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Guru
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Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 11:48 AM

I live in the UK and for the first time in years the sky is really deep blue.

Having lived here, in Dunstable, for 28 years, I am living under a main aircraft route, I think its the transatlantic route.

Most of the time the high flying airplanes leave vapour trails which due to the number of aircraft can make the sky quite hazy.

Today, with the flying ban due to volcanic ash in place, the sky is unmarked and the sun is incredibly hot - unusual for England!!!

Has anyone done an analysis on the effects of the vapour trails left by aircraft on the weather at ground level? and if so what were the results???

John.

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#1

Re: Can airplane vapour trails cause climate problems???

04/17/2010 12:08 PM

I read something about this a long time ago. It was not a significant amount, but as the frozen vapor trails spread out they did reflect some sun which could cause a slight decrease in temp at the ground.

I don't think the article described it as a big problem though.

I find it odd that the sky seems more clear, I always heard that dust storms and ash from a volcano would block more sun than even a high level cloud. They are supposed to create some spectacular sunsets too.

Drew

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#2

Re: Can airplane vapour trails cause climate problems???

04/17/2010 12:09 PM

Interesting , to say the least . The vapour trails , and your sunny day will attest to this - create a reflective surface in the upper atmosphere . A series of frozen prizms .

This reflects much of the Sun's energy back upward , away from Earth.

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#3

Re: Can airplane vapour trails cause climate problems???

04/17/2010 2:15 PM

the vapour trails are a result of cool air being heated and the water in the air becoming visible then condense back so there is on loss, and as the trails happen quite low ie below the ionsphere there cant be any significante effect on the planet.

Unlike the burnt fuel gases that you cant see.

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#4
In reply to #1

Re: Can airplane vapour trails cause climate problems???

04/17/2010 3:01 PM

Looking at the satellite pictures it seems the volcanic dust is more to the north of us (Scotland?) and so the skies are clear around London.

I was sitting here this afternoon and felt extremely hot with the sun shining in and the clear blue sky, which is unusual.

I just wondered if the lack of any jet trails could have helped ??

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#5
In reply to #3

Re: Can airplane vapour trails cause climate problems???

04/17/2010 3:04 PM

Yes.... I used the word 'climate' in the title instead of the more generalised 'weather', not meaning to refer to climate change , or the lack of etc... but the effective weather change under a jet vapour trail covered sky....

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#6

Re: Can airplane vapour trails cause climate problems???

04/17/2010 4:22 PM

This whole story strikes me as a bit weird. No doubt a high concentration of volcanic ash could abrade turbines that attempt to fly through it, but is anyone actually tracking the ash cloud and doing any arithmetic? We now hear about skies bluer than Seattle's [old TV show], and no planes flying. What's up with that?

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#7
In reply to #3

Re: Can airplane vapour trails cause climate problems???

04/17/2010 5:23 PM

I thought one of the products of fuel combustion was H20 and that is what caused high altitude vapor trails.

At lower altitudes you can see the vapor in the air coming off the wingtips and propeller tips of aircraft. When the weather is right you can even see a small vortex being drawn into jet engines.

Drew

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#8

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 7:12 PM

Some of the guys who are talking about doing geoengineering are thinking about putting fairly small amounts of sulfur dioxide into the atmosphere to reflect sunlight. The amount required is fairly small and one of the expected side effects is that the sky will be pale.

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#9

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 7:35 PM

There were reports on US temperatures after the 911 groundings. I don't recall the details. I do recall being suprised to the point of doubting them when they were reported. A little Googling and you should be able to find them.

Bruce

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#10

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 8:08 PM

What you are experiencing my friend is the result of Global Warming! The lack of vapor trails is a mere coincedence, although the heat created by the planes is contributing to the problem. If we do not quickly implement a plan for mankind's demise, this planet will not survive!

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#11

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 11:19 PM

Contrails are thought to be relatively harmless. However there are some discharges from exhaust of airplanes connected to global warming and we have a host of people who want to abate such discharges. Perhaps these contrails may contain more sinister aerosals.

On the other hand the contrails can be turned to chemtrails and be used to cool the climate. Sulfur is the usual chemical of choice and relatively harmless again. It is also said(?) that the NATO forces add aluminum to the chemtrails to help cool the climate. Both chemicals can be used to reflect the sun back to space. It is not unlike the discharge from a volcano where a lot of sulfur can cool the climate for an extended period of time. The manipulations of airplane contrails to cool the climate is called geo-engineering. And of course it is controversial and becoming a hot button with environmental movements. Too hot vs too cold? One danger with chemtrails is if the terra-formers cool the climate and then a natural incident or two like Iceland happens they could cool things too far and ruin my summer. A good book on geo-engineering is Stewart Brand's Whole Earth Discipline: An Ecopragmatist Manifesto.

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#12

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 11:41 PM

There was a tv show (or special) concerning a weather researcher's study about the changes in temperatures found when all flights in the U.S. were grounded during 9/11. He felt the the normal trails caused the day/night temperature differences to be more when the skies were clear. The show lasted for an hour discussing several long term climate issues he felt related to this observation. I don't remember all of it. It was probably something on the Science Channel. Sorry I couldn't be more specific.

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#13

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/17/2010 11:41 PM

I have wondered about this for many years. I have seen so many clouds that appeared to have been initiated by contrails (anecdotal - no scientific evidence other than the shape and altitude of the clouds). Clouds need moisture and particles upon which that moisture can condense. Airplanes add both, so when the air is clear, but almost saturated with water vapor, it's pretty easy to see that an airplane passing through could increase the probability of cloud formation.

Here in the western US, we have not (yet) been affected by the ash plume, so nearly the normal number of airplanes are flying, and we had plenty of high clouds today. We have a fairly major storm coming the next few days, so I probably won't be able to tell any further effects 'till the latter half of the week.

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#14
In reply to #13

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 4:18 AM

Given the polution given out by the USA China India And all the other countries who are polluting the atmosphere, that i am wondering why on earth you all are waisting your time worrying about jet vapour trails.

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#15

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 6:30 AM

Google "global dimming", it will answer some of your questions, but opens up a whole new ball game!

Pete

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#16

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 7:48 AM

Hi there tumbling Panda buddy.
Yeah I suddenly had a flash back to the peace and quiet of the fifties yesterday, there's normally a fair old buzz of air traffic being so near to Stansted.
Mind it so sunny this afternoon it brought ot the mowers, (mind only the low flying mowers)
Del

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#17
In reply to #16

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 10:17 AM

Hi Del.... yes its another bright sunny day again, that usually attracts the gardeners!!

Those vapour trails surely must effect the local area underneath them, sometimes I've seen the sky just fill with trails that turn into a general haziness.

I would love it if someone could find the report about temperature changes after the 9/11 disaster and subsequent flight ban in the USA....

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#18
In reply to #9

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 10:21 AM

Hi Bruce I've tried a little googling but the results are staggering, I am hoping someone could remember that programme by name, date or author(s) etc...?

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#19

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 10:32 AM

The amount of water vapor generated by an airplane is negligible with respect to the volume of vapor at atmospheric level but..

The chain reaction produced by a disturbance in an equilibrium system is not always negligible. It is well known that the atmosphere is often filled with over-saturated water vapor and even sub-freezing water droplets. It is possible to have water below zero C in the right conditions.

Once you mechanically disturb this system, a chain reaction of this stored energy can produce a change much greater than the initial mechanical energy supplied by the plane.

An example is from the maple sap cans picked up in a cold Quebec (eastern Canada)spring morning. After a cold night, most of the cans were frozen solid but some were not. It was interesting to see that those with liquid water would freeze instantaneously when hit, shaken or when a small piece of bark would be dropped in them. The "stored cold" of the sub-freezing temperature water (sap) only needed a small action to trigger a large reaction.

I believe that similar reactions can happen in the atmosphere. This is one of the energy storage producing the chaotic atmosphere that we know.

Knowing this, one can believe that a plane flying in the right conditions can trigger rain fall where it would not have rain otherwise. Of course, this means that somewhere else, rain will not come or won't be as abundant.

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#20
In reply to #10

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 11:07 AM

We have a lot of plans, we just can't get on the same page. Bill Gates is putting spokes in the wheels of the old standby pestilence. There's always "the war to end all wars" but we have nuclear accords because no one wants to go first (that water looks cold). And there's the unreliable blunt instrument, famine - we've put some serious effort into that these past couple of years - but, as always, the cannibals will survive it.

I'm putting my money on "Pigs in Space" - space based solar. It has everything going for it, new frontiers, glamour, grandiose benignancy and hubris - Last Days of Atlantis - lots of stage construction going bust. I love it.

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#21
In reply to #19

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 11:40 AM

Ah yes Marcot, the old chaos theory of a butterfly's wing causing a hurricane etc...

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#22

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 11:53 AM

It was a University of Wisconsin study which found an increase of 1 degree C for day and night temperatures after the grounding of all planes after 911. They proposed that contrails acted like cirrus clouds reflecting sunlight. The effect is especially evident at busy 'intersections' of high flying jet routes.

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#23

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 12:00 PM

google 'chemtrails'

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#24

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 12:17 PM

I found an article at a " Green " site that mentions 9/11 and contrails. It mentioned Patric Minnis from Nasa Langley's Atmospheric Atmospheric Research Center. The brief article implied contrails contributed to higher nighttime temperatures helping to cause global warming. I don't remember if the science show I saw related to him or not. FYI

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#25

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 1:16 PM

Google Chemtrails. Read em' and weep.

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#26
In reply to #19

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 8:24 PM

Is this true? When condensation nuclei is added to a super saturated gaseous solution rapid condensation (and solidification if the temperature is low enough) occurs? That when this occurs both the latent heat of condensation and solidification is released.

Isn't the climactic effect of contrails the change in albedo more than the added condensation nuclei or latent heat?

Gavilan

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#27
In reply to #26

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 9:33 PM

Yes! I can't testify from personal experience re: changing from vapor to solid, although the 80 cal/g for freezing is pretty small compared to the 540 cal/g for condensation, so I have little doubt that it's possible. Even adding the ≈100 cal/g to go from condensed vapor to the freezing point, the conversion from liquid to solid is still easier than the conversion from vapor to liquid.

I can testify from many demonstrations I did while teaching physics re: the effect of adding condensation nuclei on cloud formation in a flask, and the supercooling of water. If anyone is interested, I have detailed directions for both experiments.

I have also observed natural supercooling of water in my rain gauge - liquid when I first observed, then rapid freezing when I lifted it to see the level with greater precision. It does not freeze solid, but the ice crystals grow rapidly from an initiation point, in a beautiful feathery pattern. The end result is a mush which is a very precise 0.0°C, suitable for calibrating the zero point of a thermometer (assuming the rainwater is not from acid rain or otherwise contaminated).

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#28
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/18/2010 10:42 PM

So consider what would happen if 500 grams of liquid water were released into the vacume of space.

What would happen? Would it instantly freeze? Where would the thermal energy go? Wouldn't the energy have to radiate out? Or would the vacume instantaneously vaporize the water - but wait - where would the thermal energy come from?

What do you think?

Gavilan

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#29
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 12:27 AM

No, it would not be instantaneous. Since by definition it was liquid, it had to be under pressure. When it was released to the vacuum of space, it must be released through some kind of an opening, resulting in a spray of droplets. Much of the molecular velocity would be in the direction dictated by that opening, but the molecules would still be bouncing against each other, and as a result the outer layer of each droplet would expand rapidly. As each molecule on the surface leaves the main body of water, it carries its kinetic energy with it, leaving the remaining water cooler, until the main body freezes.

Once it freezes, the crystals of ice will sublimate, but that is a much slower process, as the Apollo astronauts discovered.

That's what I think!

Dick

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#30
In reply to #11

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 5:48 AM

Sulfur is the usual chemical of choice and relatively harmless

Eh? So why have we taken all the sulphur (a superb lubricant) out of vehicle fuels?

Because it combines with Hydrogen to form evil smelling H2S and with Oxygen to form Oxides of Suphur (SOx) which are very corrosive and cause...Acid Rain.

An added advantage is that without sulphur in the exhaust gases, the oxidation catalyst don't get poisoned, so further CO, HC, PM and NOx treatments are possible.

For a whole bunch of reasons, I think you've been misinformed, misled, or are misunderstanding what you've been told.

I'm not starting on the aluminium question.

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#31

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 11:42 AM

THE EFFECT OF CONTRAILS ON SOLAR RADIANCE IS HUGE...

Recent studies in Israel and California have shown that solar radiance striking the earth has decreased almost 30% since similar studies were performed in the 1950's. Search for "Solar Irradiance Studies" and you can vet the sources and methodology yourself.

The good news is that since most commercial flights take place during the day, the increased "cloud" cover reflects most of the 30% lost insolation back into space. With decreased flights at night, heat is then radiated at infrared wavelengths into "clear" skies. This reduces global warming, if such a thing exists.

The bad news is recent legislation requiring refiners to provide ultra-low sulfur and low particulate content in diesel and jet fuel lowers the amount of "cloud" produced in contrails due to lower particulate emissions. This will lower the reflective effect of contrails and areas around busy airports will experience increased local solar heating. Call back in about 10 years to see if local incidence of skin cancers rise as well in those areas.

Keep up your astute observations!

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#32

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 12:48 PM

Has anyone considered that this was just a , "Nice spring day!"

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#33
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 4:17 PM

Hello English Rose:

The geo-engineering of contrails has been proposed as a method of cooling the planet. The addition of sulfur sounds counter to good environmental practice because it can lead to acid rain. It is in theory a solution to global warming if it is needed. However, I am far from an expert in the area of climatology and atmospheric conditions. I have read several articles on the subject and have understood that barium sulfate and magnesium sulfate ( I have also read sulfur dioxide) are the chemicals proposed to be used to create aerosols in the stratosphere to reflect radiation from the sun. In effect this action is supposed to dim the sun even if we cannot see the dimming. It increases the albedo effect. Testing of contrails has been undertaken to see what is normally being discharged. And others (mostly lay environmentalists) are collecting rain samples but have poor interpretation skills. And of course yell the sky is falling.

Aluminum(NA) or aluminium(UK) is one of the alternative elements being proposed as geo-engineering and dumped into the atmosphere. Another chemical is barium sulfate and the barium is reported by these lay environmentalist as radioactive?? Units of reporting are changed from μg/L to mg/L without a conversion factor other than 1:1. In the meantime there is a lot of BS being spouted similar to the climate-gate hyperbole.

It is not only airline contrails that are considered but also the use of balloons to reach the stratosphere and discharge reflective agents.

I can only guess cars are more polluting than aircraft so the airline fuels may be different than used by automobiles. Go figure. Either way, it gives the climate debaters more fodder. If I sound a little jaded, I think it is because over my 65 years of which I worked 40 in the environmental field with government agencies and running my own company, there has been a constant stream of issues that never amount to much in the long run. Stewart Brand, an old time environmental activist has come full circle and advocates chemtrails and geo-engineering.

I specialized in ground water microbiology and geochemistry not climates. Actually, I have seen improvements in water and sewage treatment plants almost everywhere in the developed world...great topic for another thread.

In the meantime may the sun shine bright on England. (My wife is British). I am hoping to get to Europe to watch my daughters play soccer, (oops football), in Northern France. We will return to England later though. These plans are provided that the Iceland volcano doesn't hold up air traffic too long.

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#34
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/19/2010 10:54 PM

Interesting reply. I gave the mass of the water to be 500 grams. I forgot to give an initial temperature of 50 degrees centigrade.

In order to simplify the hypothetical case let us assume that the water is a sphere placed into the ideal vacuum. Since it is an ideal vacuum the only way thermal energy can be dissipated or absorbed is through radiative cooling or heating.

I would look at this as a thermodynamic process using the known values of specific heat, heat of fusion, and heat of vaporization to look at the overall process. What I come to conclude is that there isn't enough thermal energy available to sublimate the entire 500 grams. The total energy available would approximate the (Temperature * specific heat * Mass) + (Heat of fusion X mass). The energy required to sublimate the entire mass would be (Heat of Vaporization X mass). Because the Heat of Vaporization is so much higher than the sum of the available specific heat and heat of fusion only a portion of the water would sublimate without some source of thermal input.

Is this correct?

Gavilan

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#35
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/20/2010 1:00 AM

Does it matter if its 500 grams or 5 grams? 50°C is a pretty generous initial temperature, but I can accept that.

So you have your water in a spherical container that suddenly shatters and disappears... OK...

In any body of matter, there is, I'm led to believe, a Gaussian distribution of molecular velocities, with the mean (or is it median?) molecular velocity corresponding to the temperature of the body. Those molecules nearest the surface and having the greatest velocities will be the first to escape the surface tension of the sphere, either immediately or after bouncing off a neighboring molecule (depending on the initial direction of motion at the instant the containing sphere disappeared).

These escaping molecules carry their kinetic energy with them, in effect providing another means of cooling (of the remaining liquid) besides radiation. I don't know how broad the Gaussian distribution is, so I have no way of calculating the rate of energy loss, but clearly the remaining water will be cooled, just as water is cooled by evaporation here on earth, only faster.

Once the main body of water has cooled enough to freeze (well below zero °C, due to supercooling), the much stronger molecular bonds will slow the escape of molecules, but not stop it. You still have radiation cooling plus the additional cooling due to the loss of higher energy molecules, until all of the ice has sublimated.

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#36
In reply to #33

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/20/2010 3:55 AM

Thanks for your detailed and polite reply.

I wasn't commenting on sulphur's efficacy at solar reflection - I freely admit I know nothing about that subject - I was only commenting on the comment that sulphur in the atmosphere is harmless, hence the quote from the OP, to direct the reader to my purpose.

As to relative pollution levels, ships are the most highly polluting, burning as they do bunker fuels and "sludge"; I believe air transport is next, then road transport and industry.

These last three all have a legislative burden to reduce their GHG and pollutants emissions. I am far more familiar with the details of the road transport requirements than the others.

In the case of aircraft, most of their emissions take place during take off and landing, since when cruising the engines are at their tuned speed and load - where, if their power generating cousins are anything to go by, the tune keeps SOx and NOx to a minimum - usually 1-10 ppm, at the limit of present measuring capability. For fuel economy reasons, at altitude they emit little other than water and carbon dioxide, i.e. no CO and no unburnt HC. I would also presume that they are operating away from the particulate matter production part of the map, although this can not be entirely eliminated.

My twopenn'orth. Enjoy your European trip (the comment on spelling was a trans-Atlantic joke...my little defiance against MS spellchecker!)

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#37
In reply to #35

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 4:11 AM

There is another way to look at this, to whit*:

Consider temperature as its fundamental (?) definition: the amount of movement/vibration of individual molecules. Now consider the bonds at the molecular level. We consider a substance to be gaseous when its intermolecular bonds are overcome by the molecules' vibrations, liquid when they are able to keep the molecules in a defined volume, but able to move about within that volume and solid when they can hold the relative positions of individual molecules fixed.

Compressiblity is a measure of how closely packed the molecules are, and pressure their "wish" to move further apart.

Anyhoo...in a vacuum there is no "constraining force" (pressure) so the molecules wander off, on their own sweet lonesome, obeying the "urge" to distribute themselves evenly about the volume available. I'm not sure that boiling/vaporising or subliming (which a liquid can not do by definition) is actually a helpful term to use, in that we instinctively associate those with the addition of heat, because that's what we need to do under conditions of (approximately) constant pressure.

A vacuum is cold simply because there are so few atoms/molecules within it to vibrate and thus transfer heat, or allow us to measure temperature. It's not Absolute Zero because there are some, and they are not at rest.

I've probably (definitely) oversimplfied, and there are plenty of areas for refinement in that explanation, however, I think I covered the main thrust of the idea I was trying to convey.

Now is light a ray or a particle?

*Thanks JDG for the reminder of this most excellent word

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#38
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 4:44 AM

The correct term is "to wit," not "to whit." "Whit" is only a noun meaning a tiny amount; "wit" can be a verb meaning something like "see" or "know." [Just an Editor Crankshaft thing.]

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#39
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 4:49 AM

Ooooh you'll be in trouble now....lecturing ER on correct English usage
...I'm going to hide under the sofa and watch the fight.
A thousand Quatlous on the lady with bow and arrow.
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#40
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 5:03 AM

You're gonna lose--maybe.

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#41
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 10:11 AM

Just thought you might be interested in this link to see real time flight control over Europe!!!

Yep.... the planes are flying again....

As its Whitsun I'm sure ER is allowed to spell Whit as she has done....

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#42
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 11:49 AM

I'm a bit concerned about the one over Leeds without a call sign... ...and the circle with a question mark at Manchester.

Thanks for the backup and sorry Del, Tornado's right...

Good catch. I'm gonna get that JDG....

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#43
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 2:10 PM

It seems to me that you have put into words the concepts I took for granted. Well Said!

Now as I think about it, one question comes to mind: Would, as I assumed, the higher energy molecules in fact be lost from the main body faster than the lower energy molecules, or would all surface molecules leave at the same rate regardless of energy?

I believe the fact that the Apollo astronauts observed the crystals of their own ejected urine confirms the idea that at least part of the liquid will indeed freeze, and therefore that the higher energy molecules do in fact leave faster, and the remaining mass does indeed drop in energy (temperature).

Your post does clarify one concept indicated by Gavilan in post #28: The energy required to evaporate/sublimate the water does not have to come from anywhere - it's already there. Energy is required to evaporate/sublimate water here on Earth only because of the atmospheric pressure. Without that constraint, no energy beyond that already held by the molecular vibration/motion of the original liquid is required.

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#44
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 11:12 PM

--------"The energy required to evaporate/sublimate the water does not have to come from anywhere - it's already there. Energy is required to evaporate/sublimate water here on Earth only because of the atmospheric pressure. Without that constraint, no energy beyond that already held by the molecular vibration/motion of the original liquid is required."

Are you sure about that?

I did not suggest that that the phase changes in a vacuum were not endothermic; just the opposite. I suggested that the vaporization caused by the vacuum would occur using the energy available from the capacitated energy from its original temperature (50degrees) and the heat of fusion as the water phased from the liquid to solid state. But because the heat of vaporization is so much higher than those combined energy sources that vaporization would stop once that limited energy was used up during the process. That for vaporization to continue some source of energy would be required.

Intuition tells me that using a heat of vaporization of 2255 Joules per gram it would require 1.1275e6 joules to vaporize the 500 grams of water.

The available latent heat from the initial temperature would be 2092 joules.

As the water phased from the liquid to the solid state it would provide about 335 Joules per gram or a total of 1.675e5 joules for the 500 grams.

The total energy made available to support the vaporization would be about 1.69592e5 joules. This would provide enough thermal potential to phase only 75 grams of the water to the vapor state leaving about 425 grams in the solid state to sublimate as energy was made available from whatever radiative source.

Did my intuition fail me here? If so, what basic principle did I miss?

Gavilan

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#45
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/21/2010 11:49 PM

My chemistry teacher described solids, liquids and gasses to us like this: He placed a series of 'molecules' on the table, the first set close together, the second further apart and the final at opposite ends of the table.

He said, as a solid, the molecules do not have much kinetic energy and remain rigid because of their molecular attraction, liquids are warmer than their solids and the molecules are further apart and loose solidity, gasses have higher energy levels and are even further apart.

He used this to describe the varying densities, and drew sketches on the board where as a solid the molecules are lined up bud sublimation could still occur because the surface layer is only being pushed on the bottom and sides. Evaporation occurs faster because the liquid molecules have a higher energy quantity and tend to bash each other more causing more collisions that result in escape from the liquid.

I visualized a liquid or solid molecules as a box full of ping pong balls where they are packed in so tight that they push on each other. Lower down they are pushed upon by all sides, but at the top where they are pushed on by the sides from other balls, but only the atmosphere is pushing on top.

This is why water boils at a higher temp when at a higher pressure, the air above is pressing them in place harder. In a vacuum there is no pressure to hold them in so their own individual velocities project the molecules away taking their kinetic energy with them thus lowering the overall energy of the system and the temp drops. Once it drops enough the remaining liquid freezes into a solid.

He went over this a few semesters ago, so I hope I have relayed what I learned well enough to be understood.

Drew

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#46
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 1:02 AM

capacitated?

The heat of vaporization is essentially the energy required to overcome atmospheric pressure and allow the molecules to become independent of each other. In the absence of pressure, essentially no energy is required.

Get out of your calculation mode and just think about it!

Dick

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#47
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 1:44 AM

The latent heats of fusion and evaporation (and their sum, sublimation) vary slightly with the pressure encountered, but I don't think they approach zero just because the absolute pressure approaches zero. I'm not sure about this, though, so it needs further review.

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#48
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 6:03 AM

dkwarner:

Thanks, much as I love using maths to describe things, sometimes you have to go back to "observations" and approximations.

I'm not sure if the higher energy ones would necessarily be lost first - I think the surface ones would be lost first, simply because the escape route, thanks to Brownian Motion, would randomly send them away from the body of the gas/liquid/solid. Of course some would be directed toward the body, but since the escaped molecules would have no way back(nothing with which to collide), the volume would decrease over time.

Drew K's model is excellent. I would add that above any non-gaseous body (but much more so with a liquid rather than a solid) there is a layer of molecules in vapour form...this layer tends to stay close, because of the surrounding air which, by way of diffusion, increases the escape route distance, so more of the molecules tend to be returned to the body during collisions with air molecules.

dkw's comment about freezing is well made - I hadn't fully considered that before. It would be interesting to be able to measure how long these persist and whether there is a minium size. In fact, I now recall that ice crystals have been observed floating in space (possibly only a "few" molecules together) so this must be the case, which means that Gavilan and Tornado (again! ) are also right in that there is a minimum value of latent heat. Which is logical if you look at it using both my "model" and Drew's model, as it's all about the individual molecule's vibrational energy (its temperature) overcoming the attractive bonds between itself and its neighbours. I'm not sure if escaping molecules cause a reduction in the vibrational energy of the remaining molecules...and that is the factor that will determine whether it freezes or not.

Going back to the not quite original question in #28, I think that if the liquid were released at rest and "magically" as dkw suggested in #35, then you probably would be left with quite a long persisting lump of ice...but that this would slowly evaporate / sublime to a minimum. If the liquid were sprayed out into space, any persisting solids would be very fine and probably already at the minimum, because the greater surface area would allow a speedier Brownian Motion dispersion and might even allow complete dissociation to individual molecules through the additional velocity energy.

We have been assuming a perfect vacuum - and space is not that, so the urine freezing observed would also have been caused by molecular vibration energy (temp) being transferred to those few other molecules in the vicinity. This is the factor not included in my "model". This would have halted the evaporation and allowed a greater volume of matter to reach the critical temperature.

Thanks everyone, this is fun and has got the grey matter smoking gently! All the accumulated dust burning off I think...

What a shame this section of the thread is Off Topic!!

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#49
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 6:10 AM

Missed this yarn in the thread before, and since Tornado hasn't picked up on it and I need to regain some credibility , I'd just like to point out that it's "must affect the local area" not "effect"

Transitive verbs vs nouns and all that.

Sorry E-man, but I do feel better now!

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#50
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 9:18 AM

Yes, you're right. As ER said, it depends on whether the vibrational velocities are active enough to break the bonds to neighboring molecules. In liquid water, they clearly are. For ice, apparently not always...

As I think about it, there must be a temperature below which water no longer sublimates even in vacuum. Otherwise they would not have found water ice on the moon.

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#51
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 10:29 AM

Ahhh.... I would like to say I put that there just for your satisfaction, but alas I didn't... My mistake

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#52
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 10:48 AM

I noticed it, but a full explanation of affect/effect is about three layers deep.

I think there are more errors in typed text than in handwriting. Where/were/we're, that/than/then, from/form, you/your/you're, etc. All are good words, but not always the right words. It seems that the fingers type reflexively, but the mind fails to check. This happens to me, too, and I miss a few.

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#53
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/22/2010 11:32 AM

... and the problem does NOT disappear with age...

I was never a good typist, but I'm definitely getting worse!

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#54
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/28/2010 10:16 PM

http://www.engineeringtoolbox.com/saturated-steam-properties-d_457.html

This is a link to the steam tables. Could someone explain to me the relationship between pressure and heat of vaporization?

Your patience is appreciated.

Gavilan

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#55
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/28/2010 11:39 PM

You're quite welcome!

Thanks for the link. I found it interesting that they listed a boiling point of somewhat less than 100°C for 1 bar pressure. Perhaps some one else can explain that!

By definition, the bonds between molecules in a liquid are strong enough to keep most individual molecules at a specific average distance from each other (constant volume), and thereby keep them from escaping the liquid volume, while NOT strong enough to keep the molecules in fixed positions (NOT fixed shape). The heat of vaporization is the added energy required to cause a standard amount of liquid to escape from the liquid condition into the vapor condition, where there is sufficient molecular velocity that two colliding molecules bounce off each other rather than sticking together, as they do in the liquid condition.

In a vapor or gas, there is neither a fixed shape nor a fixed volume, except as provided by a container (which may effectively include gravity - as in the Earth's atmosphere). There is a variation in velocity among molecules. If you could somehow follow a single molecule, its velocity would change every time it collided with another molecule, but on average it will have a velocity which corresponds to the temperature of the gas or vapor. The pressure of the gas depends on the velocity of those collisions, and also on the number of collisions. In other words, at a given temperature, the pressure is directly proportional to the number of molecules per unit volume, which is effectively the density of the gas.

When there is a boundary between the liquid and a gas, such as air, the molecules nearest the surface of the liquid have fewer neighbors holding on to them.

If a certain molecule on the surface of the liquid phase happens to bounce against a neighboring molecule in such a way that its velocity is increased by the collision, and that velocity is directed away from the surface, then that molecule is a candidate for escaping the liquid. If there are few gas molecules nearby, then the given molecule may escape the liquid and become a vapor molecule. If there are gas molecules nearby, the escaping molecule may collide with one or more gas molecules. These collisions may reduce the velocity of the escapee, and/or redirect its motion back into the liquid. It should be more or less obvious that a higher gas pressure (more gas molecules per unit volume) increases the probability of the escapee colliding and being redirected back into the liquid, so with higher pressure, the escaping molecules have to have more energy on average than would be the case with fewer gas molecules.

I hope this helps...

Dick

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#56
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Re: Can Airplane Vapour Trails Cause Climate Problems?

04/29/2010 12:25 AM

"I found it interesting that they listed a boiling point of somewhat less than 100°C for 1 bar pressure. Perhaps some one else can explain that!"

Perhaps it has something to do with the units used. In the MKS system (The Standard International System) temperature is given in Kelvin and pressure is given in Pascals. In the steam tables the unit for pressure is the bar which is equal to .987 standard atmospheres on which the boiling point is based?

Anyway; as you can see, as the pressure decreases from .987 atmosphere (1 bar)to .01974 atmosphere (.02 bar) the heat of vaporization actually increases by about 8.2 percent.

I still don't understand how this can be given the Kinetic Theory of Gases.

What is meant by Saturation Steam Table? Perhaps this would explain it?

http://www.engineeringtoolbox.com/saturated-steam-properties-d_457.html

Absolute
pressure
Boiling pointSpecific volume (steam)Density (steam)Specific enthalpy of liquid water (sensible heat)Specific enthalpy of steam
(total heat)
Latent heat of vaporizationSpecific heat

(bar)

(oC)

(m3/kg)

(kg/m3)

(kJ/kg)

(kcal/kg)

(kJ/kg)

(kcal/kg)

(kJ/kg)

(kcal/kg)

(kJ/kg)

0.0217.5167.0060.01573.4517.542533.64605.152460.19587.611.8644
0.0324.1045.6670.022101.0024.122545.64608.022444.65583.891.8694
0.0428.9834.8020.029121.4129.002554.51610.132433.10581.141.8736
0.0532.9028.1940.035137.7732.912561.59611.832423.82578.921.8774
0.0636.1823.7410.042151.5036.192567.51613.242416.01577.051.8808
0.0739.0220.5310.049163.3839.022572.62614.462409.24575.441.8840
0.0841.5318.1050.055173.8741.532577.11615.532403.25574.011.8871
0.0943.7916.2040.062183.2843.782581.14616.492397.85572.721.8899
0.145.8314.6750.068191.8445.822584.78617.362392.94571.541.8927
0.260.097.6500.131251.4660.062609.86623.352358.40563.301.9156
0.369.135.2290.191289.3169.102625.43627.072336.13557.971.9343
0.475.893.9930.250317.6575.872636.88629.812319.23553.941.9506
0.581.353.2400.309340.5781.342645.99631.982305.42550.641.9654
0.685.952.7320.366359.9385.972653.57633.792293.64547.831.9790
0.789.962.3650.423376.7789.992660.07635.352283.30545.361.9919
0.893.512.0870.479391.7393.562665.77636.712274.05543.152.0040
0.996.711.8690.535405.2196.782670.85637.922265.65541.142.0156
199.631.6940.590417.5199.722675.43639.022257.92539.302.0267
1.1102.321.5490.645428.84102.432679.61640.012250.76537.592.0373
1.2104.811.4280.700439.36104.942683.44640.932244.08535.992.0476
1.3107.131.3250.755449.19107.292686.98641.772237.79534.492.0576
1.4109.321.2360.809458.42109.492690.28642.562231.86533.072.0673
1.5111.371.1590.863467.13111.572693.36643.302226.23531.732.0768
1.5111.371.1590.863467.13111.572693.36643.302226.23531.732.0768
1.6113.321.0910.916475.38113.542696.25643.992220.87530.452.0860
1.7115.171.0310.970483.22115.422698.97644.642215.75529.222.0950
1.8116.930.9771.023490.70117.202701.54645.252210.84528.052.1037
1.9118.620.9291.076497.85118.912703.98645.832206.13526.922.1124
2120.230.8851.129504.71120.552706.29646.392201.59525.842.1208
2.2123.270.8101.235517.63123.632710.60647.422192.98523.782.1372
2.4126.090.7461.340529.64126.502714.55648.362184.91521.862.1531
2.6128.730.6931.444540.88129.192718.17649.222177.30520.042.1685
2.8131.200.6461.548551.45131.712721.54650.032170.08518.322.1835
3133.540.6061.651561.44134.102724.66650.772163.22516.682.1981
3.5138.870.5241.908584.28139.552731.63652.442147.35512.892.2331
4143.630.4622.163604.68144.432737.63653.872132.95509.452.2664
4.5147.920.4142.417623.17148.842742.88655.132119.71506.292.2983
5151.850.3752.669640.12152.892747.54656.242107.42503.352.3289
5.5155.470.3422.920655.81156.642751.70657.232095.90500.602.3585
6158.840.3153.170670.43160.132755.46658.132085.03498.002.3873
6.5161.990.2923.419684.14163.402758.87658.942074.73495.542.4152
7164.960.2733.667697.07166.492761.98659.692064.92493.202.4424
7.5167.760.2553.915709.30169.412764.84660.372055.53490.962.4690
8170.420.2404.162720.94172.192767.46661.002046.53488.802.4951
8.5172.940.2274.409732.03174.842769.89661.582037.86486.732.5206
9175.360.2154.655742.64177.382772.13662.112029.49484.742.5456
9.5177.670.2044.901752.82179.812774.22662.612021.40482.802.5702
10179.880.1945.147762.60182.142776.16663.072013.56480.932.5944
11184.060.1775.638781.11186.572779.66663.911998.55477.352.6418
12187.960.1636.127798.42190.702782.73664.641984.31473.942.6878
13191.600.1516.617814.68194.582785.42665.291970.73470.702.7327
14195.040.1417.106830.05198.262787.79665.851957.73467.602.7767
15198.280.1327.596844.64201.742789.88666.351945.24464.612.8197
16201.370.1248.085858.54205.062791.73666.791933.19461.742.8620
17204.300.1178.575871.82208.232793.37667.181921.55458.952.9036
18207.110.1109.065884.55211.272794.81667.531910.27456.262.9445
19209.790.1059.556896.78214.192796.09667.831899.31453.642.9849
20212.370.10010.047908.56217.012797.21668.101888.65451.103.0248
21214.850.09510.539919.93219.722798.18668.331878.25448.613.0643
22217.240.09111.032930.92222.352799.03668.541868.11446.193.1034
23219.550.08711.525941.57224.892799.77668.711858.20443.823.1421
24221.780.08312.020951.90227.362800.39668.861848.49441.503.1805
25223.940.08012.515961.93229.752800.91668.991838.98439.233.2187
26226.030.07713.012971.69232.082801.35669.091829.66437.013.2567
27228.060.07413.509981.19234.352801.69669.171820.50434.823.2944
28230.040.07114.008990.46236.572801.96669.241811.50432.673.3320
29231.960.06914.508999.50238.732802.15669.281802.65430.563.3695
30233.840.06715.0091008.33240.842802.27669.311793.94428.483.4069
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Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 5989
Good Answers: 242
#57
In reply to #56

Re: Can Airplane Vapour Trails Cause Climate Problems?

04/29/2010 1:16 AM

Thanks again! Hopefully we are clarifying each others' understanding...

I had forgotten that 1 bar is not quite one atmosphere... That explains the difference from 100°C.

Unless I am mistaken, 'Saturation Steam' is the condition in the space above a quantity of water that has been boiling in a closed (or at least restricted, as in a pressure cooker or steam boiler) container for sufficient time that the number of molecules evaporating from liquid has reached equilibrium with the number of molecules re-entering the liquid from vapor in a given time. Thus the atmosphere above the liquid is saturated with water vapor.

I believe the increase of energy of vaporization with lower pressure is because at lower pressure, the initial liquid temperature (the initial molecular kinetic energy) is lower. It takes more energy to vaporize a 20°C water molecule than it does to vaporize a 100°C molecule

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Associate

Join Date: Dec 2008
Posts: 26
#58
In reply to #12

Re: Can Airplane Vapour Trails Cause Climate Problems?

05/01/2010 1:40 PM

Personally I feel that aircraft emissions and their effect on climate change have been minimized - perhaps an example of being "unable to see the trees because of the forest".

Water vapor and CO2 and the main components of aircraft emissions. I read recently that a single trans-Atlantic flight emits the same amount of CO2 as a car does in 50 years. Assuming the average flight is 5 hours, this would mean that a single flight emits the same as about 85,000 cars during its trip. Multiply that by the number of daily flights of the same duration, plus add those that are longer and shorter, the daily effect on the atmosphere is considerable.

The second point about flight is the emissions are made at elevations of 20,000 to 40,000 feet where winds then widely disperse the material - compare that to a single point emitter on land such as a coal-fired generator and think of the effort needed to get that CO2 up into the atmosphere (keeping in mind CO2 is heavier than air and has a tendency to sink to the earth rather than rise).

I recently spent time in Arizona where the morning sky would be an incredible blue but by mid to late morning it turns hazy - the result of the many high flying aircraft that criss cross overhear. You can see the con-trails being dispersed by the winds that contribute to the haziness.

Unfortunately many climate change proponents have instead decided to focus on earth-generated CO2 as it is only from that argument that the trade and cap business and the financing of the undeveloped world through an emissions tax can take place.

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