ENSO refers to the periodic “shift” in sea surface temperatures across the equatorial Pacific Ocean that affects climate in a large portion of the world. The acronym ENSO comes from two such climate shifts, one known as El Nino (which corresponds to changes in precipitation and temperatures in the Eastern Pacific), and the other known as the Southern Oscillation (which refers to changes in surface air pressure in the Western Pacific).

This Reading provides background information on the underlying concepts in the Activities included in the Project Earth Science: Meteorology, Revised 2nd Edition. The Reading goes beyond what is found in the background information in the activities. The Reading can be used as supplementary information for the teacher, or to enhance classroom discussions.