EGU 2013: a bumpy ride for transatlantic flights

environmentalresearchweb blog
Posted on Apr 8, 2013 8:43 pm
By Liz Kalaugher

If, like me, you're a nervous air passenger, the news from today's European Geosciences Union General Assembly wasn't good. Speaking at a press conference just 15 minutes after the publication of his paper, Paul Williams of the University of Reading, UK, revealed how climate change is likely to bring stronger and more widespread clear air turbulence for transatlantic flights.

A doubling of carbon-dioxide concentrations, which could well occur by the 2050s, would increase the average strength of clear air turbulence by 10-40%, Williams and colleague Manoj Joshi of the University of East Anglia, UK, calculated. The amount of airspace containing significant turbulence would also increase by 40-170%; Williams said the most likely figure would be 100%.

To come up with these results, the pair employed the GFDL-CM2.1 climate model to simulate 20 years' worth of data for pre-industrial and doubled carbon dioxide concentrations, using 21 separate measures of turbulence. They analysed clear air turbulence during the winter, when it's at its most intense, along the North Atlantic flight corridor, one of the busiest in the world, with 300 flights in each direction each day.

This turbulence isn't just a problem for scaredy cats. It can injure, or even kill, passengers and aircrew; it can damage planes, for example breaking off engines or parts of the wing; and it currently costs society about $150 million each year in injuries, damages and investigations. As a result of the additional turbulence, airlines may have to reroute flights, boosting fuel consumption, increasing air pollution, and potentially causing delays and increasing ticket costs.

So why the increase? As climate changes, the atmosphere is warming above our heads as well as at ground level, explained Williams, leading to higher wind speeds. Or, to put it another way, a stronger jetstream is destabilizing the atmosphere and the random fluctuations in upwards and downwards winds push against aircraft wings.

The atmosphere strikes back

Worse still, unlike the turbulence caused by clouds or storms, clear air turbulence is hard to detect. You can't see it, and satellites or aircraft electronic systems don't pick it up. Some ground-based radar systems can detect it, but only the very powerful ones, said Williams, as could radiosondes on balloons, which measure the amount of wobble along a single trajectory.

In their calculation of the amount of airspace containing significant turbulence, Williams and Joshi used the industry definition of moderate-or-greater turbulence, which produces an acceleration in the plane of 5 m/s2 or more, a force equivalent to half a G. This is enough to bounce the aircraft around, make it hard to walk and knock over drinks, said Williams.

"Aviation is partly responsible for changing the climate in the first place," he said, in a University of Reading press release. "It is ironic that the climate looks set to exact its revenge by creating a more turbulent atmosphere for flying."

The study is published in Nature Climate Change.