Contrails, the thin tracks that jet planes leave behind as they move through the sky, are not as harmless as they seem. These long, thin clouds created by high-flying planes are surprisingly damaging to the environment. Their formation involves a layering process that mixes hot exhaust gases with the cold upper layers of the atmosphere.

Under certain conditions, these hazy patches of condensed water vapor spread out and become retrograde cirrus clouds. These clouds trap heat rather than radiating into space, causing more than half of aviation’s total climate impact.

Impact of backtracking on climate

Fangqun Yu, a senior research associate at the University at Albany Atmospheric Science Research Center, recently led a study on this disturbing phenomenon.

The study took a closer look at the track formation process by examining the role of non-volatile (soot) particles and volatile particles. The research reveals possible strategies to reduce the negative impact on the climate and implement more ecological practices in aviation.

The mystery of the comeback is being solved

“Soot particles formed during the combustion of fuel in aircraft engines are known to dominate the formation of inverted ice particles,” Yu explained.

“As the aviation industry moves towards cleaner fuels and new engine technologies, soot emissions are decreasing significantly and analyzing the particulate matter produced in engine exhaust (after emissions) becomes important.”

This in-depth study aims to expand our understanding of the mechanism that drives the number of plume ice particles produced during flights by focusing on both soot particle size and volatile particles in plume formation.

The information collected for this study was made possible by a team of experts from NASA Langley Research Center and the German Aerospace Center. Researchers conducted flight simulations using data collected during recent ECLIF (Emissions and Climate Impacts of Alternative Fuels) field trips.

Contrary to previous findings showing that particulate matter only comes into play when soot emissions are greatly reduced during flights, this new study suggests otherwise.

“Our study shows that volatile particles may contribute to increased ice particles in average soot emission levels and average air temperatures, expanding the range of conditions in which these particles become a factor,” Yu explained. “This is important because we estimate the impact of backtracking on the climate, both during current flights and for more sustainable flights in the future.”

Shaping the future of aviation

The research focused on size-resolved particle microphysics and aerosol-cloud interactions affecting climate change. Yu. He has been studying the microphysics of atmospheric particles (including the formation of backtracks) and their effects on the environment for more than two decades. Yu’s previous work involves developing a complex model to simulate particle formation and backtracking, and he is the author of numerous scientific papers on the subject.

Yu is currently working with the GE Research team to gain a deeper understanding of the effects of clean jet fuel and new engine technologies on smog formation. Last year, the team conducted a series of experiments in the Altitude Simulation Chamber at NASA’s Glenn Research Center in Cleveland.

A way to reduce back scars

As the aviation industry seeks to mitigate its environmental impact, alternative fuels offer a promising way to reduce jet lag and its warming effects. Environmentally friendly aviation fuel (SAF) produced from renewable sources not only produces fewer soot particles during combustion, but also has the potential to reduce heat-trapping cirrus clouds.

Recent flight tests have shown that jet aircraft equipped with SAF compounds can significantly reduce soot emissions, underlining the importance of a broader industry change. However, for SAF to create serious change, there is a need for wide-scale implementation in the aviation sector.

Aviation practices and climate targets

Ongoing research will play a critical role in driving this transformation, ensuring that every step taken aligns aviation practices with global climate goals. Through continued innovation and commitment, a future with cleaner skies and fewer climate impacts is more than just an aspiration; It is a valid reality for future generations. The study was published in the journal Environmental Science and Technology.