Green Energy Transition and Environmental Transformation in Türkiye: Fourier-Based Evidence from the Renewable Energy Kuznets Curve and Environmental Kuznets Curve Hypotheses

The relationship between economic growth and environmental sustainability has become one of the major research areas in the economics literature in recent years. In this context, renewable energy plays a crucial role not only in mitigating environmental degradation, but also in addressing energy poverty within the framework of sustainable development. According to the Renewable Energy Kuznets Curve (RKC) hypothesis, renewable energy consumption initially declines during the early stages of economic growth due to the relatively lower cost of fossil fuels. However, as income reaches a certain threshold, renewable energy consumption increases alongside income, indicating a U-shaped relationship between income and renewable energy use. In contrast, the Environmental Kuznets Curve (EKC) hypothesis suggests that environmental degradation increases in the initial stages of economic growth, reaches a turning point at a certain income level, and subsequently declines as income rises further and environmental policies become more effective. Accordingly, this study investigates the validity of the RKC and EKC hypotheses in Türkiye over the period 1990–2024 by employing Fourier-based time series techniques. The results of the Fourier ADL cointegration test reveal the existence of long-run relationships among the variables. Furthermore, the findings obtained from the Fourier FMOLS, DOLS, and CCR estimators confirm the validity of both the RKC and EKC hypotheses for Türkiye. Additional empirical findings indicate that fossil fuel energy consumption increases carbon emissions, while financial development contributes to reducing environmental degradation. Moreover, increases in financial development and urbanization are found to reduce renewable energy consumption. Overall, the findings suggest that sustaining economic growth in harmony with environmental sustainability and promoting the widespread use of renewable energy can accelerate the achievement of environmental objectives.