With the formation of the World Climate Programme after the 1979 World Climate Conference, the World Meteorological Organization and the United Nations Environment Programme - together with the International Council of Scientific Unions - signalled their determination to pursue climate and climate change studies. Their joint efforts reached a decision stage at the International Conference on the Assessment of the Role of Carbon Dioxide and of Other Greenhouse Gases in Climate Variations and Associated Impacts (Villach, Austria, 1985)the findings of the Conference and subsequent meetings on the subject laid the foundation for the current international activities on global wanning. A major contributor to the activities is the Intergovernmental Panel on Climate Change (IPCC), jointly established by our two organizations in 1988 under the Chairmanship of Professor Bert Bolin. The Panel formed three Working Groups (a) to assess available scientific information on climate change (Working Group I), (b) to assess environmental and socio-economic impacts of climate change (Working Group II), and (c) to formulate response strategies (Working Group III) and a Special Committee on the Participation of Developing Countries to promote the participation of those countries in its activities. The IPCC First Assessment Report was completed in August 1990 and consists of: the Overview, the IPCC Scientific Assessment, the IPCC Impacts Assessment, the IPCC Response Strategies (the last three including the respective Policymaker Summaries) and the Policymaker Summary of the IPCC Special Committee. The Report has now become a standard-work of reference, widely used by policymakers, scientists and other experts and represents a remarkable co-ordinated effort by hundreds of specialists from all over the world. Anticipating a continuing need for the most current information on climate change in the context of the ongoing negotiations on the Framework Convention on Climate Change and the United Nations Conference on Environment and Development (Rio de Janeiro, June 1992), and as mandated by the governing bodies of our two organizations, the IPCC requested its three Working Groups in March 1991 to produce updates of their 1990 reports. The result is the 1992 IPCC Supplement which was completed in February 1992. This volume contains the Supplement and the 1990 Overview and Policymaker Summaries.