Can aircraft trails affect climate?

Nature News ^ | 31 December 2008 | Anna Barnett

[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.

Theory or fact?

Two studies^1,2 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.

Up in the air

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.

• References

  1. Travis, D. J., Carleton, A. M. & Lauritsen, R. G. Nature 418, 601 (2002).
  2. Travis, D. J., Carleton, A. M. & Lauritsen, R. G. J. Climate 17, 1123–1134 (2004).
  3. Hong, G., Yang, P., Minnis, P., Hu, Y. X. & North, G. Geophys. Res. Lett. 35, L23815 (2008).
  4. Kalkstein, A. J. & Balling, R. C. Jr Climate Res. 26, 1–4 (2004).
  5. Dietmüller, S., Ponater, M., Sausen, R., Hoinka, K-P. & Pechtl, S. J. Climate 21, 5061–5075 (2008).

[Kevmo]

It actually makes us look like some here believe their non scientific BS!
***There were people like that on FR, and you’ve been around long enough to see it.

Here’s a standard example below...

http://www.freerepublic.com/focus/news/2156668/posts?page=159#159

To: Star Traveler
Can you imagine, being here on Free Republic and then finding that 8 years later, people are still looking for documents, while Obama is building his Presidential Library... :-)
Look, this is nothing in the annals of FR lore.

Remember the weeks of speculating that Gary Condit’s wife has no thumbs? We survived that, didn’t we?

-PJ

159 posted on Wednesday, December 31, 2008 7:26:42 PM by Political Junkie Too (You can never overestimate the Democrats’ ability to overplay their hand.)
[ Post Reply | Private Reply | To 109 | View Replies | Report Abuse]

[dalereed]

“Can you imagine, being here on Free Republic and then finding that 8 years later, people are still looking for documents, while Obama is building his Presidential Library... :-)”

Why would they quit looking just because he was building his mud hut in Kenya for his library?

[Kevmo]

That reminds me, did the Vince Foster thing ever get resolved?

[Perchant]

This is funny because I posted this google news archive excerpt from the 1970's a few days ago. They spent our parents' money back then to determine that airplane traffic was causing global cooling, and it meant that we were doomed.

Experts Fear Great Peril If SST Fumes Cool Earth E-MAIL Save By WALTER SULLIVAN

December 21, 1975, Sunday

Page 32, 1057 words

A federally sponsored inquiry into the effects of possible climate changes caused by heavy supersonic traffic in the stratosphere has concluded that even a slight cooling could cost the world from $200 billion to 500 times that much in damage done to agriculture, public health and other effects.

[dalereed]

“did the Vince Foster thing ever get resolved?”

No!

The broom rider isn’t in prison!!!!

[Kevmo]

My point is well made.

[exnavy]

LOL

[WorkerbeeCitizen]

I feel dumber for having read this.

[raybbr]

Anna Barnett:

Interests:
Climate change and its effects on ecology, socioeconomics and policy. I’m new at NRCC as of November 2007 but have been a copyeditor for NPG since 2005. Before that, I studied molecular and marine biology [no mention of a degree](with a dash of the history and sociology of science), taught English in Slovakia, and edutained children in nonprofit theatre projects.

Another "educated scientist" brings up any old theory to further the global warming lie.

I wonder how she "edutained" children about global warming?

[Wonder Warthog]

"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."

You've got it backwards. "If" CO2 induced warming is real, you want to INCREASE the effect of contrails (which cause COOLING). To do this, you would change the fuel formulation used during "cruise at altitude" to increase the sulfur content, but use low-sulfur fuel for takeoffs and landings.

It is a proven fact that the injection by volcanoes of sulfur compounds into the stratosphere increases high-altitude cloud coverage, which increases albedo and reflects more sunlight back into space---causing cooling.

[EVO X]

http://www.pbs.org/wgbh/nova/sun/contrail.html

[Wilhelm Tell]

You have to listen to Art Bell late at night on his Coast to Coast radio show.

Once in a while I listen to that. Sometimes it amuses me and sometimes I get so annoyed at the stupidity I have to turn it off after a few minutes. Bell's guests have obviously never heard of Occam's Razor. Sometimes it is amazing to hear some crank go from one bizarre theory to the next - the cranks will spin one thing after another out of nothing -
A crank will present the theory that no one really landed on the moon because space aliens won't allow it because the space aliens are controlled by Hitler's brain that is kept in a secret UFO base in Antarctica and the Israelies run this base and, by the way, are behind the Kennedy assasination - just like Nostradamus predicted! Oh, yeah, I almost forgot that the "face" on Mars was drawn by aliens from Andromeda and there is a secret code in the Bible that tells all about it, or something like that. A really good crank will go on like that for an hour or more.
Sometimes it amuses me as I try to keep up with the BS and sometimes it annoys me or bores me - I guess it depends on what mood I am in.

[Vaduz]

How many tons of fuel do airline dump per year it may have a part in a change???.

[steelyourfaith]

 

Beam me to Planet Gore !

[TXnMA]

Simple test: have the weather "experts" produce plots of any and all measured variables all across the nation and across the date range of, say, 1995 - 2005 -- but with no date-range scale indicated. (i.e a truly "blind" test....)

Then, invite any and all to attempt to locate a three-day timespan within that data that appears to be "anomalous".

If the three flight-free days are truly "anomalous", a "consensus" should form -- focused on those dates.

~~~~~~~~~~

My guess is that there will be hundreds of three-day spans that are "stranger" than those three days -- if the data is examined by those who are looking at "the big picture", rather than trying to find something odd about those specific three days.

Bottom line: the "three-day 'witch hunt'" approach used in the cited "scientific" study virtually guaranteed that the search would continue until something anomalous about those three days was found. That is not only lousy science, it is intellectual dishonesty.

[ßuddaßudd]

Dimming the Sun

[JustDoItAlways]

If the contrails are “White”, does that not mean they are also reflecting light photons back to the ground as well as reflecting incoming sunlight.

This study would need to measure the incoming EM radiation blocked/reflected back to space as well the outgoing EM radiation blocked/reflected back to the ground.

[WildWeasel]

Messin’ with Sasquatch.

[Balding_Eagle]

Chemtrail nonsense is old stuff. Even my mother laughed about it when I was a kid during the 50’s - 60’s.

[clamper1797]

why not after all cow farts cause globull warming.BUT the greatest contributor to globull warming is the sun. If these idiots had their way ... they would ban that too