The Evolution of Communicating the Uncertainty of Climate Change to Policymakers: A Study of IPCC Synthesis Reports

Abstract

The Intergovernmental Panel on Climate Change (IPCC) reports on climate change have served to alert both the public and policymakers about the scope of the predicted changes and the effects they would have on natural and economic systems. The first IPCC report was published in 1990, since which time a further four have been produced. The aim of this study was to conduct a content analysis of the IPCC Summaries for Policymakers in order to determine the degree of certainty associated with the statements they contain. For each of the reports we analyzed all statements containing expressions indicating the corresponding level of confidence. The aggregated results show a shift over time towards higher certainty levels, implying a 'Call to action' (from 32.8% of statements in IPCC2 to 70.2% in IPCC5). With regard to the international agreements drawn up to tackle climate change, the growing level of confidence expressed in the IPCC Summaries for Policymakers reports might have been a relevant factor in the history of decision making.