The effectiveness of any agreement depends on the perception of fairness by all parties involved. This is particularly the case where agreements require cooperative action, as under the United Nations Framework Convention on Climate Change (UNFCCC).  In analysing the key arguments of various approaches to equity, this paper reflects on the basis and relevance of equitable access to sustainable development (EASD) in the UNFCCC negotiations. The author goes on to present a perspective on an Equity Reference Framework (ERF), and considers how it may form part of future agreements. The history of EASD in negotiations is reviewed, looking at the emergence of principles such as ‘common but differentiated responsibility’, the various wordings that have defined responsibility and goals in previous agreements, and the recognition of the necessity for facilitating sustainable development. The theoretical and expressed approaches of equity are covered, with a focus on distributive and corrective justice, as well as metric and non-metric approaches. The paper makes a case for an ERF whose underlying philosophy is the universal application of egalitarian principles, and incorporates historical, current and potential inequities with regard to contribution to emissions. As such, it is corrective in character and distributive in approach. Furthermore, rather than simply proposing binding commitments on a minimum emission reduction, parties should have the flexibility to include a mix mitigation, adaptation, and financial and technological investment in their efforts. The structure of the ERF is premised on maintaining the Convention structure of Annexes. The developed countries commitments focus on economy-wide emissions reductions and financial and technological support for adaptation and mitigation, whilst developing countries recognise domestic adaptation and mitigation investment. Technical details on the integration of the concept of an ERF to the Ad hoc Group on the Durban Platform for Enhanced Action are provided, outlining a possible path toward a final text to be adopted at COP20 or 21. The report concludes that the UNFCCCs principles provide an adequate basis to establish fairness. There is a case for a reference framework against which fair efforts may be judged, allowing flexibility for individual countries to account for national circumstances when addressing their responsibility. Combining metrics and non-metrics in a non-binding ERF will allow for the facilitation of ambition in the commitment of parties.