Contrails - Research, comments and links

Contrails and Aviation-induced Cirrus Clouds

Stratospheric Ozone Depletion (01)

Stratospheric ozone depletion exacerbated by the almost continuous injection of aircraft emissions into the atmosphere at near-tropopause level

Dear Mr. VanWaning,

Thank you for your reply. I'm very happy to hear from you.

I would like to send you an account of what I think in regard to the cumulative effects of aviation emissions and will try to write up a little something over the next week or so. At the moment, I am looking specifically at the effect of aircraft exhaust on the stratospheric ozone layer.

As you undoubtedly know, the water vapor and particulate matter [soot] from the aircraft emissions are providing the conditions for facilitation of cloud-formation in the lower stratosphere where it would normally be too dry, among other things, for cloud-formation to occur. The research community is reporting an increase in the incidence of polar stratospheric clouds specifically - and it is upon the surface of these emissions-facilitated clouds that the chemical interactions, involving ambient chlorine and bromine, take place and destroy stratospheric ozone.

I have felt for years that our biggest problem, among many, is the problem of stratospheric ozone depletion - and that this is being exacerbated by the almost continuous injection of aircraft emissions into the atmosphere at near-tropopause level. Most people think ozone depletion has taken place only in the southern hemisphere and that it's not going to be a major concern in the northern hemisphere. Not true. The northern hemisphere's problem is just beginning - and is accelerating rather quickly since this last 12-18 months. The Europeans are, in my observation, much more aware of this reality than are most people in the United States and Canada.

What I'm writing here does not begin to convey the depth of my concern - or what I have learned - regarding the effects of aviation emissions on our atmospheric systems, the ramifications of which will also affect our marine and terrestrial systems.

I definitely want to stay in touch with you and will check in and maybe send a few links over the next couple of weeks as time allows.


Those Obnoxious NOx Emissions

Ozone production and the recent thinning of the ozone layer are other environmental concerns that have been reported on throughout the world. What are they and why are they important? High concentrations of ozone near the surface of the Earth has been linked to respiratory diseases. But there is beneficial ozone. Ozone in the upper atmosphere (about 15 miles up) shields the surface of the Earth from the Sun's ultraviolet radiation. Increasing occurrences of skin cancer are being attributed to the thinning of this protective ozone layer.

Ozone in the upper atmosphere�the ozone layer�is both increased and destroyed by ultraviolet radiation. As long as the amount of ozone created equals what is being destroyed, the ozone level remains the same. Although other factors�the seasons, Sun cycles, winds, and volcanic eruptions�affect ozone levels, there is insurmountable evidence that human activities are disrupting the balance.

Oxides of nitrogen (chemically abbreviated as NOx and pronounced "nocks") increase the production of ozone at typical cruise altitudes of subsonic air travel. These emissions are formed as a result of burning fossil fuels at very high temperatures. Therefore, aircraft emissions containing NOx increase the production of ozone. Aircraft emit significant amounts of NOx when their engines are at their hottest during takeoff and slightly smaller amounts while cruising.


Vliegtuigen die sneller vliegen dan het geluid, zoals de Concorde, veroorzaken door de uitstoot van zwaveldeeltjes waarschijnlijk meer schade aan de ozonlaag dan tot nu toe werd aangenomen. Misschien geldt dit voor alle vliegtuigen die vanaf vijftien kilometer hoogte in de stratosfeer vliegen.  De Amerikaanse onderzoeker D.Fahey heeft vastgesteld dat zwaveldeeltjes in de brandstof na uitstoot uiteindelijk worden omgezet in zwavelzuur. Dit vormt een dichte mist van kleine deeltjes, die (net als stikstof) de ozonlaag aantasten. Wellicht hebben vliegtuigen die op grote hoogte het Noordpoolgebied passeren bijgedragen aan de snelle vermindering van de ozonlaag aldaar.
(Bronnen: Geophysical Research Letters en NRC Handelsblad.)

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