It’s official: a weak La Niña came into fruition in late December and is expected, with significant uncertainty, to last until sometime between February and April, the U.S. National Oceanic and Atmospheric Administration announced. La Niña often brings wetter conditions to Southeast Asia and the Brazilian Amazon, while cooling global temperatures overall, potentially easing recent extreme heat.
Over the past nine months, climate scientists observed an odd phenomenon. The atmosphere showed signs of a La Niña, with above-average winds blowing from east to west and drier conditions in the middle of the Pacific Ocean. But the cooler ocean surface temperatures that typically accompany these atmospheric conditions weren’t present — until now.
“It’s unusual to see a strong atmospheric component of La Niña without the corresponding cooler-than-average tropical Pacific surface temperature,” Emily Becker, associate director of NOAA’s Cooperative Institute for Marine and Atmospheric Studies, told Mongabay by email.
La Niña is part of a natural climate dynamic, along with the better-known El Niño, called El Niño–Southern Oscillation (ENSO). La Niña is ENSO’s cool phase, while El Niño is its warm phase. NOAA’s weather models show there’s a 59% chance the current La Niña conditions will last until sometime between February and April, and a 60% chance that the ENSO dynamic will reach a neutral state between March and May, meaning the sea surface temperature with be within an average range.
Following a powerful El Niño in 2023-2024, one of the top five strongest on record, the arrival of a weaker La Niña may mean less extreme weather over the next season.
However, as climate change continues to drive extreme weather events, irrespective of La Niña or El Niño conditions, regions that don’t normally experience such conditions events could still face them this year and in the future, according to Ben Clarke, a researcher at Imperial College London’s World Weather Attribution.
The recent El Niño, exacerbated by climate change, drove historic droughts in the Amazon Rainforest, Indonesia and other regions over the past two years. La Niña tends to drive opposite conditions. Wetter weather is expected in parts of Southern Africa, Southeast Asia, some regions of Brazil, including the Amazon, and the U.S. Pacific Northwest.
“There is typically a slight decrease in global average temperatures during La Niña, so it is unlikely that 2025 will be hotter than 2024,” Clarke wrote to Mongabay in an email.
“However, we will still experience a hot year compared to recent decades because countries are still emitting huge amounts of planet-warming greenhouse gases,” Clarke added.
Banner image: La Niña was confirmed after below-average ocean surface temperatures matched atmospheric conditions. Image courtesy of NOAA.
This story first appeared on Mongabay
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