What are usually quoted as periods are better referred to as characteristic time scales. (tamino.wordpress.com)
Finally, we find that a series of damped random walk models provides a good fit to the 10Be data with a fixed characteristic time scale of 1000 years, which is roughly consistent with the quasi-periods found by the Fourier and wavelet analyses. (aanda.org)
Nor do I claim that they don't show characteristic time scales — just that the evidence is often sketchy at best. (tamino.wordpress.com)