Climate Change Caused By Commercial Airliners?

[Ivan Seeking]

Those wispy streams of vapor that follow jetliners across the sky may not be as innocuous as they appear.

A new NASA study claims man-made cirrus clouds formed by commercial jet engine exhaust may be responsible for the increased surface temperatures detected in the United States between 1975 and 1994.

Climate data shows there has been a 1 percent per decade increase in cirrus cloud cover over the United States, which the NASA paper says is likely due to commercial air traffic.

Cirrus clouds, whether natural or artificial, play an important climatological role because they trap heat in the atmosphere by reflecting infrared radiation emitted from the Earth's surface.

The study, which appeared in the April 15 issue of the Journal of Climate, estimates that cirrus clouds from jet engine condensation trails, or contrails, increased the temperature of the lower atmosphere by anywhere from 0.36 to 0.54 degrees Fahrenheit per decade. These findings tend to agree with National Weather Service data that shows temperatures at the surface and lower atmosphere rising by almost 0.5 degrees per decade between 1975 and 1994. [continued]

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[Andre]

The probable warming curve could match the increase of airliner activity and there are studies argueing that high clouds tend to have a warming effect. And the areas that experienced the most warming (Northern hemisphere contiments, especially Europe) also have the greatest density of airline traffic. Moreover, the water vapor brought in at higher levels is just about the strongest nmatural greenhouse gas. However satelite observation show a cooling trend at higher altitudes, attributed to the thinning of the ozone layer.

Other possible causes that are seldomly mentioned:
- Direct absorption of energy in the lower atmosphere by soot and haze
- decreasing albedo (reflectivity) of the Earth surface due to reforrestation and urbanisation
- abnormal oceanic behaviour (increasing strong el ninos) enhanced THC, etc
- abnormal weather flow patterns, increasing the equator to polar circulation, effectively transporting more tropical heat to the moderate areas.