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What is El Niño?

El Niño and La Niña are terms which describe the biggest fluctuation in the Earth's climate system and can have consequences across the globe. The fluctuation sees changes in the sea-surface temperature of the tropical Pacific Ocean which occur every few years.

Video: What is El Niño?

What causes El Niño?

These events are due to strong and extensive interactions between the ocean and atmosphere. They are associated with widespread changes in the climate system that last several months, and can lead to significant human impacts affecting things such as infrastructure, agriculture, health and energy sectors.

The name 'El Niño' nowadays is widely used to describe the warming of sea surface temperature that occurs every few years, typically concentrated in the central-east equatorial Pacific. 'La Niña' is the term adopted for the opposite side of the fluctuation, which sees episodes of cooler-than-normal sea surface temperature in the equatorial Pacific.

These episodes alternate in an irregular inter-annual cycle called the El Niño Southern Oscillation (ENSO). Southern Oscillation is the term for atmospheric pressure changes between the east and west tropical Pacific that accompany both El Niño and La Niña episodes in the ocean. ENSO is the dominant feature of climate variability on inter-annual timescales.

Our research helped show that El Niño and La Niña cycle has impacts all over the world. For example, El Niño years are one factor that can increase the risk of colder winters in the UK. We now better understand these impacts and reproduce many of them in our climate models.

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