Putting a price on contrails

The 'low-hanging fruit of aviation’ emission abatement

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Photo by Terence Pereira on Unsplash

Eliminating contrails is the most cost-effective abatement opportunity available to the aviation industry as it seeks to reduce the impact of flying on global warming.

Although estimates vary on the extent of the impact, contrails are thought to account for between 35% and up to 60% of the total global warming impact of air travel. The sector accounts for around 2.5% of global greenhouse gas (GHG) emissions, but once you incorporate contrails, the global warming impact of aviation is likely to be more than 4%.¹

The white streaks you see coming off high-altitude airplanes, contrails are formed when water vapour condenses and freezes around aerosols in an aircrafts exhaust. Depending on the atmospheric conditions, contrails might dissipate after a few minutes, or hang around for up to 18 hours.

Planes fly most efficiently where the air is thin, but this is also the altitude where contrails form easily. Meanwhile, contrails that form at night interfere with the Earth’s natural cooling. A process known as radiative forcing acts to prevent heat from escaping.

Only a small fraction of flights produce contrails. Researchers from Imperial University in London analysed flight data over Japan and found that ~80% of the total contrail warming impact is caused by only ~2% of flights. In particular, those involving long haul flights and night time air travel.

However, the impact of contrails on global warming is likely to get worse as air traffic continues to grow and there is an increase in the amount of long-haul flights. A study published in 2019 projects that global contrail cirrus radiative forcing will increase by a factor of 3 between 2006 and 2050.²

Source: Google

Regulation and markets are evolving to tackle the issue

From the beginning of 2025, new EU regulations will require airlines to monitor and report their non-CO2 emissions (contrails, nitrogen oxide, and sulphur). The mandate covers all flights, entering or leaving the European Economic Area (EEA), as well as intra-EEA. It’s worth noting that the shipping industry has been subject to a similar monitoring, reporting, and verification (MRV) mandate covering non-CO2 emissions since the start of 2024.