03-17-2006 - Earth

sagar: Author=’Eleanor Imster’ program=’4821′ video=”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”:http://www.geog.psu.edu/people/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”:http://www.nasa.gov: explore, discover, understand.

Written by EarthSky