From Irregular Swings to Predictable Climate Rhythms

The study suggests that within the next 30 to 40 years, ENSO may transition from its current irregular El Niño-La Niña cycles to a more consistent pattern of strong oscillations marked by larger sea surface temperature (SST) fluctuations (Figure 2, linked below).

"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," says Prof. Malte F. STUECKER, lead author of the study and Director of the International Pacific Research Center at the University of Hawaiʻi at Mānoa, USA. "Enhanced air-sea coupling in a warming climate, combined with more variable weather in the tropics, leads to a transition in amplitude and regularity," he adds.

Synchronizing Global Climate Systems

The high-resolution simulations indicate that a stronger, more rhythmic ENSO could also align with other climate systems, including the North Atlantic Oscillation (NAO), the Indian Ocean Dipole (IOD), and the Tropical North Atlantic (TNA) mode. This process resembles several pendulums gradually swinging together at the same frequency.

"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," says Prof. Axel TIMMERMANN, corresponding author of the study and Director of the IBS Center for Climate Physics at Pusan National University, South Korea.

He continues, "The increased regularity of ENSO could improve seasonal climate forecasts; however, the amplified impacts will necessitate enhanced planning and adaptation strategies."

Advanced Climate Modeling Confirms a Global Shift

To reach these conclusions, the team used the Alfred Wegener Institute Climate Model (AWI-CM3), which offers a detailed resolution of 31 km in the atmosphere and 4-25 km in the ocean, to test climate responses under a high-emission greenhouse gas scenario. They also analyzed real-world observational data and compared results with other climate models for validation.

​"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," says Dr. Sen Zhao, co-lead author of the study and researcher at the University of ​Hawaiʻi at Mānoa.

Global Implications of a Changing El Niño

The findings suggest that human-driven climate change could fundamentally reshape ENSO's behavior and its influence on distant regions, including parts of Europe. ​"Our findings underscore the need for global preparedness to address intensified climate variability and its cascading effects on ecosystems, agriculture, and water resources," ​says Prof. Axel Timmerman.

In the future, the team will explore the underlying global synchronization processes also in other high-resolution climate model simulations, including those with 9 km and 4 km resolution recently conducted at the IBS Center for Climate Physics on the Aleph supercomputer in South Korea.