My worst experience on a flight was about 20 years ago. I was crossing the Rocky Mountains on the way to Denver, Colorado – a route known for turbulence. Fortunately, the drinks service was over, the cabin crew seated and the seatbelt sign was on. I was seated near the back of the plane, often a bumpier ride. The aircraft started to move around a bit and then came a big jolt. The aircraft dropped dramatically. I was lifted out of my seat but held down by my seatbelt, fastened tight. My drink splashed the ceiling and then back into my lap. All around me passengers gasped and scrambled to hold onto their drinks. Just like that, within a moment, the plane returned to its smooth flight. All of this happened over the course of a minute.
It was a classic severe turbulence event, but unlike the two recent ones involving a Singapore Airlines and a Qatar Airways flight, it had been fully anticipated. The crew ensured we were all strapped in and so, while unsettling, there were no injuries, no media reports, just a few stained items of clothing.
The two episodes that occurred last month had very different outcomes – the first resulted in more than 30 injuries, many serious, and one fatality. The second caused more than 10 injuries. Together they have raised questions about whether turbulence is becoming more severe and if flights will get even bumpier with climate change. They have cut to the heart of people’s fear of flying.
The cases will be scrutinised by the airlines and air safety investigators to understand the causes and events that contributed. Lessons learnt will likely be incorporated into pilot training or aircraft operations, ultimately improving flight safety. It is important not to draw conclusions prior to the completion of such critical investigations. We also need to recognise that attributing the role of climate change to specific turbulence events is impossible given the current state of the science on this topic. The two cases occurred in different locations, under different weather conditions, and were subject to different operational decisions. Their proximity in time was bad luck rather than any evidence of a significant trend.
The upheaval on my Denver flight was anticipated, most likely due to an earlier plane having encountered turbulence. It is the surprise events that are most dangerous to passengers and crew. In such cases, the seatbelt sign may be off, people might be walking around the cabin, food carts might be in the aisle. Many seated passengers will have their seatbelts undone or only loosely fastened. The vast majority (more than 97 per cent) of injuries on flights are among those not wearing seatbelts. Turbulence encounters with multiple serious injuries are extremely rare – they occur only about once a year globally. Considering thousands of commercial aircraft are in the sky at any given time, an incredibly low proportion of passengers are injured in flight. This is partly because airlines and pilots do an excellent job of avoiding turbulence and making sure people are seated and secure when it is expected.
I have studied the weather patterns and systems that cause aircraft turbulence for almost 25 years – exploring cases of severe turbulence and the conditions that might lead to unexpected encounters. I’ve analysed large amounts of data from commercial airlines to understand the statistics of when and where turbulence might occur. My job means I’m also a frequent flyer, travelling more than one million kilometres over the past few decades. During those years I’ve experienced severe turbulence, such as in my Denver flight, only a couple of times. I’ve felt the roller-coaster of moderate turbulence perhaps only about 20 times, and short choppy passages more frequently. My experiences closely resemble the turbulence data we analyse. Commercial air travel is smooth and uneventful nearly all the time.
Turbulence occurs in the atmosphere when the wind is disrupted by a weather feature, causing it to be more erratic. These turbulent winds will move in all directions, including up and down. How fast the upward or downward movement, and over what distance, will determine the severity of what is experienced by a passing aircraft. The weather systems that cause turbulence include thunderstorms, wind flowing over large mountain ranges, and regions of strong winds in the upper atmosphere, known as jet streams. The ways these weather systems create turbulence are mostly linked to the strength of the wind shear, which is how quickly the wind changes with altitude.
Thunderstorms are incredibly turbulent, with the fluffy or cauliflower-shaped turrets hiding strong upward and downward motions. Pilots avoid such storms using en route guidance: typically a combination of visual cues, onboard radar to detect the storms and satellite imagery and weather forecasts for route planning. Thunderstorms can also cause turbulence in the non-cloudy air around them. The air above is particularly risky, and an enhanced risk can extend up to 100 kilometres away horizontally. This turbulence, along with the mountain range and jet stream varieties (often called clear-air turbulence), is invisible. It cannot be detected using instruments onboard commercial aircraft and so poses the greatest risk of unexpected encounters.
That said, many resources are available to pilots and flight dispatchers to help avoid such encounters. In addition to communications with aircraft ahead of them, a key tool is weather forecasting. The computer models used to predict our day-to-day weather on the ground are used at flight level as well. Knowledge of the links between weather systems and aircraft turbulence has enabled complicated algorithms that can identify regions of likely events. These forecasts, along with those of thunderstorms, are used for route planning and flight operations to minimise flight hazards. These methods are not perfect but they are highly effective.
The nature of turbulence in the atmosphere also helps make severe encounters rare. Patches are typically localised and short-lived. This means that a large region identified as more likely to be affected might have only a small number of active turbulence areas at any one time. The patches are normally pancake-shaped, meaning a slight variation in flight altitude can effectively avoid them. So even if a region has increased atmospheric turbulence, the chance of an aircraft hitting severe disruption remains very low.
It is true recent research suggests atmospheric turbulence will increase with climate change. Studies from the University of Reading in Britain show increases in the strength of jet streams around the globe, leading to greater potential for aircraft turbulence in some regions. Yet many of these regions, especially in the southern hemisphere and across Australia, do not overlap with existing flight routes. The good news is there have been essentially no significant increases in jet stream turbulence over the past four decades in Australian airspace. Worst-case scenario climate projections suggest up to about a 35-50 per cent increase in the potential for severe turbulence between 2030-2050, but these changes are limited to the southern portion of the continent.
Jet streams occur outside the tropical regions, so these trends are less relevant there. Thunderstorms are the dominant source of turbulence in the northern parts of Australia and for international flights as they pass through the tropics. Research into how climate change will affect turbulence from thunderstorms is a work in progress. We do know, however, that as air heats up it can hold more water vapour, and it is anticipated that the strongest thunderstorms will be more intense as the climate continues to warm. It follows that stronger thunderstorms would have a higher risk of severe turbulence.
Although there is an obvious link, changes in atmospheric turbulence do not necessarily translate to more affecting flights. Atmospheric turbulence is only part of the story, with operational decisions playing an important role in improving flight performance and avoidance. Although scientists do partner with many airlines to study their data, the record of quality data is not yet long enough to make rigorous conclusions about trends in actual turbulence encounters.
I am confident commercial air travel will remain safe. Aviation weather predictions are getting better every year. Forecasting models are rapidly improving, enhancing the realism and accuracy of predictions further and further into the future. Weather satellites are increasingly able to identify fine-scale details of clouds and storms. Pilots also have increasing data available to them in the cockpit to help choose the safest route. This includes the ever-improving onboard weather radar, new data streams and aircraft flight technology to make flights smoother. That said, advancing turbulence avoidance methods is not easy and requires a great deal of ongoing investment, research and development activity over the coming decades. In my view, however, our capacity to keep flights safe will improve at a faster rate than any increases in turbulence due to climate change.
I am often asked whether my research has made me a more worried flyer. The answer is no. Commercial air travel remains among the safest forms of transportation. My work has, however, led me to adjust my in-flight habits. I always have my seatbelt fastened properly when seated and make sure my family does too. I pay attention to the weather outside a little more. I also try to get a seat closer to the front of the plane, where it is slightly less bumpy. I worry more about getting to the airport on time, queues at check-in and security, and carbon miles than I do about the safety of my flight.
For me, air travel remains an enjoyable experience. Despite the occasional bump, flying is a bit of quiet time to listen to music, watch a movie and stare at the tops of the clouds that I spend so much time studying when my feet are on the ground.
This article was first published in the print edition of The Saturday Paper on
June 1, 2024 as “Turbulent times”.
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