Isabelle Gerretsen / BBC:

Over the coming months, a vast body of warm water will slosh slowly across the tropical Pacific Ocean in the direction of South America. As it does so, it will trigger the start of a climate phenomenon that will bring dramatic shifts in weather patterns around the world. Climate scientists are now warning there is now a 90% chance of an El Niño weather pattern taking hold through the end of this year and the first months of 2024. And they are warning it could be a strong one.
If that turns out to be the case, then the impacts could be significant. Scientists have already warned that with rising emissions and a strong El Niño there is a 66% chance the world will break through a key 1.5C global warming limit at least one year between now and 2027. But it could also bring damaging extreme weather such as heavy rainfall and flooding to communities in the US and elsewhere this winter.
“We’re projecting an above 90% probability that there will be El Niño conditions through the winter,” says David DeWitt, director of the US National Oceanic and Atmospheric Administration’s Climate Prediction Center. “There’s an 80% probability that we’re going to be in El Niño in July.” The effects of this could also reverberate for some time to come – a recent study by researchers at Dartmouth College, Hanover, New Hampshire, estimates that an El Niño starting in 2023 could cost the global economy as much as $3.4tn (£2.7tn) over the following five years. And they say that following two previous very strong El Niño events in 1982-83 and 1997-98, the US gross domestic product was 3% lower half a decade later than it otherwise would have been. If an event of a similar magnitude was to happen today, it could cost the US economy $699bn (£565bn), they calculated.
It is worth noting that coastal tropical countries such as Peru and Indonesia, however, suffered a 10% drop in GDP following the same El Niño events, the researchers say. They project that global economic losses will amount to $84 trillion (£68 trillion) this century as climate change increases the frequency and strength of El Niño events. “El Niño is not simply a shock from which an economy immediately recovers. Our study shows that economic productivity in the wake of El Niño is depressed for a much longer time than simply the year after the event,” says Justin Mankin, co-author of the study and assistant professor of geography at Dartmouth College.
“When we talk about an El Niño here in the United States, it means that the types of impacts that we’ll see, floods and landslides, aren’t typically insured against by most households and businesses,” says Mankin. In California, for example, 98% of homeowners don’t have flood insurance. Other economic impacts in the US could include infrastructure damage from flooding.