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: Archives of climate proxies were developed : in 1993 Raymond S. Bradley and Phil Jones composited historical records, tree-rings and ice cores for the Northern Hemisphere from 1400 up to the 1970s to produce a decadal reconstruction.