ارتباط بین انتشار دی اکسید کربن، مصرف انرژی و رشد اقتصادی در کشورهای خاورمیانه و شمال آفریقا (MENA): شواهدی از مدل های معادلات همزمان

This paper examines the nexus between CO2 emissions, energy consumption and economic growth using simultaneous-equations models with panel data of 14 MENA countries over the period 1990–2011. Our empirical results show that there exists a bidirectional causal relationship between energy consumption and economic growth. However, the results support the occurrence of unidirectional causality from energy consumption to CO2 emissions without any feedback effects, and there exists a bidirectional causal relationship between economic growth and CO2 emissions for the region as a whole. The study suggests that environmental and energy policies should recognize the differences in the nexus between energy consumption and economic growth in order to maintain sustainable economic growth in the MENA region.

The nexus between environmental pollutant, energy consumption and economic growth has been the subject of considerable academic research over the past few decades. According to the Environmental Kuznets Curve (EKC) hypothesis, as output increases, carbon dioxide emissions increase as well until some threshold level of output was reached after which these emissions begin to decline. The main reason for studying carbon emissions is that they play a focal role in the current debate on the environment protection and sustainable development. Economic growth is also closely linked to energy consumption since higher level of energy consumption leads to higher economic growth. However, it is also likely that more efficient use of energy resources requires a higher level of economic growth. In literature, the nexus between environment and energy and growth has attracted attention of researchers in different countries for a long time. Roughly, we can categorize past studies in this field into three strands. The first focuses on the validity of the Environmental Kuznets Curve (EKC) hypothesis. The EKC hypothesis postulates that the relationship between economic development and the environment resembles an inverted U-curve, e.g. Ang (2007) and Saboori et al. (2012). That is, environmental pollution levels increase as a country grows, but begin to decrease as rising incomes pass beyond a turning point. This hypothesis was first proposed and approved by Grossman and Krueger (1991). Dinda (2004) offer extensive review surveys of these studies. Further examples consist of Friedl and Getzner (2003) and Managi and Jena (2008). However, a higher level of national income does not necessarily warrant greater efforts to contain the CO2 emissions. Recently, Jaunky (2010) investigated the Environmental Kuznets Curve (EKC) hypothesis for 36 high-income economies (including Bahrain, Oman and UAE) over the period 1980–2005. Unidirectional causality running from GDP per capita to CO2 emissions per capita has been identified in both the short- and the long-run. However, Holtz-Eakin and Selden (1995) establish a monotonic rising curve and an N-shaped curve has been found by Friedl and Getzner (2003). On the other hand, Richmond and Kaufmann (2006) concluded that there is no significant relationship between economic growth and CO2 emissions. The second strand of researches focuses on the nexus between energy consumption and economic growth. This nexus suggests that higher economic growth requires more energy consumption and more efficient energy use needs a higher level of economic growth. Since the pioneer work of Kraft and Kraft (1978), Granger causality test approach has become a popular tool for studying the relationship between economic growth and energy consumption in different countries, e.g. Stern (1993), Belloumi (2009), Pao (2009) and Ghosh (2010). However, Belloumi (2009) has used a VECM Model and showed that, in Tunisia, there is a causal relationship between energy consumption and income over the period of 1971–2004. Similarly, Altinay and Karagol (2004) investigated the causal relationship between electricity consumption and real GDP in Turkey over the period of 1950–2000. They showed that both used tests have yielded a strong evidence for unidirectional causality running from the electricity consumption to income. This implies that the supply of electricity is vitally important to meet the growing electricity consumption, and hence to sustain economic growth in Turkey. Finally, most previous studies have shown that economic growth would likely lead to changes in CO2 emissions. It has also found that energy consumption is often a key determinant of CO2 emissions. It is therefore worthwhile to examine the nexus between economic growth, energy and CO2 emissions by considering them simultaneously in a modeling framework. In this strand, Ang (2007) and Soytas et al. (2007) initiated this combined strand of research. Recent works include Halicioglu (2009) and Zhang and Cheng (2009) for a single country study. Halicioglu (2009) and Zhang and Cheng (2009) extended the above mentioned multivariate framework further by including the impacts of foreign trade and urban population, respectively into the nexus, in order to address omitted variable bias in econometric estimation. Also, based on panel error-correction model (PECM), Arouri et al. (2012) have tested the relationship between CO2 emissions, energy consumption, and real GDP for 12 Middle East and North African Countries (MENA) over the period 1981–2005. They showed that the real GDP exhibits a quadratic relationship with CO2 emissions for the region as a whole. The econometric relationships derived in this study suggest that future reductions in carbon dioxide emissions per capita might be achieved at the same time as GDP per capita in the MENA region continues to grow. Table 1 summarizes some previous findings on the linkages between CO2 emissions, energy consumption, and economic growth including the method used, the techniques and main findings. More than 15 studies are considered in a wide range of countries, including MENA countries, France, Turkey, India, Malaysia and others. The number of studies dealing with the nexus between CO2 emissions, energy consumption, and economic growth seems considerably fewer than those dealing with causality between energy consumption and real GDP.The results of studies on the relationship between CO2 emissions, energy consumption, and real GDP differ from country to another and vary depending to the used methodology. It is difficult to succinctly clarify these variations. First, some studies found that CO2 emissions can influence the GDP and/or energy consumption. For example, Soytas and Sari (2009) and Ang (2007) found this relationship for Turkey; and Arouri et al. (2012) for MENA countries. These results imply that more CO2 emissions lead to economic growth. Second, if the relationship goes from energy consumption to GDP and/or CO2 emissions, then GDP and/or CO2 emissions can increase through more energy consumption. For example, Belloumi (2009) found this relationship for Tunisia; and Ozturk and Acaravci (2010) for Turkey. Finally, some studies showed the causality relationship goes from GDP to energy consumption and/or CO2 emissions. For example, Halicioglu (2009) found this relationship for Turkey; and Lotfalipour et al. (2010) for Iran. Compared to previous studies (see Table 1), this paper used simultaneous equations based on structural modeling to study of the nexus between energy consumption, CO2 emissions and economic growth in the Middle East and North Africa (MENA) region. As we can see, about the emerging economies, our literature review generally indicates that little attention has paid to smaller emerging economies, particularly in MENA region. This region has some of the largest energy reserves in the world. Yet, while the region is trying to industrialize and modernize its economies, there are the challenges of the carbon emissions. Moreover, energy consumption is the most significant source of pollution and, in terms of particulate matter concentrations; MENA represents the second most polluted region in the world – after South Asia – and the highest CO2 producer per dollar of output. The model allows examining at the sometime the interrelationship between CO2 emissions, energy consumption, and economic growth in case of 14 MENA countries over the period 1990–2011 estimated by the GMM-estimator. However, to the best of our knowledge, none of the empirical studies have focused to investigating the nexus between energy–environment–growth via the simultaneous-equations models. Specifically, this study uses three structural equation models, which allows one to simultaneously examine the impact of (i) CO2 emissions and energy consumption on economic growth, (ii) CO2 emissions and economic growth on energy consumption, (iii) economic growth and energy consumption on CO2 emissions. The rest of the paper is organized as follows. Section 2 describes the data and the econometric methodology. Section 3 presents the results and discussion. Section 4 concludes this paper with some policy implications.

The present study investigates the three-way linkages between CO2 emissions, energy consumption and economic growth using the Cobb–Douglas production function. While the literature on the causality links between emissions–energy–growth has increased over the last few years, there is no study that examines this interrelationship via the simultaneous-equations models. The objective of the present study is to fill this research gap by examining the above interaction for 14 MENA countries over the period 1990–2011. Our results suggest that energy consumption enhances economic growth. We found a bidirectional causal relationship between the two series. Our results significantly reject the neo-classical assumption that energy is neutral for growth. This pattern is similar to the findings of Oh and Lee, 2004 and Mahadevan and Asafu-Adjaye, 2007, Ang (2008), and Apergis and Payne (2009). Thus, we conclude that energy is a determinant factor of the GDP growth in these countries, and, therefore, a high-level of economic growth leads to a high level of energy demand and vice versa. As such, it is important to take into account their possible negative effects on economic growth in establishing energy conservation policies. Our empirical results also show that there is a unidirectional causal relationship from energy consumption to carbon dioxide emissions without feedback. This implies that due to the expansion of production, the countries are consuming more energy, which puts pressure on the environment leading to more emissions. Hence, it is very essential to apply some sorts of pollution control actions to the whole panel regarding energy consumption. It is found that bidirectional causality between economic growth and CO2 emissions implies that degradation of the environment has a causal impact on economic growth, and a persistent decline in environmental quality may exert a negative externality to the economy through affecting human health, and thereby it may reduce productivity in the long run. The main policy implications emerging from our study is as follows. First, these countries need to embrace more energy conservation policies to reduce CO2 emissions and consider strict environmental and energy policies. The research and investment in clean energy should be an integral part of the process of controlling the carbon dioxide emissions and find sources of energy to oil alternative. These countries can use solar energy as the substitute of oil. Thus, implementing the environmental and energy policies and also reconsidering the strict energy policies can control carbon dioxide emissions. As a result, our environment will be free from pollution and millions of peoples can protect them-selves from the effects of natural disasters. Second, high economic growth gives rise to environmental degrading but the reduction in economic growth will increase unemployment. The policies with which to tackle environmental pollutants require the identification of some priorities to reduce the initial costs and efficiency of investments. Reducing energy demand, increasing both energy supply investment and energy efficiency can be initiated with no damaging impact on the MENA's economic growth and therefore reduce emissions. At the same time, efforts must be made to encourage industries to adopt new technologies to minimize pollution. Finally, given the generous subsidies for energy in the exporting countries, there is a relatively more scope for more drastic energy conservation measures without severe impacts on economic growth in these countries. Indeed, it is unlikely that the elimination of energy price distortions restrain economic growth in the oil exporting countries. However, subsidy reform should be embedded in a reform program that engenders broad support and yield widespread benefits.