چكيده لاتين :
The gaseous composition of the Earthʹs atmosphere is changing at an accelerated rate because of the
influence of human activities. Different factors increase the air contamination by CO2• Understanding factors
affecting atmosphere gaseous is important for managing and reducing air contaminants. The natural presence
of the so-called ʹgreenhouse gases ʹ (water vapor, carbon dioxide, nitrous oxides and methane) in the
atmosphere is essential for life. Greenhouse gases trap heat in the lower atmosphere and keep the Earth far
warmer than it would be without such gases. Over the Earthʹs long history, the concentration of these gases
has markedly decreased. This decline has occurred due to complex transformation processes that operate at
different time scales and involve transfer of materials between the three carbon reservoirs: atmosphere, land
biosphere and oceans. However, over the past century human activities have been releasing greenhouse gases
(GHGs) at a rate unprecedented in geologic time. As a consequence of this acceleration in the rate of
emissions, the concentration of GHGs in the atmosphere has increased by 300/0, since pre-industrial times.
Among the greenhouse gases, CO2 is the most important and about 60 percent of greenhouse gases derived
by human activities are related to CO2 emission. The main resource of CO2 emission is fossil fuels that
unfortunately nowaday are the basic tools to generate energy in industrial-economic systems. Furthermore,
energy is a main factor to achieve economic development which is highly needed for developing countries. It
is worth noting that the report of greenhouse gases emission in 1994 (the base year for preparing the
inventory of greenhouse gases in developing countries) in different sectors of the countries shows that the
energy sector has had the biggest part (840/0) in C02 expanse.
Recent empirical researches on relationship between certain environmental indicators of environmental
degradation and per capita income concluded that, in some cases an inverted U relationship or
Environmental Kuznets Curve (EKC), exists between the mentioned variables. But unfortunately in spite of
the importance of this issue, a few studies have been developed on this subject in Iran. Therefore, the aim of
this paper is to investigate factors affecting CO2 emission in Iran by using Environmental Kuznets curve.
According to the environmental Kuznets curve (EKC) hypothesis, at the first stage of economic development
environmental pressures would increase as per capita income increases, but after a critical turning point these
pressures diminish along higher income levels. The name is due to the similarity with the relationship
between the level of inequality and per capita income considered by Kuznets (1955). The explanatory factors
that most frequently appear in the literature are, first, environmental quality is considered as a luxury good
whose demand increases at higher income levels; second, production composition changes with economic
development and the increasing importance of the service and industry sectors, which is a ʹmore
environmental friendlyʹ sector, reduces the environmental impact of economic activity; and third,
technological progress linked to economic growth causes a decrease of environmental pressures.Empirical model to test the EKC hypothesis in Iran for the period from 1974 to 2003:
CO 2t = f(Et,Tt,Pt,St)
Where:
C02t: CO2emission in year 1.
E: per capita income (constant 1997 prices) in year t
T,; Deviation from mean temperature (Co) in year t
Pt: price of fuel in year t
St: share of value added in the industry sector ofGDP (As an index of structural change) in year 1.
The main purpose kuzents curve is to study the relation between CO2and E, in Iran. But as it was mentioned
other factors must be involved. As the high rate of structural change is an inseparable part of the growth
process and important components of this structural change are: gradual displacement of economic activities
from agriculture to industry and lately from the industry to the services, and as the most amount of emission
is from the energy and fuel sector, then two variables P and S can prevail the relation between CO2emission
and economic structure of Iran. In this study, fuel price was measured by the amount of consumes, thernlal
expenses and value of the different net fuels and was considered as a criteria for the total price of consumed
fuels. The last variables that was considered in this model, was the deviation from mean temperature.
The purpose of importing this variable is to check the indirect energy consume. Hence due to the high
amount of energy consume in winters for heating, deviation from the average of winter temperature was used
in this study to show this factor. It is predicted that in winters because of the temperature reduction, the CO2
emission will be increased by the extra amount of fuel usage. Also it is worth noting that the most important
purpose of this study is to test the Kuznets Curve hypothesizes for greenhouse gases in Iran.
Due to stationary test results, the auto regressive distribution lag (ARDL) is used to estimate the model.
Considering the limited time period of this study, to determine the number of optimal lags of pattern
variables, Schwarts Bayesian Criterion we used. The Result of estimation shows that considering the
Schwarts Bayesian Criterion are chosen as ARDL (1.1.0.0.2.2.).
Also econometric tests confirmed the classic hypothesizes and there is no problem of auto correlation,
specification error and non-normality of disturbance terms. The obtained determined coefficient is 990/0, in
other word this indicates that almost 99 percent of the dependant variable changes are explained by
independent variables. In addition, the hypothesis of existence long term relation between modelʹs variables
was tested.
Since the critical content presented by Benerjee, Dolado & Master, is equal to -3.82, so the zero hypothesis is
repelled and the result shows that there is a balanced long term relation between variables of Kuznets model
in Iran. The estimated model is shows in Table 1.The sign of variable coefficient of per capita income is positive and sign of variable coefficient of square per
capita income is negative, which illustrates there is second degree and inverted U shape between growth and
CO2 emission. In other words, this relation confirms the existence assumptions of Kuznets in Iran and shows
that when per capita income increases, CO2 emission increases first, and then from a point called turning
point when per capita income increases, emission decreases. In this study turning point of curve is obtained
7.11 million Rials. This result of per capita income and CO2 emission for Iranian economy according to used
data in this study was showed in Figure 1.Moreover, one can see that the share of value added of industrial sector from gross domestic product has
positive and significant effect on emissions and in fact expresses the fact that changing economic structure,
namely, the growth of industrial sector, increases emissions.
The sign of variable coefficient of deviation from the average of mean winter temperature as predicted is
negative and significant and this result shows that whatever the temperature in winter is more than average of
temperature in winter, itʹs required less energy to warming of places and in fact with less energy
consumption, carbon dioxide emissions also decreased. In addition, fuel price variable also shows negative
effect on emission. It is worth noting that the effect of this variable is significant at the level of 11 percent,
and this shows low sensitivity of CO2 emission into change of fuel price. Here can deduce that increasing of
fuel price, decreases demand of it which reduces the carbon dioxide emissions indirectly.
In order to study relation between short-term emission of carbon dioxide and other variables that studied the
error correction model (ECM) was used. The results of short-term pattern are the same as long-term relation.
In addition, first order difference of fuel price variable isnʹt achieved significant in the short-term. Error
correction sentence in ECM is significant and its sign is predictable (negative). The value of this coefficient
is estimated -0.15 and can elicit such that in each year 0.15 of imbalance of a period will adjustment in the
model of after period. In the other words, environmental policies in the form of carbon dioxide control takes
time for about 6 years to reveal its full effect on the Iranʹs economy. Therefore adjustment towards balance
can be done even though the process takes long time.
