This report documents the results of work with the IEA/ORAU Long-Term Global Energy-CO/sub 2/ model to analyze model predictions of future global carbon emissions from fossil fuel use and the uncertainty surrounding such forecasts. The methodology utilized state-of-the-art techniques of uncertainty analysis along with review and revision of the IEA/ORAU model structure, and review and description of uncertainty surrounding model assumptions and parameters to explore uncertainty in fossil fuel CO/sub 2/ emissions over the period 1975-2075. Possible interrelationships among assumptions and parameters, and their effects on overall forecast uncertainty are explored. The major findings include: (1) the median rate of CO/sub 2/ emissions grow at an average annual rate of 1.0% per year; (2) overall uncertainty in the emission rate was found to be considerable; (3) low and declining CO/sub 2/ emissions rates appear more likely than past research has indicated; (4) the three most important determinants of variation in CO/sub 2/ emissions were labor productivity, rate of improvement in end-use energy efficiency, and the income elasticity of demand of energy in the developing world; (5) based on the analysis of potential correlation among assumptions, model structure plays a key role in the determination of median estimates of fossil fuelmore » CO/sub 2/ for energy emissions; and (6) conspicuously absent from the list of key variables were the rate of interfuel substitution and the fossil fuel resource base by fuel type. « less