April 24, 2010

Flight Bans, Volcanoes And Our Climate

Iceland's volcanic eruption, which grounded air traffic for days, may provide rare clues as to how flights encourage climate change, adding to evidence from a ban on US flights after the World Trade Center attacks on September 11, 2001, according to a recent Reuters report.

How jet fuel being burned at high altitudes affects climate is poorly understood, largely because scientists cannot often compare plane-free skies with the everyday air traffic that clutters many regions.

Not since 2001 have scientists had a chance to study plane-free skies in a wide region to see what effects the lack of planes may have on the atmosphere. Also, they hope to find if the empty skies will yield a sun-dimming effect from Iceland's volcanic cloud.

David Travis, of the University of Wisconsin-Whitewater, told Reuters that the presence of volcanic ash makes it more challenging to analyze the event. Travis, who found that an absence of vapor trails influenced US temperatures after the September 11 attacks, told Reuters that it could be possible to study areas in Europe where ash was minimal and flights were canceled as a precaution, but it still may be a challenge to measure.

Aviation could be a topic in any UN climate deal if any progress is made in finding what impact flights have on the atmosphere. Currently, international flights are exempt from emissions bans under the UN Kyoto Protocol for combating climate change until 2012.

If emissions becomes a big deal in aviation, it could push up ticket prices for flights dramatically. In 2007, European flights generated 205 million US tons of carbon dioxide in 2007, according to the European Environment Agency.

It is estimated by many scale models that aviation accounts for 2 to 3 percent of global warming from human activities.

In Travis's 2002 study, he found that an absence of vapor trails from flights during the September 11 - 14, 2001 shutdown of commercial air traffic led to bigger swings in daily temperatures. The finding was evidence that jets can affect temperatures, but it doesn't conclude that the contrails boosted climate change or not.

Climate experts working with the UN believe that aviation is damaging the climate and that non-carbon -- such as nitrogen oxides or soot -- factors may have a greater affect on the climate than carbon dioxide alone.

High clouds -- which includes contrails -- tend to trap heat, preventing it escaping from the thin atmosphere. In sharp contrast, lower clouds usually dampen climate change since their white tops do a better job reflecting sunlight.


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