Crisscrossing the sky, as I look up on a clear day, there are civil aircraft going about their business. People travelling across the Atlantic or coming back or on a day trip to Glasgow.
These shiny pinpoints of light in motion, set against a blue sky, are all the more visible because of the vapour trails they leave behind. Aircraft speed through the rarified atmosphere to leave a momentary trail as evidence of their presence.
Up with the aircraft in flight are natural clouds. Up at 30,000 feet there can be Cirrus clouds[1]. There might not be much air pressure at that altitude but there’s enough moisture to support cloud formation. The word “wispy” sums them up.
Aircraft create condensation trails that are known as contrails. How the English language likes to shorten. They are not mysterious or generate with evil intent in mind. It’s simple physics.
In my bathroom, with hot water gushing from the shower, moisture is the air. When that moist air meets a cold surface, like a window, condensation is sure to be seen. Airbourne it’s not so different. Hot emissions from powerful jet engines shooting out into a cold low-pressure environment and guess what?
Typically, contrails don’t last long. If there’s appreciable wind at high altitude, then they get dispersed quickly. Not only that but the icy temperatures up there soon return things to the status-quo. There are days, when the air is still, that the sky can become a crisscross of contrails where dispersion is more like a gentle merging.
The theory goes that the cumulative impact of lots of high-altitude flying is like the impact of additional cloud formation. It’s water vapour after all. It’s known, high altitude clouds can contribute to the greenhouse effect.
The point I’m getting to here is that lots of flying contributes to climate change. Primarily because of the burning of significant amounts of fossil fuel. As a secondary consideration there’s the issue of contrails across the globe.
This leads to the question – can their formation be avoided? Even, is there something useful to be gained in doing so. Trials and research are trying to establish the answer to these questions[2].
Initially, contrail avoidance sounds like it should be relatively easy to do. However, like so many good proposals it’s not so easy. Change needs to involve air traffic management, flight operations and international regulators.
First the atmospheric conditions need to be detected or predicted in a given location and then an avoidance needs to be planned and undertaken in coordination with everyone flying at high altitude at a given time. Lost of data to crunch.
It’s possible, in oceanic airspace, a dynamic aircraft system could perform this avoidance function. It would be an interesting design challenge for an avionics company to take up.
#Net Zero #SustainableAviation
[1] https://weather.metoffice.gov.uk/learn-about/weather/types-of-weather/clouds/high-clouds/cirrus
[2] https://news.aa.com/esg/climate-change/contrail-avoidance/
John Vincent 