On the nonlinear relationship between energy use and CO2 emissions within an EKC framework: Evidence from panel smooth transition regression in the MENA region

This paper proposes a new approach for analyzing the dynamic relationships between carbon dioxide (CO₂) emissions, energy use, and income for the Middle East and North African (MENA) region. Our study implements a class of regime-switching models, namely a nonlinear panel smooth transition regression (PSTR) framework. Two kinds of estimates for carbon emissions are provided. On the one hand, we measure the impact of energy consumption on CO₂ concerning the level of income per capita, as countries with a similar energy usage level would have different levels of energy intensity. On the other hand, we estimate the impact of output growth on emissions concerning energy usage variation, as a higher economic growth does not necessarily mean energy-intensive activities. Our empirical findings support these intuitions as they indicate that pollutant emissions respond nonlinearly to energy consumption and GDP growth. We find an inverted U-shaped pattern for the impact of energy on CO₂, in the sense that environmental degradation is declining beyond a given income threshold, which is estimated endogenously within the PSTR model. Also, our results underscore that GDP growth significantly impacts carbon emissions only for higher energy consumption growth.