Yahoo Finance The net zero dogfight dominating Europe’s skies
Airlines are usually rather good at presenting a united face to the world, particularly when it comes to lobbying global policymakers.
But a recent move by the EU to clampdown on so-called contrails, the vapour that spews from an aircraft’s jet engines in a thin cloud-like formation, has set carriers at each other’s throats.
The International Air Transport Association (Iata), which counts most of the world’s flag-carriers among its members, has lobbied Brussels to limit the mandatory monitoring of contrails to only flights within the bloc, in an effort to ease the burden of data collection.
But it has stoked the ire of low-cost operators including EasyJet and Ryanair. The two carriers, which get almost all of their revenue from intra-European services, argue that it would be perverse to ignore contrails produced by long-haul flights when the rule comes in next year.
“Unless the full global scope of monitoring is retained, the science will be incomplete and the places in which contrails are estimated to be most abundant will be excluded,” says David Morgan, chief operating officer at EasyJet.
The clash speaks to concerns that financial penalties or requirements for jets to follow diversionary routes may be focused on those regions where data gathering takes place.
The EU’s CO2 emissions trading scheme is itself confined to flights within the European Economic Area after pushback from overseas carriers.
However, the public row between airlines has distracted from more fundamental questions about just how much contrails affect global temperatures in the first place.
While carriers worldwide have pledged to achieve net zero carbon emissions by 2050, they are far less accepting of potential measures for reducing the production of contrails.
That stance is based partly on a unique property of the vapour trails. While scientists find that they contribute to global warming by aiding the formation of high-altitude clouds that stop heat from escaping the atmosphere, they have other benefits. Under certain conditions they can equally reflect solar energy back into space, preventing it from reaching the surface and helping to cool the planet.
Iata cites research suggesting that, on average, 14pc of flights leave contrails, of which close to 30pc may have a cooling effect.
What’s more, predicting where contrails will appear is an inexact science, so that changing flight paths to avoid the supercooled air necessary to their formation may spawn trails elsewhere, when the original route would actually have produced none.
And whether diversions are effective or not, they’re certain to increase emissions of CO2, which once in the atmosphere lingers for millennia. Contrails, by contrast, are fleeting and trap heat only for the time – usually less than 12 hours – during which they streak the sky.
A paper published last year by the Royal Society of Chemistry warned: “It is problematic to recommend definitive courses of action on aviation non-CO2 emissions since they may be of limited effect or have unintended consequences.”
David Lee, professor of atmospheric science at Manchester Metropolitan University, who led the study, says governments and climate groups should resist confusing reasonable caution about how contrails affect warming with ill-founded arguments against limiting carbon output.
“Producing extra CO2 is a red line,” he says. “Contrails are a different story. There are so many things we don’t yet understand about them.”
Willie Walsh, Iata’s director general and the former boss of British Airways, has told the EU that its plans “will require airlines to provide large amounts of data for all flights with an insufficient potential for positive impact.”
EasyJet and Ryanair say in their own letter to the European Commission that long-haul flights generate half of the industry’s carbon emissions yet account for just 6pc of services.
About 10pc of the skies above the North Atlantic are covered by so-called control cirrus produced by long-haul aircraft, compared with 0.06pc coverage elsewhere, they add, citing a recent study by Iata itself.
The clash is not the first between low-cost and full-service carriers over their relative contributions to carbon emissions.
Earlier in the climate debate Lufthansa boss Carsten Spohr criticised discount operators for encouraging needless trips with bargain-basement flights.
Ryanair chief Michael O’Leary hit back by pointing out that low-cost airlines have the youngest aircraft fleets and highest seating densities in Europe, so that their carbon emissions per passenger are far lower than at their flag-carrier rivals.
How contrails arise, at least, seems relatively clear. A soot particle produced in the burning of aviation fuel attracts water vapour, also emitted by the engine, to form a water droplet.
Exposed to temperatures of around minus 50C, the droplet quickly transforms into an ice crystal, trillions of which are formed for every kilo of fuel burned. Under most conditions, that’s the end of the story.
But at temperate latitudes, aircraft flying at 28,000-34,000 feet regularly encounter so-called ice-supersaturated zones, where the crystals absorb more and more water vapour from the atmosphere and swell 10 times in volume – forming a contrail.
Even then, only if trails from a number of flights coalesce, blown together by variations in wind speeds to form so-called contrail cirrus clouds stretching for hundreds of miles, do they have the potential to warm the atmosphere.
In a further complication, soot particles that stay in the atmosphere after contrails have dispersed can interact with regular high-altitude clouds to have a net cooling effect.
The EU’s stance is particularly important because the bulk of contrails are found in Europe and the US, and along the North Atlantic flyway between them, a “goldilocks zone” where the temperate climate coincides with some of the world’s busiest skies.
The supercooled air pockets that give birth to contrails are generally at too high an altitude in tropical areas and too low at the poles for aircraft to encounter them, while the temperate areas of the southern hemisphere are comparatively lacking in flights.
One obvious response to the contrails dilemma would be to greatly reduce the number of flights at night, when there is no sunlight to be reflected back into space and those contrails that do form can only serve to trap heat.
However, with some 97pc of eastbound services from the Americas to Europe operating overnight and hence saving passengers a day of travel and a night in a hotel, such a radical change to airline timetables is regarded as a non-starter.
Other possibilities include hydrogen-fueled aircraft, which would produce no soot particles and greatly diminish contrails, and new engine designs that could capture water vapour, though both technologies have barely left the drawing board.
For now, the focus is on developing protocols for avoiding areas where contrails might form.
But this is harder in practice, requiring accurate predictions of where those zones are at any one time and what warming impact contrails from a specific flight will have.
The potential negative climate impact of diverting a plane would also need to be assessed, along with any possible risk to safety, such as encountering turbulence or thunderstorms and flying with reduced separation from other aircraft.
Without improvements in weather forecasting and modelling, satellite imaging, humidity sensors and data transfers, addressing such issues remains mired in difficulty.
A more immediate route to tackling contrails may come in the form of the increased use of sustainable aviation fuel (SAF), recycled from cooking oil or created synthetically.
While airlines use SAF to help cut carbon emissions, the fuel also emits far fewer soot particles than kerosene, significantly reducing the opportunity for contrails to form.
The first-ever transatlantic flight using 100pc SAF, operated by Virgin Atlantic last November, slashed carbon emissions by almost two-thirds. Just as significantly, lab tests showed that production of non-CO2 particulates fell by 40pc, according to data released this month.
A Virgin Atlantic spokesman said: “More research is needed, but this suggests the use of SAF could have a material impact on reducing the formation of persistent contrails.”
The problem with relying on SAF to resolve the contrails issue, however, is its poor availability and high price. It makes up only about 0.2pc of the global jet fuel mix, and while IATA says that should rise to 0.5pc this year, the fuel will add a projected $2.4bn (£1.9bn) to costs.
For now, the trade group’s director general Walsh says that airlines should be left to focus on curbing CO2 emissions while scientists refine their understanding of how contrails affect warming and how their formation can be better predicted.
Only after 2040, IATA contends, is the diversion of aircraft likely to become feasible. Whether that’s a reasonable response to the evidence or a case of kicking the can down the road is open to debate – and one that most climate scientists feel they can’t yet help resolve.
“We know how CO2 works and how long it stays in the atmosphere, so the message there is clear,” says Manchester Met’s Lee. “But our understanding of contrails and how they contribute to warming is just nowhere near so exact.”