Simulation Results
Radiative forcing due to the formation of contrails for present-day climate conditions and (a) present-day air traffic volume, and (b) for air traffic volume expected for the year 2050. Panels on the right hand side show the radiative forcing for climate conditions expected for 2050 and (c) air traffic volume for the year 2050, and (d) air traffic volume for the year 2050 assuming an increase in fuel efficiency and a 50% decrease in soot emissions. The numbers in the boxes show the global mean radiative forcing for each simulation. Bock and Burkhardt, Atmos. Chem. Phys., 2019

The impact on the climate caused by aeroplane contrail cirrus has been largely neglected, even though it has contributed more to global warming than all CO2 emitted by aircraft since the beginning of aviation. But as per a new study, the climate impact of contrail cirrus will be more significant in the future, tripling by 2050.

Contrails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure and the contrail cirrus is responsible for the changes in global cloudiness, which creates an imbalance on the Earth's radiation, called 'radiative forcing,' and this imbalance makes the earth warmer.

As per Lisa Bock, a researcher at DLR, the German Aerospace Center and lead author of the new study, "It is important to recognise the significant impact of non-CO2 emissions, such as contrail cirrus, on climate and to take those effects into consideration when setting up emission trading systems or schemes like the Corsia agreement," which is an UN's scheme to offset air traffic carbon emissions from 2020, but it ignores the non-CO2 climate impacts of aviation.

However, the new study showed that these non-CO2 climate impact cannot and should not be neglected, as the research team estimated that the contrail cirrus radiative forcing will be 3 times larger in 2050 than in 2006.

Bock and her colleague Ulrike Burkhardt also found that the increase in contrail cirrus radiative forcing is due to air traffic growth and it is expected to be four times larger by the year of 2050 compared to 2006 levels.

The study also suggested that the impact on the atmosphere due to contrail cirrus will be stronger over Northern America and Europe which are the busiest air traffic areas on the globe. But the researchers estimated that the impact will also increase in Asia as the air travel is also growing in that region.

Burkhardt stated that the contrail cirrus' main impact is that of warming the higher atmosphere at air traffic levels and changing natural cloudiness but the impact on the surface temperature and possibly on precipitation due to the cloud modifications is still unclear.

In addition, Bock said that there are still unsolved equations related to the overall climate impact of contrail cirrus, especially their impact on surface temperatures but it's clear that they warm the atmosphere.

It should be noted that cleaner aircraft emissions would solve the issue highlighted by the researchers in this study, as the reduction of the number of soot particles emitted by aircraft engines decreases the number of ice crystals in contrails and that means climate impact of contrail cirrus will also be reduced.