Faster jet stream as a result of climate change could add 70,000 tonnes of CO2 annually to transatlantic flights
Thu 18 Feb 2016 – Last month a British Airways Boeing 777-200 achieved a ground speed close to that of sound on a flight from New York to London, arriving an hour and a half before schedule in a time of 5 hours 16 minutes, reported the Daily Telegraph. The aircraft’s pilots were taking advantage of an unusually strong winter jet stream but such flying times across the Atlantic could become the norm as a result of climate change accelerating jet stream winds, particularly in the winter. However, a study by atmospheric scientists at the UK’s University of Reading found the effect of the jet stream on westbound transatlantic flights would mean longer journeys than currently normal and there would be a net increase in time, fuel and emissions on a round trip. The researchers calculated transatlantic aircraft would spend an extra 2,000 hours in the air every year when predicted concentration levels of CO2 are reached sometime this century.
Jet streams are fast-flowing air currents within the upper atmosphere that typically flow from west to east, fuelled by differences in air temperature. During the winter, the temperature difference between the colder Arctic and the warmer subtropical regions is far greater than during the summer, so producing a stronger jet stream. Climate change is intensifying the winter temperature difference as the subtropical and tropical regions are warming faster than the polar regions.
The research team, led by Dr Paul Williams, fed synthetic atmospheric wind fields generated from climate model simulations into a routing algorithm of the type used by flight operations planners, focusing on flights between London and New York and how they could be impacted when the atmospheric CO2 concentration is doubled compared to pre-industrial levels.
The average jet stream winds along the flight route between London Heathrow and New York JFK are predicted, say the researchers, to become 15% faster in winter, increasing from 77 to 89 km/hr, with similar increases in the other seasons.
The study, published in the journal Environmental Research Letters, found that a strengthening of the prevailing jet stream winds causes eastbound flights to significantly shorten and westbound flights to significantly lengthen in all seasons but do not cancel each out. Eastbound and westbound crossings in winter become around twice as likely to take under 5 hours 20 minutes and over 7 hours 00 minutes respectively.
Under the scenario, the winter jet stream would result in an eastbound flight from New York to London taking four minutes fewer to complete on average. However, a flight in the opposite direction, having to avoid the jet stream, would take five minutes and 18 seconds longer, so resulting in a round trip taking an extra one minute 18 seconds.
“This effect will increase the fuel costs to airlines, potentially raising ticket prices, and it will worsen the environmental impacts of aviation,” said Williams. “The aviation industry is facing pressure to reduce its impacts, but this study shows a new way in which aviation is itself susceptible to the effects of climate change.”
Even without an increase in traffic, he estimates the extra time in the air will cost airlines $22 million in fuel annually on transatlantic routes from burning an extra 32.7 million litres (7.2 million gallons) of jet fuel, and result in an additional 70 million kg of CO2 emissions, equivalent to the annual emissions of 7,100 British homes.
And, adds Williams, the impact is not just limited to transatlantic flights. “The jet stream encircles the globe and there is one in the southern hemisphere too,” he said. “It is possible that flights elsewhere in the world will also suffer from a similar jet stream effect.”
Williams and his team carried out a study two years ago that warned transatlantic flights would also experience considerably more turbulence as a result of a doubling in atmospheric CO2 concentrations (see article).