Contrails and Aviation Smog
The BBC weather forecast for Bolton in the North West of England on Saturday 3rd June 2006 was sunny (uninterrupted sunshine and no cloud), as the weather symbol for Sunday shows. The reality was more like my new symbol for Saturday - the sun partly obscured for most of the day by contrails created by dozens of airline passenger jets flying overhead. This form of atmospheric pollution is a widespread problem and is also known as aviation smog.
For anyone living under busy flight paths in certain parts of the world, a clear blue sky seems a thing of the past. Meteorologists promise blue skies and then jets fly over, changing the weather as their contrails dissipate into cirrus-like steaks of high cloud which fuse into a thin haze that often lasts the whole day. The long term global warming effects of CO2 emissions from air travel are of course well known, but it's surprising there aren't more objections to the immediate visible effects of jet planes overhead.
Aerial graffiti over sunny Manchester
For example, the skies over Manchester, England on the 3rd June 2006 looked like aerial graffiti (view picture gallery). These man-made clouds are caused by the same process through which one sees exhaled breath on a cold damp day. When steam from jet engine exhausts emerges into supersaturated and very cold air (minus 40 Celsius) at altitudes of 30,000 to 40,000 feet it condenses into ice crystals before it can evaporate.
Flying at lower altitude would eliminate contrails but the denser air increases fuel burn, resulting in higher CO2 emission. Other options are cleaner engines that exhaust less sulphur, or for jets to avoid flight paths through atmospheric conditions conducive to contrail formation. Measurements of relative humidity in the atmosphere show that the layer of supersaturated air is often only about 1,500 feet deep and could be avoided if the information was relayed to pilots or obtained from sensors on the aircraft.
Even if air travel had no global warming or chemical pollution effects at all, I would be in favour of higher prices if only to restore the skies to their natural appearance. Strangely, some members of the new Cloud Appreciation Society (whose manifesto refers to clouds as Nature's poetry) seem to be enthusiastic about contrails despite the resultant smog being anything but poetic.
Dear Patrick, thank you for your interest in Contrails and Aviation Smog, and for the excellent pictures you took on June 3rd. I fully agree with your comments.
Since 1995 I have been making pictures of this phenomenon. A selection of these can be seen at http://www.contrails.nl.
The worst part of Contrails is, as you mentioned, their fading into 'a thin haze that often lasts all day'. The result is a sky that no longer is as blue as meteorologists promised it would be… Rather a sort of milky blue.
Contrails and Aviation Smog not only ruin 'cloudless' days, but they also influence the sun's radiation, partly reflecting it back into space, partly absorbing it, partly spreading the rest. It is obvious that Aviation Smog has an effect on quality and quantity of the sun's radiation (including: sunlight) that reaches the surface of Earth. This cannot remain without unwanted consequences.
Aviation Smog also is a major source of condensation nuclei, which in their lifespan lead to more clouds and more (and heavier) rainfall, snow, and hail in some areas, and thus to less rain etc. in other areas.
Aviation Smog is a 'clearly visible public secret' that is generally ignored by meteorologists, politicians and journalists alike, because flying is very popular…
Hello,
I just wanted to make a comment and disagree with the comparison with Chemtrails to the breathing on a cold day for the simple fact that once your breath is gone so is the white fog. These chemtrails not contrails stay all the day long and spread through out the sky! I don't have all the facts about these chemtrails, yet but I just didn't like the comparison as the temperature changed why doesn't the so called cirrus cloud dissipate?