El Niño has intensified by 37% due to climate change

This natural climate phenomenon occurs when the surface waters of the central and eastern Pacific Ocean heat intensely and interact anomalously with the atmosphere, altering weather patterns across the planet.

El Niño exacerbates droughts, floods, forest fires, or episodes of coral bleaching; and has important impacts on agriculture and public health.

Several El Niño events of unusual intensity have occurred in recent decades, with warming spreading across much of the tropical Pacific.

However, due to the scarcity of data and the great natural variability of the phenomenon, it has been difficult to determine whether its severity is caused by human-caused warming.

To verify this, the authors of the study have resorted to high-resolution paleoclimatic models, specifically they have reconstructed the sea surface temperatures of the last 1,000 years using geochemical measurements obtained from corals from the Galapagos Islands, both modern and fossilized.

Since the Galapagos are located in the center of the region affected by El Niño, in the eastern Pacific, the chemical composition of their corals offers a sensitive record of ocean temperature changes related to the phenomenon.

Corals grow between one and two centimeters a year by secreting layers of calcium carbonate. And the chemical composition of these layers provides a record of the temperature of the sea water in which they grew.

The researchers tested whether the observed changes could be explained by natural variability by comparing them with pre-industrial climate simulations (before around 1850) from 12 climate models.

The results show that the variability of El Niño has increased considerably in tandem with global warming and that the most pronounced increase has occurred in the last 40 years.

Modern variability is, specifically, 36.5% greater than during the pre-industrial era, largely due to the fact that El Niño phenomena are more frequent and intense.

“We have not observed any time in the past in which El Niño events have been as intense as they are today. For 40 years the severity of the phenomenon is not normal compared to the last thousand years,” says lead author Julia Cole, director of the Department of Earth and Environmental Sciences at the University of Michigan.