Too hot to fly? Climate change may take a toll on air travel

22 June 2017 | Adaptation

In recent days, airlines have been forced to cancel more than 40 flights in Phoenix. The reason: With daytime highs hovering around 120 degrees, it was simply too hot for some smaller jets to take off. Hotter air is thinner air, which makes it more difficult — and sometimes impossible — for planes to generate enough lift.

As the global climate changes, disruptions like these are likely to become more frequent, researchers say, potentially making air travel costlier and less predictable with a greater risk of injury to travelers from increased turbulence.

“We tend to ignore the atmosphere and just think that the plane is flying through empty space, but of course, it’s not,” said Paul D. Williams, a professor in the Department of Meteorology at the University of Reading in Britain who studies climate change and its effect on aviation. “Airplanes do not fly through a vacuum. The atmosphere is being modified by climate change.”

The problem in Phoenix primarily affected smaller jets operated by American’s regional partner airlines. “When you get in excess of 118 or higher, you’re not able to take off or land,” said Ross Feinstein, a spokesman for the airlines, referring to the smaller aircraft.

This is only one of many evolving events that demonstrate a trend towards more extreme life-threatening events. It will, over time, despite...

Bigger jets like Boeing 737s and Airbus A320s have higher operating thresholds (126 and 127 degrees, respectively), he said. All three of those maximum temperatures are specific to the Phoenix airport; aircraft have different maximum operating temperatures depending on a variety of factors, including airport elevation.

But even though bigger planes weren’t affected, Mr. Feinstein said, American decided to give passengers on any flight to or from Phoenix between 3 p.m. and 6 p.m. — the hottest part of the day — the option to change their trips. Over all, more than 350 flights were potentially affected by the hot weather in Phoenix.

Aviation is a major producer of carbon dioxide, responsible for about 2 percent of human-made emissions each year.

Researchers are just beginning to explore how climate change affects aviation and planes’ ability to fly. Because there is so little data available and so many factors at play — aircraft design, airport size and location, the weight of passengers and cargo, to name just a few — it can be hard to attribute any one service disruption to global warming.

Depending on their locations, airports may experience the effects differently. High-altitude airports like Denver have thinner air by nature, so lift is even more affected by higher temperatures.

La Guardia Airport in New York could also be affected, even though it is at sea level. La Guardia has a short runway relative to other major commercial airports, and on particularly hot days that can be a problem: Planes might not have enough distance to achieve the speed and lift needed to get airborne.

In 2015, Radley Horton, a research scientist at Columbia University’s Earth Institute, published a joint study with a Ph.D. student, Ethan Coffel, on the effect of extreme heat on aviation. The conclusion: “We can say with confidence that there will be more weight-restricted days, and larger weight restrictions,” he said.

Already, since the 1980s, airports have seen an increasing number of weight-restricted summer days, their research found. “One thing that’s become abundantly clear,” Dr. Horton added, “is this is an underexplored area.”

How Stronger Winds Affect Flying

At cruising altitudes, winds are becoming stronger and more turbulent. Since the jet stream generally travels from west to east, this means that flight times could get longer heading westbound and shorter heading eastbound. This would probably increase overall travel time and fuel consumption across the industry.

The study examined conditions at four airports: La Guardia; Ronald Reagan Washington National Airport, which also has relatively shorter runways; Phoenix Sky Harbor International Airport; and Denver International Airport. Some airports, like Denver, could counteract rising temperatures by extending their runways. That option is less workable for a location like La Guardia, however, as it is hemmed in by the East River.

As global temperatures continue to rise, some of the heaviest planes on the longest flights may eventually be unable to depart during the hottest part of summer days, Dr. Horton said. Like an ocean liner waiting for the right tide to leave port, airplanes may be grounded until the air is cool and dense enough for takeoff at full capacity.

He also pointed out that a no-fly window of even a few hours at a particular airport could have a ripple effect across airline operations while further squeezing airlines’ already tight profit margins.

Extreme heat on the ground also affects airport workers; loading and unloading luggage and servicing planes between flights could become more onerous. 

Places like Phoenix, already known for summer heat, are measurably warming up. Data from the National Centers for Environmental Information show that every year since 1976 has been hotter than the city’s historical average. Seven of the 10 hottest years on record there have been in the past decade.

With forecasts predicting record-breaking temperatures in Phoenix on Tuesday — and some flights being canceled pre-emptively — many passengers stayed away from the airport entirely. Security lines had almost no wait. The terminals were so empty, one traveler was spotted riding his bike through the airport.

One of the most important changes for global travel involves the jet stream, the powerful upper-atmosphere winds that aircraft must navigate. Jet stream patterns influence flight routes, travel time and airline fuel economy because long-distance air corridors are designed to take maximum advantage of prevailing weather patterns, which give a tailwind to eastbound flights and a headwind to westbound ones.

Jet stream winds at high altitudes are getting more intense, researchers say, which not only makes flights bumpier but also potentially affects travel times. Dr. Williams pointed out that from Jan. 8 to Jan. 12, 2015, a strong jet stream forced some flights from Europe to the United States to make unscheduled refueling stops on the East Coast before reaching their final destinations, even though they should have had enough fuel to make it all the way.

On the other hand, flights in the other direction during that time with the jet stream at their backs made the trip faster than usual. In fact, a British Airways flight broke the conventional passenger jet trans-Atlantic speed record, making the trip in 5 hours and 16 minutes, Dr. Williams pointed out. Only the supersonic Concorde has done it faster.

It may seem counterintuitive, but the gains flying east aren’t enough to offset the losses flying west. Dr. Williams has researched this, too, and he found that fighting the headwind slowed a flight more than flying with a stronger tailwind sped it up. This would eventually produce longer round-trip flight times, and higher fuel consumption.

Transcontinental flights over the United States may in the future have to make midroute stops more frequently, too. On a calm-weather day, a nonstop flight from New York to Los Angeles already approaches the maximum range of a Boeing 737 or Airbus A320, common aircraft on that route and others like it.

Airlines, of course, could also use jets with longer ranges on such routes. But as Dr. Williams points out, “It might be preferential to break it up into two shorter segments.”

Dr. Williams published another paper, in May, which suggested that incidents of turbulence could increase and become more severe. He said a stronger jet stream resulted in less stable air, so turbulence could become more likely even if there are no storms, something that is known as “clear air” turbulence. Eastbound flights would be more likely to be affected because they tend to fly more directly in the jet stream to take advantage of the tailwind.

Although modern aircraft are better able to respond to turbulence than their predecessors, passengers may still notice bumpier rides in the future. Since the 1980s, Dr. Williams said, “the number of serious injuries being caused by turbulence has a clear upward trend.”

Manufacturers are working to make aircraft more adaptable to bumpy rides, and to provide technology that can better predict and detect clear-air turbulence.



Source: The New York Times