Loehle and Scafetta paper reception
Let us be clear, there are apparent cycles in the climate record. But it is not known whether or not
(a) they are real (i.e. they are harmonic oscillations and/or forced effects of real phenomena)
(b) they are merely apparent (i.e. all varying data can be represented as a sies of oscillations).
The best one can do with a chaotic (or quasi-chaotic) system is to identify a set of apparent oscillations and to extrapolate them. This can work for some time (as several stock market predictions have shown) but is prone to be misleading in the medium or long term (as all stock market predictions have shown).
The Loehle and Scafetta method may work as a predictive method for the short-term but has high risk of being wrong in the longer term if no mechanisms governing its cycles are identified.
And if the method is not predictive then it is an incorrect model. But an incorrect model cannot identify processes (e.g. AGW) that contribute to changes in the time series.
Hence, I consider the analysis of Loehle and Scafetta to be interesting but should be subject to much caution until the cause(s) of its 60 and 20 year cycles are identified.
[Start of the comments on WUWT on the discussion on the Loehle and Scafetta paper, are mixed about the results. But as the discussion rambles on into the later posters Tall bloke and Lief S get on into the meat of the cycles periods of the planetary drivers]