A recent study puts to rest concerns that altering flight paths to prevent climate-warming contrails might unintentionally exacerbate climate change.
A recent study puts to rest concerns that altering flight paths to prevent climate-warming contrails might unintentionally exacerbate climate change.
Researchers from Sorbonne Universite and the University of Reading discovered that, for the majority of flights in the North Atlantic that generate contrails, the environmental advantages of avoiding these contrails outweigh the additional carbon dioxide emissions produced by taking alternative routes.
To determine contrail avoidance, it is essential to evaluate the climatic impacts of carbon dioxide in comparison to contrails, known as CO2 equivalence. Various methodologies have been suggested, and the selection of one over another has often been politically motivated. Scientists have expressed concerns that certain methods may provide misleading representations, falsely suggesting that avoidance is beneficial for the environment while actually being harmful.
Published today (Sunday, 15 September) in Atmospheric Chemistry and Physics, the study reveals that for the vast majority of North Atlantic flights, the act of avoiding contrails would yield positive climate outcomes, no matter how CO2 equivalence is calculated.
Understanding Contrails
Contrails – the white trails left by aircraft in the sky – can capture heat in the atmosphere, thereby contributing to global warming.
This new research expands on earlier studies which indicated that rerouting planes to prevent contrail formation might help mitigate climate impacts. However, the balance between the advantages of avoiding contrails and the disadvantages due to increased CO2 emissions remained unclear.
Professor Nicolas Bellouin, a co-author from the University of Reading, stated: “Rerouting flights to bypass contrails could theoretically diminish the climate impact of aviation and promote more sustainable air travel. Our results eliminate a significant barrier to the implementation of contrail avoidance, but we need improved forecasting methods and real-world trials to effectively apply this in practice.”
The findings indicate that, regardless of how the balance between contrail avoidance and increased CO2 emissions is assessed, rerouting is unlikely to inadvertently worsen climate conditions. The research evaluated nearly 500,000 flights over the North Atlantic in 2019 to gauge the extent of warming caused by the carbon dioxide emissions and contrails from these flights.
The researchers first analyzed the warming effects over time from the existing flight routes. They predict that the emissions and contrails from these flights will warm the climate by roughly 17 microKelvins (μK) by 2039 and approximately 14 μK by 2119. A microKelvin represents an extremely small change in temperature.
They then envisioned a scenario in which planes could entirely avoid contrails by burning just 1% more fuel. In this hypothetical situation, the overall warming would see a notable decline. By 2039, the warming would lessen by about 5 μK, which is a 29% reduction compared to the original flight paths. By 2119, the reduction would be about 2 μK (14%).
The researchers employed nine distinct approaches to evaluate climate impact. In most instances, all methods concurred that rerouting flights would benefit the environment, assuming successful contrail avoidance as expected.
It’s important to note that the researchers caution there is still considerable uncertainty surrounding the exact locations of contrail formation and the extent of warming they produce. They recommend that initial rerouting efforts focus on flights creating the largest warming contrails, where the environmental benefits are most evident.
