Date published: 2006/06/15
The BBC says:
Night flights by aircraft are much more damaging to the environment than air travel during the day, a study shows.
The reason, says a UK team, is that vapour trails from aircraft have a greater warming effect during darkness.
Writing in the journal Nature, they say cutting night flights could help minimise the climate impact of the aviation industry.
Winter flights have a bigger effect on global warming than flights during the rest of the year, they add.
The warming effect is due to condensation trails (contrails) created by aircraft. They have two opposing influences on the climate; warming from trapping heat leaving the Earth like a blanket, and cooling from reflecting sunlight back into space.
Although these two factors are balanced out during daylight to a certain extent, on average the warming (greenhouse) effect slightly exceeds the cooling effect, contributing a small amount to global warming as a whole.
However, at night the cooling effect does not apply, producing a bigger contribution to global warming.
"During the night-time, we don't have the Sun out and so the greenhouse warming effect is no longer balanced," said principal researcher Nicola Stuber of the University of Reading.
"That's the reason why night-time flights have such a large contribution to the daily warming effect."
Take this with a pinch of salt. It's only one study and based on results from one location, and with a small effect. Most night flights are not there for frivolous reasons but because they make sense from a time point of view (e.g. most flights from North America to Europe).
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