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

Research conducted by a group of scientists at Duke University, published on PNAS on October 21. New modeling research shows that the natural global climate phenomenon, El Niño, and its associated cold event, La Niña, have occurred over the past 250 million years. Although these complex weather patterns are the driving force of today’s extreme weather changes, research shows 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 Pacific Ocean. equator. Under normal conditions, trade winds blowing west along the equator carry warm water from South America to Asia.

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

Hu and colleagues show 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, besides 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 has done, he said, the El Niño Southern Oscillation is active, and “it’s almost stronger than what we have now, some stronger, some a little bit stronger,” Hu added. .

The researchers were unable to model every year in this simulation, due to the significant time period it represents, but they were able to assess conditions in “slices” every 10 million years. This simulation took months to complete, but it provided a model for thousands of years.

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

At various times in the past, solar radiation reaching the planet was about 2% lower than today, but at the same time, CO2 concentrations were higher, making the atmosphere and oceans warmer than today.

In particular, 250 million years ago, during the Mesozoic period, South America was located in the middle of the supercontinent Pangea, and weather fluctuations took place to the west, in Panthalassa – the vast super ocean surrounding the vast landmass.

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

Thus, this new study shows that ENSO will be significantly affected in the future, due to changes in the thermal structure of the ocean and atmospheric turbulence, along with all the uncertainties that come with it. “If we want a more reliable future forecast, we first need to understand past climate,” Hu said.