As mentioned several times in this review, there is a problem of separating the possible impacts of a climate change from other changes that are being produced by a rapidly growing, high consumption society. This fact has led to attempts to produce assessments that consider a much wider field of influence than simply the change in a crop or forest produced by the changing climate. One of the most ambitious assessments of climate change impacts was conducted by a coalition of research groups focussing on the midwestern United States [ Rosenberg, 1993]. The MINK study selected climate sensitive sectors in the states of Missouri, Iowa, Nebraska, and Kansas (hence the acronym), described and characterized the total economy of this region, and then subjected these activities to a climate change scenario based on the actual weather recorded in the same region in the 1930s (the ``Dust Bowl'' years). The authors also projected the present activities to the year 2030 and subjected this new set of activities to the 1930s scenario. The study was integrated in the sense that an attempt was made to estimate the overall economic result of the sum of the climate change impacts. As the authors emphasize, they did not consider the possible synergistic effects of the impacts. The economic integration of the results emphasized the small total effect on the regional economy of the climate change; the details of the study showed large impacts on particular locales or sectors.
An integrated study focussing on identifying vulnerable sectors of an economy--in this case in Mexico--and applying the output of several climate models to these sectors, was attempted by Liverman [1992]. This author emphasizes that impacts are strongly dependent on the characteristics of the region and of the people involved.
A number of studies have attempted to calculate the damage to a specific product by a climate change [e.g., Hodges et al., 1992], or the cost of preventing a particular form of damage [e.g., Titus, 1991]. But so far, in attempting to integrate this information into a broader picture, economic modelers have faced difficulties similar to those that limited the value of early equilibrium climate models--high degree of aggregation, omission of relevant processes, and lack of ability to simulate past events. Econometric models designed to simulate energy use and cost of decreased fossil fuel use have been reviewed by Cline [1992a]. These models have usually carried projections five or more decades into the future, during which time they project large growths in population and in average individual wealth. Such changes in other societal measures, and the uncertainties in these other changes, tend to relegate calculated costs of preventing a climate change to the noise level [ Schneider, 1993], even if impacts on certain regions are severe. In addition, even though there have been attempts to estimate the damage due to acid rain, urban air pollution, low altitude ozone, and other consequences of fossil fuel use, economic modelers have not in general considered these activities while studying increases in fossil fuel use that would cause a climate change [ Cline, 1992b]. This feature of the models, combined with the usual assumption of unlimited substitutability of capital investments for natural ecosystems, limits the value of these models in describing the total impact of climate change.