> For predictor selection, both proxy climate and instrumental data were linearly detrended over the 1921–1990 period to avoid inflating the correlation coefficient due to the presence of the global warming signal present in the observed temperature record. Only records that were significantly ([pre]p<0.05[/pre]) correlated with the detrended instrumental target over the 1921–1990 period were selected for analysis.
That isn't a typo, it is just being wrong. I'm glad they re-did the work to confirm it was still true, but it's hard to argue with folks who didn't think the claim was supported by the data.