One might assume that jet aircraft exhaust would contribute to pollution and to whatever effect “greenhouse gasses” are having on the climate. But there’s another effect that jet aircraft have that seems even more significant.
NASA scientists have found that cirrus clouds, formed by contrails from aircraft engine exhaust, are capable of increasing average surface temperatures enough to account for a warming trend in the United States that occurred between 1975 and 1994.
“This result shows the increased cirrus coverage, attributable to air traffic, could account for nearly all of the warming observed over the United States for nearly 20 years starting in 1975, but it is important to acknowledge contrails would add to and not replace any greenhouse gas effect,” said Patrick Minnis, senior research scientist at NASA’s Langley Research Center in Hampton, Va. The study was published April 15 in the Journal of Climate. “During the same period, warming occurred in many other areas where cirrus coverage decreased or remained steady,” he added.
“This study demonstrates that human activity has a visible and significant impact on cloud cover and, therefore, on climate. It indicates that contrails should be included in climate change scenarios,” Minnis said.
Minnis determined the observed one percent per decade increase in cirrus cloud cover over the United States is likely due to air traffic-induced contrails. Using published results from NASA’s Goddard Institute for Space Studies (New York) general circulation model, Minnis and his colleagues estimated contrails and their resulting cirrus clouds would increase surface and lower atmospheric temperatures by 0.36 to 0.54 degrees Fahrenheit per decade. Weather service data reveal surface and lower atmospheric temperatures across North America rose by almost 0.5 degree Fahrenheit per decade between 1975 and 1994.
Interesting. I’m not sure what it means, but it might be wise to plan your overseas trip before someone decides to outlaw air travel …
(For an amazing picture of contrails over the US, see here.)
(via BoingBoing)
Hmmm…
Nova did a show on this about ten years ago. Must have been based on a similar study.
Also, NPR had a blurb this morning on a study that Things are warming up much faster then previously modeled, and the currents might shut down within the decade instead of 30 years out.
Good times.
Wow, that picture was amazing.
It makes sense that if car emissions are a problem then jet emissions would be, too–they both burn hydrocarbons. Maybe they’ll figure out some sort of catalytic converter dealie for jets.
Never underestimate the ability of our species to rise to a challenge.
Well, there’s the danger of the jet exhaust (and, in fact, jets are a lot cleaner these days than they used to be, since that usually translates into fuel efficiency and noise reduction, too). The contrail effect, though, as to do with water vapor being released — not generally considered a pollutant, but in this case evidently provoking cloud coverage.
Can the exhaust be “dried” before release (bearing in mind that the release is what propels the vehicle, as opposed to cars where it’s just a byproduct)? Dunno. Might be interesting to find out, though.
Imagine, then, how much Europe has been warmed up from all the squadrons of bombers flying over it during WWII!
One has to wonder how significant this is compared to a single volcanic eruption.
I’m still trying to figure out how *more* cloud cover translates to warmer temperatures myself. You would think it would have the opposite effect as less sunlight hits the ground to warm things up. Wasn’t that the whole concept of “nuclear winter”?
*shrug*
Clouds cause a greenhouse effect; they are transparent to incoming infrared (if not visible).
The nuclear winter scenario had less to do with water vapor clouds than with particulate clouds, which would indeed bounce heat and light off. That’s what happens in a major volcanic eruption.
Cloud stuff is tricky because once you get clouds started, they tend to condense further on their own (see the whole concept of cloud seeding). If contrails are in fact creating more clouds, it’s not just the contrails themselves, but what they trigger.
We’ll see.