What causes the pacific ocean to become warmer off coast of Peru?

The El Niño-Southern Oscillation (ENSO) is a natural climate pattern that causes the surface temperature of the Pacific Ocean to vary. During the warm phase of ENSO, known as El Niño, the surface temperature of the Pacific Ocean off the coast of Peru becomes warmer than normal. This warming of the ocean can cause changes in weather patterns around the world, including increased rainfall in Peru and droughts in other parts of the world.