Posted on 12/31/2008 11:41:11 PM PST by neverdem
Grounding planes after the 11 September attacks may not have caused unusual temperature effects.
When all commercial air traffic in the United States was grounded after the terrorist attacks of 11 September 2001, scientists got an unexpected opportunity to test ideas about the climate effects of the condensation trails left behind by jets.
A study in 20021 suggested that these contrails could have a significant effect on daily temperature patterns (see 'Air-traffic moratorium opened window on contrails and climate'). But a new analysis now claims that altered US temperature patterns during the three flight-free days can be explained by natural variations in cloud cover, rather than the absence of planes.
Aircraft contrails can spread into cirrus-like clouds high in the atmosphere. Similar to natural clouds, they are thought to have an overall warming effect on the planet. But they can also moderate daily temperature extremes by trapping heat that escapes from the ground and reflecting sunlight. This raises the lowest overnight temperatures and, to a lesser degree, reduces the highs during daylight hours, scientists have suggested.
With air traffic projected to grow by 2–5% per year in the near future – amounting to at least a tripling in traffic by 2050 – the effects of contrails are expected to become an increasingly important factor in climate change. But atmospheric scientists are still unsure about the scale of the contrails' impact.
Two studies1,2 noted that when planes stopped flying on 11–14 September 2001, the average daily temperature range in the United States rose markedly, exceeding the three-day periods before and after by an average of 1.8 °C. The unusual size of the shift, says David Travis of the University of Wisconsin–Whitewater, who led both of the earlier studies, implied that an absence of contrails gave the temperature range a significant boost. But that idea, he says, was "more like a hypothesis" than a firm conclusion.
Research led by Gang Hong, an atmospheric scientist at Texas A&M University in College Station, now suggests that this hypothesis is wrong3. Examining patterns of cloud cover and temperature in early September at US weather stations from 1971 to 2001, Hong and his colleagues found that thicker, low clouds are the dominant influence on temperature extremes, whereas high clouds such as contrails have a minor effect at most. They add that the 2001 temperature swings seem to be within the range of natural variability over those decades.
Hong's work doesn't prove that the contrails have no effect on temperature, just that they are unlikely to have a major role, says Ulrich Schumann, director of the Institute of Atmospheric Physics at the German Aerospace Center in Oberpfaffenhofen, near Munich.
But that contrail effect, Schumann cautions, has been exaggerated in public discussions because the events of 2001 were so shocking. "Some not very good scientific arguments were misused," he says.
The research by Hong and his colleagues, published in Geophysical Research Letters, follows other studies arguing that the September 2001 temperature variations can be explained by the clear, dry weather on the crucial days4, and that climate-modelling results do not support the contrail effects claimed by Travis's group5.
Travis, however, stands by his findings. Absent contrails were never assumed to be the sole cause of the large temperature ranges, he emphasizes. "We've always said it's a combination of the lack of airplanes and the natural weather conditions," he says.
Because Hong's analysis studied high-level clouds in general – and not contrails in particular – Travis says that specific conclusions cannot be drawn about the role of contrails from the survey. "Their calculation of cloud influences was without any consideration of contrails," he says. "They were just looking at natural clouds, and not actually at the presence or absence of contrails."
He adds that Hong's study shows that an increase in the average daily temperature range of 1.8 °C is extremely rare. And although previous events on that scale can be explained by local meteorological effects, says Travis, the jump seen in 2001 cannot be accounted for in this way.
Travis maintains that contrails are an important factor in climate change. "Eventually these impacts will be felt," he says.
calling Art Bell...
You know....if I were to believe any part of the grand “cabon issue”....this would be the one thing that I’d connect to it and say it has potential. The interesting thing is that prior to the early 1970s....the vast public didn’t travel by jet. Only when discount airlines appeared and the prices went down in cost....did the public jump on and ride in abundance.
But here is the thing....if we ever did come to believe in this as the major contributor....the only answer (NOT taxes, trust me)....is to simply cut off jet travel. Either you go by boat, blimp, car or train to wherever you want. Airports would die off quickly and bankrupt a huge portion of America. The airline industry would dissolve away completely.
So I’m open to this if Al Gore wants to make this the “cause”. But for some funny reason, I don’t think he will. It really doesn’t help his agenda...stealing from the rich and middle-class.
You mean you don’t believe they are really chem trails dropping aluminum sulfate. Some believe they are con trails.
This before factoring in the Chemtrail phenomenon.
chem trails are the province of trailer park pseudo science.
This article is not about chem trails, although the premise is stupid no matter how mainstream.
Butterfly farts are far more dangerous than airplane contrails.
I thought everyone knew this.
Sure if cow farts can, anything can.
Amazing! Scientists say a super volcano eruption, a thousand times bigger than the Mt. St. Helens blast, would give us a few years of volcanic winter but it wouldn’t change the climate long term. But vapor trails and car exhaust would. Truly amazing!
Jet contrails only persist when the atmosphere at that altitude is near saturation anyway. A general blanket of cirrostratus coming in would not be unlikely anyway. The article says ‘scientists have suggested’, not ‘science has proved’. Suggestions are cheap on this topic.
Thanks for posting this. It removes the excuse of “this makes FR look bad” from the trolls on the CertifiGate threads.
“chem trails are the province of trailer park pseudo science.”
I agree, but I have seen real chemtrails !!! From the crop duster that flew over my cotton field in Tennessee.
Of course he was only 25 feet above the ground, hahaha.
The idea that the common vapor trails are chem trails belongs
only to the kook to kook fans and morons.
Somehow I’ve missed the whole chemtrail thing. This thread is the first I have heard of it. Strange since I watch Discovery and History channels all the time. /not sure whether to put s tag here
You have to listen to Art Bell late at night on his Coast to Coast radio show.
He also has flat earth callers, and callers that can prove we didn't land on the moon.
“Somehow I’ve missed the whole chemtrail thing.”
You have to be on the kook fringe to know about, or believe
in them.
Being in Europe, Coast to Coast AM, what I call Kook to Kook,
comes on at 7 AM. It is my morning entertainment via online radio.
It does, on occasion, have some great guest and information,
but you have to separate the wheat from the tons of chaff.
There is a big group that think that all the contrails are really chemtrails, put out to alter our minds, kill us, or whatever.
I guess that passenger planes don’t make any of that smoke, hahaha
Definitly. Talk to an AC-130 gunship fire-control guy. You need shovels and barrels to empty out the spent 20mm and 150mm howitzer shells. They blow off really fast. Water-cooled gun barrels.
And don't forget the flares they launch also before going in. Afghan could be warmer with white phosphourus rounds from those 20mm guns. Everything burns down fast.
He just needs another grant or two and he will be able to prove it. Really. /s
” It removes the excuse of “this makes FR look bad” from the trolls on the CertifiGate threads.”
It actually makes us look like some here believe their non scientific BS!
Contrsils are nothing but frozen water vapor that revert back to water vapor when they melt and disapear.
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