Temperatures are expected to soar further across large parts of the world after the El Niño weather pattern emerged in the tropical Pacific for the first time in seven years, the World Meteorological Organization said on Tuesday.

El Niño, a warming of water surface temperatures in the eastern and central Pacific Ocean, is linked to extreme weather conditions from tropical cyclones to heavy rainfall to severe droughts.

“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,” WMO Secretary-General Petteri Taalas said in a statement.

WMO said there was a 90% probability of El Niño persisting in the second half of 2023, and that it was expected to be “at least of moderate strength”.

The statement from the global body confirmed a report last month from the US National Oceanic and Atmospheric Administration’s Climate Prediction Center that the phenomenon had returned.

The WMO noted that El Niño’s effect on global temperatures is usually felt most strongly within a year of its onset - in this case in 2024.

Since 2020, the world has been affected by an exceptionally long La Niña - El Niño’s cooling opposite - which ended earlier this year.

And yet, the UN has said the last eight years were the warmest ever recorded, despite La Niña’s cooling effect stretching over nearly half that period.

Without that weather phenomenon, the warming could have been even worse.

“The declaration of an El Niño by WMO is the signal to governments around the world to mobilise preparations to limit the impacts on our health, our ecosystems and our economies,” said Taalas.

“Early warnings and anticipatory action of extreme weather events associated with this major climate phenomenon are vital to save lives and livelihoods.”

The world’s hottest year on record, 2016, coincided with a strong El Niño - though experts says climate change has fuelled extreme temperatures even in years without the phenomenon.

Even that record could soon be broken, according to the WMO.

The organisation said in May that there was a strong likelihood that at least one of the next five years, and the five-year period as a whole, would be the warmest on record due to El Niño and anthropogenic global warming.

“To tell you whether it will be this year or next year is difficult,” Wilfran Moufouma Okia, Head of Regional Climate Prediction Service at WMO, told reporters in Geneva.

“What we know is that throughout the next five years, we are likely to have one of the warmest years on record.”

The World Health Organization said last month it was preparing for an increased spread of viral diseases such as dengue, Zika and chikungunya linked to El Niño.

During El Niño, winds blowing west along the equator slow down, and warm water is pushed east, creating warmer surface ocean temperatures.

The phenomenon occurs on average every two to seven years, and can last nine to 12 months, according to the WMO.

It is typically associated with increased rainfall in parts of southern South America, the southern United States, the Horn of Africa and Central Asia.

In the past, it has caused severe droughts in Australia, Indonesia, parts of southern Asia, Central America and northern South America.