The El Niño event, a phenomenon characterized by a giant patch of warm ocean water in the tropical Pacific Ocean that can disrupt global rainfall patterns, has been present for at least 250 million years. Researchers from Duke University conducted a modeling study that demonstrated the presence of the El Niño Southern Oscillation, as well as its cold counterpart La Niña, in the deep past. The temperature swings associated with these oscillations were more intense than what is observed today, and they occurred even when the continents were positioned differently than they are now.
Using a climate modeling tool similar to the one used by the Intergovernmental Panel on Climate Change (IPCC), the researchers ran simulations backward in time to examine the historical fluctuations of El Niño and La Niña. These simulations covered 10-million-year increments due to the computational intensity of the model. The researchers found that variations in land-sea distribution, solar radiation, and atmospheric CO2 levels played significant roles in influencing the intensity of the El Niño oscillation in the past.
In the Mesozoic period 250 million years ago, when the supercontinent Pangea was intact with South America in the middle, the El Niño oscillation occurred in the Panthalassic Ocean to the west. The study identified the thermal structure of the ocean and atmospheric noise from surface winds as the two most important variables affecting the magnitude of the oscillation historically. While previous studies have primarily focused on ocean temperatures, this research emphasizes the significant influence of surface winds in shaping El Niño patterns.
The researchers likened the El Niño oscillation to a pendulum, with atmospheric noise serving as a random kick to the system. By incorporating both the ocean thermal structure and atmospheric noise into their model, the researchers were able to better understand why El Niño events were much stronger in the past compared to the present. This study highlights the importance of considering past climates in order to make more reliable future projections regarding the behavior of El Niño and La Niña events.
The findings of this research have important implications for climate scientists seeking to improve their understanding of the El Niño Southern Oscillation and its impacts on global weather patterns. By examining the historical behavior of these phenomena and identifying key variables that influence their intensity, researchers can enhance their ability to predict and mitigate the effects of El Niño events in the future. This study was supported by grants from the National Natural Science Foundation of China and the Swedish Research Council Vetenskapsrådet, with simulations conducted at the High-performance Computing Platform of Peking University.
