US support was probably critical to IPCC’s establishment. And why did the US government support it? Assistant Undersecretary of State Bill Nitze wrote to me a few years later saying that our group’s activities played a significant role. Among other motivations, the US government saw the creation of the IPCC as a way to prevent the activism stimulated by my colleagues and me from controlling the policy agenda.
I suspect that the Reagan Administration believed that, in contrast to our group, most scientists were not activists, and would take years to reach any conclusion on the magnitude of the threat. Even if they did, they probably would fail to express it in plain English. The US government must have been quite surprised when IPCC issued its first assessment at the end of 1990, stating clearly that human activity was likely to produce an unprecedented warming.
The IPCC’s first assessment laid the groundwork for negotiation of the UN Framework Convention on Climate Change (UNFCCC), signed at the Earth Summit in 1992. In a sense, the UNFCCC and its progeny, the Kyoto Protocol, were unintended consequences of the US support for establishment of IPCC – not what the Reagan Administration had in mind!