The Intergovernmental Panel on Climate Change – the IPCC – is the global authority on climate science and behind some of the most important policy changes in the history of industrial society. It is therefore probably the most influential scientific body in the world. Yet the surprising story of how it came to prominence is little known. Its origins can be traced back to earlier panics over the effects of supersonic transportation and ozone layer depletion, which taught political elites that science-based scares could be powerful drivers of policy action. It was as an authority fit to deliver the required evidence on climate change that the IPCC came into being. However, in the rush towards a climate treaty, IPCC scientists continued to report that evidence of manmade climate change was scarce and that confirmation of a manmade effect should not be expected for decades. Without a `catastrophe signal' that could justify a policy response, the panel faced its imminent demise.