Continued global warming may alter El Nino, La Nina, says study report

The world's weather and climate patterns are driven by the El Nino-Southern Oscillation (ENSO) phenomenon, of which El Nino and La Nina form the 'warm' and 'cool' cycles, with the former related with an increase in temperatures and rainfall and the latter with opposite effects

El Nino and La Nina climate cycles could undergo fundamental changes over the next 30-40 years under continued global warming, shifting from current irregular patterns towards highly regular ones, potentially magnifying fluctuations in sea surface temperatures, according to a new study.

Findings published in the journal Nature Communications highlight how human-caused climate change can alter the fundamental characteristics of the El Nino-Southern Oscillation (ENSO) and its interactions with other climate processes, researchers said.

The world's weather and climate patterns are driven by the ENSO phenomenon, of which El Nino and La Nina form the 'warm' and 'cool' cycles, with the former related with an increase in temperatures and rainfall and the latter with opposite effects.

Researchers, including those at the University of Hawai'i at Manoa, US, show that the ENSO could sync with other climate processes and the resonance could have "wide-ranging whiplash impacts on regional hydroclimates".

"In a warmer world, the tropical Pacific can undergo a type of climate tipping point, switching from (a) stable to (an) unstable oscillatory behaviour. This is the first time this type of transition has been identified unequivocally in a complex climate model," said lead author Malte F Stuecker, director of the international pacific research center at the University of Hawai'i at Manoa.

"(An) 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 added.

The researchers analysed publicly available climate models and projected that the stronger and more regular ENSO cycles could also sync with other climate drivers, such as the North Atlantic Oscillation and Indian Ocean Dipole -- similar to how multiple weakly connected pendulums adjust to swinging with the same frequency.

"Our simulation results, which some other climate models support, show that ENSO's future behaviour could become more predictable, but its amplified impacts will pose significant challenges for societies worldwide," Sen Zhao, one of the lead authors and researcher at the University of Hawai'i at Manoa, said.

Enhanced climate planning and adaptation strategies would be required to deal with amplified effects due to an increasingly regular ENSO, the researchers said.

Further, effects of fundamental changes to the ENSO could be felt in regions far away from the equatorial Pacific and therefore, global preparedness is important, they added.

"Our findings underscore the need for global preparedness to address intensified climate variability and its cascading effects on ecosystems, agriculture, and water resources," author Axel Timmermann, director of the Institute for Basic Science's center for climate physics at Pusan National University, South Korea, said.

The study looked at the Alfred Wegener Institute Climate Model. "Here, we demonstrate that in response to warming, a state-of-the-art high-resolution climate model simulates a rapid transition from a moderate-amplitude irregular regime, as observed in the current climate, to a highly regular oscillation with intensifying amplitude," the authors wrote.