The arrival of a climate-heating El Niño event has been declared by the UN’s World Meteorological Organisation (WMO), with officials warning that preparation for extreme weather events is vital to save lives and livelihoods.

The last major El Niño was in 2016, which remains the hottest year on record. The new El Niño comes on top of the increasing global heating driven by human-caused carbon emissions, an effect the WMO called a “double whammy”. This can supercharge extreme weather, and temperature records are already being broken on land and at sea across the globe.

The WMO said there was now a 90 percent probability of the El Niño event continuing to the end of 2023 at a moderate strength or higher. The chance of a strong and even hotter El Niño at the year’s end was put at 56 percent by U.S authorities in an estimate in early June.

Natural variations in winds and ocean temperatures in the Pacific drive the irregular switches between El Niño and its cooler opposite La Niña. It is the planet’s biggest natural climate phenomenon and affects billions of people.

El Niño usually brings more flooding in the south of the U.S, the south of South America, the Horn of Africa and central Asia, while severe heatwaves and droughts often strike eastern Australia, Indonesia, south Asia and Central America.

“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,” said Petteri Taalas, the WMO secretary-general. “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.”

Record temperatures have been recorded in recent months. In the UK, the average temperature record for June was beaten by nearly a degree and an unprecedented heatwave hit the country’s seas. Sea ice around Antarctica has also hit a record low.

Scientists said this was the climate crisis playing out as they had warned, rather than an unanticipated surge in heating. Some researchers think El Niño could drive 2023 to become the hottest recorded year, though the greater pulse of heat will appear in 2024.

A recent report by the WMO and the UK Met Office estimated a 66% chance of global annual temperatures exceeding pre-industrial levels by 1.5C for at least one year by 2027.

“This is not to say that in the next five years we would exceed the 1.5C level specified in the Paris agreement because that refers to long-term warming over many years,” said Chris Hewitt, the WMO’s director of climate services. “However, it is yet another wake-up call that we are not yet going in the right direction to limit the warming to within the targets designed to substantially reduce the impacts of climate change.”