This morning on the way to work and listening to PBS, I learned of a new website that allows visitors to input their assumptions about the likelihood of various future energy policies being implemented and then calculates the resulting effect on the Gross Domestic Product and economic growth in the US. This neat little trick is the product of a "meta-analysis" synthesizing the 27 leading economic models by Robert Repetto of Yale University who writes that the synthesis "... reveals what the crucial assumptions are and how changing those assumptions affects the predicted economic costs of reducing greenhouse gas emissions by specific percentages below the business-as-usual path by 2030. Surprisingly, only a handful of key assumptions account for most of the differences among model predictions of the economic costs of reducing emissions."
Check the results of your own assumptions at http://www.climate.yale.edu/seeforyourself/ - and See For Yourself!