Wednesday, December 23, 2009

Aircraft Emissions Contribute To Global Warming

A Stanford University analysis of emissions from commercial airline flights shows that they are responsible for 4–8% of surface global warming — equivalent to a temperature increase of 0.03–0.06 °C overall. This is the first use of actual emissions data — from 2004 and 2006 — to calculate warming from commercial aircraft flights. There are around 35 million commercial airline flights every year.

Stanford engineer Mark Jacobson, right, presented the analysis on December 17 at the American Geophysical Union's annual meeting in San Francisco, California. Jacobson and his team developed a model for aircraft emissions that accounts for atmospheric composition, cloudiness and the physical properties of emissions, particularly of black carbon — a major part of soot. Jacobson analysis shows that if black-carbon emissions from aircraft could be reduced 20-fold, warming would be halted and a slight cooling would occur from plane-created vapour trails. The team's study is being peer reviewed and is expected to be published soon.

The new analysis reveals that aircraft emissions increased the fraction of cirrus clouds where vapour trails were most abundant, and actually decreased the cirrus fraction in several locations by increasing the temperatures in the lower atmosphere, reducing the relative humidity in such locations.

The European Union is considering levying a carbon tax on aircraft emissions. (Nature News, 12/21/09)

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