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Notes on the Subject of Contrails

The day the sky stood still

by Matt Rasmussen

Published in the September/October 2003 issue of Orion magazine



Photograph by Michael Grinley, used with permission

January 23: Mid-afternoon. A line of cumulus clouds dangles over the hills south of town. Crayon clouds—the kind a child might draw over a bed of tulips. Two contrails slash across the sky, north to south, almost parallel. Their tails are directly above me, wide and smudgy, blue sky soaking through the thin spots. Far to the south, the contrails sharpen to points. Their tips almost touch, like knitting needles ready to tease apart wads of yarn.

I’ve taken to watching contrails this year. I look at them carefully, observing how they drift, how they grow, or how they quickly evaporate into nothing at all. I jot down my observations in a little notebook I keep with me.

My wife, Anne, thinks I’ve gone a bit batty. I point them out to her with excessive relish, perhaps, especially if I’ve spied an unusual specimen. I ask her: Why is it thin here, or thick there? See how it seems to morph into a wispy cloud on its tail end? Can you make out the plane in front of it? Not long ago I pulled off a busy street and leaned my head out the window to get a better look at one. I didn’t care what other people might think. For years, I failed to notice contrails. I took them for granted. Now I’m beginning to appreciate how striking they are, how multifarious of form.

By turns I think contrails beautiful and appalling, just as any human construction can be viewed with admiration or disdain. I’m not sure which perspective is winning me over, now that I’ve stopped to ponder the question.

It takes a good long time to make up your mind about such things. You first have to open yourself to the possibility that something so commonplace, so trivial, could be an object of great interest, something worthy of concerted attention. Something important, even.

To come to conclusions about contrails, you have to look up. Not many people do that these days.

February 7: Remarkably clear this morning, breezy and crisp. All afternoon planes course southward, leaving long contrails behind. Far away, where the contrails are almost too faint to see, they seem to take a slight dogleg to the east. It’s as if the planes are following the Pacific coastline, turning left at Cape Mendocino. Could that be? Mendocino is two hundred fifty miles away. How far can you see a contrail on a clear day?

A contrail is not smoke, as I fancied as a child. It’s not even an emission, really, at least not in the true sense of the word. Much of what you see when you look at a contrail is water that was present in the atmosphere before the jet came along. A contrail is a cloud, as surely as a thunderhead boiling up over a prairie on a summer afternoon. A cloud of ice, birthed by the happenstance of a passing jet.

When jet fuel combusts, it forms water as a byproduct. Tiny droplets shoot out in a blast of hot air as the plane soars along, thirty-five thousand feet above the Earth. So do minute particles of oxidized sulfur and nitrogen. What else? Impurities or additives, in minute quantities. Metal particles, soot, that sort of thing. These “minims” give the water vapor already in the air something to cling to. Just as important, though, is the condition of the air through which the jet flies—namely, its temperature and humidity. Contrails don’t always appear behind high-flying jets. In fact, they usually don’t. They form about a third of the time, on average.

Humidity and temperature: The forces that create a contrail are quite similar to the forces that make your breath visible on a cold, damp day.

Shoot a plume of hot air laden with tiny particles into the upper atmosphere, where the temperature is, say, sixty below zero and the humidity is somewhat high. The air is suddenly unable to hold its water. Vapor condenses and clings to the matter in the jet’s plume. The air soon mixes and cools and the particles of water freeze. A contrail is born.

What happens next also depends on atmospheric conditions. If the air is just barely humid enough and cold enough to allow water vapor to condense, a contrail appears but doesn’t stick around. From the ground, you see the gleam of the jet and a short contrail that melts almost as quickly as it appears. The plane looks like a comet chased by a squattish tail.
If the air is sufficiently frigid and humid, a contrail forms easily, stretching out leisurely over the heavens, coaxing tiny ice crystals out of the atmosphere. Chances are on days like these (especially if you live under a busy flight path, as I do in Eugene, Oregon), the sky will be marred—or graced, it all depends on how you look at it—with the cicatrices of contrails, roughly parallel, varying in density and width. On days like these, a contrail can persist long after the jet has passed. The contrail splays out and takes the appearance of a flattened snakeskin.

A perfectly apt name for contrails is “faux cirrus.” Cirrus, as you may know, are those high, feathery clouds that sailors believe augur foul weather. (There’s a certain logic to that—cirrus, and contrails, tend to form on the front edges of jet streams and cyclonic masses, which often usher in storm fronts.) There are differences in the composition of contrails and cirrus, but they are minute.

If the conditions are just right, a sort of critical mass is achieved. The contrail grows and grows, fattening out, sweeping upward and outward. Watch from the ground, patiently, and you’ll see a contrail transmogrify into a cirrus cloud, indistinguishable from the real thing. A cloud where there was none before.

April 3: A contrail forms a dashed line north to south, broken in three places. The segments have drifted with the wind at slightly different rates. They don’t quite line up. On both sides of the second segment, cirrus clouds hang in frozen swirls, milky brush strokes against the blue. There are currents up there, currents that allow contrails and cirrus to form here but not there. Something akin to ocean currents pushing masses of warm water into cold seas.

My dad says he first saw a contrail in 1947. He was walking with friends down a street in St. Louis. That was forty-four years after the Wright Brothers’ flight, twenty years after the Spirit of St. Louis touched down in Paris. My dad was eleven then. I asked him about it earlier this year and he recalled a streak of pure white and a low rumble. A tiny plane atop the expanding line. I imagine my father and his chums standing there, a bit slack-jawed. Crewcuts, white t-shirts and denim pants with the cuffs rolled up to show plenty of sock. Chins up. Squinting. They knew this must be a jet airplane—they’d read about jets and had even seen images of them in magazines and on newsreels. They stood there until the plane was gone, until the clang of a streetcar out-decibled the fading jet, until the odd white line had slipped back into the ether.

When I was a kid I had a dog named Babe. We adopted her when she was a tiny pup, plucked her out of a soggy cardboard box in front of a grocery store. The owner claimed she was part coyote. She was deathly afraid of contrails. We lived in the country, in a house with a big, open back yard. Babe helped me nurture a successful high school baseball career. My dad pitched tennis balls and I peppered the back yard with line drives. When I hit the ball, Babe broke into a dead sprint, snared the ball in her mouth, and proudly carried it back to my dad. Then she resumed her position (shortstop usually), and waited expectantly for another one, tongue hanging low. She loved playing ball, but she never forgot to look for contrails. She glanced up with worried brown eyes every ten seconds or so. If she saw one, she dropped the ball straight away and slunk with her tail between her legs under the deck of our house. Game over.

I don’t know if Babe really was part coyote, but she surely had a streak of wildness. Something in her knew what the sky was supposed to look like.

May 5: Six in one view. A crisp, fresh contrail is forming right above me, stretching rapidly to the south, the probing point of another visible still farther to the south. An older, wider contrail trending slightly to the west crosses them both. An even fainter one behind me, to the west. Farther to the east are two more, parallel to the others but formed by north-flying jets. The airspace over Eugene seems to carry southbound planes, the airspace to the east, the northbound planes. Traffic lanes for jets.

A few people spend a lot of time thinking about contrails. Generals, for instance. Contrails are a pain in the ass to the Pentagon. For sixty years wartime pilots have lamented that having a contrail form behind your plane is like being followed by a gigantic finger. Or by a neon sign: “Here I am. Shoot me.” During World War II allied bombers flew in fear of leaving contrails. Likewise, during the Cold War, contrails were bane to pilots on super-secret reconnaissance missions over the Soviet Union.

The Pentagon has committed untold hours trying to develop a reliable method to forecast when and where a plane flying at a certain altitude will produce a contrail.

A fellow named Herbert Appleman developed a formula in 1953 designed to do just that. But it was complicated and fraught with uncertainties. You needed to know the temperature of the air through which a jet was going to fly, the relative humidity, the atmospheric pressure. And you needed to know the temperature and water content of the plane’s exhaust plume. Appleman’s algorithm, as it became known to the Air Force Weather Agency, successfully predicted contrail formation about a quarter of the time—a rather dismal success rate, it would seem, if you’re a pilot in hostile airspace. More important, though, the method was ninety-eight percent successful in predicting when a jet would not create a contrail.

The contrail problem is rather self-evident when it comes to the air force’s B-2 stealth bomber program. I should pause here to point out that the U.S. military establishment doesn’t like to talk about the stealth program. So my information is a bit shaky. What’s clear, though, is if a stealth bomber leaves a contrail, the air force’s prized secret weapon becomes just another readily visible, albeit striking, high-altitude bomber.

This much is known: the air force has grappled with the contrail problem from the outset of the B-2 program. Early on, technicians developed a chemical that could be added to a jet’s exhaust and somehow managed to prevent contrails from forming. The stuff, alas, was too caustic—apparently it ate through the metal of the containers that held it. More tests were conducted and someone came up with a winner. In 1994 the government awarded a $16 million contract to the Northrop Corporation to fine-tune stealth bombers in a number of ways. One retrofit involved the installation of five “contrail management systems.” How do those work? Beats the hell out of me. Ask the air force and you’ll get a terse “no comment” along with a citation of national security issues.

July 12: Five p.m., watching a truncated contrail chase a jet southward as I lie flat on my back. Third day in a row near ninety degrees. A half-dozen swallows (or are they swifts?) pinwheel high above, rushing back and forth across the fresh white line. A point of perfect red drifts languidly above the birds, crosses the contrail. A balloon, liberated from a car lot or a child’s hand.

It doesn’t really matter what you take interest in, as long as you take the time to be truly interested in something. The learning, the close observation—those are their own rewards.

I look up more carefully now. I can tell when the farmers out in the valley are discing their fields because the sky turns ever so slightly brown. I notice when the atmosphere begins to curdle at the end of a sultry day, little proto-thunderheads popping out like a rash. I appreciate the determination of cottonwood trees, how they fill the air with frizzy seedheads lofted over my house, some drifting gamely on to other places, some easing themselves down into my own back yard, where they are snared by blades of grass.

July 23: The sky has been clear for days, the lawn is going stiff and brown. No contrails today. This morning I sat out on the deck and looked hard at the sky, wondering if all jets had forsaken the airspace above the Willamette Valley. At last I saw a sliver of metal—way, way up, a jet cruising north to south. It sailed along cleanly and silently, as if it had ventured so high, so fast, it had somehow achieved orbit. I looked hard for ten minutes and counted three others.

Contrails have their absurdities. Across the country, a fraternity of suspicious sky watchers look upward with uneasy eyes, a bit like my old dog Babe. Listen to them:

“Yeah, sure, we know about contrails, all that BS about jet exhaust. You believe that crap? You think the government doesn’t know how to keep secrets? Come on, friend, wisen up. All those contrails crisscrossing the continent. Wafting over reservoirs and highways. Settling over farmland. Over cities!

“Let me tell you something. Could those expanding white streaks in the sky be something a little more complicated than ice? Could they, say—just maybe now, hear me out—could they be chemicals of some sort? Chemicals that could brainwash us, could control us, could do God knows what to us!

“Go ahead, look it up. Type the word chemtrails into a search engine. Read and learn, my friend.”

Chemtrails: 18,600 hits on Google. A lunatic fringe of dittoheads, convinced Doom is wafting down on the populace via 747s and DC-10s. A whole subculture of contrail conspiracy freaks. God bless ‘em, at least they’re looking up.

August 19: A cirrus circus. Once again, they seem to congregate in loose bands trending east and west, as if they can only form within certain currents. I saw a contrail earlier in the afternoon, but there are none now. At least I think there are none—possibly some of this cirrus began as contrails.

If you were a lawyer charged with prosecuting the perps of global climate change, you could put together a pretty strong case against contrails.

Consider, if you will:

Exhibit A. The world is cloudier than it was a few decades ago—as much as five percent cloudier over the United States and Europe.

Exhibit B. The increased cloud cover has coincided with the advent of jet travel.

Exhibit C. The places that have grown cloudier are the same places that accommodate the most passenger jets. One study found increased cloud cover at stations beneath major jet lanes in the Midwest and Northeast, but not at stations beyond.

Exhibit D. Cirrus clouds account for the bulk of the additional cloudiness.

Exhibit E. Contrails, like cirrus clouds, require the presence of minute particles to give ice crystals something to attach to. A 1996 study found that more than half of such particles detected in the troposphere came from jet engines.

Exhibit F. Cirrus clouds are heat-trappers. They let solar radiation pass through and strike the Earth, but tend to reflect radiation that bounces back from the Earth’s surface and would otherwise return to space.

Prisons full of criminals have been convicted on flimsier evidence. Scientists, though, are more cautious than prosecutors. They want more testimony, more evidence. They point out that we still lack some of the most basic information, such as how many contrails are really up there.

September 12, 2001: I’m shocked, like everybody else. I wonder if anyone I know is among the dead. At the same time I’m thrilled by the sight of a perfect, untouched sky. No contrails, no jets, no planes of any sort. A bit like draining Lake Powell and reveling in the restored redrock canyon. Untilling the Great Plains and seeing tallgrass and buffalo. Like looking across the Hudson from the reeds of New Jersey, admiring the primal granite and forest of Manhattan.

In the days following the terrorist attacks—late summer in this year of considering contrails—people looked up.

Climatologists in particular. They knew they’d been given a unique opportunity: the chance to see what would happen if you snapped your fingers and halted all airplane traffic over an entire continent for a few days. They gathered weather data collected during the hiatus and compared them with historical records. Their findings seem to bolster the theory of contrails as climate changers. Temperature swings in North America were about two degrees Fahrenheit wider than normal during those days. The anomalies were especially pronounced at locations under busy jet routes.

It wasn’t just the scientists who looked up, though—ordinary people did, too, even those usually too busy with the down-to-earth grit of daily existence to spend much time contemplating the heavens. They looked up with dread, I suppose, that horrible image of a passenger jet slicing low against a New York sky already seared into their consciousness. If they lived in cities, they may have seen a military jet patrolling above. Mainly, though, they saw nothing.

I turned off the television and drove along a country road one evening. Lambent sky stretched out in all directions, over the Willamette Valley, over the foothills, away to the east to meet the crest of the Cascades. I contemplated those dark mountains against the sky. They somehow seemed more imposing than usual—more wild, despite the clearcuts I knew were there, the roads, the reservoirs, the power lines, the ski slopes, the sundry scars of human activity. I’d never before appreciated that it’s the sky that gives shape to the land, that gives definition to everything on it.

All that sky, just as it was a thousand years ago, nothing but birds daring to strike a path across it. The mountains, wild and beautiful for the perfection of that September sky.

Contrails. I think I could do without them.

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This article has been abridged for the web.

MATT RASMUSSEN is a lapsed newspaper reporter and former editor of Forest Magazine. He watches jets fly up and down the West Coast from his home in Eugene, Oregon.

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