Climate change may make for more turbulent flights: study

Heads up frequent fliers, nervous fliersand everyone in between: climate change could make air travel a whole lot bumpier.

A new study conducted by atmospheric scientist Paul Williams, of the University of Reading in the United Kingdom, suggests that an increase in carbon dioxide concentrations in our atmosphere could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence.

In fact, according to the study, by the middle of the century, the volume of airspace experiencing light turbulence could increase by about 59 per centand severe turbulence would increase by 149 per cent.

The impacts of climate change on the aviation industry is a fairly new field of research, but studies are steadily accumulating. This latest paper actually builds on a 2013 study in the journal Nature Climate Changethat found an increase in moderate to severe turbulence in the North Atlantic as a result of climate change.

Williams used the same set of conditions and models but extended the research to investigate the effects on all ranges of turbulence,from light to severe. The study also quantifies byhow much different kinds of turbulence will increase.

A warmer, bumpier forecast

Clear-air turbulence the kind that happens without the presence of clouds is the result of wind shear, a change in wind speed and/or direction over a relatively short distance in the atmosphere. That rapidchange in airflow is what can lead to bumpy conditions.

Although many other factors can lead to turbulence, previous work on the subject has shown that the jet stream contains about three times more clear-air turbulence than the rest of the atmosphere. The jet stream that narrow band of fast-moving air in the upper atmosphere is driven by the collision of air masses with very different temperatures.

The jet stream is also wherecommercial airlinestake advantage of that fast-moving air when travelling from west to east, saving time and fuel.

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Some research has already begun to detect changes in large-scale atmospheric currents. One of those projected changes may be an increase in the wind shear at altitudes of 9,000 to 12,000 metres (30,000 to 40,000 feet). It's at these heights that the air above the tropics is warming faster than the air above the Arctic, resulting in an increase in temperature differencethat drives wind shear.

Williams's workimagines a scenario where CO2 concentrations are twice the pre-industrial concentrations an outlook that most moderate climate scenarios project for future emissions.

He examined 21 different wind-related characteristics known to be indicators of air turbulence levels, including wind speed and changes in airflow direction (wind shear), and found an increase in turbulence across the spectrum as a result of climate change.

"We find that the temperature patterns and the wind patterns in the high-altitude atmosphere are very tightly coupled together.So if we change the temperature pattern [which is what we are doing with the CO2 emissions], wind patterns are changing as a consequence. Specifically, those high-altitude winds are getting stronger becauseof climate change,and that's increasingthe probability of the instability," Williams told CBC News in an interview.

It should be noted that even with a 149 per centincrease in severe turbulence, severe turbulence would still be an extremely rare occurrence for passengers. Williamsexplained that "something like 0.1 per cent of the atmosphere at typical cruising altitudes contains severe turbulence.That sounds small, but given the large number of planes in the sky at any moment, sooner or later one of them is bound to encounter that 0.1 per cent purely by accident. However, even if this figure tripled later this century, which is at the top of the range of projections in our study, it would still be only 0.3 per cent."

What does this mean for the aviation industry?

Williams also points out that the projected increase in the prevalence of clear-air turbulence does not necessarily imply more in-flight injuries or greater levels of passenger discomfort. In the future, the skill of clear-air turbulence forecasts and in-flight detection may improve, meaning pilots will be better equipped to divert around patches of clear-air turbulence.

Someaircraft already have automatic responses to the first signs of turbulence to dampen vertical motion, and that technology may also improve.

Williams suggests future work should examine other seasons, flight levelsand geographic regions, as well as model resolutionand sensitivity.

Williams also adds: "The airlines have a treasure trove of turbulence data to help test our theories and forecasting algorithms, but obtaining access to the data can be difficult.It would be great if the airlines were more open to sharing their turbulence data with atmospheric scientists like me, to help keep flying as pleasant, safeand comfortable as possible."

When CBC asked Transport Canada what they make of the new research, they said:"Transport Canada constantly reviews the latest research to support evidence-based policy decisions. Our experts look forward to reading this paper; thank you for bringing it to our attention."

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