A reconstruction of temperatures over the past 1 000 years that was given prominence in the Intergovernmental Panel on Climate Change Third Assessment Report. The hockey stick has a long flat handle showing roughly constant temperatures in the pre-industrial period, but it has a sharp 20th-century uptick which was seen as the confirmation of global warming. The hockey stick was constructed from a principal components analysis of proxy data (such as tree rings and ice cores). A generous assessment would say the methodology behind the construction has now been shown to be questionable. Given that later analysis has revealed problems with the data, with the statistical techniques, and with the statistical significance it is probably fairer to say it has now been discredited. A. W. Montford, who wrote an influential book on the history of the hockey stick, goes as far as describing it as a ‘corruption of science’. See also climate change; global warming.