American Astronomre A E Douglass, who had a strong interest in studying the climate, developed the method around 1900 (4).
He theorised that tree rings could be used as proxy data to extend climate study back further than had previously been permissible.
Most importantly, assuming there are no gaps in the record (and even if there are short gaps), it can tell us the precise year that a certain tree ring grew (4).
The potential then, even with these two simple sets of data that we may extrapolate from the tree ring data, is enormous.
In each growth season, trees create a new ring that reflects the weather conditions of that growth season.
On its own, a single record can tell us only a little about the environmental conditions of the time in a specific year of the growth of the tree, and of course the age of the tree at felling, but when we put hundreds and thousands of tree-ring records together, it can tell us a lot more.
Dendrochronology is the study of the growth of tree rings and we can learn much from their study.
They come in all shapes and sizes from the smallest saplings up to the colossal redwoods of North America - it could be said that we take them for granted, yet they are vital to teaching us about many aspects of our past. Before then, tree ancestors may have looked slightly tree-like but they were not trees in any proper sense.
The dawn of the age of true trees came with the evolution of wood in the late Devonian period.
Most people who enter into studying tree rings typically come from one of several disciplines: Though dendrochronology also has uses for art historians, medieval studies graduates, classicists, ancient and historians due to the necessity to date some of the materials that the fields will be handling in their research projects.
Typically, a bachelor's degree in any of the above disciplines are enough to study the data that comes out of dendrochronology.