Hyderabad:A new study by Duke University researchers reveals that the El Niño and La Niña oscillations, which significantly impact global rainfall patterns, existed at least 250 million years ago and were often more intense than those observed today.
A study published in the Proceedings of the National Academy of Sciences reveals that past temperature swings were more intense, with El Niño Southern Oscillation (ENSO) activity being stronger than today, even when continents were positioned differently. Shineng Hu from Duke University notes that all experiments showed active and often stronger ENSO events compared to the present.
Climate scientists study El Niño and La Niña because these phenomena significantly impact global weather patterns, such as altering the jet stream and affecting rainfall. Researchers used a climate modeling tool to simulate past climate conditions, running it backwards in 10-million-year intervals due to the high computational demands.
Shineng Hu explained that various boundary conditions, such as different land-sea distributions, solar radiation levels, and CO2 concentrations influenced the model experiments. Each simulation ran for thousands of model years to ensure robust results, taking months to complete. Hu noted that in the past, solar radiation reaching Earth was about 2% lower than today, but CO2 levels were much higher, making the atmosphere and oceans significantly warmer. During the Mesozoic period, 250 million years ago, South America was part of the supercontinent Pangea, and the oscillation occurred in the Panthalassic Ocean to its west.
Xiang Li, the study's first author, highlighted that the two most important variables in the historical magnitude of the oscillation were the ocean's thermal structure and the "atmospheric noise" of ocean surface winds. Hu added that previous studies focused mainly on ocean temperatures, but this study emphasizes the importance of considering atmospheric noise and understanding changes in surface winds.
Hu compared the oscillation to a pendulum, explaining that atmospheric noise, such as winds, can act like a random push to this pendulum. Both ocean thermal structure and atmospheric noise are crucial for understanding why past El Niño events were stronger than those today. Hu emphasised that understanding past climates is essential for making reliable future climate projections.
