The latter is the opposite of the former and make up an oscillation known as ENSO. Understanding them requires knowledge of a broad range of data from multiple disciplines. Typically,researchers who understand the processes and study their causes and effects have post-graduate degrees in such disciplines a so angora physical, geography,climatology and meteorology.The phenomena and the data extrapolated from them,have applications for paleoclimatology (the study of climate in the past),anthropology,palaeobotany and archaeology,particularly in what we can extrapolate from the changes to tree ring data (dendrochronology)