chance of being on a record-breakingly fast eastbound flight across the Atlantic. However, they will also have a significantly increased chance of experiencing delayed arrivals in North America."

The transatlantic route is extremely busy, with around 600 crossings of the North Atlantic flight corridor per day. The extra 7.2 million gallons of jet fuel burnt as a result of the atmospheric changes would emit 70 million kg of carbon dioxide.

"Airlines are constantly monitoring the wind patterns, and using some complicated mathematics to calculate the fastest routes," said Williams. "I have used those same mathematical routing algorithms, but instead of applying them to today's winds, I used winds generated from climate model simulations. We can crank up the carbon dioxide in the model, look at the effects on the winds, and then see how the flight routes are modified."

Williams modelled flight times for 20 years under a doubling of carbon dioxide, comparing them to flight times calculated for daily winds from a control run of the climate model under pre-industrial climate conditions.

The average tailwind to London at typical flight cruising altitudes, Williams calculated, would increase by nearly 15%, from 21.4 to 24.6 m/s. For comparison, the cruising speed of the plane could be ten times higher, at around 250 m/s. In winter, eastbound journey times would be around four minutes shorter, while westbound journeys would be on average over five minutes longer.

"Car journeys must take place along the network of roads, but plane journeys are obviously not constrained in this way," said Williams. "Planes are free to vary their route from one day to the next. They do this to benefit from wind patterns and reach their destinations as quickly as possible. We know that climate change is altering the winds at high altitudes. However, very little was known about the impacts on flight routes and journey times."

In winter, eastbound crossings will become roughly twice as likely to take less than five hours 20 minutes, Williams found, with the probability in the model increasing from 3.5% to 8.1%. The current record flight time for New York to London stands at five hours 16 minutes, which was achieved on 8th January 2015 under an unusually fast jet stream. Westbound crossings, however, will be twice as likely to last over seven hours (with the probability rising to 15.3% from 8.6%), increasing the risk of flight delays.

"We have previously studied how aircraft turbulence will respond to climate change," said Williams. "We projected large increases in both the amount and strength of clear-air turbulence on transatlantic flights. Looking at the impacts of climate change on flight routes was a natural next step."

Other teams have investigated the effects of warmer, less dense air on lift and take-off weights, and whether it's worth rerouting flights away from ice-supersaturated air to avoid contrail formation and the consequent climate warming.

"So far, I have looked only at transatlantic flight routes," says Williams. "However, the high-altitude atmospheric winds all across the globe are changing in response to climate change. A future research priority will be to study the impacts on other flight routes."

Williams published his findings in Environmental Research Letters (ERL).

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