El Niño and La Niña have occurred over the past 250 million years.

New modeling research shows that El Niño and La Niña that have existed for the past 250 million years have influenced Earth's climate.

The study, conducted by a team of scientists at Duke University, was published in PNAS on October 21. The new modeling study shows that the natural global climate phenomenon , El Niño, and its accompanying cold event, La Niña, have occurred over the past 250 million years. While these complex weather patterns are the driving force behind today's extreme weather changes, the study shows that they were significantly stronger in the past.

El Niño (Spanish for boy) and La Niña (little girl) are part of the El Niño-Southern Oscillation (ENSO) cycle, which results from variations in ocean temperatures in the equatorial Pacific Ocean. Under normal conditions, trade winds blow westward along the equator, carrying warm water from South America to Asia.

The model shows that the El Niño-Southern Oscillation (which emerged in August 2023) has been influencing weather for much longer than previously thought. (Photo: NOAA).

Using climate modeling tools like those from the Intergovernmental Panel on Climate Change (IPCC), the team simulated weather conditions from 250 million years ago. These tools are often used by climate scientists to predict future developments due to climate change, but they can also be run backwards to see what happened.

Hu and colleagues point out that the strength of past oscillations depends on two factors: the thermal structure of the ocean and what they call the "atmospheric turbulence " of ocean surface winds.

'So part of our research is that, in addition to the thermal structure of the ocean, we also need to pay attention to atmospheric turbulence and understand how those winds will change ,' Hu said. In every experiment the team did, he said, they saw the El Niño Southern Oscillation in action, and ' it was almost stronger than what we have now, some stronger, some a little bit stronger,' Hu added.

The researchers couldn't model every year in this simulation, given the significant time span it covered, but they were able to assess conditions in "slices" every 10 million years. The simulation took months to complete, but it provided a model for thousands of years.

'Model experiments have been affected by different boundary conditions, such as different land-sea distributions (with continents in different places), different solar radiation, different CO2,' said Shineng _Hu , assistant professor of climate dynamics at Duke University's Nicholas School of the Environment .

At various times in the past, solar radiation reaching the planet was about 2% lower than it is today, but at the same time, CO ₂ concentrations were higher, making the atmosphere and oceans warmer than they are today.

In particular, 250 million years ago, during the Mesozoic era, South America was in the middle of the supercontinent Pangaea , and weather fluctuations took place to the west, in Panthalassa - the vast superocean surrounding the landmass.

These simulations are valuable for understanding how ENSO might behave as climate change continues. This topic has been debated for some time, and previous studies have shown that weather events could become more intense in the future as the climate continues to warm.

So this new research suggests that ENSO will be significantly affected in the future, due to changes in the ocean's thermal structure and atmospheric turbulence, along with all the uncertainties that come with it. "If we want to have a more reliable forecast of the future, we first need to understand the past climate ," Hu says.