Factors Influencing CO2 Emission Changes in Iran with Emphasis on the Role of Urbanization; A Decomposition Analysis

The need to energy for doing economic activities, and meeting the growing population demand have increased in the recent years. Energy consumption is a prerequisite for economic progress in societies, and its increasing consumption has led to environmental problems, the most important of which is air pollution emissions resulting  from fossil fuel combustion. Due to the wide range of effects of air pollution on local to planetary scales, identifying the factors affecting pollution like carbon dioxide and determining the share of each can be a guide for environmental management in any country. Therefore, this study seeks to investigate and analyze the share of factors affecting the emissions of air pollution in Iran. The innovation of this study is emphasizing on the effect of urbanization along with population growth on air pollution. There are many theories about the effect of urbanization on the environment. Some believe that urbanization is an important factor in increasing environmental pollution and climate change. Others believe that urbanization is a factor in improving the quality of the environment due to high efficiency in energy consumption, and can lead to air pollution reduction. In this study, the amount of CO2 emissions is considered as an indicator of air pollution, and the impacts of factors including population change, urbanization growth and energy intensity on CO2 emissions changes in Iran is analyzed during the period 1997 -2016.2. Study AreaIn Iran, per capita carbon dioxide emissions in 2014 was equal to 8.4 metric tons, and its emission growth during 1990-2014 was about 127 percent, i.e., more than doubled (World Bank, 2014). Energy consumption and energy intensity in Iran have decreased in some years due to the relatively low increase in energy consumption compared to the urban population and have increased in some other years. Considering increasing energy consumption, carbon dioxide emissions have increased by the whole economy.
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The first method (IPAT) for analyzing the main factors of environmental degradation is determined by the destructive effect on the environment (I), multiplied by population (P), economic prosperity in terms of the level of production or consumption (A), and technology as the environmental effect of economic activity (T). Some studies replaced the concept of IPAT with IMPACT. In IMPACT model, technology is divided into two parts; the term technology (T) and another term in the sense of energy relative to GDP (C). In this study, complete decomposition method was used to analyze the factors affecting the emission changes. Four factors have been selected in this study: the pollution coefficient effect, energy intensity effect, population structure (urbanization) effect, and population effect. The pollution coefficient effect is determined by the rate of carbon dioxide emission and energy consumption, which is called the carbon dioxide emission intensity. This variable evaluates fuel quality, fuel change (fuel replacement), and the installation of pollution reduction technologies. The energy intensity of urban household effect is determined by the rate of energy consumption and urban population. The energy consumption is mostly related to some variables such as economic and urban structure, transportation efficiency and energy systems of the city, energy use technologies, energy prices, energy saving policy and investment to reduce energy consumption. Urbanization effect is determined by the ratio of urbanization to population. This coefficient measures the relative position of the urban and rural population in an economy and changes with the evolution of urban structure. The population effect is expressed in the size of the total population in an economy.

The results show that the effect of carbon intensity is the most important factor influencing on the increase of carbon emissions. This shows that fossil fuels are widely used, and substitution for clean fuels and pollution reduction technologies in the economy are low. During the considered period, the energy consumption of the urban population has decreased. Decreases in the energy intensity can be due to increased energy efficiency, acceptance of new manufacturing technologies, reduced use of fossil fuels, or changes in fossil energy prices. Despite the declining energy consumption of the urban population, there is still great potential for reducing energy intensity due to the gap in the production process, technology, and level of management.In the whole period of 1997 to 2016, both population and urbanization changes have increased the emissions of carbon dioxide. Urbanization has contributed 52% to carbon emissions change over the entire period. Although urbanization has had a declining effect on carbon emissions between 2007 and 2011, it has had a positive effect throughout the whole period. So, it can be said that the expansion of urbanization in Iran is a factor in increasing air pollution. In previous studies done on Iran, less attention has been paid to the effect of these two variables, and more attention has been paid to the effect of economic growth and the structure of society's products.

Considering the rapid growth of industrial activities and urbanization, the consumption of different types of energy plays an important role in influencing the local environment and changing the global climate. Increasing environmental degradation at the local, national and global levels has raised policymakers' concerns about the side effects of energy consumption and related social welfare. Recognizing the important factors influencing on pollution emissions, and determining the share of each can help in better dealing with this environmental problem. Therefore, the purpose of this study was to investigate the factors affecting changes in carbon dioxide emissions with emphasis on two important factors of demographic change and urbanization in Iran. For data analysis, the computational model of decomposition analysis has been used. The results show that both population and urbanization have played an important role in increasing energy consumption and carbon dioxide emissions. According to the results, strategies such as reducing pollution by changing fuel and switching to cleaner energy, implementing energy optimization plans and upgrading equipment technology, guiding household consumption toward improving fuel consumption patterns, and enforcing pricing and incentive policies should be considered for carbon decrease and sustainable development.