A recent research study merges ancient shell data with advanced climate modeling to explore potential changes in El Niño weather patterns in an increasingly warm world.
The last ice age, reaching its peak approximately 20,000 years ago, was characterized by vast ice coverage and significant shifts in climate that transformed Earth’s oceans, scenery, and ecosystems. A study from the University of Arizona indicates that the last ice age can provide important insights into future El Niño weather occurrences. El Niño is a major climate pattern that impacts global weather significantly.
This study, published in Nature, integrates data from ancient marine organism shells with sophisticated climate models to better understand how El Niño patterns could evolve as the planet warms.
El Niño is a climate phenomenon known for the irregular yet recurring rise in sea surface temperatures in the central and eastern Pacific Ocean. This abnormality disrupts global weather systems, leading to severe conditions such as droughts, floods, and intense heat waves.
“El Niño is a powerful natural force — it triggers droughts, floods, and wildfires, impacting both marine and land ecosystems globally, with wide-ranging implications for various sectors, including agriculture and aviation,” noted Kaustubh Thirumalai, co-lead author of the study and an assistant professor in the U of A’s Department of Geosciences.
El Niño events tend to occur roughly every two to seven years, and predicting how these events may change in the future presents a significant challenge for climate scientists.
“There are several advanced climate models available, and they predict varying responses of El Niño to ongoing and future human-induced warming,” Thirumalai explained. “Some models indicate an increase in El Niño fluctuations, while others expect a decrease — it’s a complex and multifaceted phenomenon. Therefore, understanding the potential changes to El Niño is a top concern in climate science.”
To tackle this uncertainty, the research team, which included experts from the U of A, University of Colorado Boulder, University of Texas, Middlebury College, and Woods Hole Oceanographic Institution, looked to history. They centered their attention on the Last Glacial Maximum, a time about 20,000 years ago when ice sheets dominated much of North America and Europe.
The team utilized the Community Earth System Model, designed to replicate Earth’s climate conditions and forecast future climate scenarios, to simulate climatic states from the Last Glacial Maximum to today. This model is a collaborative effort primarily driven by the National Center for Atmospheric Research, with input from multiple research institutions. The modeling aspect of this study was carried out by co-lead author Pedro DiNezo at the University of Colorado Boulder.
To verify their model, Thirumalai and colleagues compared its outcomes with data obtained from tiny marine organisms known as foraminifera. These organisms are collected from seabed samples containing layers of sediments that have accumulated over thousands to millions of years.
“These delicate, microscopic beings float in the upper ocean and create shells that encapsulate the ocean temperature at the time of their existence,” Thirumalai remarked.
As foraminifera develop, they create their shells using materials dissolved in the seawater around them. The chemical makeup of these shells alters in response to water temperature, preserving a snapshot of ocean conditions when the shell was formed.
After their brief life, foraminifera shells eventually sink to the ocean floor, becoming part of the sediment. By examining shells from different sediment layers, scientists can reconstruct historical ocean temperatures and contrast them with model predictions of past climates.
The research team focused on individual foraminiferal shells, allowing them to assess seasonal temperature differences that would be difficult to detect otherwise.
“We concentrate on a specific segment of the sediment core and analyze several individual shells from the same level. This approach allows us to gather a range of Pacific Ocean temperatures from a brief time frame, enabling comparisons between the ice age and the present,” Thirumalai stated.
The findings indicated that El Niño variability was considerably reduced during the Last Glacial Maximum compared to today, suggesting that extreme El Niño events could become more frequent as global temperatures rise. This could result in more severe and recurrent weather disruptions across the world. Crucially, these results indicate a shared mechanism for extreme El Niño variations during both ice age and projected future conditions, confirming the model’s predictions.
“This enhances our confidence in the model’s projections for the future,” Thirumalai concluded. “If it accurately simulates historical climate changes, it’s more likely to provide dependable forecasts about upcoming variations in the El Niño system.”
