More contrails might increase climate warming
Andrew Carleton told Earth & Sky that it's?not the big puffy contrails that cause concern among scientists. He said that, as contrails thin, they act like natural cirrus clouds and hold in heat. Some studies suggest that the number of contrails in our skies is bound to increase. ?That increase in contrails might add to global warming.
DB: This is Earth & Sky. The jet contrails you see crisscrossing the sky are similar in some ways to natural clouds.
JB: But they’re made by the combustion of fossil fuels in jet engines. And, if it seems you’re seeing more of them, it’s not your imagination. Andrew Carleton researches contrails at Pennsylvania State University. His research reports increasing numbers of contrails since the mid-1970s, due in part to changes in Earth’s upper atmosphere, increasing jet traffic and bigger jets.
DB: Studies predict that air traffic will continue to increase for at least the next 30 to 50 years. And that, Carleton said, probably means more contrails, with a possible effect on Earth’s climate.
Andrew Carleton: The studies nowdays – not all of them because some of them disagree quite strongly – but there are studies . . . that actually suggest that contrails have been enhancing global warming and will continue to do so in the future.
JB: Airlines could cut down on contrails, but Carleton said it’s expensive. The biggest thing, he said, is to forecast air that’s favorable for contrails, and then avoid it: re-route jets around it or change the altitude of flight paths. Here in the U.S., those changes aren’t on the horizon.
Andrew Carleton: The airlines have been having such financial problems in recent years that contrail production is not high on their list of priorities right now.
_DB: More at earthsky.org.
Our thanks today to NASA: explore, discover, understand.
(image courtesy of NOAA)
Does commercial jet traffic affect climate?
Plane exhaust putting heat on climate, study suggests, from USA Today.
What is a contrail and how does it form? Find out here, from the National Weather Service.
Additional Teacher Resources
NASA: Contrails Over the Midwest
When the hot, humid air from a jet engine mixes with colder, drier air in the surrounding environment, condensation trails, or “contrails,” streak the sky. If the air through which the airplane is flying is already close to being saturated with water vapor, the condensation trail will last longer than it will if the air is dry. A contrail that lingers can spread out into a layer of cirrus (thin, wispy clouds).
PBS: The Contrail Effect
Whether contrails cause a net cooling or a net warming, even whether their effect is something to worry about, remains unclear. But with air traffic expected to double or even triple by 2050, leading contrail researchers say the influence of these artificial clouds cannot be ignored.
