An inter-comparison of the climate impact of short-, medium-, and long-range aircraft

Abstract

Aviation has a growing impact on the earth’s climate, due to its emissions causing an increase in the global near-surface temperature. In order to better understand the dynamics by which different aircraft types contribute to this global warming and how this can be mitigated, the impact of different aircraft categories is analysed and compared. These categories are constructed by dividing aircraft into groups with a similar number of seats. Two approaches are employed to assess the climate impact of these categories. First of all, a global aviation emission inventory is used together with a climate response model, to evaluate the temperature change caused by each individual category. It is found that in absolute terms the middle category with 152-201 seats, and the largest aircraft with over 302 seats will cause cause the largest temperature change by the year 2100, compared to 1940. At the same time, per amount of generated capacity in the form of available seat kilometres, the middle category shows the smallest climate impact of all, with the largest aircraft being the second worst. From historical positional data of aircraft, flight trajectories are identified, to which an aircraft performance model is applied. This leads to the conclusion that the optimal distance in terms of fuel use is »2500 km, with an increase in fuel burn for both longer and shorter distance flights. The NOx emission increases for increasing flight distance, due to higher thrust settings and a higher rated thrust of the engines used. Next to being able to fly longer distances, the three largest aircraft categories cruise at a higher Mach number, increasing fuel use and NOx emission. Additionally, by flying in a less busy airspace, such as above the Atlantic, the impact of contrails is larger for these aircraft, as there is a smaller atmospheric capacity to form contrails in these areas. Another reason that the largest aircraft perform worse is the higher level of comfort provided to the passengers. It is shown that increasing the seating density to maximum capacity leads to a reduction in fuel use and NOx emission per available seat kilometre especially for the largest aircraft, narrowing the gap with the smaller aircraft categories which already make use of a high density seating. Based on the outcome it is suggested to adjust the policies dealing with aviation’s climate impact, to reflect the differences between the impact of the different aircraft types. Additionally, a direct reduction in aviation’s climate impact can be achieved by making use of the most climate efficient aircraft type for a givenmission.