There are measured ring-width chronologies from all over Europe. Years which are hot and dry give small amounts of tree growth; wetter years give more growth.

There are measured ring-width chronologies from all over Europe. Years which are hot and dry give small amounts of tree growth; wetter years give more growth. The sequence of thick and thin rings correlates across large regions, allowing the dating of oak wood with a sufficient number of rings -- about 100 for good certainty. In many cases it is possible to identify a much finer location where trees were grown. While there is some correlation between (say) weather in Sweden and Germany, the correlation is much higher in nearby locations. It is often possible to locate wood to a specific forest just based on the ring widths.