UK Met Office claim contrail form below -57C

David Fraser

Senior Member.
Recently Look-Up.org.uk made a claim that the Met Office had informed him that the temperature for the formation of contrails must be -57C

https://www.facebook.com/permalink.php?story_fbid=1416500845255774&id=1410029482561123&stream_ref=10

Date: Mon, 20 Jan 2014 12:54:48 +0000

From: 'Enquiries' <enquiries@metoffice.gov.uk>

Subject: re: Geoengineering today


Dear *******,

Thank you for your email.



As far as the Met Office is concerned there are only contrails - persistent and non-persistent. We do not recognise such things as chemtrails. We do realise there are others who do not agree and take a more sinister view that chemtrails exist and are causing damage to our atmosphere but we have no evidence to support that view.



The exhaust from jet engines contains the by-products of the combustion of aviation fuel. These by-products contain aerosols (microscopic particles suspended in the air) and also water vapour (water in its gaseous form). In certain atmospheric conditions these aerosols and water vapour can enhance the likelihood of condensation taking place (hence contrails).

There are fundamentally two forms of contrails; those that are non-persistent and those that are persistent:

If humidity and temperature are in the right balance (temperature must be below – 57 °C) these condensed trails cannot evaporate again and so persist for some time and can be dispersed into broader patterns by the wind at high altitudes. These persistent contrails can combine with the contrails from other aircraft to form what can effectively be described as high cloud. This can be very noticeable, especially if it occurs near air traffic route “hubs” where many aircraft converge.

On other occasions when prevailing humidity at altitude is low, the contrails can readily evaporate again and so are non-persistent.

The vast majority of global aviation is from commercial airlines. Military aircraft account for, by comparison, a very small portion of all contrails.

The effects of persistent contrails can reduce the amount of the sun’s energy reaching the surface of the earth (the so-called “global dimming” effect). This effect is small but measurable and has a very small cooling affect. Contrails during the night however, trap the earth’s heat and so have a warming effect. The net effect is therefore difficult to establish. The carbon dioxide emission from the burning of aviation fuel has a much more significant impact on the climate. Carbon dioxide is a greenhouse gas and so aviation, along with all other fossil fuel burning transport forms, is contributing to human caused global warming.



I hope this helps to clarify the matter for you and thank you for taking the time to contact us with your concern.



Kind regards,



Chris

Content from External Source
I contacted the Met Office myself and I received the same response as above. I challenged the figure of -57C and after a few emails I received this response.


Dear David,
Thank you for your email.
Contrail formation is dependent on three major factors: the engine exhaust characteristics; the air temperature; and the humidity of the air. Changes airliner jet engines and their exhaust characteristics can effect both the air temperature and humidity needed for a contrail to form. Therefore the figure given as the 'required' temperature will vary depending on these other two factors.

With the current generation of airliner jet engines, contrail formation typically occurs at temperatures below about minus 45 °C, with some dependence on the humidity of the ambient air. At such temperatures, the cloud particles forming in the contrail freeze almost instantaneously to leave a cloud of small ice crystals. The temperature conditions required for contrail formation typically occur at altitudes of 30,000ft and above, the typical altitude for many airliners in cruising flight. They may occasionally form at slightly lower altitudes provided that the temperature and humidity conditions are appropriate.

I agree that the standard lines sent in reply to your initial question may be misleading and I will ensure these are updated to more clearly explain the conditions in which contrails form.

Thank you for taking the time to contact the Met Office.

Kind regards,

Trish
Content from External Source
Simply they made a mistake and hopefully are in the process of correcting their standard email about contrails.
 

Mick West

Administrator
Staff member
Very good. Although the revised statement "contrail formation typically occurs at temperatures below about minus 45 °C", could be a little misleading, as it's just specifying a typical range, and is not setting a warmest limit, which is typically given as the nice round figure -40°C/-40°F, although exhaust contrails can also form at slightly warmer temperatures.
 

Ross Marsden

Senior Member.
It would be really useful if they could include in the explanation about the need that as the exhaust progressively mixes with the environment, water saturation must be reached for condensation to occur. That is the Appleman Criterion and is at the foundation of how we understand contrail formation. After that qualitative discussion, some numbers can be offered for typical conditions in practice.

This is The Met Office. You'd think they would have this right.
 

Jason

Senior Member
Does an error like this bode well for the "chemtrailers" or give them ammunition?
 
Last edited by a moderator:

KC-10FE

Senior Member.
I posted this on another thread, you can see Look-up uses that 57 degrees in one of their comments when trying to argue with this one lady that actually has a pretty good point. However, Look-up blatantly told her that her comments were going to be deleted anyway

Look up.png
 

cloudspotter

Senior Member.
It all gives them ammunition. They see it as proof now, but if they correct it, they will just see it as covering it up.

Despite the fact that the correction will bring them in line with all the scientific literature. Ian also quotes 37000ft as the official figure for the minimum altitude for contrail formation but I have no idea where he got that altitude from. I get the feeling he just made it up
 

WeedWhacker

Senior Member
Ian also quotes 37000ft as the official figure for the minimum altitude for contrail formation

Perhaps Ian might read this thread, in which case I personally can attest that this is incorrect. Here is someone else with actual video evidence also, showing contrails...these many flights are not "ALL" above 37,000 feet!:

This is what's known as 'proper' documentation. This bloke acquired a very, very good camera set-up, and coordinated his plane-spotting with FlightRadar24 in order to identify these flights accurately.

Here's another effort, maybe not as good (meaning, 'expensive') camera set-up, but we see the altitudes annotated:

If you don't wish to watch the video, this is the list of airliners and altitudes, taken from the video description:

1,Boeing-777 Emirates (35,000 feet)
2,Boeing-747 Korean Air (33,000 feet)
3,Airbus A380 Emirates (37,000 feet)
4,Airbus A340 Lufthansa (37,000 feet)
5,Airbus A340 Etihad Airways (39,000 feet)
6,Boeing 737 Malev (30,000 feet)
7,Airbus A330 Qatar Airways (38,000 feet)
8,Airbus A320 Wizz Air (35,000 feet)
9,Boeing 747 Korean Air (25,000 feet)
10,Boeing 747 China Air (34,000 feet)
11,Boeing 747 Lufthansa (33,000 feet)
12,Airbus A340 Lufthansa (33,000 feet)
13,Airbus A380 Emirates (35,000 feet)
14,Boeing 767 Transaero (35,000 feet)
15,Boeing 777 Qatar Airways (35,000 feet)
16,Airbus A320 Vladivostok Air (35,000 feet)
 

cloudspotter

Senior Member.
Perhaps Ian might read this thread, in which case I personally can attest that this is incorrect. Here is someone else with actual video evidence also, showing contrails...these many flights are not "ALL" above 37,000 feet!:

This is what's known as 'proper' documentation. This bloke acquired a very, very good camera set-up, and coordinated his plane-spotting with FlightRadar24 in order to identify these flights accurately.

Here's another effort, maybe not as good (meaning, 'expensive') camera set-up, but we see the altitudes annotated:

If you don't wish to watch the video, this is the list of airliners and altitudes, taken from the video description:

1,Boeing-777 Emirates (35,000 feet)
2,Boeing-747 Korean Air (33,000 feet)
3,Airbus A380 Emirates (37,000 feet)
4,Airbus A340 Lufthansa (37,000 feet)
5,Airbus A340 Etihad Airways (39,000 feet)
6,Boeing 737 Malev (30,000 feet)
7,Airbus A330 Qatar Airways (38,000 feet)
8,Airbus A320 Wizz Air (35,000 feet)
9,Boeing 747 Korean Air (25,000 feet)
10,Boeing 747 China Air (34,000 feet)
11,Boeing 747 Lufthansa (33,000 feet)
12,Airbus A340 Lufthansa (33,000 feet)
13,Airbus A380 Emirates (35,000 feet)
14,Boeing 767 Transaero (35,000 feet)
15,Boeing 777 Qatar Airways (35,000 feet)
16,Airbus A320 Vladivostok Air (35,000 feet)

Doesn't matter. Those are automatically chemtrails because they're lower than the magic altitude as far as he is concerned. I don't know if someone has told him and he's accepted it without question or he's made it up and convinced himself it's true or he's made it up and he knows full well it's incorrect, but as far as he is concerned any trail lower than that height is a chemtrail.
 

WeedWhacker

Senior Member
Doesn't matter. Those are automatically chemtrails because they're lower than the magic altitude as far as he is concerned.

Well then....Ian, if you're reading this...try to explain this video (yeah, it's been posted before, elsewhere on MB):


From the description:
Countering one of recurring arguments: "Contrails can't last as long as chemtrails do." We look at just how long an actual contrail can be, and how big the sky is.
Content from External Source
Starting at 00:15, the video maker (a fellow pilot himself) describes how he videoed another jet's contrail, one that passed by him in the opposite direction (along the same route..at 27,000 feet)...and this other jet's contrail extended (and persisted) for over 400 miles.

Of particular import is beginning at 2:00, when it is imperative to explain to "chemtrail enthusiasts" just how BIG the sky is. Don't let the math daunt you...in fact, check the math as much as you wish, and pay close attention to what the narrator is describing.

(Spoiler alert: In the math he uses for this example, any "chemical" that is potentially being "sprayed" would be at a concentration so low as to be equivalent to taking 1/100th of an aspirin tablet and dissolving it in 7 1/2 gallons of water. Time reference 3:15.)
 
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