Climate change making El Niño events stronger, study finds

Washington: El Niño events are becoming significantly more powerful as human-driven warming raises global temperatures, a new study has found, warning that stronger episodes could intensify heatwaves, floods, droughts and other climate-related disasters around the world.

Research published in the journal Science on Thursday found that El Niño events are now over 36 per cent stronger than they were before the industrial era began in the mid-19th century. The study also noted a 16 per cent increase in their intensity over the past four decades, indicating that the strengthening trend is accelerating.

The findings come at a time when a powerful El Niño, which emerged a few months ago, is expected to reach record levels in the coming months.

El Niño is a periodic warming of sea-surface temperatures in parts of the equatorial Pacific Ocean. Though it is a natural climate phenomenon, it can disrupt weather patterns across the globe, triggering unusually high temperatures, heavy rainfall and flooding in some regions, while causing severe drought in others.

Such events can inflict enormous economic losses, with damage from major El Niño episodes estimated to run into trillions of dollars.

“Strong El Niños have much stronger impacts on climate hazards and extremes worldwide,” said Julia Cole, a paleoclimate scientist at the University of Michigan and the lead author of the study.

Cole said the researchers compared evidence of past El Niño activity with records of global temperatures and found that the rise in El Niño strength closely tracked warming caused by human activities, particularly the burning of fossil fuels.

The study examined El Niño patterns over nearly 900 years, using historical and climate records to reconstruct the intensity of past events.

“El Niño is the most violent aspect of climate variability worldwide, with effects ranging from local fisheries collapse, to widespread coral die-offs to severe droughts and food shortages around the world,” said Boris Worm, a marine scientist at Dalhousie University, who was not associated with the research.

Referring to the late climate scientist Wallace Broecker’s warning that the climate system was “an angry beast”, Worm said human emissions were effectively provoking increasingly dangerous climatic outbursts.

Scientists determine the strength of an El Niño by measuring sea-surface temperatures in a defined central equatorial Pacific region and comparing the three-month average with normal conditions.

An El Niño is declared when temperatures in the area rise by at least 0.5 degrees Celsius above the average. Events with temperatures exceeding 2 degrees Celsius above normal are classified as “very strong”.

The latest weekly measurement has reached 2.7 degrees Celsius above average, according to Columbia University’s El Niño tracker. The phenomenon is expected to continue strengthening for another two to four months.

Scientists have long anticipated that global warming would make El Niño events more intense, since the phenomenon is linked to changes in ocean temperatures. However, direct instrumental records of Pacific Ocean temperatures extend back only around 75 years, making it difficult to establish a clear long-term trend from modern observations alone.

To overcome that limitation, researchers have used indirect evidence to identify historical El Niño events. These include records of major shifts in rainfall, droughts and other weather patterns in different parts of the world.

Scientists have, for instance, reconstructed evidence of the exceptionally powerful 1877 El Niño by studying the widespread climatic disruptions associated with it.