Curious to learn more about the El Niño–Southern Oscillation (ENSO) cycle and its phases La Niña and El Niño? The El Niño–Southern Oscillation (ENSO) is a naturally occurring cycle in the climate system describing the shift in ocean temperatures along the equator in the Pacific Ocean that leads to changes in the overlying atmospheric circulation patterns. There are 2 active phases of this cycle: La Niña and El Niño. During El Niño, waters in the central or eastern tropical Pacific Ocean are warm