This paper seeks to contribute to a re-framing of the debate on the equitability and ambition of actions to address climate change. It examines a sample of seven ‘burden-sharing’ approaches to setting mitigation targets which have been proposed during discussions about a new international agreement on climate change. The paper then analyses the indicative levels of ambition that would be required by the major emitters of greenhouse gases under each of the seven ‘burden-sharing’ approaches, if a particular top-down formula were to be implemented. This analysis concludes that, with the exception of a ‘carbon budgets’ approach, the resulting levels of mitigation effort that would be required from the major emitters under different approaches to ‘burden-sharing’ tend to be clustered around similar outcomes. This is because these approaches are driven by two factors: the requirement to reach an ambitious global end-point target, in terms of limiting the rise in global mean surface temperature, and the growth in the economic size of countries and regions.