Missing the obvious #2 - Why are short haul flights bad for the environment?

Flying short haul is THE most carbon intensive way to travel per mile (with the possible exception of flying to space). Long haul flights are more efficient per mile but they are also pretty bad for the planet because they make it easy to travel thousands of miles at once, offsetting their greater 'per mile' efficiency.

Why is short haul worse? It's obvious but hadn't sunk in to my thick skull. When you are flying, the efficient part of the journey is when the aircraft has reached cruising altitude. This is like sitting at 56mph on the motorway in your car. The inefficient part of the journey is when the aircraft is sitting at the traffic lights, well, taxiing on the runway. Even more inefficient is the part of the flight which is like accelerating hard in your car - climbing to altitude. For a short flight, a greater proportion of the energy used is in taxiing and climbing so the overall per mile efficiencies become very poor.

Environmentalists often argue about whether one thing is better than another. For example, there is a lot of noise about Biofuels and people on different sides of the arguement. However, with short haul flights environmentalists are clear. Don't take short haul flights! I think they are so clear about this because they can see that there are good alternatives available to taking short haul flights that are much more efficient and often not much slower at all, like the train, especially the nuclear powered and ultra fast TGV in France.