Scientists are able to detect an El Niño event and its effects on the climate through a variety of technological and natural sciences. One of these natural sciences is dendrochronology, or the study of tree rings. Dendrochronologists study the rings of a tree in order to understand climatic conditions during specific time periods. Thin rings often indicate drier seasons while fatter rings indicate rainy seasons. Depending on where the tree is, scientists can see past El Niño events in trees that exhibit signs of much rainier or drier seasons that normal.