From the American Geophysical Union weekly highlights:
Estimating climate effects of contrails
In a new study, Voigt et al. directly measured ice particle sizes and numbers in 14 contrails from 9 different aircraft of the present-day commercial fleet, including the largest operating passenger aircraft. They obtained an extensive data set of contrails from which they determined the contrail optical depth, a measure of how much light is attenuated by these man-made clouds.
They use their measurements to estimate that the radiative forcing of line-shaped contrails is about 15.9 milliwatts per square meter, which represents a small positive contribution to the anthropogenic global warming. Yet an expected doubling of aircraft passenger transport within the coming two decades will enhance contrail effects on the atmosphere. The detailed contrail measurements will help modelers working to assess the actual and future impact of aviation on climate.
Source: Geophysical Research Letters, doi:10.1029/2011GL047189, 2011
http://dx.doi.org/10.1029/2011GL047189
Title: Extinction and optical depth of contrails
Authors: C. Voigt: Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany; and Institut für Physik der Atmosphäre, Johannes-Gutenberg University, Mainz, Germany;
U. Schumann, P. Jessberger, T. Jurkat, and A. Petzold: Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany;
J.-F. Gayet: LaMP, University Blaise Pascal, Clermont-Ferrand, France;
M. Krämer: IEK-7, Institute for Energy and Climate Research, Forschungszentrum Jülich, Jülich, Germany; T. Thornberry and D. W. Fahey; Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, Colorado, USA.
================================================================
Some basic science behind contrails from http://cimss.ssec.wisc.edu/wxwise/class/contrail.html:
The condensation trail left behind jet aircrafts are called contrails. Contrails form when hot humid air from jet exhaust mixes with environmental air of low vapor pressure and low temperature. The mixing is a result of turbulence generated by the engine exhaust. Cloud formation by a mixing process is similar to the cloud you see when you exhale and “see your breath”. The figure below represents how saturation vapor pressure varies as a function of temperature. The blue line is the saturation vapor pressure for ice as a function of temperature (in degrees Kelvin). Air parcels in the region labeled saturated will form a cloud. Imagine two parcels of air, A and B as located on the diagram. Both parcels are unsaturated. If B represents the engine exhaust, then as it mixes with the environment (parcel A) its temperature and corresponding vapor pressure will follow the dotted line. Where this dotted line intersects the blue line is were the parcel becomes saturated.
==================================================================
NOTE: Any commenters that discuss or link to “chemtrail” discussions will have the comment automatically deleted. No exceptions, and no, I don’t care if it upsets you – Anthony
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Wow, I had to look up what Chemtrails was. That was good for a laugh. Thanks.
Otherwise, a good step in the right direction for actual science.
Oh come on. Aren’t there more important problems to deal with?
I guess it’s nice to know even if I never use the information again, I’m interested though in how they measured particle size, etc. Also interested that they studied contrails for the effect on light, but what about regular H2O emissions from jet aircraft? The moisture is still put into the atmosphere whether contrails are formed or not.
I’m skeptical about contrails having much effect. I don’t remember ever feeling cooler from a contrail passing in front of the sun. I usually feel cooler as a cloud passes in front of the sun.
Also, did this paper take into account that most flights are during daylight hours? In the case of cirrus clouds the warmist claim is that the surface heat relected is more than the sunlight lost because clouds reflect heat 24 hours, but only reflect sunlight for 12 hours. That wouldn’t apply to contrails.
Chemtrail, chemtrail, chemtrai….this is a test.”
[Thin ice ahead. ~dbs]
Would a giant tinfoil hat protect the planet from contrails?
Look up in the sky anywhere on earth and you don’t see a lot of contrails at any time. Are contrails another butterfly effect?
air of low vapor pressure…..
No, not really. They should have written “low pressure”. The “vapor pressure” isn’t relevant until the jet exhaust mixes with the cold, low pressure air. In fact, the lower the vapor pressure of the air, the more water must be in the jet exhaust to make a mixture that will condense the vapor from the jet exhaust.
“but also by preventing terrestrial radiation from escaping the Earth’s atmosphere. ”
WHEN I see some empirical evidence of this ?crap? then I will agree with the corrupt and unsubstantiated false “consensus.” This simplistic idea simply does not hold water, as shown by the last 10-15 years’ data. And logic!
Just to be more pedantic, I should have written, “vapor pressure of the water in the air”.
“NOTE: Any commenters that discuss or link to “chemtrail” discussions will have the comment automatically deleted. No exceptions, and no, I don’t care if it upsets you – Anthony”
Why not?
What happened to open scientific debate?
I am old enough to know for a fact that jets did not always leave lines in the sky.
I do not know for sure but it feels like this has climate related implications (geoengineering).. why not discuss it?
[Reply: As guests on Anthony’s site we should respect his wishes. Also, chemtrails discussions tend to get completely out of hand. ~dbs, mod.]
wow geoengineering for free!
Ok so if we don’t use the aviation fuel (it’s part of the oil), we’ll have to burn it off, so is it better to use it and fly around or just get a smoke stack and burn it in the air.
The Note at the top made me laugh, about the Chem trails LOL!! This thread would become Chem Trail city ROFL
I’ve yet to be persuaded that the “downward reflection” exceeds the upward. Selective albedo is a pretty tricky characteristic to prove and quantify, IMO.
I think some wise person said a little knowledge is dangerous. I guess that is true if one acts on the little knowledge on the assumption it is some how greater then reality. I guess a little is just that a little ice.
Dammit, I have been asking this same question for about 5 years now, and still don’t have a decent answer: WHY is it hotter in Phoenix than in Atlanta in the summer, when Atlanta has more than three times as much greenhouse gases as Phoenix? Day AND NIGHT!. Same latitude and elevation. Where can we actually have some empirical evidence about that mythical? damn “greenhouse effect?”
Those things cause Global Dimming. Haven’t ever of GD? It’s the next big thing to destroy the Earth! Watch this BBC documentary and then go promptly into hysterical mode!
What does that warning about comments mean? I understand moderators hate seeing the same thing over and over again, but since I’ve never heard of the term and probably many others haven’t, maybe a slightly more thorough explanation makes sense.
“I am old enough to know for a fact that jets did not always leave lines in the sky.” (ShaneCMuir, June 23, 2011 at 7:31 pm)
Careful, Mr Muir, you might be dating yourself here. Actually, even fast prop planes, going back to WW I, will leave distinct and long con trails under the right temperature and air humidity conditions. Dirigibles won’t, though 🙂
ShaneCMui doesn’t think contrails were generated in the past…
The fact is that even piston powered aircraft generate them. B17 bombers generated contrails over Germany. That, or the USA was violating the Geneva convention. You must be old enough to remember that!
Jae:
I would guess it is hotter in Phoenix because it is surrounded by the desert, and air there isn’t exchanging much, whereas Atlanta is near the ocean, and there is always a breeze. In short, Phoenix has a ventilation problem.
@Mark: Try Google.
You do know that all those small fighter/bomber military type jets don’t have on board latrines, right? They add a tiny bit more moisture to the atmosphere occasionally.
ShaneCMuir says:
June 23, 2011 at 7:31 pm
I am old enough to know for a fact that jets did not always leave lines in the sky.
=============================================================================
Thats right, because prior to the late 1960’s commercial jets didn’t have enough power to fly above about 27,000 feet (if I remember correctly from my time at a jet engine manufacturer). Therefore, the atmospheric pressure was generally too high to form contrails. Now almost all flights of any length have a cruising altitude above 35,000 feet.
Correct Wilky. Contrails were a big issue for the USAAF in WWII. The were a dead giveaway for German air defence.
Moving on, in Europe last spring there was about a month of clear skies and zero aircraft/zero contrails. The data must exist for a nice study in min/max temperatures.
Why is this not a zero-sum game? If the same contrail blocks incoming (reflects back into space) and blocks LWIR outgoing, then the result should be a NULL. If it is not, and something needs to be done about it, reformulation for a NULL effect should be pursued. Seems to me that is what research is for.
I’m not so sure about Jet traffic doubling, what with a global economic downturn and high prices for fuel. People are getting fed up with all the fees and extra charges that have no end in sight. Then you toss in all the inspections, and the Friendly Skies are not so pleasant anymore.