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By Esme StallardBBC News Climate and Science

Global temperatures and rain patterns are affected by a climate phenomenon called the El Niño Southern Oscillation (ENSO) system.

It has two opposite states - El Niño and La Niña - both of which significantly alter The Weather across the globe.

What happens during these events?

For The Last few years, The World has been in successive La Niña periods, which has lowered temperatures and brought heavy rains to Canada and Australia.

Winds blowing along the Equator above the Pacific Ocean - from South America in The East towards Asia in The West - were stronger than normal.

These " Trade Winds " pile warm water off the coast of Asia, raising The Sea surface level. In The East , near the Americas, Cold Water flows upwards to The Surface .

During El Niño The Opposite happens - weaker Trade Winds mean the warm water spreads out back towards the Americas, and less Cold Water rises towards The Surface .

The Phenomenon was first observed by Peruvian fisherman back in the 1600s.

They noticed that the warm waters seemed to peak near the Americas in December, and nicknamed it " El Niño de Navidad" Christ Child in Spanish.

What impact do El Niño and La Niña have on our weather?

Not every El Niño or La Niña event is the same, But scientists have observed some typical effects:

Temperatures

Global temperatures increase by about 0. 2C during an El Niño episode, and fall about 0. 2C during La Niña.

This is because El Niño means warmer water spreads further, and stays closer to The Surface .

This releases more heat into the atmosphere, creating wetter and warmer air.

The hottest year on record, 2016, was an El Niño year.

Between 2020 and 2022, the northern Hemisphere had three La Niña episodes in a row.

Despite the La Niña triple, on Tuesday said 2022 was the fifth warmest year globally.

Prof Adam Scaife from the Met Office said: " Global average temperature over The Last three years has been at near record levels, But it would have been Even Higher without the cooling effects of a prolonged La Niña. "

A 0. 2C temperature rise would add about 20% to the existing global temperature rise from Climate Change .

He went on to say that the Met Office expects La Niña to end later this year, " raising the prospect of Even Higher global temperatures".

Changes to rainfall

During El Niño events, the warmer water pushes The Pacific Jet Stream 's strong air currents further to The South and The East across the Americas.

This brings wetter weather to the southern states of the US and The Gulf of Mexico, whilst areas in the North of the US and Canada can be drier.

Asia, Australia, and Central and Southern Africa typically experience drought.

In La Niña events The Opposite is seen: drought in southern US, and heavy rains in Canada and Asia.

In October 2022, and flooding driven by La Niña.

Tropical storms

La Niña also generates more hurricanes in The Atlantic - affecting Florida and other southern states of the US - But fewer tropical storms in The Pacific .

The Opposite is true of El Niño events.

How often do these episodes happen?

El Niño and La Niña episodes occur every two to seven years, on average, and usually last nine to 12 Months .

They don't necessarily alternate: La Niña events are less common than El Niño episodes.

How do these events affect us?

The Extreme Weather events caused by El Niño and La Niña affect infrastructure, food and energy systems around The World .

The 2014-16 El Niño event caused drought in Canada and Asia, resulting in crop failure and damaging the food security of More Than 60m people,

During El Niño events less Cold Water rises to The Surface off the coast of the Americas which would bring nutrients from the bottom of The Ocean .

That means there is less food available for marine species like squid and salmon, in turn reducing fish stocks for South American fishing communities.

Is Climate Change affecting The Phenomenon ?

In 2021, the UN's climate scientists, the IPCC, said the ENSO events which have occurred since 1950 are stronger than those observed between 1850 and 1950.

However, it also said that historical evidence like tree rings, corals and sediment records shows that there have been variations in the frequency and strength of these episodes since the 1400s.

The IPCC concluded that Climate Change has affected El Niño or La Niña events.

Source of news: bbc.com