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regions studied. In this respect, they differ from this report, which examines the possibilities for greenhouse gas reductions from individual technologies and attempts to make the estimates mutually consistent by manual calculations.

A second important difference between the Nordhaus (1991) survey and this report is that the survey estimates the cost function for reducing greenhouse gas emissions beginning from the point at which all the "negative-cost" options have been employed. In most economic models, the market equilibrium is this point; in one model, where market failures are allowed, the results have been recast so that the cost estimates begin from the point at which market failures have been allowed for. It is important to note, then, that the negative-cost part of the cost function, should it exist, is excluded from this survey.

The models represented in the survey encompass a wide variety of approaches to energy sector modeling. The studies surveyed (Nordhaus, 1991) were the following, listed roughly in order of their chronological development:

1.  A series of mathematical-programming models, developed by Nordhaus and his associates, that use a technological specification for supply and econometric estimates for demand.

2.  A purely behavioral or econometric model developed by Nordhaus and Yohe for the 1983 NAS study, Changing Climate, with a simplification for estimates of the impact of different taxes.

3.  A series of models developed by Edmonds and Reilly, which are a mixture of technological data on the supply side and behavioral assumptions on the demand side.

4.  A series of studies by Manne and Richels, which have much the same analytical structure as study 1 but are generally smaller and provide less detail on the demand side.

5.  Estimates by Bodlund and associates for Sweden, using largely a mathematical optimization model with many alternative technologies.

6.  Studies by Kram and others using a linear programming model of the Netherlands economy with a structure similar to that in study 5

7.  A six-region computable general equilibrium model developed by Whalley and Wigle that includes the energy and nonenergy sectors. The energy sector is purely behavioral and is not econometrically estimated.

8.  A series of optimization models developed by the European Community that include both supply and end-use technologies for five European countries. These models allow for market failures in the energy-using sectors.

9.  An extension of the Jorgenson approach by Jorgenson and Wilcoxen to include CO2 emissions. The estimates are purely econometric but are based on extensive data and estimation.