Richard Staley: "The Undead in Climate History: On the Birth, Life and Uncertain Death of the Medieval Warm Period"

  • Date: –15:00
  • Location: Zoom-meeting:
  • Organiser: Department of History of Science and Ideas
  • Contact person: H. Otto Sibum
  • Seminarium

Office for History of Science Seminar

Richard Staley, Cambridge University & Copenhagen University

This paper takes up the birth and potential death of a concept that has played a major role in defining the contributions of dendrochronology to climate science, shaping debates between climate scientists and sceptics, and sharpening tensions between local and global understandings of climate: the Medieval Warm Period. Resting primarily on Hubert Lamb’s early work on climate in England, which drew on a variety of sources and was regionally focused, the concept is arguably a misbegotten child. Its most influential instantiation came in a diagram published by the IPCC in 1990 whose general labelling and schematically global form belied a brief but notably more cautious description in the text. In the mid 1990s dendrochronologists and historical meteorologists questioned the probity of the concept, asking whether, where and when there may have been a ‘medieval warm period’. Michael Mann’s infamous ‘hockey stick graph’ offered a potential obituary which has been supported by later studies – at least in general terms. However, the concept has remained important for sceptics as an illustration of a warm period in which carbon dioxide increase played no role, and renaming practices amongst both sceptics (who paste ‘MWP’ over unlabelled graphs from others) and climate scientists (who offered ‘medieval climate anomaly’ as an alternative) indicate that it is still a testing ground for the negotiation of the status of local and global climate signatures. This paper offers a case study of respects in which the life, death and generality of a concept depended upon both research practices and discourse practices amongst an emerging community of researchers. What can the potential death of an object of research, a climate period, tell us about the past of our planet, and the nature of climate science?