Not all countries do their fair share in the effort of preventing dangerous climate change. This presents those who are willing to do their part with the question whether they should 'take up the slack' and try to compensate for the non-compliers' failure to reduce emissions. There is a pro tanto reason for doing so given the human rights violations associated with dangerous climate change. The article focuses on fending off two objections against a duty to take up the slack: that it is unfair and ineffective. We grant that it is unfair if some have to step in for others but argue that this does not amount to a decisive objection under conditions of partial compliance. With regard to the charge of emission reductions being ineffective, we argue that the empirical case for this claim is missing and that even if it were not, there still remains the option of taking up the slack in other forms.