A new study reveals that the El Niño-Southern Oscillation (ENSO) could intensify and synchronize with other climate patterns due to global warming, potentially leading to more extreme weather by mid-century. Researchers predict a tipping point around 2050 in the tropical Pacific, shifting ENSO from irregular cycles to strong, rhythmic oscillations. This change may heighten risks of rainfall extremes and climate whiplash in regions like Southern California and the Iberian Peninsula.
The study, published in Nature Communications on October 24, 2025, was conducted by an international team from South Korea, the USA, Germany, and Ireland. Using the high-resolution Alfred Wegener Institute Climate Model (AWI-CM3), which simulates the atmosphere at 31 km resolution and the ocean at 4-25 km, the researchers examined ENSO under a high-emission greenhouse gas scenario. They also validated findings with real-world observational data and other climate models.
Currently, ENSO features irregular swings between El Niño and La Niña events, driving global climate variability through changes in sea surface temperatures (SST). The model projects that within 30 to 40 years, enhanced air-sea coupling in a warming climate will trigger a transition to more regular, amplified oscillations. This shift, resembling a climate tipping point, could lock ENSO into intense cycles by around 2065, as shown in simulations of eastern equatorial Pacific SST anomalies.
"In a warmer world, the tropical Pacific can undergo a type of climate tipping point, switching from stable to unstable oscillatory behavior. This is the first time this type of transition has been identified unequivocally in a complex climate model," said Prof. Malte F. Stuecker, lead author and director of the International Pacific Research Center at the University of Hawaiʻi at Mānoa.
The intensified ENSO is expected to synchronize with modes like the North Atlantic Oscillation (NAO), Indian Ocean Dipole (IOD), and Tropical North Atlantic (TNA), amplifying global impacts. "This synchronization will lead to stronger rainfall fluctuations in regions such as Southern California and the Iberian Peninsula, increasing the risk of hydroclimate 'whiplash' effects," noted Prof. Axel Timmermann, corresponding author and director of the IBS Center for Climate Physics at Pusan National University.
While greater regularity might improve seasonal forecasts, the amplified effects demand better adaptation. "Our simulation results, which some other climate models support, show that ENSO's future behavior could become more predictable, but its amplified impacts will pose significant challenges for societies worldwide," added Dr. Sen Zhao, co-lead author from the University of Hawaiʻi at Mānoa.
The findings highlight human-driven climate change's potential to reshape ENSO, urging global preparedness for effects on ecosystems, agriculture, and water resources. Future research will use even higher-resolution models on South Korea's Aleph supercomputer.