It is no longer seriously disputed that, in the face of climate change, carbon emissions must be reduced. There is agreement internationally that responsibility for making these reductions should be shared with equitable differentiation. In contemporary debates, however, the question of how responsibilities should be differentiated has been all but eclipsed by contestation over how emissions rights should be apportioned. (1) The shift is significant--conceptually and practically. There is, of course, a clear rationale for this shift of focus: Determining a responsibility not to emit more than a certain amount of C[O.sub.2] is, in effect, to license emissions up to that amount, and it is this amount that people want to know and negotiate about. Yet the risk in debating this question is that we lose sight of how addressing the causes of climate change has fundamentally to do with responsibilities for reducing emissions. The focus on rights instead of responsibilities tends to encourage claims of a self-interested character, the competition between which has an inherently expansionary logic. Rights, moreover, can give normative force to imperatives other than that of reducing emissions. This is particularly pronounced when emissions rights become property rights to be traded on markets and, additionally, acquired by such means as the Clean Development Mechanism (CDM), which creates emissions entitlements on the basis of putative emissions forgone rather than actual reductions. When emissions rights take on a life of their own in this way, there is good reason for critical scrutiny of how appropriate they are as a means to the end of aggregate reductions. There is also the question of whether such means tend to promote, or militate against, justice in the distribution of access to the atmosphere's capacity to absorb emissions.