Condensation trails are the white line-shaped clouds that can appear after aircraft as their exhaust mixes with the ambient air. In certain conditions, these can survive for hours and develop into cirrus-like clouds. These are believed to be one of the largest contributors to non-CO2 emissions from aviation, impacting global warming. They can have both a warming and a cooling effect, depending on the balance of inbound shortwave radiation and outbound longwave radiation. The net total is, however, a warming effect. Various mitigation strategies have been proposed. In this work, navigational avoidance by altitude adjustments is studied within the context of Swedish airspace. This is achieved by analysing historical flight trajectory data and meteorological data for the year 2024 using open-source contrail models, aircraft performance models, and aircraft trajectory optimisation models. Two contrail models — the Contrail Cirrus Prediction Model (CoCiP) and an algorithmic Climate Change Function (aCCF) from CLIMaCCF — are compared against each other. As expected, there are clear seasonal and diurnal effects, both regarding which altitudes that are contrail-prone, and which hours that see a net warming and net cooling effect. Geographical effects are more difficult to discern, especially due to the sharp decrease in air traffic north of 60°N. The relationship between navigational avoidance and other mitigation strategies is also discussed based on findings from related works.
Tobias Elneros (Wed,) studied this question.