Book excerpt: It now seems incontrovertible (as Alessandra Giannini has demonstrated) that the series of Sahelian droughts that began in the early 1970s were driven by changes in sea surface temperatures and that they were not caused by local land use mismanagement in the Sahel itself. Combined with the apparent re-greening of the Sahel, these findings effectively close a long-standing policy and scientific debate (in which the lead authors of this book participated) on the causes and extent of desertification in the Sahel. The opportunity now presents itself to treat this debate as a historical object lesson in the relationship between science, the formation of public opinion, and international policy-making in the context of climate change. In short, what might the ‘great Sahelian desertification boondoggle’ have to tell us about current attempts to come to grips with climate change?