Climate, leaves, and the legacy of two giants

Paleobotanical novices have no simple script to follow for using angiosperm fossil floras to test climatic hypotheses in the geological record. Many methods and approaches have been used, none of which can be verified with iron-clad independent methods. This is the current nature of the field. In this issue of New Phytologist, Peppe et al. (pp. 724–739) advance the latest cycle of recalibration of taxonfree leaf-climate methodology, using an expanded set of modern sites. The research is energized by nearly 100 calibration sites and the adoption of ‘digital leaf physiognomy’. Thus, three upgrades have occurred: an analytic method for data capture, a geographic expansion, and a move to multiple linear regression. The global calibration, compared to previous applications of digital leaf physiognomy (Royer et al., 2005), was achieved by adding some of Jack A. Wolfe’s (1993) worldwide sites to earlier datasets, plus c. 30 new sites collected by the authors.