In this paper, we examine the economic costs of stabilizing global CO2 emissions at 1990 levels. Previous analyses of the costs of emissions abatement have tended to be deterministic. That is, no attempt was made to assign probabilities to various scenarios. Policy-makers need information both on the range of possible outcomes and on their relative likelihood. We use a probability poll to characterize the uncertainty surrounding critical parameters and to construct probability distributions over the outcomes of interest. The analysis suggests a wide range for abatement costs. In order to stabilize global emissions, the annual price tag lies between 0.2 and 68 percent of gross world product. This distribution is highly skewed. The expected costs are approximately 1.5 percent.