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The El Niño Pacific Ocean warming effect that has contributed to a spike in global temperatures is expected to swing to its opposite La Niña cooling phase from late summer, say weather experts, but without slowing long-term climate change.
A rapid transition from one extreme to the other in the tropical Pacific would see more parts of the world battered by weather events, not long after the strong El Niño warming event has wreaked havoc on rainfall patterns and commodity prices.
The World Meteorological Organization of the UN said there is now a 70 per cent chance of La Niña occurring between August and November.
The cyclical La Niña effect is “likely” to start later this year, the WMO said, while El Niño shows signs of ending after driving deadly flooding in Brazil last month.
La Niña is typically linked to its own cascade of localised knock-on effects including a surge in Atlantic hurricanes, flooding in Canada and western North America, and drought conditions in parts of South America.
“We’ve really been swinging back and forth between one extreme to the other,” said Nathaniel Johnson, a meteorologist who works on the US National Oceanic and Atmospheric Administration’s forecasting of Pacific Ocean temperature changes.
There was some evidence that climate change had contributed to the strength and speed of these naturally-occurring swings, he added.
La Niña describes cooling of the ocean surface temperatures in parts of the vast Pacific Ocean and associated changes to winds, pressure and rainfall.
It has the potential to cause temporary dips in global average temperatures. But this would “not mean a pause in long-term climate change as our planet will continue to warm due to heat-trapping greenhouse gases”, said WMO deputy secretary-general Ko Barrett.
The agency highlighted that the past nine years had been the warmest on record in spite of a long and rare “triple-dip” La Niña effect that took place between 2020 and early 2023.
Land temperatures are expected to keep exceeding historical averages this year after 12 consecutive months of record temperatures, while sea surface temperatures outside the affected parts of the Pacific Ocean also remain “exceptionally high”.
The WMO said while the chances of La Nina were increasing, it was still too early to predict the phenomenon’s strength and duration with certainty.
It anticipated more rainfall than normal this year in parts of the Caribbean, the Horn of Africa and south-west Asia, consistent with the typical start to La Niña cycles.
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