Mannomatic smoothing: technical details

Climate Audit

This post is rather technical, and it is intended mainly for the historical completeness. So unless you are very, very interested in the tiny technical details of the HS saga, you can safely skip this.

As most readers are aware, and stated in my post few hours after CG broke out, Mike’s Nature trick was first uncovered by UC here. He was able to replicate (visually perfectly) the smooths of MBH9x thereby showing that the smooths involved padding with the instrumental data. The filter used by UC was the zero-phase Butterworth filter (an IIR filter), which has been Mann’s favourite since at least 2003. However, there was something else that I felt was odd: UC’s emulation required a very long (100 samples or so) additional zero padding. So about two years ago, I decided to take an additional look at the topic with UC.

Indeed, after digitalizing Mann’s smooths…

View original post 390 more words

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