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Clare

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Contrails & artificial clouds
« on: October 14, 2013, 01:02:39 AM »
I recently saw this Youtube doco about contrails, artificial clouds, the widespread use of cloud seeding with iodine salts etc. The narrator guy was obviously very concerned about all this. I am wondering if any of you Forum Friends might be able to point me in a not tooooo technical direction on this please. (I can see there are some conspiracy theory ideas around this subject wrt to chemicals but I dont want to 'go there'!)
His website:
http://artificialclouds.com/
& video


I understand clouds are a complicated subject in relation to CC, their warming influence (high thick clouds can reflect, lower ones trapping heat) etc etc, I've looked at this article & some others.
http://phys.org/news/2013-02-jets-contrails-contribute-heat-trapping-high-level.html
I know there is a lot of air traffic over the Arctic so thought I should try & find a bit more about all this!
(I often see the trails from the USAF Globemasters flying south to Christchurch during the summer Antarctic season, they can remain visible for hours. Obviously there will be a lot fewer this season once the US folk have been brought back off the ice cos of the shutdown)

So any pointers gratefully received.
« Last Edit: October 14, 2013, 04:23:34 AM by Clare »

ccgwebmaster

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Re: Contrails & artificial clouds
« Reply #1 on: October 14, 2013, 01:55:08 AM »
One of your links mentions the effects of 911 - this one also mentions it:

http://www.pbs.org/wgbh/nova/space/contrail-effect.html

Quote
Travis's team discovered that from roughly midday September 11 to midday September 14, the days had become warmer and the nights cooler, with the overall range greater by about two degrees Fahrenheit.

That's quite a big effect we can expect if/when the contrails stop being formed (as is inevitable at some point). What the context of that effect would be is harder to predict, additional warming during a heat wave wouldn't be pleasant - but night time temperatures are the primary killer as I understand it (if the body gets insufficient recovery time). Exceeding pollen viability temperature for crops at the wrong time might be somewhat problematic and more frequent at that point (this can already happen during an extreme heat wave in some regions).

With respect to cloud seeding, the only nation I know of offhand that goes in for this is China. To my knowledge it is of limited usefulness and would only have any effect when the conditions are suitable - which is to say that the lack of suitable condensation nuclei is the only factor preventing rainfall.

http://www.theguardian.com/environment/2009/sep/23/china-cloud-seeding

http://www.scientificamerican.com/article.cfm?id=cloud-seeding-china-snow

Although both no doubt have some climatic effect, I personally have no time for the bunch of people that run around claiming massive geoengineering via "chemtrails" is underway. That particular rabbit hole goes very deep into some very strange and irrational territory from what I've seen. Generally into the same territory where people deny climate change, and believe it's a scam to undermine their way of life.

I don't know much about either offhand but if I see any promising papers I'll try to remember to put them on this thread (clouds in general seem to be insufficiently understood with respect to their operation within the earth system).

Clare

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Re: Contrails & artificial clouds
« Reply #2 on: October 14, 2013, 05:25:10 AM »
Thanks ccg,

Yes those studies during 9/11 were interesting.
Thanks for your link, I could follow that & have now even braved looking at the AR5 report in chapter 7.2.7.1 on this:
"Based on these two studies we assess the
combined contrail and contrail-induced cirrus ERF for the year 2011 to be +0.05 (+0.02 to +0.15) W m–2 to
take into uncertainties on spreading rate, optical depth, ice particle shape and radiative transfer and the
ongoing increase in air traffic (see also Supplementary Material). A low confidence is attached to this.."
which certainly is a v small amount.
But obviously a lot more work needs to be done if their confidence is so low.

The guy in the video said there were lots of countries actively cloud seeding (?50) but yes that whole "chemtrails" topic area seems fraught so I'll leave digging around on that for now!
So best back to working on my Coursera CC course assignment on 'climate refugees' instead of letting myself get sidetracked.
But if anyone else has more on this I'd appreciate it!

ChrisReynolds

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Re: Contrails & artificial clouds
« Reply #3 on: October 15, 2013, 10:25:04 PM »
Chemtrails is nutcase bunkum.  ::)

Experiments have been done with cloud seeding. In the UK the Lymouth flood disaster may have been linked to a cloud seeding experiment.
http://www.bbc.co.uk/devon/news_features/2002/lynmouth_flood.shtml

The wikipedia page is useful
http://en.wikipedia.org/wiki/Cloud_seeding

IPCC 5th Assessment report has a section on contrails  - copied from a draft copy of the report. Tis is the detailed backing for the section you found
Quote
7.2.5.1 Contrails and Contrail-Induced Cirrus
20
21 Aviation jet engines emit hot moist air, which can form line shaped persistent condensation trails (contrails) in environments that are supersaturated with respect to ice and colder than –40°C. The contrails are composed of ice crystals that are typically smaller than those of background cirrus (Frömming et al., 2011; Heymsfield et al., 2010). Their effect on longwave radiation dominates over their shortwave effect (Burkhardt and Kärcher, 2011; Rap et al., 2010a; Stuber and Forster, 2007) but models disagree on the relative importance of the two effects. Contrails have been observed to spread into large cirrus sheets which may persist for several hours, and observational studies confirm their overall positive net RF impact (Haywood et al., 2009). Aerosol emitted within the aircraft exhaust may also affect high-level cloudiness. This last effect is classified as an aerosol-cloud interaction and is discussed in Section 7.4.4. Rap et al. (2010b) confirmed the assessment that aviation contrails are very unlikely, at current levels of coverage, to have an observable effect on surface temperature or diurnal temperature range.

33 Forster et al. (2007) estimated the 2005 RF from contrails as +0.01 (–0.007 to +0.02) W m–2 ,and quoted Sausen et al. (2005) to update the 2000 forcing for aviation-induced cirrus (including linear contrails) to +0.03 (+0.01 to +0.08) W m–2 . Lee et al. (2009) scaled these estimates upward 18% to account for revised fuel use estimates, propulsive efficiency and flight routes for year 2005. Kärcher et al. (2010) obtain a range of +0.008 to +0.020 W m–2 for contrails in the year 2000. Traffic distance has further increased by 22% between 2005 and 2010, so that overall we adopt a RF estimate of +0.02 (+0.01 to +0.03) W m–2 for persistent (linear) contrails for 2010.
 
Satellite estimates of contrail-induced cirrus forcing estimates (e.g., Boucher, 1999) may unintentionally include cirrus changes not directly caused by aviation. Schumann and Graf (2012) constrained their model with observations of the diurnal cycle of contrails and cirrus in a region with high air traffic relative to a region with little air traffic, and estimated an AF of +0.045 to +0.075 W m–2 for contrails and contrail induced cirrus in 2006, but their model has a large SW contribution, suggesting larger estimates are possible. An alternative approach was taken by Burkhardt and Kärcher (2011), who estimated for year 2002 a global RF of +0.03 W m–2 from contrails and contrail cirrus within a climate model (Burkhardt and Kärcher, 2009), after compensating for reduced background cirrus cloudiness in the main traffic areas. Combining these estimates with uncertainties on spreading rate, optical depth, ice particle shape and radiative transfer (Markowicz and Witek, 2011) and accounting for the ongoing increase in air traffic, we assess a combined contrail and contrail-induced cirrus AF for year 2010 to be +0.05 (+0.02 to +0.15) W m–2.

The Travis 2002 paper about 911 is here:
http://www.atmos.washington.edu/~rennert/etc/courses/pcc587/ref/Travis-etal2002_Nature.pdf
Their 2004 paper is here
http://areco.org/climatepapermar04.pdf

But this has been challenged, sorry but as I do sea ice I've not bothered to chase up the argument and don't know where it stands.

Actually just found one of the other papers:
http://www.x-noise.net/fileadmin/aeronet_files/links/documents/DLR/PA_Contrails.pdf

I quote:
Quote
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.

idunno

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Re: Contrails & artificial clouds
« Reply #4 on: October 16, 2013, 08:37:59 AM »
Worth noting though that since the end of the cold war and the reemergence of China that the number of routes and flights that cross the Central Arctic has grown from near zero to, IIRC, around 80,000 p.a. today.

If we say; at random, that each of those flights deposits 3,000 kilometres of contrail in the Arctic upper atmosphere, that multiplies up to 240 billion km of contrail per year. I would be highly surprised if this were not much more significant than the effect of icebreakers (which are absolutely insignificant).

Niall Dollard

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Re: Contrails & artificial clouds
« Reply #5 on: April 27, 2020, 12:55:52 PM »
Recent conversations in the general melting thread have brought up the subject of contrails. And in particular what effect would reduced air travel have on global and/or Arctic temperatures.

I couldnt find a more recent thread specifically on contrails and didnt want to mix it up with the aerosol thread which is a bigger topic.

Most of the literature I see out there say that aviation-induced radiative forcings (CO2, nitrogen oxides (NOx) and contrail/cirrus cloud formation) have a net warming effect. . NOx creates ozone and destroys methane and is a net warmer. As are the contrails and resultant cloud formation which trap radiation escaping from the Earth.

It's not all one way traffic though and this study in Nature found that contrail cirrus cause a significant decrease in natural cloudiness, which partly offsets their warming effect.

https://www.nature.com/articles/nclimate1068

So in reply to F.Tnioli post in the melting thread, would the reduced aircraft over the Arctic have a slight cooling effect overall ?
« Last Edit: April 27, 2020, 01:06:38 PM by Niall Dollard »

oren

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Re: Contrails & artificial clouds
« Reply #6 on: April 27, 2020, 02:06:25 PM »
Very interesting question, which I would separate to the warming issue and the insolation issue, specifically for the Arctic. I believe sea ice might be affected more by the latter than by the former. In other words, if lack of contrails enables both more incoming insolation and more escape of heat, this could cause increased snowmelt, melt ponds, and ice melt, even while air temps might go down a little. Of course this is way beyond my pay grade.

F.Tnioli

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Re: Contrails & artificial clouds
« Reply #7 on: April 27, 2020, 04:17:22 PM »
Recent conversations in the general melting thread have brought up the subject of contrails. And in particular what effect would reduced air travel have on global and/or Arctic temperatures.

I couldnt find a more recent thread specifically on contrails and didnt want to mix it up with the aerosol thread which is a bigger topic.

Most of the literature I see out there say that aviation-induced radiative forcings (CO2, nitrogen oxides (NOx) and contrail/cirrus cloud formation) have a net warming effect. . NOx creates ozone and destroys methane and is a net warmer. As are the contrails and resultant cloud formation which trap radiation escaping from the Earth.

It's not all one way traffic though and this study in Nature found that contrail cirrus cause a significant decrease in natural cloudiness, which partly offsets their warming effect.

https://www.nature.com/articles/nclimate1068

So in reply to F.Tnioli post in the melting thread, would the reduced aircraft over the Arctic have a slight cooling effect overall ?
The way i see it, whenever insolation is close or at 24/7, incoming radiation is much higher than what Earth surface is able to "bleed back" to near-Earth space. Thus sunny places like equator are hot, ain't it. So during polar day, clearer sky - in particular, less contrails, - is definitely major warming of Arctic surface layers. Much of the summer, as we all know, insolation in Arctic is higher than even at the equator. High albedo slows the melt, of course, and it's a kind of balance which can and will be affected.

To me it's in general that simple: contrails are a sort of insulation, and as such it works both ways. I.e., slows down both cooling and warming: whichever would naturally happen given no contrails are present - would still happen, just slower: the more contrails, the slower temperature change will happen on average, if we speak the surface of Earth, that is.

As since for most of this winter we had "normal" amount of contrails over Arctic (let's not forget they don't entirely dissipate same day flights stop happening, far from), there was "slower/less cooling than it'd be without contrails" for freezing season, thus resulting in less ice thickness, weaker ice, warmer ice temperature on average, etc; but now with contrails gone, this "weak freezing season" - weak as is in compare to the old days, pre-1980s, - will be followed by "stronger (than recent years - with plenty contrails)" melt season.

So, before someone drops a vial with some coronavirus 2.0 - please tell 'em to wait about doing it all the way till NH summer, right? This way next "no contrails" season will happen in NH winter, clearer skies = more freezing. Then at least it'd be somewhat good for the ice outta next outbreak of the kind, eh...



To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

RoxTheGeologist

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Re: Contrails & artificial clouds
« Reply #8 on: April 28, 2020, 08:58:10 PM »

Contrail cirrus is an interesting problem. Soot from contrails can produce more and wider cloud, and it's particularly prevalent in cooler air.

Current LCA models do not allow for contrail cirrus. If they did they are estimated to increase the GWP 2x to 4x the amount of other emissions.

Contrails act to warm the earth, not cool it.

dnem

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Re: Contrails & artificial clouds
« Reply #9 on: April 28, 2020, 11:31:58 PM »

Contrails act to warm the earth, not cool it.

While that might be true overall, it might not hold for the arctic, where direct insolation over a few clear weeks around solstice can make a huge difference in a melting season.