Dr. Roger Pielke Senior writes:
Ben Herman of the University of Arizona has responded to the post…
…with the following insightful information.
“I read your recent post concerning the possible effects of contrails on global warming. While the effect of contrails in low humidity atmosphere may be something to think about, such is not the case. The water vapor trails only occur in a saturated, or near saturated environment, as witnessed by their presence being almost entirely limited to regions where cirrus clouds are present, or to regions in close proximity to cirrus clouds. The point here is, in such an environment, the water vapor and/or ice crystals already present are most likely absorbing a good deal of the IR radiation that would be absorbed by contrails in a dry environment. Therefore the increase of absorption is certainly quite limited. Of course a more thorough investigation of this is required for an accurate estimate of the actual effect of contrails, but this was apparently not considered, or at least not mentioned in the Reuter’s article you referred to in your blog.”
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The original WUWT version of the article can be seen here
Note: this thread will not discuss theories on “chemtrails”. Moderators, as in that previous article. please delete any comments that reference them even obliquely.
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Ok, so if the contrails are causing so much warming … how come it isn’t warming? If you would consider that the US probably has more contrails than anywhere else on the planet, why has the continental US temperature been dropping like a rock since 1998?
Nice hypothesis but for the “it isn’t warming” part.
Ok. Why don’t we just put this contrail thing to rest with a few very simple experiments?? There’s got to be a hungry atmospheric physicist out there with a good grant proposal talent, and a funding agency, like NSF, NASA, DOE, or even the EPA just dying to fund a project to prove contrails create warming.
You contract a jet and instrument it to fly at altitude, in the right conditions, and make a contrail. While it’s on it’s initial pass, you’re measuring broad-spectrum radiation hitting the top and bottom of the aircraft and simultaneously creating the contrails. You turn the plane around, fly just under the brand new contrail you’ve created, and measure the radiation hitting the top of the aircraft that’s below and shaded by the contrail, then compare the two values. Just for fun, fly back over the top of it and measure the upward reflected radiation and integrate that into the mix.
Let’s quantify this.
$300,000 grant anyone???
Have I missed something?
Since when do contrails make clouds that spread out over the entire sky?
This famous quote tells us they are, at the very least, considering geoengineering.
..but, what if, they have already started geoengineering.
Would it really be that big of a shock?
It also changes the calculations on the effects of these contrails because, we are not just dealing with water vapour, there will be other particles in these geoengineering clouds that will need to be considered.
Would it make a difference if there was aluminium particles those clouds?
For most of us we can use an extract of Kevin’s quote and say:
“We cannot account for what is happening in the climate system” full stop
Jer0me says:
April 7, 2011 at 4:00 pm
If you have the chance to observe contrails in an unstable atmosphere (with globs of dry and wet air) you will see broken lines as the jet enters/leaves the moist air.
Isn’t the major contrail effect going to be to the albedo? If so, then satellite image analysis ought to give the answer.
It could also give evidence in the case of clouds being part of the feedback loop. With increasing contrails should we see a compensating decrease in natural cloud formation?
“””The water vapor trails only occur in a saturated, or near saturated environment, as witnessed by their presence being almost entirely limited to regions where cirrus clouds are present, or to regions in close proximity to cirrus clouds. “”””
Utter tripe.
I fly through contrailing regions every day, and they are most certainly not all associated with natural cirrus cloud. Most of the cirrus, is actually spread out contrails from previous aircraft. This is doubly so when one considers that most aircraft fly above the natural cirrus levels. At 38 – 42,000 ft, we are very rarely in any natural cloud formations, apart from spreading CBs – but they do not last too long.
Contrailing occurs where there is a saturated atmosphere that will sustain the vapour from the engine for a reasonable period of time. So most contrails are entirely man-made and are an additional factor on the weather/climate.
Since most flights are scheduled in daylight hours, it would seem axiomatic to me that the net effect of contrails should be a cooling of the earth.
.
Since we are hyperventilating about atmospheric events lets consider lightning. Commercial aircraft are struck on average once in every 5,000 to 10,000 hours of flying time.
France has an electronic lightning detection network, Meteorage, that records some 800,000 lightning bolts that strike the ground each year. That is just in France!
A short description of lightning that occurs in thunder clouds:
“The electric current that flows, astronomically high and virtually instantaneous, heats the air in the leader channel to a temperature greater than 30,000 degrees C (55,000F), four or five times the temperature of the surface of the Sun. The initial expansion of the air produces a pressure 100 times normal atmospheric pressure and a shock wave heard as thunder.”
Bear in mind that all that energy was TRANSPORTED UPWARDS from the surface by molecules of water vapour.
Ralph says: April 8, 2011 at 12:23 am
Utter tripe (about contrails at cirrus cloud levels).
Yeah, have a look at the images of the contrails given above by
Stephen Skinner April 7, 2011 at 3:13 pm
Notice how much is coming from the engines and how much from the wings and bodies of the aircraft. Is it not simplistic to say the kero done it, gallon for gallon, when there is ample visual evidence of pressure changes causing nucleation? So, what nucleates cirrus clouds lower down? I do not know, but I do know an incomplete explanation when I see one.
Remember, until recent camera on tail devices, most pilots could not see where the contrails from their own aircraft originated, engines or wings. Sometimes you can see shadows way down below you and sometimes you can see 2 lines from a twin and 4 lines from a Jumbo. But this does not prove that the engines did it with their kero.
Seems to me that a contrail arises from the temporary pressure disturbance of a tiny amount of energy deposited by a passing aircraft and that its effect on global temperature is about nil. Try looking up at the sky in Central Australia and buying yourself a Fosters if you see a contrail. MAAN! (Much Ado About Nothing).
Geoff Sherrington,
Maybe: Much Ado About Nearly Nothing.☺
Today over southern England vapour trails are short and completely dissipating between 5 and 10 secs. This must mean all the airliners are cruising with engines throttled right back?
Willis Eschenbach says:
They do include ocean-rift heat. However, as you indicate, the estimates of ocean-bottom heat are just that … estimates.
Estimates….perhaps UNKNOWN is more appropriate…
Like so many other parameters in the real work energy budget.
From my layman’s POV, this is the way I understand contrails, and please correct me if I’m wrong because I’m here to learn :):
Below freezing temperature + Supercooled Water (metastable water below the freezing point) + Relative Humidity Over Ice (RHI) > 100% + Seed Particles (Nucleus) = Ice.
Reference: http://www.rhsystems.net/papers/RH_WMO.pdf
All of the above + engines from an aircraft generating the seed particles and the water that is then quickly supercooled = contrails.
Low air pressure at high altitudes, although related to water vapor, is not a prerequisite for contrails, as they can form at very low altitudes given the above requirements. It is well documented that in the 1940’s piston powered aircraft routinely generated contrails over Europe, and their flight levels were generally between FL180 and FL250 feet.
It seems counter-intuitive to me that ice crystals at high altitudes should create warming. The opposite should be true but I don’t have enough knowledge on the subject to make that determination.
Best,
Jose
Jose Suro says:
April 8, 2011 at 6:28 am
“…It seems counter-intuitive to me that ice crystals at high altitudes should create warming. The opposite should be true but I don’t have enough knowledge on the subject to make that determination”
Indeed
I remember an earlier IPCC report on aviation that actually used the words “clouds heating the surface”. The report admitted it could find no affect to the environment caused by aviation. However by putting various projections together they were able o show that aviation was going to be serious threat to the enviornment by 2050. The only thing that could be pinned on aviation were the contrails and thus the idea that clouds heat the ground, and the word used was ‘heat’.
I found this in Wikipedia on Cirrus clouds and their effect on climate:
“When cirrus clouds are only 0.1 km (0.062 mi) thick, they reflect only around 9% of the incoming sunlight, and yet they prevent almost 50% of the Earth’s emitted infrared radiation from escaping. This raises the temperature of the lower atmosphere beneath the cirrus clouds by an average of 10 Kelvin (18 Rankine).”
This is a very careless comparison as the heat coming in is much more than that going out, so this is an apples and oranges comparison. In addition does reality confirm this?
I just pulled up a google satellite view of my area. There’s a huge military base and very busy international airport. Not a contrail in the sky in the sat photo. Going outside just now with the base 50 miles north and international airport 22 miles south it’s maybe 50% cloudy. Good contrail conditions. The contrails not occluded by clouds above can’t possibly occupy more than a percent of my view of the sky and this is prime time for them.
Nothing convinces me that on a global basis contrails occlude any more than a tiny fraction of otherwise clear sky. Nothing convinces me that contrails have a warming vs. a cooling effect in the first place. Contrails are generally considered aerosols and ostensibly have a cooling effect:
http://en.wikipedia.org/wiki/Global_dimming#Causes_and_effects
I’m gonna have to call bullshit on any notion that contrails have any significant effect on global climate and in some restricted locales with frequent good conditions and plenty of air traffic to generate contrails they actually have a measurable cooling effect which was noted in a few places over the US when all air traffic was shut down for 3 days following 9/11/2001.
>>Geof
>>Yeah, have a look at the images of the contrails given above by
>>Stephen Skinner April 7, 2011 at 3:13 pm
>>Notice how much is coming from the engines and how much from the
>>wings and bodies of the aircraft. Is it not simplistic to say the kero done it,
Those images are very rare, and I suspect are low level images in humid climates.
In the upper atmosphere the air is very dry, and I have never seen condensation from the back of a wing from an aircraft passing over or under us, when at cruise altitude. The only contrails are from the engine exhaust.
.
This is the link into the wikipedia article which specifically mentions contrails.
http://en.wikipedia.org/wiki/Global_dimming#Probable_causes
I think it was already mentioned but commercial jet contrails are ice crystals. Nowhere on the planet is 30,000 feet (10 kilometers ASL) not somewhere south of fifty degrees C below zero.
What’s having more of an effect is Mexico’s slash & burn agriculture hundreds of miles to the south dimming the sky here quite noticeably for the past several days. Once in a while under the right conditions it can turn the whole sky a light brown.
The photo of an airplane trailing dark squiggly lines off of its wingtips, in the Print view of the Reuters article, looks more like what is often seen on approach. (Note the landing lights are on, and the flaps are well extended.)
Those are from the wingtip vortices, whereas contrails are from engine exhausts!
(That airplane’s engines are on the fuselage, visible just above the landing lights – nothing visible from the engines.)
Reuter’s blows it again.
“”””” Stephen Skinner says:
April 8, 2011 at 8:23 am
Jose Suro says:
April 8, 2011 at 6:28 am
…………………………………
………………………………..
I found this in Wikipedia on Cirrus clouds and their effect on climate:
“When cirrus clouds are only 0.1 km (0.062 mi) thick, they reflect only around 9% of the incoming sunlight, and yet they prevent almost 50% of the Earth’s emitted infrared radiation from escaping. “””””
“”””” “When cirrus clouds are only 0.1 km (0.062 mi) thick, they reflect only around 9% of the incoming sunlight, (THAT HITS THEM) and yet they prevent almost 50% of the Earth’s emitted infrared radiation (THAT HITS THEM) from escaping. “””””
So let’s do the math again. Wiki says the thin cirrus prevents the escape of “nearly” 50% of the outgoing LWIR. Well of the radiant energy that is absorbed by the cloud, about half escapes, and half returns, since the cloud re-emission is isotropic; so either wiki is saying the thin cloud absorbs “almost” 100% of the earth emitted LWIR, or else they are saying the cloud captures “almost” 50%; of which half returns, and half escapes, so only 25% of the total emission is prevented from escaping.
NOTE !! for the incoming sunlight, that 9% is REFLECTED , not ABSORBED, so ALL of that is a loss to the earth.
So now we have 9% incoming loss to 25% outgoing retained (2.8 to one) unless they mean 9% incoming loss to 50% outgoing retained, and 100% cloud absorption of outgoing (which is about as likely as the sun rising in the west tomorrow morning).
BUT !! that 9% is the REFLECTION LOSS. What about the direct absorption loss of incoming sunlight by the cloud between 700 nm and 4.0 microns wavelength; that can be as much as 20% of the solar spectrum energy (absorbed by water). Well by the same argument as above, only halfg of that energy is a net loss, since the re-emission in the LWIR spectrum is also isotropic, so half escapes, and half reaches the ground; NOT AS PENETRATING SUNLIGHT, BUT AS SHALLOW ABSORBED LWIR. But still the cloud attenuation of incoming sunlight is clearly greater than 9%, because of the absorbed fraction.
So that 2.8 ratio is a max for out/in cloud interference.
Remember Trenberth’s cartoon global energy budget. It starts out with a 4:1 ratio between WHAT REALLY IS COMING IN, and the number in Trenberth’s picture; so the incoming sunlight that hits the cloud and is reflected, is really four times higher than Wiki’s number; so that 2.8:1 max ratio, now looks more like a 0.7 :1 out/in ratio.
Ooops !!! I almost forgot; the sun only shines on one half of the earth surface at a time; whereas the surface radiates 24-7, so the incoming sunlight blockage is only active half the time, so the 0.7:1 ratio should be moved back up to 1.4 :1, out/in. since the incoming is blocked only half the time of the outgoing.
Well there is another problem for that outgoing blockage. The outgoing emission is essentially isotropic, so it is spread over 2 .pi steradians of solid angle, whereas the incoming sunbeam is 0.5 degrees total divergence. The cloud shadow on the ground is essentially the same as the area of the thin cloud layer, and blocks its percentage of the incoming sunlight over that same cloud shadow area on the ground. The outgoing emission from that shadow zone nearly all completely misses the cloud; and the higher the cloud layer is the smaller the fraction of the outgoing energy, that hits the cloud; and remember that the cloud only interracts with the radiation that hits it.
So there’s a big attenuation factor now in favor of blocking incoming over outgoing; and you can clalculate that yourselves for whatever cloud height you want.
Now the cloud will also block some oblique LWIR emissions from the rest of the surface outside the shadow zone; but there’s a cosine^4 th obliquity attenuation, and of course the inverse square of cloud altitude fall-off as well. For a Lambertian emitted radiation pattern (from an optically flat surface) the total flux is pi times the axial (normal) intensity; but for an isotropically 4emitting surface, the axial intensity drops by another factor of two because of that 2 pi steradian solid angle.
So don’t believe that 5.5 to one factor of outgoing LWIR interception to incoming sunlight reflection; the cloud can only absorb what hits it, and most of the energy going out down’t hit the cloud. For a complete cloud layer over the entire surface, you still get that factor of 2 pi lower diffuse absorption verus direct beam absorption for the incoming sunlight; and of course the sunlight absorption would now be 24 hours per day as well, instead of 12.
It is simple. We pilots have a control knob specifically set up to adjust the size and duration of a contrail. Bigger engines, bigger contrails. More engines, more contrails. Bigger plus more is directly proportional to contrail exaggeration. Thus, the contrail exaggeration controller, or CEC. How else could the poor schmuck behind you find their way? And at night or instrument meteorological conditions (IMC) , we use special color coded injections that glow, but only can be seen through the specialized eye wear device (SEWD) that only pilots can acquire.
I hope this “clears the air” regarding contrails. (I waive my usual fee)
My memory of digging into contrails a couple of years ago to counter an idiot conspiracy theorist is that they are caused by soot particles in the exhaust, and newer engines are cleaner so not nearly as likely to generate contrails.