Final answer:
El Niño affects the climate primarily around the Pacific Ocean, where it causes a shift in air pressure and weather patterns, influencing global weather conditions and extreme weather events.
Step-by-step explanation:
El Niño is the warm phase of the El Niño Southern Oscillation (ENSO) and has significant effects on the climate around the world. The ocean that is primarily affected by El Niño is the Pacific Ocean, where a band of warm ocean water develops in the central and east-central equatorial regions. This event not only impacts the local weather patterns but also extends its influence to global weather phenomena, contributing to extreme weather conditions in various regions.
During El Niño, there is a notable change in air pressure, with high air pressure observed in the western Pacific and low air pressure in the eastern Pacific. These atmospheric changes are associated with shifts in rainfall and temperature patterns far beyond the Pacific. For example, it can lead to increased rainfall in the southern United States and Peru, and drought in the western Pacific, affecting economies dependent on agriculture and fishing.