While this is interesting, it really strikes me that there isn't that much data available. Would this pattern hold if you saw another 100 years into the past? Will it hold an additional 100 years in the future?<p>Cute, but... doesn't seem very significant?
That is a true statement on a 150 year timescale (or possibly even a millennial timescale) but on a geologic timescale it is very false. Also, it is misleading to attribute this deviation solely to the activities of man when solar output has been on the rise for nearly two centuries (<a href="http://en.wikipedia.org/wiki/File:Solar_Activity_Proxies.png" rel="nofollow">http://en.wikipedia.org/wiki/File:Solar_Activity_Proxies.png</a>)