The upper-level jet stream gives a slight tailwind boost to aircraft headed from the United States to Europe, while making the return trip a bit slower. But new research predicts that climate change will speed up these winds, forcing transatlantic aircraft to spend an extra 2,000 hours in the air each year, and adding millions of dollars to fuel costs.
The study published in the journal Environmental Research Letters, looked at the effects of doubling the amount of CO2 in the atmosphere, which will occur within the next few decades unless emissions are cut quickly.
The average jet-stream winds along the flight route between London's Heathrow airport and New York's John F. Kennedy International airport are predicted to become 15 percent faster in winter, increasing from 77 to 89 km/hr (48 to 55 mph), with similar increases in the other seasons.
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As a result, London-bound flights will become twice as likely to take under 5h 20m, implying that record-breaking crossing times will occur with increasing frequency in future. On the other hand, New York-bound flights will become twice as likely to take over 7h 00m, suggesting that delayed arrivals will become increasingly common.
Paul Williams, an atmospheric scientist at the University of Reading and author of the new study, explained that the jet stream is driven by temperature difference between equator and the pole, and by the laws of fluid dynamics.
"Climate change is increasing that temperature difference," Williams told Discovery News. "When we run the detailed supercomputer simulations that is what they show."
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Due to the extra time spent in the air, transatlantic flights will burn an extra $22 million worth of fuel annually, and will emit an extra 70 million kg of CO2 – equivalent to the annual emissions of 7,100 British homes. And this might only be the tip of the iceberg.
Since the jet stream encircles the globe in both the northern and southern hemispheres, Williams expects the same effect on cross-country flights from Los Angeles to New York, for example, or Sydney to Sao Paulo.
In some of Williams' previous work, he calculated that air turbulence will also increase because of the faster winds, making for a bumpier ride for passengers. The faster winds will keep airlines busy in an attempt to save fuel.
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"Airlines employ mathematicians every day to calculate the fastest route," Williams said. "They take in the wind speed from satellite observations and weather forecasts, plug it into an algorithm and out pops the fastest route. What I have done is using same routing algorithms, but generating the winds in a climate model."
Williams says airplanes can't just fly faster to compensate because of another effect, air friction that builds up as the plane gets closer to breaking the sound barrier.
"Airplanes fly at about 550 miles per hour, or 75 percent speed of sound (767 miles per hour)," he said. "The closer they get to 80 percent, the fuel efficiency drops off a cliff and the airline has to put an afterburner, real gas guzzlers. That's why they don't go any faster."
There is one bright spot, Williams noted. North-south routes should not be affected by the jet stream winds.
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Kristopher B. Karnauskas, an atmospheric scientist at the University of Colorado, Boulder, said that Williams' calculations suggest that the carbon footprint of Trans-Atlantic flights could increase by 70 million kilograms of CO2 per year. Karnauskas found in his own research that the carbon footprint of Hawaii-west coast flights would increase by about a tenth as much, or by around 5 million kg CO2.
"I think Dr. Williams' results are an important step forward in filling in the overall puzzle that is this intricate relationship that we humans have with the climate system," Karnauskas said in an email to Discovery News.