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Small changes to aircraft flight paths to avoid the atmospheric conditions that create condensation trails – known as contrails – could reduce aviation’s global warming impact by nearly half, a new study suggests.

The study, led by researchers at the University of Cambridge including , pictured, suggests that changing cruising altitude by a few thousand feet, either up or down, could prevent contrails from forming. Reducing or avoiding contrail formation in this way would also be faster and cheaper than other climate mitigation measures for the aviation industry, since the practice can be adopted with existing aircraft and fuel.

However, the researchers say that time is of the essence and that the sooner airlines adopt contrail avoidance policies, the bigger the positive climate impact will be. .

“Contrail avoidance can often be as simple as changing the flight paths,” said lead author Dr Smith, from Cambridge’s Department of Engineering. “Often it’s even simpler than that – just moving slightly to a higher or lower altitude to avoid the areas of the atmosphere where contrails form.”

Contrails are the thin white streaks seen behind aircraft flying at high altitude, and form when hot exhaust gases mix with cold, humid air at cruising altitude. Under the right conditions, the water vapour freezes into ice crystals, forming clouds that can persist for hours.

Contrails also trap heat in the atmosphere. Aviation contributes around 2–3% of global carbon dioxide emissions, but its total climate impact is larger because of non-CO₂ effects such as contrails. Interest in contrail avoidance has grown rapidly in recent years as governments and airlines search for ways to reduce aviation’s climate impact while the sector transitions to lower-carbon fuels.

Read the full article on the University of Cambridge website: