Focus on contrails: climate change threatened by invisible clouds!

Focus on contrails: climate change threatened by invisible clouds!

Above the clouds, freedom must be limitless - but how much does this freedom cost us in the form of climate damage? A current study, published in the journal *Nature Communications*, brings new insights into the effects of contrails on the climate. In a collaboration between the University of Cologne and partners such as the Jülich Research Center and the Universities of Mainz and Wuppertal, it was found that over 80% of long-lasting contrails do not arise in cloud-free skies, as previously assumed, but in natural ice clouds, the so-called cirruses.

These thin ice clouds, which are located at altitudes between 5 and 12 km, act as effective heat stores. When contrails form in cold, moist air, they can last for several hours and therefore have a greater impact on the climate than direct CO2 emissions from aviation. The climate impact cannot be assessed in general terms: in cloud-free conditions they increase the greenhouse effect, while in dense clouds they reflect sunlight and thus have a cooling effect.

The climate footprint of aviation

However, aviation's impact on the climate is not limited to contrails. According to a report by n-tv Emissions from passenger aircraft contribute significantly to global warming. In addition to CO2, it is primarily aerosols and nitrogen oxides that are responsible for more than 60% of climate damage. The EU has already taken steps to require detailed reports on the climate impact of aviation.

In Germany, intensive research is being carried out into flying around air masses with long-lasting contrails. However, reliable data is in short supply, which makes route optimization difficult. An interesting finding: It could be enough to reroute just 3% of flights to avoid 80% of climate-damaging contrails, while the additional kerosene consumption could remain below 5%. The expected benefits for the climate could potentially be 15 to 40 times greater than the disadvantages resulting from higher fuel consumption.

New approaches for climate-friendly aviation

Three partners from Germany – that German Aerospace Center (DLR), the Max Planck Society and the Karlsruhe Institute of Technology – have now carried out a comprehensive analysis of 85,000 flight routes. This resulted in an impressive 73% reduction in the climate impact of contrails with minimal CO2 emissions. Such strategies could not only promote climate protection, but also help airlines comply with EU requirements.

But what about the challenges? These include, among other things, the lack of reliable weather data and the high coordination effort in the existing flight network. Optimized flight planning is crucial not only to minimize CO2 emissions, but also to reduce the harmful effects of the short lifespan of contrails.

Research into environmentally friendly aviation has grown in recent years. However, less attention is still paid to non-CO2 effects. Future studies need to address these challenges and improve understanding of the interactions between contrails and natural cirrus clouds. Developments in this area could be key elements for a sustainable future of air transport.

The kijkt into the clouds could help to gain a better understanding of our influence on the climate - and to ensure the freedom to continue flying above the clouds in the future.