رابطه بین انتشار کربن، مصرف انرژی و رشد اقتصادی در کشورهای شرق میانه: تحلیل داده های پانل

The environmental Kuznets curve (EKC) hypothesis assumes that there is an inverted U-shaped relationship between environmental degradation and income per capita. In other words, as a country grows, it is assumed that its environmental quality improves. In this study, we aim to test the EKC hypothesis for 12 Middle East countries during the period 1990–2008 by employing recently developed panel data methods. Our results provide evidence contrary to the EKC hypothesis. We found evidence favorable to the U-shaped EKC for 5 Middle East countries, whereas an inverted U-shaped curve was identified for only 3 Middle East countries. Furthermore, there appear to be no causal links between income and CO2CO2 emissions for the other 4 countries. Regarding the direction of causality, there appears to be a unidirectional causality from economic growth to energy consumption in the short-run; in the long-run, however, the unidirectional causality chain runs from energy consumption and economic growth to CO2CO2 emissions. We also suggest some crucial policy implications depending on these results.

Global warming and climate change are serious environmental problems of our world. Especially, as a dominant contributor to the greenhouse effect, the increasing amount of carbon dioxide (CO2CO2) appears to be aggravating environmental problems. These increasing environmental threats have led scholars and policy-makers to assess the impacts of global warming on the world economy and to debate over reducing greenhouse gases (GHGs) emissions to alleviate global warming since 1990s. Furthermore, the mitigation assessment of greenhouse gas emissions has been an integral part of national and international climate policy agendas (Haggar, 2012, p. 358). After a while, industrialized countries have started to arrange important environmental agreements and agendas in order to decrease and control atmospheric concentration of GHGs emissions. For instance, the United Nations Framework Convention on Climate Change (UNFCCC), adopted in 1992 and opened for signatures at the United Nations Conference on Environment and Development in Rio de Janeiro, is one of the best known environmental conventions. The main aim of UNFCCC is the contracting and converging of CO2CO2 emissions across countries to combat global climate change and greenhouse effects arising from high atmospheric carbon concentration. In addition, another international agreement, the Kyoto protocol, has been signed during the UNFCCC. It was adopted on 11 December 1997 in Kyoto and entered into force on 16 February 2005 with the aim of setting binding targets for 37 industrialized countries and the European community to reduce their GHGs emissions. According to the Kyoto protocol, the contracting parties from developed countries are committed to reducing their greenhouse gas emissions by at least 5% from 1990 levels between 2008 and 2012. As a result of an increasing environmental consciousness over the last 2 decades, scholars have started to analyze the environment–economy nexus in the framework of environmental economics. For instance, the relationship between environmental degradation and income is one of the most important topics being debated under the name of the environmental Kuznets curve (EKC). The EKC was derived from the original Kuznets curve, testing an income–inequality nexus, proposed by Kuznets (1955). The EKC hypothesis indicates that there is an inverted U-shaped relationship between environmental degradation and economic growth. During a country′s early stage of development, economic growth leads to environmental degradation until a turning point is reached. However, this situation is reversed beyond this turning point. In other words, according to the proponents of the EKC hypothesis, emissions are considered to be a function of income whereby as income increases, emissions increase until a threshold level of income is reached after which emissions start to decline (Apergis and Payne, 2010, p. 650). Testing the validity of the EKC hypothesis or exploring the causal links between income and CO2CO2 emissions is crucial when designing appropriate policy tools for protecting the environment, fighting against global warming, and ensuring sustainable economic development. In addition, as stated by Narayan and Narayan (2010), examining the relationship between economic growth and environmental quality allows policymakers to judge the response of the environment to economic growth. Apart from the EKC hypothesis, the second most debated topic in the framework of environmental economics concerns the connection between energy consumption and economic growth. Economic development is closely related to energy consumption given that more energy consumption leads to higher economic development level via productivity enhancement (Ang, 2007). In addition, using energy in a more efficient way requires a higher level of economic development. Thus, as stated by Ang (2007), energy consumption and economic development may be jointly determined and the direction of causality cannot be determined a priori. The final and third research area concerning environmental economics focuses on the relationship between energy consumption, environmental degradation, and economic growth. This is a synthesis of the first (EKC) and the second (energy consumption–economic growth nexus) research areas. In this study, we examine the relationship between energy consumption, environmental degradation, and real per capita income. Additionally, we test the validity of the EKC hypothesis for 12 Middle East countries by taking CO2CO2 emissions as an environmental quality indicator. Moreover, we examine the direction of causality among economic growth, energy consumption, and CO2CO2 emissions in the framework of panel vector error correction (PVEC) model. Our sample of countries consists of Bahrain, United Arab Emirates (UAE), Iran, Israel, Egypt, Syria, Saudi Arabia, Turkey, Oman, Jordan, Lebanon, and Yemen. The Middle East countries attract a special interest for energy economists due to their abundant natural resource reserves, such as crude oil and natural gas. For instance, Iran has about 15% of the world′s total reserves of natural gas (Farhani and Rejeb, 2012). The Middle East′s share of worldwide oil reserves is about 57.5%. Among Middle East countries, Saudi Arabia, Iran, Iraq, Kuwait, and United Arab Emirates are the major oil producing countries. For instance, according to the statistics of Energy Information Administration (EIA, 2012,http://www.eia.gov), Saudi Arabia was the world′s largest producer and exporter of total petroleum liquids in 2010, and the world′s second largest crude oil producer behind Russia. Its economy remains heavily dependent on crude oil and oil export revenues have accounted for 80–90% of total Saudi revenues. In addition, according to the report published by the World Bank (2007), Iran and Saudi Arabia are the 13th and 16th highest CO2CO2 emitters, having produced 402 and 365 million metric ton in 2004, respectively. Furthermore, among the top 20 countries ranked by percentage growth in emissions between 1994 and 2004, there are six Middle East countries, namely Iran, Oman, Saudi Arabia, Turkey, Egypt, and UEA. Thus, it is of great interest to examine the nexus of energy consumption, CO2CO2 emissions, and economic growth in Middle East countries. Contributions of our study to the literature are two-fold. First, our panel, consisting of 12 Middle East countries, has not been studied before. There are three panel studies analyzing the relationship between energy consumption, GHGs emissions, and real income in Middle East and North African (MENA) countries. However, we differ from them in that we exclude North African countries. In addition, to the best of our knowledge, there are few panel studies (see for instance, Arouri et al., 2012, Haggar, 2012 and Jaunky, 2011) that have taken into account both cross-sectional dependence and slope heterogeneity issues while testing the EKC hypothesis. We employ recently developed panel data methods, i.e. second generation panel unit root tests and panel cointegration test instead of first generation panel tests. This is the novelty of this study. The rest of paper is organized as follows. In Section 2, we present the literature review. In Section 3, we present methodology and empirical results, and in Section 4, we conclude the study and suggest some policy implications.

In this study, we aimed to test the EKC hypothesis for 12 Middle East countries over the period 1990–2008 by employing recently developed panel data methods. We took cross-sectional dependence and slope homogeneity issues into account in our estimation procedure. For that purpose, we first analyzed the integration orders of variables of interest using Smith et al.'s (2004) panel unit root tests that allow for cross-sectional dependence and slope heterogeneity. Having established that all variables are integrated of order one, we examined whether CO2CO2 emissions, energy consumption, real GDP, and squared real GDP are cointegrated or not. Next, based on the presence of a long-run relationship, we estimated cointegrating vector (long-run parameters) employing the FMOLS estimator of Pedroni (2000). The results of the panel FMOLS estimator provided evidence in support of a U-shaped relationship between CO2CO2 emissions and real income, contrary to the EKC hypothesis. Hence, it could be stated that CO2CO2 emissions decrease with economic growth, stabilize, and then increase. Furthermore, we also reported the country-based FMOLS results under the presence of slope heterogeneity. The individual results provided evidence favorable to the U-shaped curves for 5 Middle East countries, namely Bahrain, Syria, Turkey, Oman, and Yemen. In addition, there appear to be inverted U-shaped EKCs for UAE, Egypt, and Lebanon whereas there is no significant relationship between CO2CO2 emissions and real output for the other 4 Middle East countries. To define the direction of long-run and short-run causalities, we estimated a panel error correction model. The results from error correction model indicated the presence of a short-run unidirectional causality running from economic growth to energy consumption. In other words, economic growth leads to increases in energy consumption. However, there appears no feedback effect from energy consumption to economic growth. Thus, this finding indicates that energy conservation policies, such as rationing energy consumption and controlling CO2CO2 emissions, are likely to have no adverse effect on the real output growth of Middle East countries considered in this study (Acaravci and Ozturk, 2010). In addition, in the long-run, there seems only a unidirectional causal link from energy consumption and real output growth to CO2CO2 emissions. This result implies that energy conservation policies may be efficient in reducing the rate of pollutant emissions in the long-run. Also, as a long-term development policy, Middle East countries need to arrange sustainable growth policies aiming to contract the emissions rate of pollutants.