WASHINGTON (WASHINGTON POST) - Flight turbulence could increase significantly under climate change, a study warns, potentially upping the risk of injury - or at least flight anxiety - for future airline passengers.
Furthermore, fuel and maintenance costs for carriers could rise.
An increase in atmospheric carbon dioxide concentrations could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence, the research conducted by atmospheric scientist Paul Williams of the University of Reading, suggests.
By the middle of the century, with no effort to reduce atmospheric concentrations of carbon dioxide, the volume of airspace experiencing light turbulence would increase by about 59 per cent.
Airspace experiencing severe turbulence could increase by anywhere from 36 per cent to 188 per cent, the study found.
"We're particularly interested in severe turbulence, because that's the kind of turbulence that's strong enough to hospitalise people," Williams told The Washington Post.
Forecasting algorithms can help pilots anticipate and avoid turbulent patches. But the research does suggest that future fliers could be in for a bumpier ride.
The paper builds on a 2013 study in the journal Nature Climate Change by Williams and colleague Manoj Joshi of the University of East Anglia, which found an increase in moderate-to-severe turbulence in the North Atlantic as a result of climate change.
The study did not investigate the effects on lighter or more severe degrees of turbulence. In the new paper, Williams expanded the study to light turbulence, and more severe conditions.
Light turbulence typically comes with only minor discomfort for passengers, perhaps an increase in nausea or anxiety. Severe turbulence has been known to cause injuries and even hospitalisations.
Williams focused on an area in the North Atlantic known for heavy air traffic, particularly between Europe and North America, and limited his simulations to winter, when turbulence is known to be at its highest.
He examined 21 different wind-related characteristics known to be indicators of air turbulence levels, including wind speed and changes in air flow direction.
The study found an increase in turbulence across the spectrum. Light turbulence was projected to increase by an average of 59 per cent, light-to-moderate by 75 per cent, moderate by 94 per cent, moderate-to-severe by 127 per cent and severe by 149 per cent, although there's substantial uncertainty associated with the more severe categories.
Williams stressed that severe turbulence would remain rare - even with the increase. But even an increase in light turbulence can cause greater wear and tear on planes or force pilots to use extra fuel redirecting their flight paths to avoid rough patches.
The increase in air turbulence may apply only to the North Atlantic, researchers not involved in the study said.
"Regional variations of this increase may be quite uncertain, particularly in the higher latitudes where other aspects of circulation change that are less well understood and more model-dependent may dominate," said Isla Simpson, a scientist at the National Center for Atmospheric Research, in an emailed comment to The Post.
Kristopher Karnauskas, an atmospheric and oceanic sciences expert at the University of Colorado at Boulder, said the behaviour of the jet stream over the Pacific may respond differently to climate change.
The study builds on an area of climate science that increasingly suggests rising global temperatures can cause changes in atmospheric airflow, including shifts in major air currents known as jet streams.
Because the equator is the warmest part of the planet, and warm air takes up more space than cold air, the atmosphere tends to be thicker around the center of Earth than at the poles.
As a result, there's a kind of downhill atmospheric slope from the equator to the poles over which air flows.
While this is happening, Earth is constantly spinning, pushing airflow eastward. In the North Atlantic, the result is a jet stream - a meandering, wavy current flowing around the planet from west to east.
As the planet grows hotter, however, warming air near the surface could bring about changes in the atmospheric slope between equator and poles. Models such as the one used in Williams's new paper have suggested that the jet stream could become stronger as a result, bringing about an increase in the types of wind patterns that lead to increased air turbulence.
Some research has already begun to detect changes in large-scale atmospheric currents. Other scientists have suggested that rapid warming in the Arctic is actually causing the jet stream to weaken.
There remains considerable uncertainty about how airflow near Earth's surface might change in the future, Simpson said. But she said scientists are becoming more confident about the changes "that we expect to happen higher up, near the altitude where planes fly."
Examining these issues can lead to a better understanding of the effects of climate change on aviation, Karnauskas said.
"I think it's been decades that all of the attention has been on the impact of such industries like aviation on climate, but this is something that's flipping it around and looking at the impact of climate on aviation," he said.
" If we can really understand the two-way street that we're dealing with, that's really going to help us understand ultimately how the climate will change in the future as a coupled system between the people and the atmosphere."