El Ni o is not caused by anthropogenic activities, but anthropogenic activities may change the magnitude and character of El Ni o events. El Ni o is a disruption of the ocean-atmosphere system in the tropical Pacific having important consequences for weather and economics around the globe. This condition results in redistribution of rains with flooding and drought. Basics of ENSO a. Western equatorial Pacific has some of the world's warmest ocean water.
Warm water moves back eastward across the Pacific, like water shifting in a giant bathtub.
The warm water and shifting winds interrupt the upwelling of cool, nutrient-rich water. El Ni o was named by Peruvian fisherman who have know about the anomalous warming of coastal waters since the 1800s. La Ni a refers to anomalously cool conditions in the same equatorial Pacific water, leading to very different climatic consequences. The water is transported by these internal waves. Kelvin waves cross the Pacific in 2-3 months and lead to a warming of the surface waters and rise in sea level along Peru.