Paul Beckwith (climate scientist) on chemtrails

skephu

Senior Member
Climate scientist Paul Beckwith has posted a Youtube video where he debunks chemtrails by proposing that cleaner jet fuel and the physical and chemical changes in the atmosphere due to global warming make persistent contrails last longer because they consist of much smaller water droplets / ice particles than before.


Basically he proposes that contrails behave very-very differently because of these atmospheric changes than they used to, and this is what leads to the large number of long-lasting trails.
 
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Spectrar Ghost

Senior Member
That may be true, but it plays right into the hands of chemtrailers. By "admitting" the skies have changed and that contrails don't behave like they used to, it's easy for chemtrailers to leap to "coverup".
 

skephu

Senior Member
I'm not really sure though whether he is completely right. I can accept his argument about a colder stratosphere and the increase in stratospheric water vapor. But he also says that because jet fuel is cleaner, the particles that serve as condensation nuclei in the exhaust are smaller, and therefore the contrail will be much more reflective and will last longer. But recent contrail research seems to suggest the contrary. For example:

Kärcher, B. "The importance of contrail ice formation for mitigating the climate impact of aviation." Journal of Geophysical Research: Atmospheres (2016).
 

Mick West

Administrator
Staff member
People have suggested climate change causing more contrails before, but I've never seen any evidence to back it up. For one thing the change in temperature is very small, but seasonal, diurnal, and weather related changes are huge. So it seems highly unlikely it would do anything more than very small average changes.

I'm rather skeptical of his claims in general.
 

Henk001

Active Member
I would like to see more numbers. A coherent set of data about the amount of (persistent) contrail coverage, increase in number of flights, atmospheric circumstances, possible feedbacks. And a scientific article about all that; not just a video.
 

Ross Marsden

Senior Member
I listened to the video and made some notes:

Firstly, I disagree that there are many contrails (certainly not persistent contrails) in the stratosphere, because the stratosphere is above the common vertical range of jet transport cruise altitude, and there is insufficient moisture for the air to be ice saturated.
So changes in the stratosphere, even lower stratosphere are not going to affect persistent contrails.
The increase in water vapor in the lower stratosphere seems very small.

It is unclear how "cleaner fuel" can "change the chemistry of the atmosphere".

Sulfur and soot are freezing nuclei, not cloud condensation nuclei (CCN).

There are plenty of natural CCN in the atmosphere that any increase provided by combustion products are not going to make any difference.

It is unclear how cleaner fuel (less sulfur) produces more and smaller contrail particles. I agree that more and smaller particles (if that were true) would make trails brighter.

It is unclear how smaller contrail particles make the contrails more persistent. I agree that if in fact they were brighter they may remain visibly detectable longer and appear to persist longer, but not to the extent of the chemtrail believers general claim (that contrails that used to dissipate now persist for hours).

I don't think climate scientist Paul Beckwith actually fully understands contrail formation and persistence.
 

skephu

Senior Member
Sulfur and soot are freezing nuclei, not cloud condensation nuclei (CCN).

There are plenty of natural CCN in the atmosphere that any increase provided by combustion products are not going to make any difference.
You sure about that?
From:
Schumann, U. (2002). Contrail cirrus (pp. 231-255). Oxford Univ. Press, Oxford, UK.
http://elib.dlr.de/9493/1/cntrcrr.pdf
 

skephu

Senior Member
I would like to see more numbers. A coherent set of data about the amount of (persistent) contrail coverage, increase in number of flights, atmospheric circumstances, possible feedbacks. And a scientific article about all that; not just a video.
Indeed. It's a hypothesis at best. But Beckwith presents it as established fact. He also seems to exaggerate the effect ("contrails behave very-very differently", etc.).
I have checked his publications and he has not published anything about contrails.
He should consult some of the actual contrail experts such as Schumann, Kärcher, Minnis, etc.
 

Mick West

Administrator
Staff member
You sure about that?
From:
Schumann, U. (2002). Contrail cirrus (pp. 231-255). Oxford Univ. Press, Oxford, UK.
http://elib.dlr.de/9493/1/cntrcrr.pdf
CCN in the exhaust change the nature of the contrail, but even a hydrogen fueled plane leaves contrails.

http://history.nasa.gov/SP-4404/ch6-4.htm
 

skephu

Senior Member
The engine burning hydrogen had produced a dense and persistent condensation trail, while the other engine operating on JP-4 left no trail.
This is not a good argument at all.
From Schumann U. On conditions for contrail formation from aircraft exhausts. Inst. für Physik der Atmosphäre; 1995.:

 

skephu

Senior Member
Again from Schumann, U. (2002). Contrail cirrus (pp. 231-255). Oxford Univ. Press, Oxford, UK.:
This contradicts Paul Beckwith's suggestion that the ice particles in contrails are smaller due to the cleaner fuel.
 

Trailblazer

Moderator
Staff member
Firstly, I disagree that there are many contrails (certainly not persistent contrails) in the stratosphere, because the stratosphere is above the common vertical range of jet transport cruise altitude, and there is insufficient moisture for the air to be ice saturated.
Correct for the second reason, but not for the first (IMHO). Plenty of passenger jets fly in the stratosphere. This week I have been looking at the soundings and the tropopause has been comfortably below 30,000 feet over the UK.

For instance see this one from Camborne a couple of days ago. The tropopause is at about 320mb, or just under 28,000ft!

image.gif

The result has been that the only persistent contrails I have seen have been unusually low, around 25-28,000ft, while higher jets have often not been leaving any trails at all, even short ones.
 

Spectrar Ghost

Senior Member
How do you get a graph like this?
The graph format is Skew-T/LogP. Search for radiosonde data. I like weather.cod.edu; it has good data for US users under Weather Analysis Tools>Analysis Data>Upper Air Soundings.

E.g. Most recent DVN sounding, just upstream of me:
 

Leifer

Senior Member
Just a note to any interested lurkers or chemtrail advocates reading this.....:rolleyes:
.....We will also argue against ideas "that may be in favor of contrails", if they don't hold up to scientific scrutiny.
 
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Trailblazer

Moderator
Staff member
How do you get a graph like this?
This was from the University of Wyoming weather sounding page: http://weather.uwyo.edu/upperair/sounding.html

Choose "GIF: Skew-T" under "Type of plot".

The tropopause is marked by the point at which the temperature line (right-hand thick line) starts heading back to the right. The example I posted was very sharply defined; sometimes it is more of a gradual curve so harder to pinpoint.
 

Ross Marsden

Senior Member
You sure about that?
From:
Schumann, U. (2002). Contrail cirrus (pp. 231-255). Oxford Univ. Press, Oxford, UK.
http://elib.dlr.de/9493/1/cntrcrr.pdf
Hmm. Yes, I have seen this before. The assumption here is that there is a 1 to 1 relationship between an initial condensation particle and an eventual ice particle. I not entirely sure that is a safe assumption. There may be a process (and I have read it somewhere) in the freezing of a droplet that produces a large number of small ice particles. I know, citation needed, and I hope I can find it.
 

Ross Marsden

Senior Member
Correct for the second reason, but not for the first (IMHO). Plenty of passenger jets fly in the stratosphere. This week I have been looking at the soundings and the tropopause has been comfortably below 30,000 feet over the UK.

For instance see this one from Camborne a couple of days ago. The tropopause is at about 320mb, or just under 28,000ft!

View attachment 18679

The result has been that the only persistent contrails I have seen have been unusually low, around 25-28,000ft, while higher jets have often not been leaving any trails at all, even short ones.
SIGWX charts such as this one https://www.aviationweather.gov/products/swh/ show the height of the tropopause (boundary between troposphere and stratosphere) as Flight Level (in 100s of feet). They are the 3-digit numbers in the boxes. The one near Florida means FL450. The trope will be quite low pole-ward of the Polar Jet.
 
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