What are El Niño and La Niña? El Niño is here and it is dangerous, warn weather scientists

The heatwave El Niño is here and it is set to claim lives, weather scientists have warned.

The climate-heating El Niño event has today been officially declared by the UN’s World Meteorological Organization (WMO), which is calling on countries to “prepare” for the extreme weather to save lives.

The group said lives and livelihoods could be lost if preparation is ignored, labelling the extreme heat plus the increase in human-induced carbon emissions a “double whammy” for disaster.

Temperature records are being broken on land and sea across the world and the WMO has said there is now a 90 per cent probability that El Niño will continue until the end of 2023.

The last major El Niño was in 2016 and it remains the hottest year on record. However, the WMO has said the chance of a stronger and hotter event this year could be high, with an even greater risk for 2024.

WMO secretary-general Petteri Taalas said: “The onset of El Niño will greatly increase the likelihood of breaking temperature records and triggering more extreme heat in many parts of the world and in the ocean.

“The declaration by WMO is the signal to governments around the world to mobilise preparations. Early warnings and anticipatory action of extreme weather events associated with this major climate phenomenon are vital to save lives and livelihoods.”

So what is the naturally occurring El Niño weather system and its opposing phase, La Niña?

What are the El Niño and La Niña weather events?

El Niño and La Niña refer to fluctuation in the Earth’s climate system, according to the Met Office. They mean little boy and little girl in Spanish respectively. It is believed that they got their names from South American fishermen in the 1600s, who noticed periods of unusually warm water. It was initially called El Niño de Navidad (which means Christmas in Spanish) because El Niño typically peaks around December.

During El Niño, the sea surface temperature rises, usually in the central-east equatorial Pacific, and it typically occurs every few years. During this phase, the tropical eastern Pacific will experience warmer-than-average weather.

On the other hand, La Niña is when the sea surface temperature becomes cooler than average, with sea temperatures often dropping by 3°C to 5°C below average. This results in cooler-than-average weather in the tropical eastern Pacific.

The Earth’s climate system experiences neutral phases when the temperatures are closer to long-term averages.

What are the impacts of El Niño and La Niña?

El Niño and La Niña affect weather around the world. For example, El Niño can increase the chance of the UK having cold winters but it also limits the development of tropical storms in the North Atlantic. These phases can last anywhere from around nine months to a few years, according to the National Oceanic and Atmospheric Administration. According to the WMO, the Earth has been in the La Niña phase for the past three years, which has “temporarily reined in the longer-term warming trend”.

However, La Niña ended in March 2023 and El Niño is forecast to develop in the coming months.

There is a 98 per cent chance of at least one of the next five years breaking temperature records, as well as a 98 per cent chance that the next five years are hotter on average than the past five years.

Will the world breach the climate threshold?

Scientists have warned that the world could breach the 1.5°C climate threshold by 2027.

Research from the WMO has found that it is highly likely that the world will experience record-breaking temperatures in the next five years. Scientists have said that the increasing global temperatures are down to both human activity as well as the developing El Niño weather system.

“A warming El Niño is expected to develop in the coming months and this will combine with human-induced climate change to push global temperatures into uncharted territory,” said the WMO’s secretary-general, Professor Petteri Taalas, in the WMO report.

He added: “This will have far-reaching repercussions for health, food security, water management, and the environment. We need to be prepared.”

What are the El Niño and La Niña weather events?

El Niño and La Niña refer to fluctuation in the Earth’s climate system, according to the Met Office. They mean little boy and little girl in Spanish respectively. It is believed that they got their names from South American fishermen in the 1600s, who noticed periods of unusually warm water. It was initially called El Niño de Navidad (which means Christmas in Spanish) because El Niño typically peaks around December.

During El Niño the sea surface temperature rises, usually in the central-east equatorial Pacific, and it typically occurs every few years. During this phase, the tropical eastern Pacific will experience warmer-than-average weather.

On the other hand, La Niña is when the sea surface temperature becomes cooler than average, with sea temperatures often dropping by 3°C to 5°C below average. This results in cooler-than-average weather in the tropical eastern Pacific.

The Earth’s climate system experiences neutral phases when the temperatures are closer to the long-term averages.

What are the impacts of El Niño and La Niña?

El Niño and La Niña affect weather around the world. For example, El Niño can increase the chance of the UK having cold winters but it also limits the development of tropical storms in the North Atlantic. These phases can last anywhere from around nine months to a few years, according to the National Oceanic and Atmospheric Administration.

According to the WMO, the Earth has been in the La Niña phase for the past three years, which has “temporarily reined in the longer-term warming trend”.

Now, the El Niño has arrived. Eecord temperatures have been recorded in recent months.

In the UK, the average temperature record for June was beaten by a degree and the sea ice around Antarctica has also hit a record low.

Scientists expect that El Niño will make next year the hottest on record, potentially pushing the world past the 1.5°C climate threshold.

Alongside making the world warmer, El Niño could result in a drought in Australia. Heavy rainfall could also occur in southern states in the US as well as in South America.