Methods of dating from tree rings
The rings are the cambium layer, a ring of cells that lies between the wood and bark and from which new bark and wood cells originate; each year a new cambium is created leaving the previous one in place.How large the cambium's cells grow in each year, measured as the width of each ring, depends on temperature and moisture—how warm or cool, dry or wet each year's seasons were.
The interlopers defaced the ships, damaged the grave goods and pulled out and dispersed the bones of the deceased.
Not all trees can be measured or used without additional analytical techniques: not all trees have cambiums that are created annually.
In tropical regions, for example, annual growth rings are not systematically formed, or growth rings are not tied to years, or there are no rings at all.
Fortunately for us, the looters left behind the tools they used to break into the mounds, wooden spades and stretchers (small handled platforms used to carry objects out of the tombs), which were analyzed using dendrochronology.
Tying tree ring fragments in the tools to established chronologies, Bill and Daly (2012) discovered that all three of the mounds were opened and the grave goods damaged during the 10th century, likely as part of Harald Bluetooth's campaign to convert Scandinavians to Christianity.
That is an issue because because since global climate change is in progress, we need to understand the physical, chemical and biological processes that effeect terrestrial carbon levels is increasingly important.