El Niño is part of a natural climate pattern called the El Niño-Southern Oscillation (ENSO). ENSO is a fluctuation in the ocean temperatures and atmospheric pressures in the Pacific Ocean, which affects the global climate. During an El Niño event, the trade winds that normally blow from east to west along the equator slow down or even reverse direction. This allows warm water from the western Pacific to flow towards the eastern Pacific, leading to an increase in the sea surface temperature.