El Niño's future: Twice the trouble in a warming world

Weather phenomena such as El Niño may occur twice as often, according to studies of ancient plankton published in "Nature".

Extreme phenomena could become twice as frequent shortly as they are today. This conclusion comes from studies of single-celled foraminifera, which lived around 21,000 years ago during the last glacial period. The research suggests that current climate models are accurate, heightening concerns that El Niño may grow significantly more intense.

According to the Polish Press Agency, El Niño, also known as the El Niño-Southern Oscillation (ENSO), is a recurring climate pattern linked to ocean water temperatures in the Pacific Ocean, particularly its central and eastern tropical regions. This phenomenon is closely tied to increased sea surface temperatures in the equatorial zone.

Warm ocean waters are poor in nutrients, which directly affects fish catches, and the weakening of trade winds halts the upwelling current. This current usually brings cold, nutrient-rich water from the ocean depths, which is replaced by warmer surface waters. The name "El Niño" comes from the Spanish term "the child", directly associated with the Christmas period when this phenomenon often intensifies. The opposite of El Niño is La Niña, when ocean waters cool down.

According to research findings, El Niño exerts a significant impact on the global climate. This is because it raises average temperatures and leads to more frequent extreme weather events worldwide. Climate models used by specialists suggest that global warming, driven by greenhouse gas emissions, results in greater variability in the El Niño cycle and more frequent occurrences of this phenomenon.

However, one significant challenge for climate researchers is that precise observations of El Niño have only been conducted for several decades, and the climate models themselves are not perfect. This makes it difficult to determine the direct impact of global warming on this phenomenon. Professor Kaustubh Thirumalai from the University of Arizona and his colleagues have sought to address this problem by developing a record of changes in El Niño from 21,000 years ago, a time when the Earth's climate was considerably cooler than it is now. The results of these studies were published in a scientific article (DOI: 10.1038/s41586-024-07984-y).

Researchers obtained climate data through chemical analysis of foraminifera shells, microscopic organisms that lived near the sea surface. The temperature of seawater affects the chemical composition of these organisms' shells, which sink to the ocean floor after death, forming a layer of marine sediments. These sediments provide researchers with historic data, which aligns with the results of contemporary climate models.

Confirmation of these models indicates an increased likelihood that El Niño will occur far more frequently in the future. This could lead to more frequent extreme weather conditions on Earth.

During the last glacial period’s cooler climate, El Niño occurred less frequently. Scientists propose that this phenomenon results from interactions between the winds in the Pacific Ocean and the layer of warm water on its surface.

As global warming continues, this layer becomes thinner, making it easier for winds and ocean currents to move warm water eastward and trigger intense El Niño events. Scientists predict that El Niño may occur once every decade, rather than once every twenty years, as it did in the past.