Because of worldwide growing concerns about global climate change, great interest has been expressed in the potential of alternative climate policies to reduce global carbon emissions. In this paper, we compare cross-country implications of alternative climate policies, including unilateral and multilateral climate policies. Our main findings are as follows. Firstly, there are large differences in cross-country effects of alternative unilateral climate policies, when the same given carbon emission reductions are achieved in each abating country respectively. Meanwhile, cross-border externalities undermine efficiency of unilateral climate policies. Secondly, there are significant differences in cross-country implications of alternative multilateral climate policies, when the same global emission reductions are allocated in several different ways among abating countries. Thirdly, it is difficult to reach a stable global climate treaty, since any abating country has the incentive to argue for small carbon emission reductions. Finally, multilateral climate policies can reduce the negative impacts of cross-border externalities, but cannot cure all cross-border externalities. Looking ahead, it will be a great policy challenge for the world to reduce carbon emissions in a cost-effective way. (C) 2014 Elsevier Ltd. All rights reserved.