By Kate Abnett
BRUSSELS, June 2 (Reuters) - The El Nino weather pattern is forming, and is expected to cause extreme weather around the world this year, the WMO said on Tuesday. Scientists say climate change will make its impact especially severe.
The World Meteorological Organization said there is an 80% chance that an El Nino event develops between June and August, and a 90% chance it will last until at least November. The statement is the clearest signal yet of the likelihood.
The El Nino phenomenon
naturally occurs every two to seven years, when weakening trade winds result in warmer waters in the eastern Pacific. The result tends to be higher global temperatures, and disrupted rainfall - meaning drought in some regions, heavy rains in others. It also affects hurricane formation.
Two things make this year's forecast particularly worrying.
The first is the chance that this year's El Nino - and its impact - will be stronger than typical.
The WMO said there was still uncertainty, and some models predict a "strong" El Nino while others do not. WMO forecasts suggest a strong El Nino is possible, defined by sea surface temperatures in the eastern Pacific of at least 1.5 degrees Celsius (2.7 degrees Fahrenheit) above average.
The second cause for concern is climate change.
Greenhouse gas emissions have increased the planet's average temperature by around 1.3C since pre-industrial times.
That higher baseline supercharges the effects of El Nino - enabling higher temperature spikes, more intense droughts, heatwaves, rains, and the resulting disasters, including bushfires, floods and crop failures.
"When we get an El Nino, because of the underlying climate change ... these things become more intensified and they're more impactful," said Piers Forster, Professor of Physical Climate Change at the University of Leeds.
The combination of climate change and El Nino has led the WMO to warn that 2027 could be the hottest year since records began. The last El Nino year, 2024, holds the record. That El Nino was regarded by the WMO as strong.
'THE RISKS ARE ENORMOUS'
Each El Nino is different, and its effects vary around the world - making it hard to predict how this one will behave.
Typically, regions including southern South America and parts of Central Asia get more rain in an El Nino, while Central America and Australia dry out. The phenomenon also intensifies heatwaves, including in regions far from the Pacific, such as Europe.
These effects can have disastrous consequences for food production, industries and human life.
In April to May 2024, floods in Rio Grande do Sul in Brazil killed more than 180 people and displaced 600,000. Scientists said both climate change and El Nino strengthened the rains that triggered the disaster.
Francisco Aquino, head of the University of Rio Grande do Sul's climate centre, said a strong El Nino this year risked causing a similar disaster.
"When you have an El Nino over what climate change already brought, the risks are enormous," Aquino told Reuters. "A strong El Nino can lead to the exact same scenario we saw then, because the world keeps getting warmer, and the temperature in the ocean keeps rising."
Climate change is also compounding the impact of El Ninos in southern Africa. There, the weather pattern reduces rainfall during the rainy season, limiting hydropower generation and cutting crop yields.
"Climate change will make that below-normal rainfall more intense, so it will last longer or have less rainfall... and that, of course, will affect agriculture, especially the rain-fed farmers in the region," said Izidine Pinto, a Senior Climate Researcher at the Netherlands Meteorological Institute.
Antonio Navarra, head of Italy's Euro-Mediterranean Center on Climate Change, said stronger Pacific cyclones were another impact governments should prepare for.
"Because the water in the Pacific will be much warmer, there will be a much more favourable environment for the formation of tropical cyclones.... El Nino will input an enormous amount of energy into the system, so everything will be more intense," he said.
Some scientists said the destruction likely from this year's El Nino could provide a foretaste of extremes that will become the norm in around five years' time even without an El Nino.
"It does give a window into the future," said Forster.
Theodore Keeping, Research Associate at Imperial College London, said El Nino's impact on atmospheric circulation means it affects weather patterns in a way that a warmer climate alone would not - but broadly speaking, it can offer a flavour of future climate change.
"You're able to kind of sample weather conditions that you would otherwise in a neutral El Nino [year] only expect to see in a warmer climate," he said.
(Reporting by Kate Abnett, additional reporting by Lisandra Paraguassu; editing by Barbara Lewis)
