Scientists are warning that global warming is disrupting the natural rhythm of the El Niño-Southern Oscillation (ENSO), potentially creating the conditions for a type of “permanent El Niño” climate state, with significant consequences for global weather patterns, food security, more extreme storms and putting large ecosystems in danger.

A study published in Nature Reviews Earth & Environment in April found that “the Northern Hemisphere mid-latitudes are now in a permanent El Niño-like state” due to rising greenhouse gas (GHG) emissions and hotter-than-ever oceans.

ENSO, a naturally recurring climate pattern originating in the tropical Pacific Ocean, alternates between El Niño, La Niña and neutral phases. However, this cyclical behaviour is increasingly being distorted by anthropogenic climate change.

El Niño refers to the warming of sea surface temperatures (SSTs) in the central and eastern Pacific Ocean, typically resulting in weaker Pacific trade winds and drier conditions in Australia and Southeast Asia, while bringing heavier rainfall to parts of South America and the southern United States. It is also associated with short-term increases in global temperatures.

La Niña, characterised by cooler-than-average SSTs in the same region, brings strengthened trade winds and generally opposite weather patterns: wetter conditions in Australia and Indonesia, and droughts in western South America. It can temporarily lower global temperatures. ENSO phases are monitored using the Southern Oscillation Index (SOI), which tracks air pressure differences between Tahiti and Darwin, Australia.

The 2023-24 ENSO cycle saw a strong El Niño event that ended in June. Meteorological agencies, including the US National Oceanic and Atmospheric Administration, now predict a transition to La Niña by late 2025. However, this year's cooling phase appears significantly weaker than previous cycles. Recent SOI readings have remained close to neutral, reflecting a diminished atmospheric response and fuelling concerns that La Niña may fail to appear.

“The long-term warming of the ocean is increasingly pushing the climate system into an El Niño-like state, even during ENSO-neutral years,” said Lee Simons, a climatologist.

Sea surface temperatures are currently off the scale as the temperature of the oceans gets hotter every year, moving the planet towards a cascade of tipping points, warn scientists. The Mediterranean is currently the temperature of bathwater as Europe swelters in a record breaking heatwave. Scientists warn that persistent warmth could amplify rainfall shifts, extend droughts and increase extreme weather events across continents. As bne IntelliNews reported, changes in rainfall patterns can be as destructive, or even more so, than extreme weather events like heatwaves or hurricanes.

Research published in Nature Climate Change indicates that a permanent El Niño-like state could lead to more erratic monsoon behaviour in Asia and reduced rainfall in the Amazon basin, threatening ecosystems and biodiversity.

“We are seeing signals that the Indian monsoon is weakening and shifting, with potentially dire implications for agriculture and water security,” said Anja Wimmer, a lead author of the study.

Growing number of wildfires, associated with climate changes, could turn the Amazon rainforest into a desert as human activity and climate change threaten “lungs of the world”, bne IntelliNews reported. The Amazon rainforest could face “large-scale collapse” by 2050 according to research released last year. Trees are “coughing not breathing” due to climate crisis stress, according to another study and going from a carbon sink to becoming a net contributor to CO₂ emissions and the crisis accelerates.

In South America, a drier Amazon and shifting precipitation patterns have already reduced forest resilience, while in Africa and Australia, prolonged droughts linked to weakened ENSO variability are expected to increase. Scientists are also observing persistent changes in the jet stream, causing longer-lasting weather extremes and slower-moving storm systems.

“ENSO is a key driver of global climate variability, and its destabilisation could have far-reaching effects on food security and carbon feedback,” said Simons.