El Niño-Southern Oscillation, or ENSO, is a climate pattern that occurs across the tropical Pacific Ocean on average every five years, but over a period which varies from three to seven years, and is therefore, widely and significantly, known as "quasi-periodic".

ENSO is best-known for its association with floods, droughts and other weather disturbances in many regions of the world, which vary with each event.

Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected.

In 1876-79, famine in northern China kills 13 million people.

5.25 million die in the Great Famine of 1876–78 in India.