Using the MIT Emissions Projection and Policy Analysis (EPPA) Model we conduct a formal uncertainty analysis of future global anthropogenic emissions of GHGs (CO2, CH4, N2O, SF6, PFC, HFC), major urban air pollutants (NOX, SOX, CO, NMVOC), NH3 and carbonaceous particulates. Within EPPA, emissions of these gases are related directly to sectors of the economy responsible for the anthropogenic activities that produce them (e.g. coal, oil, and gas use, energy production, electricity production, agriculture, industrial production, households). As such, the projections for each gas are consistent with underlying economic trends and emissions projections for each species from an EPPA scenario are jointly consistent with one another. We propagate uncertainties in the underlying parameters of the economic model and in emissions coefficients of different species of gases to generate consistent probabilistic projections. We present probability distributions of emissions of all species, and define a range of likelihood (95% confidence). We compare the range generated using EPPA and these formal uncertainty techniques to the emissions scenarios reported in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES). We argue that the uncertainty approach we employ provides a basis for estimating the likelihood of emissions falling outside a given range. Our scenarios when used as input to climate models thus advances the goal of providing probabilistic statements about climate change whereas the SRES scenarios do not provide such a basis.