Climate whiplash effects due to rapidly intensifying El Niño cycles
Changes in ENSO could reshape global rainfall patterns. Credit: Todd Diemer via Unsplash.
A new study published in the journal Nature Communications reveals that the El Niño-Southern Oscillation (ENSO), a key driver of global climate variability, is projected to undergo a dramatic transformation due to greenhouse warming. Using high-resolution climate model simulations, an international team of researchers led by the University of Hawai‘i (UH) at Mānoa found that ENSO could intensify rapidly over the coming decades and synchronize with other major climate phenomena, reshaping global temperature and rainfall patterns by the end of the 21st century.
The study projects an abrupt shift within the next 30-40 years from irregular El Niño-La Niña cycles to highly regular oscillations, characterized by more dramatic fluctuations in sea surface temperature.
“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 Malte F. Stuecker, lead author of the study and director of the International Pacific Research Center at the UH Mānoa School of Ocean and Earth Science and Technology. “Enhanced air-sea coupling in a warming climate, combined with more variable weather in the tropics, leads to a transition in amplitude and regularity.”
Synchronization leads to ‘whiplash’ effects
According to the high-resolution computer model simulations analyzed in the study, the stronger and more regular ENSO cycles are also expected to synchronize with other climate phenomena, including the North Atlantic Oscillation, the Indian Ocean Dipole, and the Tropical North Atlantic mode, similar to how multiple weakly connected pendulums adjust to swinging with 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,” said Axel Timmermann, corresponding author of the study and director of the IBS Center for Climate Physics at Pusan National University, South Korea. “The increased regularity of ENSO could improve seasonal climate forecasts; however, the amplified impacts will necessitate enhanced planning and adaptation strategies.”
The research utilized a high-resolution version of the Alfred Wegener Institute Climate Model to simulate climate responses under a high-emission greenhouse gas scenario. Observational data and simulations from other climate models were also analyzed to validate the findings.
“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,” said Sen Zhao, co-lead author of the study and researcher in the SOEST Department of Atmospheric Sciences.
The new study highlights the potential for anthropogenic climate change to fundamentally alter the characteristics of ENSO, and its interactions with other climate processes, even in regions far away from the equatorial Pacific, such as Europe.
“Our findings underscore the need for global preparedness to address intensified climate variability and its cascading effects on ecosystems, agriculture, and water resources,” said Timmermann.
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.
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