Testing the heterogeneous effect of air transport intensity on CO 2 emissions in G20 countries: An advanced empirical analysis.

This study investigates the heterogeneous impact of air transport intensity, air passenger transport, and air freight transport on air transport carbon emissions in G20 countries for the period of 1990-2016. The paper employs a robust and advanced fixed-effect panel quantile regression model that considers unobserved discrete and distributional heterogeneity. Our empirical results show that the impact of the independent variables on air transport carbon emissions is quite heterogeneous across various quantiles. More specifically, the effect of air transport intensity, air passenger transport, and air freight transport on carbon emissions is positive and becomes more assertive with the increasing trend at upper quantiles and is quite heterogeneous across all quantiles. Economic growth, urbanization, and tourism are significant contributing factors in enhancing air transport CO 2 emissions, while crude oil price significantly reduces CO 2 emissions. The Dumitrescu and Hurlin causality test estimates indicate that a bidirectional relationship extends from air transport intensity, air passenger transport, and air freight transport to air transport CO 2 emissions. The findings underline the need for cleaner, renewable, and environmentally sustainable energy sources for air transport operations.