Comparing CO2 Emissions and Contrail Formation from Short- and Long-Haul Air Traffic Routes from London Heathrow Airport.

This paper considers the relative climate impacts of long- and short-haul air travel. This is particularly important in the context of changing markets for air travel. New competing aircraft technologies will enhance competition between the hub and spoke model of aircraft operations and that of smaller aircraft operating direct routes for long haul trips. The relative environmental impacts of short and long haul flights is also effected by the substitution of shorter trips by high-speed rail as this may free otherwise constrained airport capacity for additional long haul flights. Previous comparisons have focused on fuel consumption per passenger km, so long haul trips, where a much higher proportion of the journey is in the relatively efficient cruise phase, are more efficient than shorter trips. This study considers the additional role of contrails, believed to be important for the net climate impact of aviation. Short aircraft trips tend not to reach the very high altitudes attained by long haul cruising aircraft and so encounter different atmospheric conditions and have different probabilities of contrail formation. By including consideration of the variability in contrail formation conditions throughout the year, estimates of the linear contrail produced along various aircraft trajectories are obtained. The potential to mitigate contrail impacts by altering the flight schedule is also discussed in the paper.