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Originally published June 10 2010

Airplane Contrails Contribute to Global Warming

by M.Thornley

(NaturalNews) The trail of vapor that marks the flight of a jet aircraft across the sky is known as a contrail. Contrails form when hot humid air from jet exhaust mixes with environmental air and low temperature (like the 'cloud' formed when someone exhales when it is cold outside). After 9/11 all aircraft in the USA were grounded for three days. Scientists seized the opportunity during this time to measure day and night temperatures to determine if contrails contributed to global warming. Although a difference in temperature in the absence of aircraft was noted, no one is sure what it means for the future or what steps, if any, should be taken to minimize the effect of contrails on temperature.

Jet contrails or exhaust can dissipate rapidly or spread and linger, depending on the humidity and the presence of wind in the upper troposphere. Contrails can increase cloud cover, especially in heavy air-traffic corridors. Cloud cover changes radiation balance by reducing solar energy reaching the surface, thus resulting in cooling. It can also minimize energy losses, resulting in warming by trapping heat in the Earth's atmosphere, known as the greenhouse effect.

After September 11, 2001, scientists had the rare opportunity to study the effects of contrails on climate when all aircraft in the United States were grounded for three days. Results showed that the difference between day and night temperatures was about 1 degree Celsius higher in the absence of contrails.

Scientist David Travis from the University of Wisconsin-Whitewater published a study widely cited that measured daily temperature range (DTR) in different locations within the three days after 9/11. He found a 2-degree Fahrenheit difference on contrail-free days, supporting the theory that contrails warm the earth by holding gasses in the atmosphere. Travis suggested that contrails may effect regional warming rather than global climate change.

A study done at the United Kingdom's Leeds University suggested it would take many more flights than currently occur for the DTR changes given by Travis' research. NASA's James Hansen agrees, arguing that aircraft CO2 emissions would be a more significant factor in future climate change than contrails.
However, air traffic is due to increase rapidly. What effect this could have on climate is not known.

Contrails could soon be eliminated as possible solutions are discussed. One idea is to use a powerful microwave beam aligned behind aircraft engines to prevent the formation of ice particles by remotely heating them and using soot in the exhaust plume.

About the author

M. Thornley enjoys walking, writing and pursuing a raw vegan diet and lifestyle.

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