We investigate how the U.S. withdrawal from the Kyoto Protocol and the provisions of the Bonn climate policy conference on sink credits and emissions trading will change the economic and environmental impacts of the Protocol in its original form. Based on simulations with a large-scale computable general equilibrium model, we find that the U.S. withdrawal and amendments of Bonn reduce the Kyoto Protocol's impact to business-as-usual without binding emission constraints. U.S. compliance under the new Bonn provisions, on the other hand, would accommodate a substantial cut in global emissions at relatively small compliance costs for OECD countries.