The Coastal Post - April, 1997

Aircraft Are Screwing Up The Atmosphere?

By Jim Scanlon

Exhaust gases from sub sonic jet aircraft are affecting the ozone layer and cloud cover over the Northern Hemisphere right now, today, every minute of every day as several hundred heavy jets fly back and forth through the North Atlantic Flight Corridor and over the United States. With commercial air travel expected to increase 200 percent over the next twenty years, the impact of jet engines on the earth's climate and the amount of ultra-violet radiation reaching the surface, will grow accordingly.

The Conference

From March 10 through March 14, I attended the eight annual NASA conference on "The Atmospheric Effects of Aviation" held in Virginia Beach, Virginia. I believe I was the only journalist among the 278 official participants who spent four and half days listening to one 20 minute presentation after another on the latest scientific research in atmospheric chemistry, meteorology, airborne field studies and computer


The conference was highly structured , highly technical, isolated and removed from reality- somewhat like jet travel itself. The participants were mostly handsome, extremely bright , highly intelligent young men and women, mostly casually dressed. American researchers predominated with Germans next, followed by a smattering of Russians and other Europeans.

There were no clear expressions of concern for the dangers involved in the exponential growth of the aviation industry-somewhat similar to the way air travelers do not show their fear and unease when traveling by plane. It seemed as if these wonderful scientists were chatting amiably about interesting aspects of a remote, unstoppable, unreformable juggernaut.

There were no members of the print or broadcast media present at this year's conference and, as far as I could tell, none were present at any of the seven previous conferences.

There was no mention of these conferences in the newspaper of record, the New York Times, Time or Newsweek, or in "Science" or "Nature" the two most prominent scientific magazines in the world.

"New Scientist", a well known British science news magazine published articles on the atmospheric effect of aircraft (contrails), but was unaware of this, and previous NASA conferences. I am in contact with the editor and a collaborative report of the latest conference should be forthcoming.

Is This a Secret?

One might reasonably ask if these conferences are secret, and the answer is no. However, if something is not actively advertised, does not appear in print of on the tube, it does not exist!

Two years ago I saw a small notice in a list of conferences in "Eos," the "trade": paper of the American Geophysical Union. My e-mailed questions to the coordinator were answered quickly and satisfactorily. I asked for the press kit, and was told there was none. It surprised me that NASA would do anything without a press release.

When I got the agenda I was further astounded that the presence of so many internationally prominent scientists attending a week long conference on such highly interesting and provocative topics had not been reported anywhere. The news of a plane crash involving a few dozen passengers is instantly flashed to millions of uninvolved people world wide, but thousands of airplanes directly affecting millions of people does not seem to merit a word.

Normally the scientific articles one reads in the newspaper are produced from press releases sent to newspapers which are usually printed as received, although large newspapers may rewrite and expand them. So, it seems that all anyone has to do to keep a subject quiet is not to pamper and spoon feed the print and broadcast media. Not that I blame any researcher dependent on grant funding lasting from one to three years.

Another Surprise

Surprisingly, S. Fred Singer, a prominent "ozone skeptic" (often quoted by Rush Limbaugh dittoheads) presented a paper arguing that the steady increase in air traffic over the last twenty years might be responsible for the nighttime warming occurring across North America.

Singer presented a study by another scientist of satellite measurements of atmospheric temperatures over the past 18 years showing an overall small negative trend-with the exception of the United States which shows a warming of .3 degrees C per decade. This warming occurs at similar latitudes where continuous growth in commercial air traffic is occurring. These flights burn millions of tons of fuel directly in the "clean" areas of the upper troposphere and lower stratosphere.

High altitude cirrus clouds are produced by contrails from air traffic, just how many is the problem.These clouds reflect heat up or down and can cool and warm depending on their thickness. Adding up the pluses and minus, aircraft induced clouds were estimated to have warmed the atmosphere significantly, mostly during the night time hours.

Singer presented Satellite and balloon data showing an acceleration of the warming during the last ten years. He also used data showing a decrease in the daily extremes of temperatures to support his contention that aviation was affecting regional, and possibly global climate.

A study using direct measurements of cirrus clouds over Salt Lake city showed an increase in such clouds in step with aircraft fuel consumption. This could be a result of the large amount of water vapor (a potent greenhouse gas) produced by jet engines and injected into the narrow layer at an altitude of 10-11 kilometers. For every kilogram of fuel burned about one and a half kilos of water vapor is produced.

Another study by the Langley Research Center using ground based observations by the US Air Force, reported contrails occurring most often during mid morning hours in winter near major commercial air traffic corridors. A strong correlation was found between contrail frequency and fuel usage above 7 km.

Measurements by German scientists from aircraft found layers of soot in seemingly natural cirrus clouds suggesting that it might be incorrect to call such clouds "natural". One scientist said that one might reasonably conclude that cloud cover over Germany had increased by as much as 10 percent.

Other German scientists processed archived cloud data from US satellites which showed a composite image of contrails criss crossing most of Europe-with the exception of Bosnia Herzgovina which showed clear, since little commercial air traffic went there. Although Singer acknowledged uncertainties, he argued that satellite and direct measurements supported his theory. "If this is true" he said, "then the climate scenario calculated for a warming based on a doubling of carbon dioxide will be reduced and also the future climate warming".

In other words all disaster scenarios based on global warming from carbon dioxide must be speeded up- since air traffic is increasing so rapidly.

There was some discussion on whether the impact of aircraft induced cloudiness from contrails would warm or cool the atmosphere. It seems to me that it doesn't really matter which way it goes-positive or negative since change is change-and either way, the climate will change.

European environmentalists seem more aware of and concerned about the environmental effects of aviation than their American counterparts, which is surprising, considering the furor in the states in the 1970s over the proposed development of a US supersonic civil transport and it's impact on the ozone layer. Several papers were presented assessing the impact of a future fleet of 500 or 1000 supersonic aircraft.

Is The Aircraft Industry Threatened?

Air travel accounts for about ten percent of the world's modern transportation industry, with millions of people paying huge amounts of money to travel billions and billions of kilometers for one reason or another. In the US, aircraft manufacturing ranks seventh in dollar value of exports and it employs thousands of people, directly and indirectly, in high skill, high paying jobs.

According to Boeing, air travel is expected to increase by 70% over the next ten years and 180% over the next twenty. Air travel allows large under developed countries to leap into a modern transportation system without having to build expensive roads, bridges, ports etc. And, if their market is big enough, like China's, they can participate in manufacturing and acquire advanced technology.

Boeing and Airbus Industries are the two remaining gigantic corporations competing ferociously for the trillion dollar aircraft market expected to develop over the next 20 years. More than 13,500 heavy jets are expected to be built, dwarfing the size of the fleet now in service. With the cost of these jets ranging from $32 to $171 million and intense competition, there appears to be little incentive to consider environmental mitigation (if that is the right word).

Is the Stratosphere Threatened?

Air travel today mostly involves sub sonic jet aircraft cruising at 9-13 kilometers in the upper troposphere.(which we blithely fly through in our pressurized capsule watching bad movies, drinking sodas and eating peanuts) Some heavily traveled air routes, like the North Atlantic Flight Corridor take sub sonic jets into the stratosphere 44 percent of the time. What goes into the troposphere stays there, at most a few weeks. What goes into the stratosphere can stay months or years. And now the latest generation of two motored heavy jets are expected to fly 2 kilometers higher, cruising more often in the stratosphere where emissions will destroy more ozone.

The exhausts from internal combustion engines in our cities and on our freeways and airport runways produce acids and ozone and eventually smog. What happens high in the atmosphere is more complicated and hard to observe directly. For example, oxides of nitrogen react with and destroy ozone in the stratosphere when exposed to ultraviolet radiation from the sun. These oxides are deactivated at night, but, during summer months at high latitudes, the sun hardly sets, so ozone destruction continues as long as there is light. Flying in the stratosphere these exhaust gases destroy ozone. Flying in the troposphere they produce ozone, a heat trapping gas in the "wrong" place.

When aircraft burn fuel they expel exhausts at high temperatures directly into the turbulent wake of the plane. Complex chemical reactions occur within this turbulent region producing soot, carbon monoxide, water, three kinds of nitric acid and sulfuric acid. These emissions form surfaces on which destructive chemical reactions can occur.

If it is cold enough, and there is enough water vapor in the background, contrails will form consisting of instant acid ice clouds, which may disappear or linger. The concern is that some may linger long enough to produce a high altitude haze indistinguishable from "natural" clouds and these will warm the air and earth below.

Although the soot, water and gases released may appear to be small in comparison to the area in which they are released a small effect can be magnified if converted into, say a hazy layer. Although soot accounts for only 1 percent of emissions, that comes to 16 million metric tons if one takes the British Airways figure of 144 million metric tons as the amount of fuel burned by the industry each year. That comes to about 3 percent of fossil fuel burned each year-which may not seem much-but it it burned where it produces the maximum effect.


Aircraft emissions are significantly affecting our atmosphere now and will continue to grow. The full extent is not known, especially considering that emissions from military aircraft and rocket launchings are not included. With sub sonic jets flying higher in the stratosphere there is little need to distinguish between sub sonic and super sonic jets. Aside from eliminating sulfur from jet fuel, reducing or even slowing aircraft emissions, will be difficult if not impossible.