They looked at how many cirrus clouds were created by planes during the global hard Lockdown in March and May 2020 and compared them to the same period in prior years. The research was led by Johannes Quaas, a Leipzig University Professor of Theoretical Meteorology, and it was recently published in the prestigious journal “Environmental Research Letters.”
Cirrus clouds, which are distinguished by their high, wispy strands, contribute to global warming. Cirrus clouds originate when giant ice crystals form at an altitude of around 36 kilometers, reflecting sunlight into space – to a limited extent.However, they keep radiated heat from escaping into the atmosphere, resulting in a net heating effect. This effect dominates cirrus clouds. Condensation trails from behind planes when the meteorological conditions are ideal. These could linger and grow into more giant cirrus clouds. In this situation, they have a far higher impact on the climate than thin contrails alone.
Professor Quaas said, “Crucially, our studies reveal a clear causal relationship. Since clouds vary considerably depending on the weather, we would not have been able to detect the effects of air traffic in this way under normal circumstances. The period of Lockdow due to the COVID-19 pandemic offered a unique opportunity to compare clouds in air traffic corridors at very different traffic levels.”