Journal of Economic Modeling Research

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Due to the potentiality of the accumulation of atmospheric carbon dioxide and its permanent nature, the actual amount of carbon dioxide in the atmosphere, the accumulation of effective per capita carbon dioxide and the accumulation of effective per capita of this pollutant in the steady state has been estimated estimated through Kalman filter approach in a Ramsey equilibrium model over the period of 1991- 2007 for Iran. Thereby the researchers were able to estimate parameters such as the coefficient of environment cleaning for carbon dioxide, the share of fossil resources in production, the rate of time preference and the elasticity of emission function with respect to reduction activities.
   The empirical results of the study concerning the minimum, equilibrium & maximum rate of the coefficient of environment cleaning, indicate that for 1991 to 2007 in Iran the elasticity of fossil energy in production function is 0.4475, the rate of time preference is 0.12, the elasticity of emission function with respect to reduction activities is 4.45 and the coefficient of environment cleaning for carbon dioxide is 0.02. The effective per capita accumulated co2 & effective per capita accumulated co2 in steady state with the coefficient of seasonal cleaning of 0.02 respectively have the average of 50.45, 52.97 metric ton based on constant 2005 (PPP). Also the average of effective per capita consumption of the fossil fuel energy and the effective per capita capital in steady state are respectively 4.468 kg and 6.56  $ based on constant 2005 (PPP). The surpassing of the average value of the accumulation of carbon dioxide in steady state compared to its accumulation average value indicates that the accumulation path of co2 will have an increasing trend in next years.

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In this study, we estimate the demand for natural gas in the subsection manufacture of basic metals of Iran using structural time series model (STSM) over the period of time 1981-2013. Such model contains unobservable elements which have been transported to state space model with the use of kalman filter and is estimated by implementing maximum likelihood approach. Also, because the Targeting of Subsidies Plan was approved by the Iranian parliament at the end of 2010, so we evaluate the role of this plan on energy demand of industrial subsectors. Finding of the research is that, first of all the nature of the trend is smooth one. Secondly, it is changing on a nonlinear basis. The estimated demand function shows that price elasticity for natural gas in the long and short run, correspondingly, are (-0.30) and (-0.79) and production elasticities of natural gas in the short and long run, correspondingly, are (0.17) and (0.38). Furthermore, Cross elasticity for electricity and gasoline in the long and short run, correspondingly, are substitute and complementary goods. In addition, the result of evaluating effect of the Targeting of Subsidies Plan show that estimated natural gas demand functions can explain the impact of this policy.