In its resolution 4/23 on keeping the world environment under review and enhancing the science-policy interface of the United Nations Environment Programme (UNEP), the United Nations Environment Assembly of UNEP requested the Executive Director of UNEP to prepare a proposal for policy-making input on the global environment, in consultation with Member States and making use of contributions from relevant stakeholders, in commemoration of the establishment of UNEP, in line with the recommendation of the United Nations Conference on the Human Environment, held in Stockholm from 5 to 16 June 1972. The fiftieth anniversary of the establishment of UNEP is an opportunity to reflect on the past, and envision the future, of UNEP. The scientific output of UNEP over its long history has made the case for environmental sustainability clear. Now, this science needs to be translated into action in the framework of a renewed science-policy interface. The renewed interface must tackle today’s environmental crises using the latest science and cutting-edge digital tools and technologies. It is also vital to have engagement with a broader range of stakeholders and a transparent, agile and inclusive process. The Environment Assembly at its special session to commemorate the establishment of UNEP may wish to recognize that UNEP exists in a very different world from that of 1972. Progress towards achieving the Sustainable Development Goals and addressing the triple planetary crisis – of climate change, nature and biodiversity loss, and pollution and waste – has not advanced at the pace and intensity required to reach internationally agreed environmental goals. The next 50 years will see a host of disruptions that will provide both opportunities and challenges. The annex to the present note, which has not been formally edited, sets out a report on progress in the implementation of resolution 4/23. The report, entitled Reflecting on the Past and Imagining the Future: A Contribution to the Dialogue on the Science-Policy Interface, provides proposals for new models for a more effective science-policy interface that is socially relevant and economically robust, and that contributes to intergenerational equity in support of global environmental governance. The report is expected to inform the discussions at the special session, in particular the high-level leadership dialogues and the multi-stakeholder dialogue. The report is also expected to facilitate an exchange of views between Member States and stakeholders on the strengthening of the science-policy interface in the context of a reinvigorated global environmental multilateralism, and as part of the overall objectives outlined in the report of the United Nations Secretary-General entitled “Our common agenda”.