Present-day Climate

El Niño-Southern Oscillation

El Niño-Southern Oscillation (ENSO) is the dominant mode of inter-annual climate variability in the present-day climate system, occurring in the tropical Pacific. It is an oscillation with a period of two to seven years between warm (“El Niño”) and cold (“La Niña”) sea surface temperatures (SSTs) in the eastern tropical pacific, and corresponding changes in surface air pressure known as the Southern Oscillation.