Methodologies for the analysis of non-linear environmental processes applied in a dynamic model of air traffic emissions

Zusammenfassung

Greenhouse gases emissions modify the radiative balance of the Earth, causing changes in its climate. Climate Change is considered one of the greatest threats to economic and social stability. Aviation is responsible for around a 2.5% of greenhouse gases emissions. This contribution is steadily increasing, hence the interest of assessing the impacts that different policies might have on it. The simple feedback model proposed here was intended as a tool in order to investigate the stabilization issue. The model was based on the relationship between the number of air traffic passengers and the associated CO2 emissions. It incorporated a representation of the feedback of the technological innovation on the emissions rate and of those of the socioeconomic response to the climatic impact on the passengers number. The model parameters were estimated using data from a variety of robust air traffic sources. It was found that neither of the feedback terms succeeded at stabilizing the emissions, although they might slow down their growth. Therefore, a nonlinear version of the model includes a representation of the passengers perception of insecurity, similar to the one experienced in the recent pandemic. This model favours the stability of both, the number of passengers and CO2 emissions, and it would be able to control unprecedented situations. In a second study, we introduce a sensitivity analysis of modelled CO2 aviation emissions to changes in the model parameters, which is intended as a contribution to the understanding of the atmospheric composition stabilization issue. The two variable dynamic model incorporates the effects of the technological innovations on the emissions rate, the environmental feedback, and a non-linear control term on the passengers rate. The results of two global sensitivity analyses indicated that the influence of the non-linear term prevailed on the passengers number rate, followed distantly by the environmental feedback. For the emissions rate, the non-linear term contribution dominated, with the technological term influence placing second. A third study tackles different aspects of the emissions stabilization issue. Different possible management options can be designed, based on the characteristics of the solutions of the system and the optimization of the parameter of the control term: i) maintaining the present number of passengers, ii) maintaining the present level of emissions, or iii) diverting the system to the next equilibrium point while keeping the oscillation amplitude at its minimum value. Each of these options leads to a different structure of growth or reduction of passengers and/or emissions that can be derived from the model results. The third option seems especially novel and promising, since only the short distance flight passengers number are severely reduced; those of the long distance and international ones are allowed to grow while their emissions would drop below the 50 % value of their current rate. Moreover, in a scenario of slow growth of air traffic (compared with historical records), as was the one seen in the last twenty years, these rates are improved, with less reductions in short distance passengers number and more in long distance and international flight emissions.