Contrails are long thin clouds of ice crystals that form behind planes that fly through freezing cold air. Usually you see them behind jets at around 30,000 feet.  If the air they fly though has enough moisture in it already, then these contrail clouds can last for a long time before they evaporate.  Sometimes you get a lot of them at once in the sky, if the weather is right. They look like this:

Note: the trails in the above photo ARE CONTRAILS (and some natural clouds).  That’s a photo taken by NASA scientist Louis Nguyen from I-95 in northern Virginia, January 26, 2001.    This is the only photo of contrails in this article.  The remaining photos are NOT contrails.

There are several things that a superficially somewhat similar, in that they involve stuff coming out of the back of an airplane and/or lines in the sky.  But these things are not contrails.

SKYWRITING

Skywriting is making patterns in the sky using smoke trails.  Done at a low altitude using small planes, it can look very like a contrail, but it’s very different as skywriting is made from smoke (made from injecting oil into the hot exhaust), and contrails are made from ice crystals.

SKYTYPING

Also known as “Dot Matrix Sky Writing”, See:

http://www.geicoskytypers.com/

Skytyping utilizes five airplanes that fly abreast, 250-feet apart and “type” up to 25-30 character messages in a dot-matrix-like pattern. Skytyping is 17 times faster than skywriting, laying out a letter every 4 seconds. During skytyping aerial exhibitions, the pilots fly their aircraft in a line-abreast formation while a computer in the lead plane sends radio signals to the smoke systems in each plane in the formation, thus creating a customized message in a dot-matrix pattern of environmentally safe puffs of smoke.

In the above photo the trails have been blurred by the wind, but you can kind of make out letters in the section to the right.

AEROBATIC SMOKE TRAILS

Rather similar to skywriting, smoke trails are used to enhance exhibitions of aerobatics, often with different colored trails.  These are the Red Arrows, in the UK.

Even gliders can perform aerobatics, and they often have wingtip smoke generators to show this off:

CROP DUSTING

More technically called “Aerial Application”, this involves spraying crops or agricultural areas with fertilizers, pesticides, fungicides, or defoliants, for a variety of reasons.  Typically done with small planes or helicopters just a few tens of feet above the crop, like this:

PEST SPRAYING

Sometimes larger areas that an few fields are sprayed for things like mosquito control.  Larger planes can be used, but they still have to spray very close to the ground.  Here’s a C-130 spraying a few hundred feet up:

RESEARCH SMOKE TRAILS

Sometimes planes have smoke emitters placed on them for research purposes – generally visualize the flow of air behind the plane, the vorticies, or “wake turbulence” which can be dangerous to other planes.  Here’s one example:

CLOUD STREETS

Atmospheric conditions can make clouds form in odd ways.  These unusual stratocumulus clouds called “cloud streets” formed over the Sea of Okhotsk, Northern Japan, on June 18th, 2007.

Here’s a satellite photo of the region showing these clouds:

More info here:

http://www.meteorologynews.com/2009/10/29/cloud-streets-photographed-over-gulf-of-mexico/

CLOUD SEEDING

People try to make clouds produce more rain by “Seeding” them with tiny particles of things like sliver iodine.  This is done using incendiary devices attached to the aircraft.  Basically flares that are burnt one at a time.  Here’s what they look like in action.

Long shots of clouds seeding are hard to come by, because it happens inside or above the cloud.   If you see a long trail coming from behind a plane, then it’s not cloud seeding.  The trail is very thin, and probably not noticeable from the ground, even if you could see the plane.

FIRE FIGHTING

Planes are often used in fighting fires, and typically drop fire retardant from a low altitude.  Often it’s bright red, but sometimes it’s just water pulled from a nearby lake.  This one is in Missoula, Montana.  Note it’s a fairly low altitude, probably 1000 feet or so.

FUEL DUMPING

When a plane takes off they are usually full of fuel.  At this point they are too heavy to safely land (it’s a lot easier on a plane to take off than to land).  If they have to cut their trip short, then they have to get rid of that excess weight.  They can just fly around for hours to burn it off, but some planes have a fuel dump system that lets them get rid of the excess fuel rapidly by just dumping it into the air.  This is often from vents at the end of the wing, but sometimes it’s mid-wing, or at the tail.

This is a Navy E-6B Mercury (TACAMO), dumping fuel from its mid-wing vents.

Here’s a rare set of shots from the ground of a jet dumping fuel

Note the difference between this and a contrail.  You can see it’s coming from the wingtips, and you can see the trails just kind of blur out as it spreads and evaporates, unlike contrails which have much more well-defined edges, even as they fade away.  See here for the full story behind this incident:

http://www.airliners.net/aviation-forums/general_aviation/read.main/3523366/

The aircraft, of of KLM’s B744 full passenger versions, registered PH-BFG, took off from SFO and somewhere around Sacramento the crew decided to turn back to SFO because the nosewheel wouldn’t retract.

See also:

http://www.modbee.com/local/story/34136.html

And a cool video:

http://www.youtube.com/watch?v=uoUBWEqPu0Q

GLIDER BALLAST DUMPING

Gliders use water for ballast, and they sometimes let some out to reduce their descent rate, usually when landing.  It looks similar to fuel dumping.  Here’s a nice example:

ROCKET TRAILS

Most rockets can produce a kind of contrail as the combustion of the fule (especially if they are hydrogen+oxygen fueled) will produce a lot of water.  But for many rockets there is also a lot of visible smoke.  It’s not always visually clear what is smoke, and what is water. When they get very high up, the trail spreads out and is lit by the sun in unusual ways.  You see this a lot with the missile tests in California.  You could call this a contrail if you wanted, so long as you note it’s a rocket contrail, and so contains smoke.

SHIP TRAILS

Generally seen best from space, large ships can create a trail in the atmosphere above it that resembles a contrail.  These are off the coast of France.  They are generally more squiggly than contrails, as the ships move much slower, so the trail is at the mercy of the wind to a greater degree.

FLARES

Military planes shoot out flares to confuse heat-seaking missiles.  These are very bright, and leave smoke trails.  Usually they shoot off in all different directions, like this:

CHAFF

Chaff is a substance that planes spray to confuse radar.  Generally it thin fibers, coated with aluminum.  I could not find ANY photos of chaff being sprayed, despite it being used since the 1940s.  This is probably because it just looks like fine dust.  It does not leave a trail (it would be rather pointless to defeat the radar, but then have a big line pointing to where you are).  It’s only visible to radar.

GUN SMOKE

This photo I originally thought was chaff, as that was how it was labeled, but then someone pointed out it was actually smoke from the guns firing. Not chaff, but not a contrail either. There are a variety of reasons why smoke can be coming from an airplane.

This is an oft-asked question. The answer is reasonably straightforward, but misunderstanding is common. To understand why a contrail can last as little as a fraction of a second, or as long as several hours, you need to understand what a contrail is, and how it forms.

Here’s another question, which has the same answer:

Q) How long does a snowflake last?

Why is this basically the same question? Because contrails are generally made of ice crystals. Jet exhaust contains a lot of water vapor (the chemical reaction actually produces more water than there was originally jet fuel), and when this gets shot out of the back of the engine at 2000MPH, it hits the frigid air (typically colder than -40 degrees), and the water vapor condenses and freezes, very quickly, into tiny ice crystals, just like snowflakes.

So why do these ice crystals sometimes stay around for a long time, and sometimes vanish in seconds? The temperature is well below freezing, so they can’t melt, can they? This is puzzling, because it involves something that most people know nothing about: “sublimation“.

Sublimation is when a substance (in this case, water), goes directly from being solid to being vapor (a gas), without actually melting into a liquid. It’s like evaporation, except instead of a liquid evaporating, it’s a solid (ice). If the air is dry (i.e. there is little water vapor in it), then the ice crystals will quickly sublimate into vapor, and the trail will vanish quickly.

However, if the air already has a lot of water vapor in it, then the ice will sublimate slower, and the trail will last longer.

If the air has so much water vapor in it already that it can’t hold any more (i.e. it’s “supersaturated”), then the ice crystals can’t sublimate, and so the contrail will stay around for a long time. The ice crystals might even attract water from the air, if there is enough, and the contrail will get thicker. Winds might make the contrail spread out to even cover the whole sky.

The above is a simplification, as other factors like temperature, pressure, and sunlight have an effect. But it explains the basic reasons why some trails last only a few seconds, and some can last for hours, and spread out to cover the sky.

Finally, there is one more way of asking the question:

Q) How long do clouds last?

This is the same question because contrails are clouds. Contrails are physically very similar to cirrus clouds (except they are long and thin), and so they act almost exactly the same. You see cirrus clouds that last for hours, so why not contrails?

The earliest known account of a contrail is a passing mention attributed to Ettenreich, who in 1919 reported of an incident from 1915 where he saw “the condensation of a cumulus stripe from the exhaust gases of an aircraft”

In a fascinating article: Wakes of war: contrails and the rise of air power, 1918-1945 Part I–early sightings and preliminary explanations, 1918-1938, (Air Power History. 54.2 (Summer 2007): 16(16).), Donald R. Baucom give an account of the rise of high altitude flight, and the inevitable accounts of contrails, both persistent and otherwise, that occurred during that time. In the autumn of 1918, in an account of Captain Ward S. Wells, Army Medical Corps, who was serving with the 60th Infantry, 5th Division, American Expeditionary Force, during the Meuse-Argonne campaign.

Our attention was first drawn to the sky by the sudden appearance of several strange and startling clouds–long, graceful, looping ribbons of white. These were tapering to a point at one end and at the other where they dissolved into nothingness 60 degrees across the sky, were about as broad as the width of a finger held arm’s distance from the eye. On close observation we noticed some distance ahead of each cloud point the tiny speck of a chasse [sic] plane…. [N]ever before had I seen a plane writing in white upon the blue slate of sky.

This is very interesting, as it’s the earliest known account of contrails (note that these are non-persistent). It was also very novel and interesting at the time, and was reported in a letter to Scientific American, (“Clouds formed by Airplanes“, Jun 7, 1919, p 60) by Wells’ brother, Everett Wells, and provoked some discussion of what might be forming these clouds.

The earliest report of both a persistent spreading contrail, with gaps, and a distrail comes very shortly after, in 1921, in the US. Air Service Newsletter.

An altitude flight was made in the morning at McCook Field recently by Lieut. J. A. Macready in a La Pere with supercharged Liberty [engine]. When the airplane reached a height of 26,000-27,000 feet at 11:50 a.m., a long feathery white streamer was observed forming behind a rapidly moving dark speck. The cloud was of the cirrus variety, well defined at the edges and apparently 10 to 15 times the width of the plane. The sky behind the first portion was clear blue with no clouds in the near neighborhood. The first streamer seemed perhaps 2 miles long. Then a gap of one-quarter mile. The second streamer formed with a background of light cirrus cloud and after 2 or 3 miles the plane seemed to go into the cirrus background, for the streamer formation ceased while an apparent path of blue continued beyond for a way in the cirrus cloud. The whole streamer may have been 3 miles long. After 20 minutes the streamer had drifted and spread until it merged indistinguishably with the other cirrus clouds visible.

Both these accounts were reprinted in the June 1921 Monthly Weather Review, in the article The Argonne Battle Cloud, which also includes an account from Captain W. H. Nead, that includes an account of iridescence in the trails:

The Rainbow Division, on the morning of October 10, 1918, was lying in what had at one time been a wood just back of Montfaucon. The sky was clear except for a few fleecy clouds to the northwest. Three airmen came from the northwest and passed almost over our regiment, continuing on to the southeast.
Behind each machine was a trail of white, which at first sight appeared to be smoke resulting from poor engine combustion, but which upon more careful observation proved too wide to have been caused by smoke. Perhaps the strangest thing of all was the fact that when the planes reached a certain point in the sky the rainbow (sundog) colors became distinctly visible.

And even back in 1921, the mysteries of contrail formation were not too difficult to discern:

The end products of complete combustion of gasoline are water vapor
and carbon dioxide, and it is found that if the water vapor were condensed,
there would result a little more than 1 gallon of water per
gallon of gasoline consumed. It was found by Wells and Thuras, in
studying the fog off the Newfoundland coast (see U. S. Coast Guard ,
Bull. 5, 1916) that there were 1,200 water droplets of diameter 0.01 mm.
in a cubic centimeter of air in a dense fog. If we assume that an airplane
travels 3 miles on a gallon of gasoline (approximately the figure
given by the Aerial Mail Service) it is possible to show that if only a
small part – a fourth or fifth – of the water vapor were condensed,
there would be abundant cloud to produce the effect observed at the
Argonne Battle. It should be stated, however, that this water vapor
would have to be discharged into air which was very cold and nearly
saturated. This seems to be the correct explanation, and is substantiated
by scientists at the Bureau of Standards, who say that they have
actually observed this cloud behind airplanes and automobiles. The
Bureau of Standards is working on a device for condensing and using
this water aboard dirigibles as ballast.

The weather review goes on to discuss how vapor trails (contrails) can form at low altitudes, even down to the ground, if it is cold and damp enough. They even give examples I’d never heard of, contrails formed by a horse, and a herd of reindeer:

A horse, warm from running over the ice, on a cold day in Greenland, was accompanied by a cloud 50 meters in height formed from its breath. Von Hann gives a similar case regarding a herd of reindeer. The human breath also has been seen to transform itself into small clouds of ice needles.

• Samples of water were collected in August 2007, in Stamps Arkansas, by leaving some bowls outside for a month
• The resultant dirty water was tested by KSLA and was found to have the same amount of barium in it as most municipal tap water.
• The reporter misunderstood the results, and said there was a lot of Barium
• The reporter now admits he was mistaken, and that he found no evidence for chemtrails

Some conspiracy theorists think that persistent spreading contrails indicate some kind of deliberate aerial spraying, probably by the government. They speculate as to what could be in these trails, and one of the most common things they claim is barium.

Some people are so obsessed by this idea that they have rainwater tested to see if it has barium in it. They usually find some, and then trumpet this as evidence that their theory is correct.

Unfortunately they are wrong. I’ll explain why, but first, some basic science.

What is Barium?

Barium is a metal, like calcium. You never find it in its metal form (outside of a lab), as it oxidizes rapidly in the air. Instead you’ll find compounds, usually barium sulfate or barium carbonate. Barium compounds are used in the plastics, rubber, electronics and textile industries, in ceramic glazes and enamels, in glass-making, brick-making and paper-making, as a lubricant additive, in pharmaceuticals and cosmetics, in case-hardening of steel and in the oil and gas industry as a wetting agent for drilling mud. Barium in water comes primarily from natural sources as it is present as a trace element in both igneous and sedimentary rocks. Barium is generally present in air in particulate form as a result of industrial emissions, particularly from combustion of coal and diesel oil and waste incineration.

µ and Parts Per …

When you measure the concentration of a substance in water, you can express it in various ways. You have to pay attention to units when converting from one way to another.

A liter of water weighs 1 kilogram, which is 1000 grams.

A milligram is 1/1000th (a thousandth) of a gram. 1mg = 1 milligram = 0.001g

A microgram is 1/1000000 (a millionth) of a gram. 1ug = 1µg = 1 microgram

Note that last line, because it’s important. The symbol µ is the greek letter “mu”. In measuring, it’s used to mean “micro”, or “millionth”. (To type µ, hold down the Alt key, type 230 on the numeric keypad, and then release the Alt key). Since it’s difficult to type, it’s often written using the letter “u”. Make sure you understand the difference between a milligram (mg, 1/1000th or a gram) and a microgram (µg, ug, 1/1000000th of a gram). A milligram is thousandth, not a millionth. It’s a little confusing sometimes.

A microgram is a millionth of a gram, so it’s a billionth of a kilogram. Since there are 1000 grams in a kilogram, and 1,000,000 micrograms in a gram, there are 1,000,000,000 µg in a kilogram. All this is basic high school science.

Concentration in water is measured as ppm, ppb, g/L, mg/L, µg/L. These are parts per million, parts per billion, grams per liter, milligrams per liter and micrograms per liter. We can convert between these easily:
1 ppm = 1 mg/L = 1000 ppb = 1000 µg/L
1 ppb = 1 µg/L = 0.001 ppm = 0.001 mg/L
(remember that 1 Liter is 1000 grams, so 1 mg in one liter is a thousandth of a gram in one thousand grams, or 1 part in a million).

Chemtrail claims

This video is very popular right now. Claiming that water was analyzed and found to have barium in it.

http://www.youtube.com/watch?v=okB-489l6MI

The video was taken in Stamps, Arkansas, which is not entirely surprising as that’s in a region of the US the might be renamed “Contrail Alley”. It’s at the intersection of the cross country routes between the West Coast, and the major airport in Atlanta, Orlando and Jacksonville. Stamps is midway between the two major regional VORs (Texarkana and El Dorado), right next to the major East-West airway Victor V278, and on the edge of a MOA that traffic has to skirt occasionally. It’s also directly below the Atlanta to Dallas, San Antonio to New York and Houston to Chicago flight routes. On just ONE of these routes (Atlanta to Dallas) there is a scheduled commuter flight, directly overhead, at contrail altitude every 15 minutes! The same frequency of flights is found on the Houston-Chicago route, which crosses at right angles almost exactly overhead. Hence, when the weather is right, it is inevitable that you will see contrails in a grid pattern, “a giant checkerboard”. See this Google Earth file: airlines-over-stamps.kmz

But back to the video. It shows a jar of dirty water (collected 9/1/2007), which was collected by Bill Nichols. He’s posted some comments on the YouTube video describing how he collected the water:

it was rainwater. i collected it in two separate bowls on the hood of a pickup truck in my backyard. we are 25 miles from the nearest interstate. this is a very poor county, the only industry is chickens, logging , farming, a little oil—no coal burners or anything like that. i wasn’t looking for attention. i was looking for answers, ksla said they would pay to get it tested. i dropped it off, and they asked my opinion

i put 2 clean bowls there specifically because i wanted to catch what was falling. i don’t recall exactly when i put the bowls there, but they were there for about a month before i contacted ksla. the goo that i caught was full of barium. have a cool day!

Pause for a second, and consider if you left a bowl out for the month of August in rural Arkansas, what would you expect to find in it after a month? Some dirty water? Perhaps a little dust? What’s dust made of outdoor? Dirt, dried topsoil. What would you expect to find in the dirt in Arkansas – one of the richest sources of barium in the US? You’d expect a bit of Barium – but did they actually find any more than you’d get in tap water?

This dirty water was tested, the test results are available in full here. You can also see the results in the video, at around 00:55 to 00:59. Here they are pieced together.

And just to be clear, here’s a closeup of the results, and the units:

That’s quite straightforward right? Barium found at 68.8 µg/L. That’s 68.8 parts per billion. Now listen to the audio at that precise point (also transcribed on the KSLA web site):

“The results: a high level of barium, 6.8 parts per million (ppm), more than three times the toxic level set by the EPA”.

Immediately you can see something is wrong here. it’s 68.8, not 6.8, and it’s not parts per million, it’s parts per billion. So it’s actually 0.0688 parts per million.

And what of “three times the toxic level set by the EPA”? They are referring to the EPA Limits, as quoted by the CDC:

“The EPA has set a limit of 2.0 milligrams of barium per liter of drinking water (2.0 mg/L), which is the same as 2 ppm [parts per million].”

So the EPA limit is 2 ppm (2000 µg/L), and the tests actually found 0.0688 ppm (68.8 µg/L), just 3.4% of the allowable limit.

That limit’s not really a “toxic level” either. There’s no evidence that it would be toxic even at that level (which, remember, is 29 times higher than what was actually found). The world health organization has set a drinking water level of 7 ppm after doing studies into the health effects of barium.

Barium has always been in water

The WHO also reported on the barium levels in drinking water (meaning, from a tap, not some dirty puddle) and they found:

“In a study of water supplies of cities in the USA, a median value of 43 μg/litre was reported; in 94% of all determinations, the concentrations found were below 100µg/litre (IPCS, 1990)“

So the average was 43 µg/L, but most were below 100µg/L. This means the amount of Barium found in this supposed chemtrail residue was about the same as was found in the municipal water supplies in the US, back in 1990. This is pretty low, it varies with geography based on the type of rocks in the aquifer. In Tuscany, Italy, the Barium in drinking water was around 1000µg/L (1ppm), high, but still within safe limits.

The amount of barium will also vary based on the weather. Very heavy rains will leach more barium out into the groundwater. So you’d expect more barium after very rainy seasons. This is actually what you find if you look at the historical records in California (which has very uneven annual rainfall). You see spikes in barium whenever there is a wet year after a dry year. Recent years like these are 1991, 1995, 1998 and 2004 (2001 and 2003 also spiked to a lesser extent). The expected peaks were confirmed by the results of Rosalind Peterson at California Skywatch.

So what’s going on here? Chemtrail theorists are constantly claiming that “chemtrails” are made of barium, and that it’s affecting our health. But whenever water is tested, it is found to have perfectly normal levels of barium, which vary as expected based on the rainfall. In the cases where they claim it’s got an unusual amount, this is just a misunderstanding of the units and limits involved.

Yes, there is barium in the drinking water, there always has been, and always will be. Trace amounts, mostly from the environment and some industrial pollution. It’s a very small amount, and not dangerous. There is no evidence to suggest it has anything to do with “chemtrails.”

Update #1: 5/2/2009

Jeff Ferrall, the reporter in the story now says:

http://contrailscience.com/barium-chemtrails/comment-page-8/#comment-23164

Yes, I did make corrections to my first report, which originally aired almost 2-years ago now… after quickly realizing my very embarrassing mistake. I was not happy with myself. Unfortunately, the first version of my report got out to the internet before I could make the correction(s), and the wrong version is shown repeatedly.
…
My feeling is, and maybe you’d agree, that if such aerosol mixes were created and loaded into jets with either a separate/independent dispersal method other than the exhaust, or actually in the fuel itself… somewhere, somehow, you’d expect someone to talk. I have not heard that yet.
…
I also interviewed the scientist who originally patented what some believe was a precursor to so-called chemtrail technology. He’s a very kind, helpful man who could not have been more helpful. He says he knows nothing about any such conspiracy.

There’s also a mention of this story In Skeptical Enquirer magazine:
http://www.csicop.org/si/show/curious_contrails_death_from_the_sky/

Update#2: 3/14/2010

More people make the same mistake.  This time someone in Austrailia, and the story was picked up by a Los Angeles environmentalist.   Again mg is confused with µg, making the results 1000 times as high:

http://www.examiner.com/x-10438-Human-Rights-Examiner~y2010m3d13-video-White-Clouds-of-Death-Aussie-exposes-geoengineered-chemtrail-contents?#comments

Some of them are very insistent that this is a practically constant assault, saying the sky is never blue any more, and there are “chemtrails” constantly criss-crossing the sky.

I think this is simply a case of observer bias.

It’s easy to amass a large collection of photos of persistent contrails. I’ve got a lot myself, and I live in Los Angeles, where we don’t really get very many days when the conditions are right. All you have to do is only take photos on days when there are contrails persisting, and it will seem like there are “chemtrails” every day.

To get a real picture of what is going on, you need to take photos every day, and then see how many have persistent contrails in them. To be really accurate, you should take photos all across the country, and even across the globe, and see how many have contrails in them. What we need is a huge database of photos of the sky taken at random places and times.

Luckily, with the advent of digital photography, we have several such databases in the form of Flickr.com and picasaweb.google.com, and several other sites, which contain millions of photos that have at least some sky in them.

How many contain contrails (persistent or otherwise?) well, it turns out that practically none of them do.

Of course if you search for “contrail” or “chemtrail”, you’ll find a bunch. But that’s just you selecting them. How do we get random photos of the sky?

A good way it to search for things where the photographer is looking up. Like, “skyscraper“, “radio tower“, “kites“, or “skyline“. This gives you a very nice random sampling of millions of photos of the sky in all different weather condition, in all different locations, over the past decade or so. Some of these tend to have a narrow field of view, which you can expand with the keyword “fisheye”, like “fisheye sky“.

And what do we find? ALMOST NO CONTRAILS!!! I had to look at hundreds of photos before I finally found ONE that had a contrail in it. Even more rare was finding a photo with several persisting contrails, and I never found one with anything like a “grid”.

Several things can be deduced from this. Firstly contrails are actually pretty rare across the country. Of course this depends on where you live, but basically on average, there are not that many visible contrails in the sky.

Secondly, there’s still lots of clear blue sky and fluffy white clouds. All kinds of skies actually. Nothing has changed.

Thirdly, “chemtrail” theorists often say “why are there no photo of contrails before 1999/1990/1980/whenever”, seeing as they can’t find any in their family photo albums. The answer is of course that there ARE photos of contrails, all through the history of aviation. You don’t see them in the old photo albums for the same reason you don’t see them on Flickr.