I built a model to measure the impact of population, wealth, technology and urbanization on greenhouse gas emissions (as measured by $N_2O$ emissions) in my country, following the STIRPAT framework, and for this I used an ARDL model on time series data from 1971 to 2014 (as per data availability). My results for the long and short runs are as follows:
As one can see, for the long run, the effect of urbanization on GHG emissions follows a U-shaped curve (the coefficient of
LNU is negative, and the coefficient of
LNU2 is positive), while for the short run, the effect of urbanization follows an inverted U-shaped curve (the coefficient of
dLNU is positive, and the coefficient of
dLNU2 is negative).
How can I interpret this result? I know that according to Urban Environmental Transition, in the long run cities enter the sustainable stage, and prioritize environmental protection and sustainability, which leads to further reductions in pollution and increased use of sustainable practices (an inverted U-shaped relationship in the long run). But this doesn't seem to show in my results.
Can someone please help me understand my results, and tell me if there exists a theoretical basis for these results? Thank you very much in advance.