claim: it later emerged that its creator Dr Michael Mann had spliced too [sic] datasets together – tree-rings showing temperatures going back hundreds of years, then recent thermometer readings for the more recent decades.
evidence: published on 10 February 2005 used a wavelet transform technique to reconstruct Northern Hemisphere temperatures over the last 2,000 years, combining low-resolution proxy data such as lake and ocean sediments for century-scale or longer changes, with tree ring proxies only used for annual to decadal resolution.
category: Hockey stick graph