The white streaks that sometimes form after aircraft – contrails – have a significant negative climate impact because they contribute to global warming just like CO2.

A new analysis from ICCT shows that contrails are particularly prevalent over Europe and the east coast of the United States, and that flights from Denmark are also higher than the EU average.

While CO2 from jet fuel refueled in Denmark in 2023 emitted approximately 2,5 MT of CO2 per year, the climate impact from contrails from aircraft from Denmark, according to ICCT, in the same year corresponds to approximately 3,45 MT (GWP20). This means that contrails have a more negative impact on the climate than the CO2 from the burned jet fuel. This is the reason why a number of organizations joined forces last week to hold an international conference on the subject in Copenhagen.

"It is absolutely crucial that we bring together the world's experts and the knowledge we have about the area, so that we have a clear picture of the climate impact, but also the opportunities to significantly reduce it," says Søren Have, program manager for transport at the think tank Concito

The conference was organized in collaboration with the environmental organization Rådet for Grøn Omstilling and the organization Blue Lines and attracted many key players from all over the world. In addition to highlighting the issue, the conference also focused on how to prevent or reduce condensation trails.

"It is certainly possible to do something about contrails and their significant climate impact. Both cleaner aviation fuels and changed flight routes can significantly reduce them. We just have to get started," says Alexander B. Hansen, advisor in Climate and Aviation at the environmental organization Green Transition Denmark and is complemented by Joachim Majholm from Bluelines

"Our knowledge about condensation trails is now so extensive that it is clear that action definitely makes sense, and that it is also one of the cheapest measures we can take to reduce climate impact."

He emphasizes that there are already experiments in the airspace over Denmark where changed flight routes are intended to reduce contrails.