What causes the phenomenon known as "El Niño"?

The phenomenon known as "El Niño" is primarily caused by changes in oceanic and atmospheric circulation patterns. These changes impact sea surface temperatures in the central and eastern Pacific Ocean, leading to a variety of weather effects globally. During an El Niño event, the trade winds that typically blow from east to west across the Pacific weaken, causing warm water to pool in the eastern Pacific. This shift alters the normal patterns of oceanic currents and atmospheric circulation, which can lead to increased rainfall in some areas and droughts in others.

El Niño's effects can influence global weather patterns significantly, including disruptions to monsoons and hurricanes. Understanding these changes is critical for predicting climate variations and preparing for potential impacts on agriculture, ecosystems, and weather systems worldwide.