Scientists flag up ATM as key in battle to control contrails

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Researchers say condensation can be avoided with more flexibility on aircraft routeing

Scientists studying aircraft condensation trails and the resulting creation of artificial cirrus clouds remain uncertain about the level of impact they have on climate change, but generally concur that air traffic management (ATM) will have a key part to play in reducing the phenomenon.

It is thought that contrails and contrail cirrus, which are produced by aircraft during the cruise phase of flight when the air is cold and damp, could prevent heat escaping from the atmosphere, therefore increasing global warming.

Speaking earlier this month at the Royal Aeronautical Society's Aviation and Climate Change: How to Address the Balance conference in London, Hermann Mannstein, a research scientist at the German Aerospace Centre's Institute of Atmospheric Physics, said there is still a "big question mark" over how much contrails and contrail cirrus contribute to climate change.

However, he notes that aircraft can avoid producing contrails in three ways: flying lower, flying higher or flying "smarter". "Contrails cannot be avoided by making better engines," says Mannstein. Instead, he adds, the solution can be provided by ATM through "higher flexibility in routeing".

This view is echoed by John Green, consultant chief scientist at the UK's Aircraft Research Association, who believes that disrupted airline schedules will be "the price to pay" to reduce any additional impact on climate change caused by contrails.

"ATM providers are the lead operators in contrails and contrail cirrus, but they are only likely to do something if mandated by the government," says Green.

Time of day is another factor being taken into consideration, because night flights are thought to produce longer-lasting contrails.

Keith Williams, a climate research scientist at the Hadley Centre - part of the UK's Met Office - says there is a "partial offsetting" of contrails and contrail cirrus during the day, due to the Sun's energy.