At http://malagabay.wordpress.com/2014/09/25/de-vries-events/ … Tim Cullen has a pop at long term solar cycles, pointing out they rely on proxy data from tree rings and ice cores (and the like) which includes C14 levels in ice cores and dust profiles created from ice cores. I found it rather intriguing that the largest amplitude of the de Vries cycle are found at 8200, 4500, 2500 and 800 years ago. The first three of these have a connection with catastrophic events (or low growth tree ring events) – well known dates at 6200BC, 2500/2300BC, 500BC, plus the odd one just 800 years ago (no answer for that one). Tim Cullen takes us through pages of quotes and graphs and ends up saying the de Vries cycle is really recording a string of catastrophic events. Nothing to do with solar activity – as far as solar output is concerned. It may well be recording solar input via the atmosphere periods of opaque sky (restricting sun shine levels).
Malaga Bay notes something else that is also interesting. That is that ice cores and tree rings display evidence of strong regional bias. Hence, they do not necessarily display the state of play at a global level – just provide some indication. His conclusion is that C14 and Be10 in these proxies only partially reflects solar activity – because the atmospheric process also produces radio nuclides (such as lightning). He then says the de Vries cycle may actually be a series of de Vries events associated, shall we say, with meteor showers – or bolides similar to the Chelyabinsk meteor of last year. In other words, lots of people reading the tea leaves from cycles produced on computers from inputting proxy data of various kinds may in effect be using evidence that has been compromised by cosmic intrusions into the atmosphere. I suppose we could extend the cycling beyond the de Vries variety and add Bond cycles to the mix – and Heinrich events and so on. Interesting points to mull upon.