The planes! The planes!

From Dr. Roger Pielke Senior: (with apologies to Tattoo)

Aircraft Contrails
Contrails southeast lrg.gif MODIS tracking of contrails generated by air traffic over the southeastern United States on January 29, 2004. Source: NASA Earth Observatory, click the image for details

There is a news article on March 29 2011 from Rueters titled

Aircraft condensation trails criss-crossing the sky may be warming the planet on a normal day more than the carbon dioxide emitted by all planes since the Wright Brothers’ first flight in 1903, a study said on Tuesday.

The text begins with [highlight added]

Aircraft condensation trails criss-crossing the sky may be warming the planet on a normal day more than the carbon dioxide emitted by all planes since the Wright Brothers’ first flight in 1903, a study said on Tuesday.”

Another excerpt reads

“The study, by experts at the DLR German Aerospace Center, estimated that the net warming effect for the Earth of contrails and related cirrus clouds at any one time was 31 milliwatts per square meter, more than the warming effect of accumulated CO2 from aviation of 28 milliwatts.”

If correct, this is a remarkable finding with respect to contrails as a climate forcing. It also shows that as we study the climate system, we find it is affected by a wider diversity of human climate forcings than concluded by the IPCC. The human effect on the climate system is not dominated by CO2 and a few other greenhouse gases.


Just a firm reminder, any comment mentioning, referring to, or paraphrasing anything to do with “chemtrails” will be automatically sent to the bit bucket. – Anthony

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March 31, 2011 12:34 pm

I should think at night and in winter – where we’re seeing the greatest increase in temperatures – would be the critical times to investigate in detail.

R. de Haan
March 31, 2011 12:35 pm

This will end the era of air travel.
As in the UK the roll out of the 11.5 billion pound smart grid is underway all we need is a personal carbon budget and our traveling days are over.
Any opposition to the green totalitarians will be punished immediately by a power cut off. That will teach the skeptic bastards.

R. Gates
March 31, 2011 12:36 pm

This effect from contrails is quite interesting and something I’ve often wondered about as I’ve watched the many contrails over my home state of Colorado. It certainly does seem to be a strong rebuttal to those who say humans can’t affect something as “large as the earth”, when in fact, the atmosphere is just a relatively thin layer and something as seemingly insignificant as contrail, when multiplied by the tens of thousands generated everyday, and then expanded in the way described in the study, you’d expect an impact. I am surprised it was this large however…

Martin C
March 31, 2011 12:36 pm

I thought that the clouds in general provided a cooling effect, and that the effect of clouds higher in the atmosphere (such as cirrus clouds) was greater due to reflecting the sunlight. Also, wasn’t there some evaluation of temperatures just after 9/11, where for three days there were NO aircraft in the sky (though I don’t remember what the finding of this were . . . ) , and how it compared to days before, or after ?

Chris D.
March 31, 2011 12:40 pm

Doesn’t this fly in the face of what NOAA (I believe) was saying about the 3 days of no flights over the US right after 9/11/01, specifically that temps spiked during that period?

R. Shearer
March 31, 2011 12:45 pm

Sounds like a world wide no fly zone could be proposed. I’d begin with private jets.

March 31, 2011 12:45 pm

Wait just a minute….I thought all those contrails were COOLING the planet by increasing reflectivity? My understanding is that the water is mostly already there but the planes exhaust just causes it to precipitate?
More “science” to confuse people….confused people are more easily deceived.

March 31, 2011 12:50 pm

I had heard previously that the effect was exactly the opposite. Didn’t someone use the post-9/11 shutdown of air traffic to evaluate the climate forcing of contrails? I seem to recall seeing this on a Nova episode (“Dimming the Sun”, Apr 18, 2006; ). Perhaps this is all “TV science”, but it’s interesting to have the Hansen set essentially contradicting the finding of this study. I have often wondered after seeing this if the Clean Air Act was not itself a climate forcing that impacted some of the trends of US temperatures in the second half of the 20th century.

P Gosselin
March 31, 2011 12:51 pm

The timing of this is suspect…just when Britain proposes a “masterplan” regarding transportation and rationing holiday flights. Hmmm
But you’re right – if true it reveals lots of gaps in IPCC knowledge.

TFN Johnson
March 31, 2011 12:51 pm

Ch**tr***s —-Why? Some Americanism I haven’t hitherto come acoss?

homo sapiens
March 31, 2011 12:54 pm

“This is a breakthrough in modeling and understanding of contrails,” Olivier Boucher, of the Met Office Hadley Center in England who wrote a related article in Nature, told Reuters.
Those models again!
So the temperature rise (unadjusted upwards) of the past 100 years due to CO2 emissions is even less than 0.3degC!

March 31, 2011 12:54 pm

Well then let me be the first to propose hydrogen-free jet fuel. Just imagine the cooling that could be achieved if we were to stop dumping water vapor into the stratosphere!
…yet another danger posed by our insatiable need to dump DHMO residue wherever we see fit, I’m afraid.

F. Ross
March 31, 2011 12:54 pm

Wouldn’t the contrails also have an effect on albedo and cool the earth a bit?

March 31, 2011 12:57 pm

If clouds are a negative feedback, then wouldn’t con trails be as well? Mind you, I wouldn’t have guessed that global warming causes snow and cold weather either. Does anything cause cooling any more?

March 31, 2011 12:57 pm

Dear Anthony,
The little red warning clause at the end certainly cooled my jets. Think of the humor foregone!!!
How about Contrailians? Can we mention those folks? UFO’s? Tinfoil hats?

Roger Knights
March 31, 2011 12:58 pm

I presume this is based on the theory that high-altitude clouds have a warming effect and low-altitude clouds have a cooling one (?)

March 31, 2011 1:00 pm

Anthony, if you’re not going to read the Tips & Notes thread then just get rid of it so people don’t waste time posting. This story was noted there at least six times before the Pielke post.
REPLY: Apologies, given what transpired today, and what I had to do yesterday to defend my work, I’ve been a little busy. – Anthony

Jeff W
March 31, 2011 1:01 pm

Wouldn’t the albedo increase caused by the predominately daytime contrails have to block more incoming solar radiation than outgoing re-radiation. I don’t get it.

March 31, 2011 1:06 pm

I see subsidized solar airplanes in our future.

March 31, 2011 1:07 pm

This might very well be true for it’s probable, however everyone seem to (dis)miss proportions.
If CO2 affect climate like a woman fart in the universe does, and them planes affect the climate like a couple of Al Bundy farts in the universe. It’s still just three farts in the universe and will take a few billion years until they really starts to smell the place up.
So how big is its effect?
Oh, sorry, essentially they just need tons of more of the tax payers money to figure that one out.

March 31, 2011 1:07 pm

Now I will have to go and read this thoroughly – as it sounds like a contradiction of the cloud providing cooling (-ve feedback) theory if contrails are going to contribute warming? Or is it just related to the height of contrails compared to real clouds?

March 31, 2011 1:12 pm

My first gut reaction is that on the scale of that photograph, actual jet contrails would be far far thinner in width than they appear on the photo. I wonder if there is a way for the public to have access the original photo just to verify its authenticity?

March 31, 2011 1:16 pm

Wait a minute – I remember a documentary a few years ago going on about “global cooling” which blamed contrails on cooling the planet, rather than warming.
There was a study done on the effect of 9/11 (all planes were grounded for 3 days) and the surface temperature, which apparently “proved” the effect.
This hasn’t been turned into warmcool has it?

Jeroen B.
March 31, 2011 1:17 pm

I seem to recall but I’m not sure that this effect was first seen just after 9/11 where the absence of contrails led to more intense temperature differences between day and night ?? (It might be I’m remembering wrong, dredging up an old memory! I’ll be happy to be corrected!)

March 31, 2011 1:19 pm

Didn’t the temperature go up a little bit after 9/11 when there weren’t any contrails when all the planes over the US were grounded?

March 31, 2011 1:20 pm

How is it possible to isolate the effect of contrails from all the other effects on climate? There are two opposite effects from contrails; first they can reflect some of the sun’s radiation away from the surface, and second they can prevent some radiation from leaving the Earth by reflecting it back down. But which is the greater? I would have thought it was impossible to find out practically, so I assume it was done using a computer programme, in which case it all depends on what data was fed into the programme in the first place.

March 31, 2011 1:21 pm

Further to the comment above IIRC the documentary was called “Global Dimming” and was by the BBC’s Horizon.

March 31, 2011 1:21 pm

No refection of sunlight back out to space then?

March 31, 2011 1:24 pm

I meant reflection…sorry.
One of our grandsons calls them ‘Aeroplane Tails’!

March 31, 2011 1:30 pm

Con-trail = Cloud
Albedo vs GH gas ?
Would the Earth totally covered with cloud be warmer than the Earth with no cloud at all ?

Bob Diaz
March 31, 2011 1:33 pm

If they waited a few days, it would have been April1.

Paul Deacon
March 31, 2011 1:33 pm

Anthony – I seem to remember a paper (?) soon after 9/11 which attempted to calculate the effect of vapour trails from aircraft based on observation (taking advantage of the fact that for a couple of days the skies in the US were free of aircraft). I recall the conclusion was that vapour trails had the effect of cooling the atmosphere (by reflecting sunlight).

March 31, 2011 1:36 pm

So that is where the “UnitRoot” has been hiding !!

Papa Bear
March 31, 2011 1:36 pm

homo sapiens says:
March 31, 2011 at 12:54 pm
You beat me to it – it is all models.
The same models that say that clouds are positive feedback …

March 31, 2011 1:43 pm

As pointed out by others. This was covered post-9/11. Look up global dimming on wikipedia for a synopsis.

March 31, 2011 1:56 pm

Self-flagellation masquerading as science.

March 31, 2011 1:59 pm

Chemtrails?? I thought that is what came through a straw from a mirror??? Nothing to do with climate or aircraft really.

March 31, 2011 2:02 pm

And here I thought clouds cooled the earth! (I notice a distinct cooling when a cloud drifts by on a hot day.) Are you sure these “researchers” haven’t got their mathematical sign backwards??

March 31, 2011 2:05 pm

This has been busted, or at least there is a peer-reviewed paper that disputes this totally.
The Hong paper made mincemeat out of the whole argument around 9/11 and this paper is just that same issue, but recycled. I didn’t tackle the issue directly, but I do cite the original papers when I was discussing the climate response time.

Vince Causey
March 31, 2011 2:20 pm

Have they taken the contrail densities from the USA and extrapolated that to the entire planet? The USA and Western Europe have the densist air corridors, and there are corridors connecting Europe, Asia and the USA. But I would imagine that covers only a few percent of the Earth’s surface. I bet under most of the globe, you would be lucky to catch sight of a single contrail all day.

March 31, 2011 2:22 pm

Simple observations…
Usually, on a nice clear summer morning, the sky is all blue without a trace of vapour or whatever. You can feel the warmth of the sun and you can see your garden being all happy to grow. Then you can see one trail, then another, and another and before noon comes the sky is always covered with a white veil of condensed vapour. Then it gets cooler but more importantly, the amount of photons reaching the surface and exciting the chlorophyll of my tomato plants is significantly reduced. Should they make a study on the effect of contrails on crop yield instead? I bet there should be a significant reduction, much more than a few tenth a degree of warming.
Now, since contrails are mainly found above continents and that the sun can still warm up the oceans, how a somewhat permanent cloud cover above land only should affect the global temperature?

March 31, 2011 2:26 pm

This will never work…
…at least until they figure out a way to tax it

March 31, 2011 2:28 pm

Funny how RAF jets contrails are absolutely… fine.

March 31, 2011 2:29 pm

I think it is disingenious to use merged photos/elapsed time photography to “illustrate” and thus “overstate” the potential impact of contrails that is suggested by yet again another model. And I am with several other commenters, even if this extremely thin layer within the thin layer of the atomosphere does have an effect, I think the albedo effect from a contrail is of greater importance that their ability to hold in heat.
Sorry R. Gates, I don’t see this report in any way being a “strong rebuttal” of my thinking on human impacts on the “earth” – which are at best regional and to which regional actions are perfectly sufficient to address. (Beijing needs to get its pollution under control for its own residents or China’s, and eventually it will, just as LA has/is doing)

Tom in Florida
March 31, 2011 2:30 pm

Whether it has a warming or cooling effect, file this under HIVES (Human Influenced Variations of Ecological Systems)

March 31, 2011 2:34 pm

[snip – links to a chemtrails website]

David L
March 31, 2011 2:37 pm

It’s worse than we thought! ( humans are having a wider impact on the climate than previously thought)

Stephen Skinner
March 31, 2011 2:41 pm

I have never ever ever been on any holiday or beach or both where any sort of cloud made it warmer. Ever. Whenever the sun comes out from behind any sort of cloud it has always felt warmer and perceivably more than temperatures like 0.92C
My first cross country attempt in a glider ended in a field very near Aldermaston in the UK. What ended it was a very high and thin layer of cloud that came between the sun and the bit of the Earth I was flying over. I was at about 4,000 ft and it took about 5 minutes for the last thermals to come up and then I couldn’t find any lift. The cloud cover was continuous and 6 other gliders landed out at the same time across 2 counties.

March 31, 2011 2:48 pm

If contrails are such a strong positive forcing, and the world hasn’t been warming since 1998, and we also had a growing CO2 positive forcing, this means that without human activities we would be… in an ice age already?
Phew. So let’s book some cheap holiday flights; keep up the good work, fellow humans!

March 31, 2011 2:55 pm

Clouds, including from aircraft, cool the climate. They dont warm it.
O but I forgot – cooling is the new warming, or “disruption”.
Aircraft harm the climate by angering the evil spirits that live in the upper troposphere, who are also responsible for malicious global warming unless offerings of money and human blood are made to appease them.

Stephen Brown
March 31, 2011 3:02 pm

Transport? Please see the EUSSR Master Plan for who can travel, when and where and by what means in the White Paper recently published.
It is ponderous in the extreme and couched in best obfuscatory language but it does show how Socialism is taking over Europe.

March 31, 2011 3:14 pm

Let’s hope it’s true. With the sun apparently entering a quiescent phase, we’re going to need all the warming we can get.

George E. Smith
March 31, 2011 3:24 pm

Does it never end ? The water vapor that is already in the atmosphere; if it condenses to form a contrail, it will still absorb solar energy just as it did as a vapor; and in addition to that it will wide angle scatter additional sunlight; which we often refer incorrectly to as “reflection”, so about half of that “reflected sunlight will head up to space, and only about half will head down; so the amount of sunlight reaching the surface MUST decrease, which most people would call acooling influence. And the higher those contrails are the smaller solid angle they subtend at the surface, so the amount of LWIR radiation from the surface, that they intercept goes down with cloud altitude (increase).
The jet engine exhaust itself, adds further moisture to the upper atmosphere, which also may form more clouds, and also block more incoming solar energy. Even the extra CO2 emitted by the engine, will absorb some incoming solar radiation in the near IR range 2-4 microns. Why do they keep pushing this positive cloud feedback notion.
The surface irradiation from LWIR capture and re-emission by high clouds falls as the inverse fourth power of the cloud height, and also by cosine to the eighth power of obliquity angle. The highly colimated incoming sunlight (0.5 deg divergence) gets directly blocked proportionate to the cloud area; in addition to the wide angle scattering.

John F. Hultquist
March 31, 2011 3:26 pm

The first letter to an editor I wrote was about this issue. The date would have been 1970 or a bit earlier as the USA’s move toward a SST was halted by Senator William Proxmire and others at that time. A magazine, Popular Science (or some such), ran an article about how clean the SST would be because it would mostly put only H2O and CO2 into the very highest levels. My comment was that even though the two molecules were thought of as non-toxic, they should still be considered as detrimental if large amounts were put into a portion of the atmosphere where they did not currently exist.
At that time there was some concern about a coming Ice Age. It was our good fortune the SST was defeated and the Ice Age was averted by keeping these molecules in the lower atmosphere – and they helped with the, so called, green revolution, also. (Don’t respond to this last bit. It’s called humor.)

Malaga View
March 31, 2011 3:40 pm

Serfs shalt not own cars….

The vast majority of British motorists will be outlaws in their own land under controversial new EU plans to ban petrol and diesel powered cars from cities.

Surf shalt not fly in planes…

The plan also envisages an end to cheap holiday flights from Britain to southern Europe with a target that over 50 per cent of all journeys above 186 miles should be by rail

Serf shalt not use electricity…

Families could see energy bills soar by £434 a year as it emerged ministers underestimated the cost of rolling out a new smart meter system.

Serfs shalt be irradiated…

If you want to spur the economy, stop global warming, and undermine the oil-fueled, terrorist-breeding, murderous theocracies of the world, the solution is simple: build nuclear power plants.

March 31, 2011 4:02 pm

Someone asked about this:
“The IPCC estimates that aviation today is responsible for 2 percent of global CO2 emissions with a total climate change impact of 3 percent. These figures have remained largely unchanged over the last two decades, despite the growth of air traffic.”

Weather to farm or not
March 31, 2011 4:30 pm

No, no, no, if I remember right, during the few days after 9/11 the daytime temps didn’t change but night time temps did. They went down. Low level and cumulus clouds reflect incoming insolation and lower temps, but contrails, cirrus and contrail induced cirrus have a net warming effect. We’ve known all this for a long time already. Nothing new here, move along folks.

Joel Shore
March 31, 2011 4:34 pm

Roger Pielke Sr. says:

If correct, this is a remarkable finding with respect to contrails as a climate forcing. It also shows that as we study the climate system, we find it is affected by a wider diversity of human climate forcings than concluded by the IPCC. The human effect on the climate system is not dominated by CO2 and a few other greenhouse gases.

This is a bit of a somewhat biased interpretation of the finding. 31 mw/m^2 is to be compared to the current forcing due to the CO2 levels elevated from pre-industrial levels of ~1.7 W/m^2. So, we are talking about an effect that is ~50 times smaller than the effect of CO2. I am a bit surprised that Roger, who surely knows these relative values, didn’t think to provide this context!
Also, if you go the Reuters link, the authors of the study also provided this additional context:

But a key difference is that CO2 lingers for decades while warming from contrails quickly ends if flights are grounded, such as after the September 11, 2001 attacks in the United States, or in Europe after last year’s Icelandic volcano eruption.
“You can get rid of contrails very quickly. You can’t get rid of CO2 quickly,” lead author Ulrike Burkhardt at DLR told Reuters.

As for those who are wondering why contrails cause more warming than cooling: In general, thin high clouds have a larger effect on reducing outward terrestrial radiation than on reducing incoming solar radiation…although it can get complicated in regards to location [e.g., tropics or mid-latitudes], height, and optical depth of the clouds. In fact, skeptic Richard Lindzen’s proposed “iris effect” ( ) made the claim that a warming climate leads to a REDUCTION of such cirrus clouds and thus to a negative feedback.

March 31, 2011 4:35 pm

George E. Smith, or anyone else who might know,
Do contrails or clouds send any more IR radiation in an earthward direction than the watervapour that formed them prior to condensation?

March 31, 2011 4:41 pm

Zeppelins do not leave contrails, do they?
Maybe they want to revive the zeppelin industry. 🙂

Les Francis
March 31, 2011 4:51 pm

During WWII there were hundreds of planes flying in formations leaving massive contrails.
Is there any data showing any temperature anomalies at that time?
So what would be the contrail temperature feedbacks for a continent such as Australia or The Antarctic?

Mac the Knife
March 31, 2011 5:07 pm

Hmmmmmmm….. Yessss……….. I think I’m beginning to see the ‘Con Trail’ effect and how the ‘Con Trail’ can be used to support additional claims of Man Made Global Warming. Yeesssss, it’s getting clearer……………….
This ‘Con Trail’ will be very similar to other Con Trails, like the Mann made ‘Hide the Decline’, etc……

Robert of Ottawa
March 31, 2011 5:10 pm

Personally, I think they increase the albedo, therefore would have a cooling effect.
I think we have a fallacy of false precision here. The incoming radiation from the Sun is about 1360 Watts/m**2. They claim an effect of some 30 milliWatts. This is some 5 orders of magnitude less; and this has been “measured” over 100 years?
They jest; they digest; they fart.

March 31, 2011 5:25 pm

The map is fascinating. At first I wondered why so many flights were starting and ending in the middle of the Atlantic! Then I realized it’s like the old trick of rubbing a pencil over paper to show the contours of an engraving. The trails show where vapor is available for condensation.

George E. Smith
March 31, 2011 5:31 pm

“”””” dlb says:
March 31, 2011 at 4:35 pm
George E. Smith, or anyone else who might know,
Do contrails or clouds send any more IR radiation in an earthward direction than the watervapour that formed them prior to condensation? “””””
How could they ? As I already explained above, IN ADDITION to continuing to absorb INCOMING SOLAR RADIATION ENERGY, cloud water droplets (if still liquid) make very nice (but aberrated) focussing lenses, and the total sunbeam that strikes a single drop, refracts that beam into an expanding cone of light (after coming to a “focus”) that spreads into a complete hemisphere of light. Now the amount that refracts beyond about 50 degrees is not large; but remember that is the result of single drop. That expanding cone of rays, will hit other droplets, and in no time you will have a completely diffuse essentially isotropic light distribution; only half of which can ever reach the ground, and that only in a very diffused spread.
Now if the water droplets freeze, which is more likely at jet plane altitudes, the ice crystals, are not going to make good lenses, like a smooth droplet, but they will still scatter the light over large angles.
You may have noticed that a fresh contrail, will either quickly evaporate, which presumably is a result of the humidity not being all that high up there, so the exhaust water vapor is still not enough to saturate the humidity; or else, the trails persist, and actually start to grow.
I have postulated, that as a result of the additional sunlight blocking underneath the trail/cloud (as seen by the sun); the air immediately adjacent to the lcoud undergoes further cooling due to the reduction in local sunlight, and that will mean the dew point gets closer, so more condensation can take place; and that results in further cooling.
I have watched these trails and clouds for hours on end, and observed, how they grow from their underside; when the humidity conditions are right. I have watched a handfull of trails over San Jose CA, eventually spread and thicken into a complete cloud layer, by late afternoon, from a handful of narrow streaks earlier in the day. But I also have seen them just evaporate, and in just a very few minutes, so you can still see the plane laying down the trail; but it peters out quickly. Just not cold enough or humid enough up there for it to grow.
Now a cloud out on the horizon, being hit sideways on by grazing sunlight, is certainly going to scatter some sunlight that otherwise would have gone straight on by, and back out into space, so that it now reaches the ground. But for the same reason. Grazing incidence sunlight that is headed for collision with the ground out on the horizon, can now be refracted into an upward direction, so that sunlight that otherwise would have reached the ground, will now be lost to space. I believe the result is a wash. I haven’t been able to explain why such horizontal cloud scattering would favor adding to the ground energy over subtracting; but the point is that any solar energy that gets captured by either H2O vapor or liquid (or solid) or any CO2 for that matter, will then becoem a source of LWIR emission that is isotropic, so only half of it can reach the ground; so that is a NET LOSS of solar energy.
More importantly the fraction of the captured incoming solar energy that does ultimately reach the ground, does so at LWIR wavelengths, and instead of propagating deeply into the deep oceans, as direct sunlight does, it is absorbed in the top few microns of the surface, which will lead to increased and prompt evaporation; and that is going to remove a lot of latent heat energy from the oceans, and put more water vapor into the atmosphere, where convection can transport that energy to higher altitudes to eventually be lost.
Now I don’t deny, that to the extent that surface emitted LWIR is captured by increased CO2 and H2O in the atmosphere, that will produce a warming trend just due to the delay in escape of that energy; but I’m not convinced that is a large effect because of the fact that any returned LWIR from the atmosphere, gets absorbed in the thinnest water surface; whereas solar spectrum energy goes deep in the oceans.

JRR Canada
March 31, 2011 5:53 pm

AWGs new motto, yes we con. More warm/cold and pleas for more tax dollars.

Pamela Gray
March 31, 2011 6:33 pm

I think any tax and spend politician worth their well-earned title looks at those trails and things $$$$$$$$$$$$$. Therefore, they must paint them in a bad light in order to have a chance at putting a tax on it. Looks like their already on step one.

March 31, 2011 6:51 pm

I tracked down the abstract at Nature Climate Science:
“Here we use a global climate model that captures the whole life cycle of these man-made clouds to simulate their global coverage, as well as the changes in natural cloudiness that they induce. We show that the radiative forcing associated with contrail cirrus as a whole is about nine times larger than that from line-shaped contrails alone. ”
Post modern science at its best. We learn what the modeler’s assumptions were. The world is assumed to be inscrutable.

March 31, 2011 6:52 pm

Thanks George, I understand what you are saying but I’m thinking about what is happening at night when there is no sunlight hitting the clouds. Does the outgoing LW radiation from the earths surface react with condensed water and ice differently to the vapour stage? i.e. are the clouds reflecting or refracting LW radiation a bit like the way foil is used as an insulating medium.

Douglas DC
March 31, 2011 7:12 pm

The water vapor is already there! As stated above. condensed yes. That ‘photo’
is misleading also stated above. you take a dry, warm, airmass you get very little
contrail formation. January 29th is the worst time to do this especially with this
cold,WET winter that was from coast to coast.
I call Bravo Sierra.

March 31, 2011 7:13 pm

Regarding 9/11 and contrails, according to this article, Dr. David Travis at the University of Wisconsin compared the temperatures for the three days after 9/11 to other days when planes were flying and concluded that “average daily temperature range between highs and lows was 1.1 degrees C higher during September 11-14 (shown graphically in Figure 2) compared to September 8-11 and September 14-17 with normal air traffic.”
However, this paper concluded that “the unusual temperatures on 11 and 12 September were a result of a particularly clear weather pattern, not a lack of jet contrails. Furthermore, the average diurnal temperature range for 11 to 14 September 2001 was only slightly above average, but well below what should have occurred based upon air masses present across the country. There is no doubt that contrails have some effect on the regional, hemispheric, and global climate system (Penner et al. 1999), but we conclude that the magnitude of this effect was overestimated by the Travis et al. (2002) study.”
According to the abstract for this paper, “None of the results herein indicates a significant impact of contrails on reducing the DTR. Hence, it is concluded that the respective hypothesis as derived from the 3-day aviation-free period over the United States lacks the required statistical backing.” However, it uses models.

Brian H
March 31, 2011 7:43 pm

If the contrail casts a shadow (however diffuse) it’s cooling. Same with any cloud. They only warm when there’s no significant DSW or DLW to block. In such cases, they’re “shadowing” outer space and the universe from Earth’s OLW.

March 31, 2011 8:11 pm

This study brought to you by Amtrak.

Steve in SC
March 31, 2011 8:49 pm

This stuff about contrails has got to be true.
In fact they had so many contrails on one particular air raid during WWII that
Dresden caught on fire. I think that Tokyo had a similar fate due to contrails.

March 31, 2011 9:12 pm

I remember that right after 9/11, when all the planes were grounded, there was a significant decrease in night time temperature. From Science Daily: “The change in the temperature difference was plus 1.1 degree Celsius, equal to plus 2 degrees Fahrenheit, above the 30-year long-term mean diurnal temperature range. The researchers compared the temperature ranges on these three days to those of the three days directly before Sept. 11 and the three days after Sept. 14, finding that the days before and after were similar, but that the three days in question differed by 1.8 degrees Celsius or 3.2 degrees Fahrenheit.”

March 31, 2011 10:09 pm

This is why you should live in Australia. Virtually no contrails in the sky – sunny days stay sunny.

March 31, 2011 10:52 pm

According to Gore, the US warmed up when Bush grounded all flights.
Al said so in his film.
So contrails cannot warm the Earth, they must shade it.

NZ Willy
March 31, 2011 11:44 pm

Tolja tolja tolja. Can I rest on my laurels now? (No — gets kicked)

April 1, 2011 12:19 am

I remembered a comment from George E. Smith in a thread last year
that pretty much settled the feedback by height issue. Best was the IPCC-1-50-50 cloud for Intergovernmental Propaganda Concensus Cloud definition.

April 1, 2011 12:21 am

I live under a a busy air corridor in Pembrokeshire, UK. During the occasional warm and sunny day during summer I bring out my solar oven and attempt to cook my favourite dish, oxtail. It must be an absolutely clear blue sky overhead for successful cooking. If there is any indication of persistent contrails overhead I won’t attempt it as I know the temperature in the solar oven drops well below cooking level if that contrail moves between the sun and my oven.
On the basis of that experience I am inclined to consign the above article to the BS bin.

April 1, 2011 12:28 am

I understood that the temperature ‘shift’ that apparently took place in the US after 9/11 was the same in Canada that had no restrictions on flights. Can anyone confirm this?
Also, it seems to me that the transient nature of con trails means that comparison with CO2 it not realistic. I assume the photograph is either totally fake or taken in a way that doesn’t represent a true instant in time.

April 1, 2011 12:45 am

Les Francis wrote:
“During WWII there were hundreds of planes flying in formations leaving massive contrails. Is there any data showing any temperature anomalies at that time?”
Didn’t most aircraft then fly at lower altitudes than modern jets do? If that was so then the effect, if any, on temperatures might have been different.

John Marshall
April 1, 2011 1:39 am

This picture looks like a time lapse collection over several hours. For that number of trails to be so persistent for so long does not equate with my experience as RAF aircrew or actually looking at the sky.
Also that number of trails during the short time of one picture would indicate a more crowded sky that is probably permitted by US law from a flight safety point of view.

April 1, 2011 3:51 am

R. Gates says:
March 31, 2011 at 12:36 pm
This effect from contrails is quite interesting and something I’ve often wondered about as I’ve watched the many contrails over my home state of Colorado.

The IPCC is learning something new every day. Water vapour is much stronger than previously thought.

“…….US government boffins report that ice breaking off the Antarctic shelves and melting in the sea causes carbon dioxide to be removed from the environment.”

Andreas Hardeman
April 1, 2011 4:38 am

In the paper, Burkhardt and Kärcher themselves recognize how shaky their own finding are:
“Besides the uncertainty due to the treatment of contrail cirrus, our radiative-forcing estimates are also affected particularly by uncertainties related to the model’s representation of upper-tropospheric humidity and clouds. Clouds are influenced by small-scale processes that cannot be resolved by a large-scale climate model and which therefore need to be parametrized. The representation of clouds is a major source of uncertainty in climate simulations. The same problems also affect the representation of contrail cirrus.”
But of course none of this is picked up in the media – why bother with such nuances…?

Dave Springer
April 1, 2011 4:48 am

Eric says:
March 31, 2011 at 12:50 pm
“I have often wondered after seeing this if the Clean Air Act was not itself a climate forcing that impacted some of the trends of US temperatures in the second half of the 20th century.”
You betcha! I’ve said that before. If we were burning fossil fuels the way God intended the cooling effect of the aerosol components would negate the warming effects of the GHG components. But noooooooooooo… the ecoloon inspired acid rain hysteria caused laws to be passed requiring that the aerosols be scrubbed from fossil fuel emissions. No wonder then that “global warming” accelerated not long after the passage of the passage of the Clean Air Act of 1963.

Dave Springer
April 1, 2011 4:51 am

@Eric (con’t)
That’s not to say I don’t like the 1963 Clean Air Act. Global cooling is bad. Global warming is good. CO2 makes plants grow faster and use less water when doing it. The unintended consequence (global warming) of the CLA in this case was a highly beneficial consequence. This just goes to show that even a blind squirrel finds an occasional acorn.

April 1, 2011 7:07 am

Since contrails only appear under certain atmospheric conditions and altitudes the solution is easy. Don’t fly that high and don’t fly into those conditions. Problem solved.
This reminds me of the Star Trek episode of the warp drive causing a wrinkle in space along a corridor. It was a global warming episode.

April 1, 2011 7:21 am

Just a question… from the NASA page featuring the image “This enhanced infrared image from the Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Terra satellite, shows widespread contrails over the southeastern United States during the morning of January 29, 2004”
Infrared… taken FROM a satellite… ABOVE the clouds that reflected.
Umm… that warms the surface how?

April 1, 2011 7:31 am

if contrails heat and we are cooling, then free flights for everyone.
on the contrary if they cool and we are heating, free flights for everyone
win win situation, start choosing where do you want to go and your favorite cocktail
Piscosour for me on my way to Eastern island, please

April 1, 2011 8:56 am

I call BS. The paleoclimate record clearly shows a relationship between cooling and increased cloud cover (determined by cosmic rays and the solar wind). Pretty much every previous study has shown this too.

Andrejs Vanags
April 1, 2011 9:24 am

Ridiculous. Obviously the contrails are nucleation points for cloud formation, increasing the earth albedo and reducing world temperature.

April 1, 2011 9:24 am

This is bad news, I suppose now environmentalists will be spray painting air travelers as they enter the airport and signs that say murderer you are killing the earth. Or maybe not.

Mike M
April 1, 2011 10:11 am

Simple, just restrict altitude to 12,500 feet or below. Y’all be careful up there!

Gary Pearse
April 1, 2011 11:11 am

Joel Shore says:
March 31, 2011 at 4:34 pm
Roger Pielke Sr. says:
It is fairly widely known that RP Sr. believes that other agents such as land use changes are at least as important as GHG. His context is therefore broader than just contrails vs CO2 and his point is that here we find another chip being taken off CO2 as the only warming cause of any magnitude.
It is interesting that the heavy-handedness of CO2 crusaders has attracted considerable new development of climate science from the skeptical side and the result is that even the IPCC has revised the weight of the CO2 effect back significantly. Before all this, when the CO2-based CAGW clique had a free rein, the the feedback multiplier was much higher and it continues to be whittled down (was it 3 down to 1.2?). Contrails would appear to chip off another piece. It seems there is a trend in the decline of CO2’s importance over the past several years. I always ask the CO2 crusaders: “Is the temperature today higher, lower or the same as you projected it would be 15 years ago?” I know Hansen’s and the IPCC’s answer to that question.

April 1, 2011 11:17 am

The 9-11 study clearly showed that contrails were a moderating (insulating) influence on the weather/climate, just as you would suspect – cooling peak daytime temperatures and increasing minimum nightime temperatures. But since there are many more daytime flights than nightime flights, the end result of many contrails should be a net cooling, which is what the study found.
Thus aircraft are beneficial, because they oppose AGW. Thus GreenPeace and PlaneCrazy should be promoting aviation, rather than opposing it.

April 1, 2011 11:23 am

>>mkelly says: April 1, 2011 at 7:07 am
>>Since contrails only appear under certain atmospheric conditions and altitudes
>>the solution is easy. Don’t fly that high and don’t fly into those conditions.
But then you run out of fuel and end up in the Atlantic rather than Paris. Aircraft fuel fuel burns are highly altitude sensitive, and to stay out of the contrailing altitude band would necessitate leaving many of the passengers and baggage behind, or simply not having enough fuel capacity to reach a given destination.
Besides, the 9-11 study demonstrated that contrails were beneficial, in cooling any perceived warming of the weather/climate.

April 1, 2011 11:38 am

I have noticed over the years that an obsession with contrails (and especially the infamous c**mtrails) is an almost universally reliable indicator of netkookery.

April 1, 2011 2:21 pm

I would like to say thanks a lot for your work you have made in writing this blog post. I am hoping the same perfect work from you down the road also.

April 1, 2011 4:32 pm

Interesting post. Persistent contrails started in 1998. The thing I notice is that they are no longer white, but have a brown hue. Whatever is going on I believe that we should go to minimum impact if possible. In this case we should study why contrails started to become persistent in 1998.

Corey Wright
April 1, 2011 4:48 pm

[snip – link to chemtrail website, see admonition at end of article]

Gee Willikers
April 1, 2011 6:20 pm

Jet contrails supposedly cause ‘global dimming’ which artificially causes global warming to be suppressed according to this BBC documentary supposedly masking how bad AGW is.
Part 1/5 (10:00 minutes)

Chicken Little The Sky Is Falling documentary. What do you think Mr. Watts of this documentary in relation to your posting?

April 1, 2011 7:59 pm

George E. Smith says:
March 31, 2011 at 5:31 pm
Out of the frying pan and into the fire.
Now that AGW is falling apart, it’s back to CO2 causes global cooling, or AGC.
Bit by bit, item by item, that is where the CO2 tax train is headed.
Give them a few more years, and they’ll be jumping up & down about Global Cooling being all your fault.

April 2, 2011 2:21 am

[snip . . abusing the host is just bad manners]

Joel Shore
April 2, 2011 5:40 am

Gary Pearse says:

It is interesting that the heavy-handedness of CO2 crusaders has attracted considerable new development of climate science from the skeptical side and the result is that even the IPCC has revised the weight of the CO2 effect back significantly. Before all this, when the CO2-based CAGW clique had a free rein, the the feedback multiplier was much higher and it continues to be whittled down (was it 3 down to 1.2?)

Since you are making this claim, I assume you have evidence, e.g., comparing the IPCC reports to back it up?

I always ask the CO2 crusaders: “Is the temperature today higher, lower or the same as you projected it would be 15 years ago?”

Actually, the runs starting in 1990 that are in the 3rd IPCC report show that we are just about where the models were projecting we would be.
How about the skeptics…Have you ever wondered how their past projections would be doing?

April 2, 2011 8:59 am

I have to point out here that by your stipulation “no ch*mtr@ils” you are essentially stating that “the science is settled”.
[snip – No, sorry, wrong. I’m simply stating that I don’t wish to discuss the topic in my own virual living room. Boorish guests who insist on violating my requests to keep the conversation focused on the actual science being discussed related to a potential climate forcing, politely get shown the door. There’s plenty of places on the net where you can discuss the ch*mtr@ils topic all you wish. Go there, enjoy. – Anthony]

April 2, 2011 9:25 am

Fair enough, WuWt remains one of my favorite “virtual rooms” in the universe and keep up the good work all. The two topics are inextricable entwined in my opinion, but I will try to refrain from boorishness and attempt to tread water with these smart guys and gals…

April 2, 2011 6:41 pm

At the risk of boorishness I would like to point out that tinfoil hats increase the surface albedo, reflecting sunlight that might otherwise be absorbed and re-radiated as heat, and therefore tinfoil hats mitigate against Thermageddon at a model-able efficiency in W/m2, more so than contrails, which may warm or cool depending on who you’re talking to, whereas tinfoil hats definitely cool the planet as well as overheated brain matter, and therefore are recommended apparel for any warmist believer who really cares.

April 2, 2011 7:04 pm

Mike D,
Your theory has merit. Tinfoil hats are a robust negative feedback. Given the large number currently in use in places like Berkeley, East Anglia, Santa Cruz, Chico, Penn State, Madison, etc., they have a greater cumulative forcing than chemtrails water vapor.☺

April 2, 2011 10:31 pm

If they would just stop adding aluminum and barium to the jet fuel mixture, the contrails would dissipate shortly after the exhaust stream like it used too. I spoke to Governor Rick Scott’s office and he got the air force to stop doing it over our state. No noticeable airplane exhaust in our skies for the past two months and our skies are now beautiful again.

Brian H
April 3, 2011 5:07 am

So are greenhouses!
Cool images of Almeria

Since the 1980s, Almería in southern Spain has developed the largest concentration of greenhouses in the world, covering 26,000 hectares. The greenhouses reflect so much sunlight back into the atmosphere that they are actually cooling the province, Spanish researchers have found. While temperatures in the rest of Spain have climbed at rates above the world average, meteorological observatories located in the so-called sea of plastic have shown them moving in the opposite direction, with a decline of 0.3 degrees per decade.

April 3, 2011 7:50 am

A quick check in IPCC Fig SPM 2 shows an estimate for forcing from contrails of 3 to 30 mW/m2. This new figure of 31 mW/m2 is at the upper end of that range, but hardly revolutionary. Pielke’s comment about IPCC is thus unfair.

Mr. Pastrami
April 3, 2011 10:06 am

Does anyone take into consideration the black budget and Geoengineering? There aren’t THAT many commercial flights!

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