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The 2023-2024 El Nino, which ended in July this year, caused a global spike in temperatures and extreme weather. This has raised questions about how El Nino will react to climate change.
Now, a new study published in journal Nature has come up with some estimates — El Nino is more extreme when climate is warm and that one in two events may fall in this category by 2050 due to climate change.
“There is a need to reliably predict whether El Nino will become stronger or more frequent in the future. Therefore, knowing how it will change as the Earth warms is one of the last missing pieces of the puzzle of predicting the impact of humans on our climate,” Pedro DiNezio from the University of Colorado at Boulder and one of the study authors, told Down To Earth.
El Nino is the warm phase of a recurring climate pattern across the tropical Pacific — the El Nino-Southern Oscillation or ENSO.
This climate phenomenon occurs when the average temperature remains more than 0.5 degrees Celsius above the long-term average for five consecutive months.
This temperature rise can shift wind patterns and ocean currents, triggering unusual weather worldwide, including heat waves, floods and droughts, the study pointed out.
When the area warms by 2°C above average, scientists classify the El Nino event as extreme. Since the 1950s, four extreme El Nino events have occurred, according to data from the United States National Oceanic and Atmospheric Administration.
According to DiNezio, during the 2023 winter, El Nino almost reached extreme magnitude. “El Nino events are difficult to simulate and predict because there are many mechanisms driving them. This has hindered our ability to produce accurate predictions and help society prepare and reduce the potential damage,” the expert highlighted.
To gain more insights, DiNezio and team studied the fossilised remains of foraminifera, unicellular organisms that build carbonate shells (same material as our bones).
These organisms’ shells capture different oxygen isotopes (variants) depending on the water temperature. The isotopes can inform researchers about the temperatures in a period when these organisms lived. They collected data on ocean temperatures over the last 21,000 years, dating back to the peak of the Earth's last Ice Age.
“Scientists have known that foraminifera are virtually unchanged by evolution. So we can collect their fossilised shells from sediments in the ocean floor and get a glimpse of what temperatures were when these organisms lived,” DiNezio explained. As these organisms have a life span of about a month, each measurement tells us the temperatures from that period.
The team collected samples from the tropical Pacific where El Nino (and its cold counterpart La Nina) occur. They fed this data into a computer model to reconstruct past temperatures.
Extreme El Nino events were uncommon during the Ice Age, when the Earth’s climate was colder, their research showed. But as the planet’s temperatures rose, the frequency and intensity of this warm phase of the climate phenomenon have been increasing.
“It’s pretty scary that 2050 is not very far away,” DiNezio said in a statement, adding that society may not have enough time to recover, rebuild and adapt if extreme El Nino’s become more frequent. The team next plans to use a new model to improve the simulation of El Nino.
