June 27 (UPI) -- Under certain conditions, airplane contrails become contrail cirrus, icy clouds that trap the sun's heat and warms the planet. New research suggests the climate impact of airplane contrails, largely ignored until now, could triple by 2050.
When contrails become clouds, they throw off the balance of Earth's radiation budget, triggering radiative forcing, whereby more of the sun's energy is absorbed by Earth's atmosphere and less is radiated back into space.
Air traffic accounted for 5 percent of anthropogenic radiative forcing in 2005. Most of the 5 percent was caused by contrail cirrus clouds.
"It is important to recognize 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," Lisa Bock, a researcher at DLR, the German Aerospace Center, said in a news release.
Researchers expect contrail cirrus clouds to proliferate as air traffic increases. Air traffic is predicted to quadruple by 2050. Air travel routes are expected to shift to higher altitudes, where conditions are more conducive to the formation of contrail cirrus.
The warming encouraged by contrail cirrus clouds will be most pronounced across Europe and North America, according to the new study, published this week in the journal Atmospheric Chemistry and Physics.
"There are still some uncertainties regarding the overall climate impact of contrail cirrus and in particular their impact on surface temperatures because contrail cirrus themselves and their effects on the surface are ongoing topics of research," Bock said. "But it's clear they warm the atmosphere."
Researchers suggest the best way to reduce the climate impact of airplane contrails is for regulators to push for cleaner aircraft emissions. A reduction in the number of soot particles emitted by aircraft engines would lead to fewer seeded ice crystals and smaller contrail cirrus clouds. But scientists warn that even a 90 percent reduction in soot particles wouldn't entirely prevent the warming effects of contrail cirrus clouds.