Assessment of the feasibility of stabilising the global climate requires consideration of trajectories for emissions of carbon dioxide and other greenhouse gases. This study presents a simple and robust analysis of feasible emissions trajectories. Consideration of feasible trajectories suggests that if the current pace of mitigation efforts is sustained, the likely outcome will be stabilisation at concentrations close to 500 parts per million. Such an outcome will imply a higher than 50 per cent probability of substantial damage from climate change and an enhanced risk of a catastrophic outcome.