There are apparently other factors to consider with flying. Off the top of my head: greenhouse gases are injected straight into the upper atmosphere, and contrails have a net warming effect (however I've never really understood the difference between a contrail and a cloud - anyone?).
There are apparently other factors to consider with flying. Off the top of my head: greenhouse gases are injected straight into the upper atmosphere, and contrails have a net warming effect (however I've never really understood the difference between a contrail and a cloud - anyone?).