Contrails' effect on warming
Patrick Minnis told Earth & Sky, "Aviation accounts for about two percent of all greenhouse gas emissions. In fact, the transportation sector altogether, that is, rail, shipping, air transport and road traffic, passenger cars and trucks, etc., constitute about 26 percent of all CO2 greenhouse gas emissions. The rest is industrial."
Experts say that, today, all of aviation accounts for about two percent of the world’s greenhouse gas emissions.
Right now, over the U.S., there are more than 27,000 flights a day. Experts say that, as air traffic increases, aviation’s contribution to greenhouse warming will increase. And air traffic is increasing around the world, especially in developing countries such as India and China.
One effect is that when jet engine combustion happens at high altitudes, it can create cloud-like contrails. Many scientists think that contrails contribute to trapping heat in Earth’s atmosphere.
Patrick Minnis: Greenhouse gases and emissions in the form of water vapor that can change the existing water vapor into contrails can have, what they estimate, is a two to four times greater impact per unit than the same emissions at the surface.
That was Patrick Minnis at NASA’s Langley Research Center. He said that as contrails dissipate, they act like cirrus clouds, which hold heat in the atmosphere.
Patrick Minnis: Their impact is still a big question mark. We’re pretty sure that they cause warming, but whether that warming it negligible or whether it’s greater than we expect from the greenhouse gases like CO2 and ozone that are produced by the aircraft exhaust, we’re not sure.
Our thanks today to NASA’s Aeronautics Research Mission.
Our thanks to:
Patrick Minnis
Senior Research Scientist
Climate Science Branch
Science Directorate
NASA Langley Research Center
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.
