NASA has detected a vast pulse of warm water in the Pacific Ocean that may signal the emergence of a major El Niño system.
The pulse is hundreds of kilometres wide and has arrived off the coast of South America.
It has the potential to cause severe weather across the globe.
In a statement, NASA’s Jet Propulsion Laboratory, which monitors satellite modelling, said several of these waves had shown up in 2026 data.
This was “a sign that El Niño will likely emerge later in the year”.
“Because water expands as it warms, a rise in elevation of an area of the ocean indicates increasing ocean temperatures,” NASA said.
“El Niños can cause heavy precipitation in some regions and deficits in others, influencing daily life and commerce around the world.”
NASA researcher Josh Willis said this year’s pulse event started a bit later than the big El Niños of 2015 and 1997.
“(However) it’s beginning to catch up,” he said. “We’ll see how big it gets.”
The warm waves typically form after brief periods when winds over the far western equatorial Pacific Ocean shift from prevailing easterlies – moving from east to west – to westerlies.
“That effect, combined with a general weakening of easterly winds along the equator, causes water in the tropics of the western Pacific to get warmer and sea levels to rise,” NASA said.
“The wave that forms then propagates east for several weeks, eventually reaching South America and causing water off the coast to heat up and rise.”
Fishermen in the 1600s coined the name El Niño (Spanish for “the boy”) – a reference to the birth of baby Jesus because it tended to intensify around Christmastime.
An El Niño effect can lead to heavy rain and snow in some areas and unusual heat and dryness in others.
In “modest” events in 2018 and 2023, impacts such as drought and flooding were mostly seen in and around the tropical Pacific.
“Large El Niños, like the one in 2015-2016, reach much farther, causing drought in Africa and flooding in California,” NASA said.
“El Niños usually peak between November and January, so it will be several months before the largest impacts become clear.”
The full NASA statement is here.
