After two years of intensive negotiations, 156 countries signed a Framework Convention on Climate Change at the United Nations Conference on Environment and Development (UNCED), convened in Rio de Janeiro, Brazil, in 1992. Bert Bolin, chairman of the Intergovernmental Panel on Climate Change (IPCC) from 1988 to 1997, believed that it would not have happened if a "well-organized and scientifically credible assessment had not been available in 1990." In turn, the IPCC assessment was possible "only because assessments initiated by the US National Academy of Sciences and the international scientific community had begun a decade earlier." As stated by Bolin, "the emergence of the climate change issue was primarily scientifically driven." But how did the issue move from the realm of science to the realm of politics? Who were the agents of this process? A series of documents produced by scientists, NGO and foundation officers, preserved in archival collections at the Rockefeller Archive Center, provides previously unexplored information about how the climate change issue broke onto the international policy making agenda in the 1980s.