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Tough questions after AirAsia 8501: Changing climate will affect the way you fly


There’s a lot we don’t know yet about AirAsia Flight 8501. What we do know is that there’s a convective weather connection: thunderstorms are becoming nastier and more numerous.

Something’s happening here, and what it is is increasingly clear: the climate of this fragile blue orb we cling to is changing, mutating much faster than many had imagined. By the end of the 21st Century, the Intergovernmental Panel on Climate Change estimates Earth’s average temperature will balloon by 2.8 degrees C. The fate of the Polar Bear aside for a moment, that’s going to affect the way we fly.

Best buckle up.

“Rising concentrations of heat-trapping greenhouse gasses are changing our climate,” says Michel Jarraud, Secretary-General of the United Nations’ World Meteorological Organization. Implications are “far reaching, and in some instances, immediate.” Already impacted by wild weather, according to the WMO’s report The Global Climate 2001 – 2010, A Decade of Extremes are places such as Eastern Europe, India, Africa and Australia. Down under, they hold the distinction of being blasted by drought and swept by floods during the same decade.

How will all of this play out for airlines, airports and the flyers that depend upon them? “I’d be very cautious about any detailed [metric] modeling of these sorts of changes,” says Dr. Michael Bennett, a teacher and researcher at the Centre for Aviation Transport and the Environment in the United Kingdom. “The only thing we can predict is there are going to be some nasty surprises out there.”

Surprises such as stronger and more frequent thunderstorms, the kind that trigger seat-gripping turbulence.

Storms, Turbulence and Weird Winds

According to the study The Impacts of Extreme Weather and Climate Events on Aviation penned by Idowu Innocent Abbas, James Kayode Ojo and P.A. Igbru and presented in Nigeria in 2009, 777 people died between 1979 and 2005 worldwide in commercial aviation accidents associated in some fashion with thunderstorm turbulence.

Expect such storms to “become more frequent and more violent,” says Bennett. “There’s more energy there; there’s more latent heat.” So, should you order a second Scotch and water and cinch your seatbelt a bit tighter for the ride ahead? He says with improved technology “We should be able to predict, detect and avoid [storm-triggered] turbulence,” but cautions such avoidance “comes at a cost.” Aircraft have to fly farther in order to circumnavigate bad weather.

Looking out his window of the World Meteorological Organization headquarters in Geneva at the parking lot that holds his hail-dented car, Dr. Herbert Peumpel says unexpectedly stormy weather is already a fait accompli on the European continent. “Geneva is not known for hail storms,” muses the WMO’s aeronautical chief. But “probably the biggest [such storm] I’ve ever observed happened in in Geneva.” Switzerland has never been considered a hotbed of convective thunderstorm activity. That sort of thing is traditionally the province of places such as the U.S., Southeast Asia or the Brazilian rain forest. No longer.

As a result of all this convective weather, a report by the air traffic control entity Eurocontrol, Challenges of Growth 2013 – Climate Change Risk and Resilience, envisions “Disruption and delay” as well as “potential safety issues if frequency and severity increases” or the ability to predict dangerous weather declines.

Disruption and delay come in assorted flavors. Mess up the traditional west-to-east flow of the jet stream – the purveyor of cooler, milder weather to Europe – and bad things happen. Such interruptions allow “bad weather to persist for weeks,” says Herbert Peumpel. He links the interrupted flow to “melting of the Arctic ice sheets.”

Wretched weather need not be destructively convective to wreak havoc. Ironically, Eurocontrol says a warming world could spawn “snow-heavy weather events” in Europe. The rationale, again, is pegged to air flow. Because the North Atlantic and Artic are warming, there will be longer periods when whether patterns are blocked. That would prevent warmer weather from spreading across the continent, setting up a scenario of more snow. Frozen precipitation and on-time airline operations are mutually exclusive.

Then there’s the little matter of that tail wind you get hurtling across the Atlantic from New York to London. A diminished jet stream could lengthen the journey and cause airlines to rejigger schedules.

Zip, zap, zoom. As climate changes, weather wrenches around in fast fashion. Consider, Peumpel says during he late winter and early spring of 2013 the Hungarian Army was rescuing people stuck in snowdrifts on the flat highway linking Vienna and Budapest. Scant weeks later the temperature had catapulted 30 degrees Celsius. “The extremes are changing more rapidly,” he says, and those extremes are “lasting longer.”


Superstorm Sandy played hell along the Eastern Seaboard of the United States in October 2012, and airports were not immune. A gradually rising sea and surging tides coupled calamitously to flood portions of New York LaGuardia Airport. Waters from Flushing Bay lapped at the tarmac. New York Kennedy International and Newark Liberty International were less severely hit.

This could be a mere foretaste of what’s to come. In the report Climate Variability and Change with Implications for Transportation, the U.S. National Oceanic and Atmospheric Administration lists a number of airports in the United States that could be in harm’s way. Among them are Louis Armstrong New Orleans International, San Francisco International, Reagan Washington National, and Boston Logan. Interestingly, New York LaGuardia was ostensibly best positioned among all these airports to withstand storm surge. It sits some 22 feet, or 6.7 m, above mean sea level.

Dr. Bennett says the immediate threat is not so much from sea level rise per se as from storm surge. “Let’s be clear, sea level rise is a gradual process. Over the last ten years we’ve been looking at about three millimeters per year.” Bennett believes this could add up to an increase of some “six inches by mid-century, perhaps more than that.”

But couple that rise with walls of water emanating from storms such as Sandy and the equation suddenly becomes soggy. He says together storm surge and sea level rise pose a real problem at “about 150 airports [airports] worldwide. “

By mid-century, such “storms will become more intense,” asserts the WMO’s Peumpel. They derive their punch from the energy extant in the atmosphere – and the best storage medium for that energy is atmospheric moisture, moisture stemming from what Peumpel says are “increased sea surface temperatures.”

Especially vulnerable are airports built on artificial islands, airports such as Osaka’s Kansai International. At KIX, Peumpel says, “there’s the problem of [ground] subsidence.” In short, the airport is sinking, even as the seas rise.

Europe has its share of low-lying airports. Consider Amsterdam. Schiphol rests 11 feet below sea level. In its report, Eurocontrol asserts one implication is “loss of airport availability” at more than 30 “at risk” European aerodromes. Echoing Bennett and Peumpel, the report cautions, “the impacts of sea-level rise [affecting Europe] are expected to be experienced over the longer term.” More ominously, “the impacts of an increase in storm surges may be more immediate.”

Immediate, as in right now.

You don’t have to fly out of a seaside airport for climate change to spoil your day. Just ask flyers who frequent Phoenix Sky Harbor International, a major hub for US Airways and a busy “focus city” for Southwest Airlines.

How Heat Affects Aircraft Performance

This past summer was a scorcher in the aptly-named Valley of the Sun in the Southwestern U.S., so much so that on a deadening 119 F-degree summer day US Airways had to ax 18 flights out of PHX. It was simply too hot to fly.

Here’s why. Warm air is less dense than cooler air. As the temperature rises, molecules of air spread out. That results in less lift, and longer takeoff rolls. The wings just can’t get the bite out of the air they need to produce sufficient lift.

“The length of a takeoff run is directly proportional to the absolute temperature of the air,” says Michael Bennett. Via this “density effect” for every three-degree increase in temperature you need a one percent increase in runway length. Most of the time, a few additional “tens of meters” will do the trick. But when temperatures soar to the significant triple-digits it could be “your existing runway is simply not long enough.”

Assuming the flying machine lifts off at all, its ability to climb can be radically reduced. If there are mountains around, as there are in the hot, western reaches of the U.S., watch out. The density effect is universal. As the Civil Aviation Authority of New Zealand puts it, “Rate-of-climb and angle-of-climb are noticeably reduced, as is obstacle clearance after takeoff” when temperature and altitude rise.

And when mountain and airplane meet, the latter is always the loser.

One way to operate in these kinds of temperatures is to limit the weight the aircraft has to carry. That may mean less fuel, equating to less range. A nonstop becomes a one-stop. Another option is to load-limit passengers and baggage. Either way, airline profit tumbles.

Performance degradation is just one issue. Bennett says the flashpoint for Jet A1 fuel is 100 degrees F, “which is fine in England. Normally, you could just throw a match into the tank and it wouldn’t burn.” Ah, but on a sizzling tarmac where the temperature is significantly higher it’s another matter. Temperatures such as those experienced in the desert Southwest of the United States, the Middle East, and other hot, arid areas can produce what Bennett calls “a highly flammable liquid.” While getting aircraft ready for flight is “doable” under such circumstances, “it just makes it more difficult.” You’ve got to be “very, very careful.”

He believes market forces may adjust automatically to increasing heat. “Clearly, this will affect European holiday-makers.” Will they continue to fly to the Greek Islands in August, “when [they] can hardly go outside…or fly in February of September, when it might be relatively pleasant?”

The World Meteorological Organization’s Herbert Peumpel says coping will become largely a matter of mitigation. No need to cancel a flight when you can adjust the schedule. It’s already happening. He says Middle Eastern airlines which fly regularly to hubs such as Dubai and Doha already hub after sunset. “If you look at their peak hours of operation, it’s nighttime. That may be the answer,” he says. “In areas that are getting extremely hot, you may have to switch mostly to nighttime operations.”


The old adage “everyone talks about the weather, but nobody does anything about it” is a tad shop-worn. We’ve all but conquered wind shear though pilot training, air- and ground-based detection. Infinitely more capable radar systems, as well as laser-based LIDAR (Light Detection and Ranging), have enabled us to ferret out weather dangers as never before.

We may not be able to avoid the weather extremes brought on by rapid climate change, but we can mitigate their impact. Airports can prepare for the shift of prevailing wind by building more crosswind runways. They can get for rising waters by elevating generators and electrical systems. Carriers can shift hot weather hub operations from day to night during the warmest times of year.

“We need to look [at] better mitigation and better planning so that we can handle a series of unusual events without a major breakdown,” says the WMO’s Herbert Peumpel. “I think aviation has always been extremely good at that.”

And it’s going to have to get even better yet before too terribly long.


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