Many works in climate ethics—including recent books by Dale Jamieson, Stephen Gardiner, Darrel Moellendorf and Donald Brown—have characterised the world’s inadequate response to climate change to date as a serious moral failure. Nevertheless, views are divided over the potential for moral discourse to promote an effective policy response to climate change. In domestic political debates, a pressing concern is that moral language may be ineffectual where a substantial proportion of citizens are sceptical of the scientific basis for human-induced global warming and thus do not see climate change as a problem at all, let alone a moral problem. By contrast, in international climate negotiations and their associated treaties moral language has long had a stronger foothold, even though national governments’ positions in the negotiations remain constrained by their citizens’ preferences. Accordingly, I argue that the more important role for moral language in multilateral negotiations is not so much to secure consensus that climate change is a moral problem, but rather to help broker an effective global agreement among countries that hold divergent reasonable conceptions of fairness. To this end, I highlight two priorities for climate policy advocates: (i) reinvigorating existing forms of moral language by discarding some of the divisive legal connotations that terms such as ‘equity’ have acquired; and (ii) identifying and employing forms of moral language that represent what John Dryzek refers to as ‘bridging rhetoric’ in preference to ‘bonding rhetoric’. I conclude with some comments on the implications of this case study for non-ideal theories of climate justice