Do you want to do something to help this planet? Stop flying.

[tama]

112. Looked and found this:

We hear much about the environmental costs of air travel. As our recent Q&A explained, the problem is not just that planes burn a lot of fuel and therefore kick out plenty of CO2 per passenger. Just as important are a host of other high-altitude impacts, including vapour trails and ozone production, that are usually estimated to cause as much warming as the CO2 itself.

Hence we often hear that although air travel accounts for only a small fraction of global emissions (relatively few people can afford to fly), one transatlantic flight can add as much to your carbon footprint as a typical year's worth of driving.

Surely it couldn't get any worse, could it? Unfortunately for green-minded air travellers, it just did. Kind of.

The wrinkle, always vaguely understood by climate geeks but finally explored in depth in a recent scientific paper, is that the relative impact of different types of travel depends not just on practical factors such as engine efficiency and occupancy rates, but also on something altogether more abstract: the time frame you care about.

The reason this is so crucial is that the effects of different greenhouse gases play out in the atmosphere at a different speeds. CO2, released by all fuel-burning vehicles, can remain in the air for centuries, causing a gentle warming effect. By contrast, most other gases and impacts – such as the vapour trails and tropospheric ozone produced by planes at altitude – cause much more potent but shorter-lived bursts of warming.

More:
http://www.guardian.co.uk/environment/blog/2010/sep/09/carbon-emissions-planes-shipping