Here is another one for you: Is radiocarbon dating based on assumptions?
Even a child should be able to understand this by now.
Lots of problems w/ that link.
If you follow the link you provided, you can see that the tree-rings don't line up very well at all. They are only marginally comparable. Then follow the link to the page that discusses the 'extension' process where pieces laying around, from peat bogs and old buildings are used and you get a much better idea of how unreliable tree-ring dating really is. There is at least as much variability and human interpretation in tree-ring dating as in anything else.
Finally, how was C14 dating modified based on tree-ring chronologies? Any at all?