Extreme El Niño events, which cause devastating impacts around the world, will occur twice as frequently due to global warming, scientists said in a report published in the journal Nature Climate Change this week.

El Niño, a weather event that involves unusually warm ocean temperatures in the Equatorial Pacific, occurs periodically. However, as average temperatures continue to climb due to rising carbon emissions in the atmosphere, the scientists said extremely powerful El Niños such as the one between 1997-98 that caused the hottest year on record will occur with more frequency—at least once a decade—adding up to twice as many extreme El Niños over the next 100 years.

As The Guardian reports:

The last extreme El Niño, in 1997-98, resulted in the hottest year on record, and the accompanying floods, cyclones, droughts and wildfires killed an estimated 23,000 people and caused £21bn-£28bn in damage, particularly to food production. But until now scientists have been unable to agree how climate change will affect the frequency of extreme El Niños. [...]

By focusing on those models known to best represent the changes in temperature, currents and clouds that occur in the real world, the researchers were able to produce a clear result for the first time. The work showed that climate change is most likely to warm the tropical Pacific waters that drive El Niño more rapidly than surrounding regions, meaning that extreme events would become twice as common.

"This is a highly unexpected consequence of global warming," said Professor Mat Collins of the University of Exeter, one of the researchers. "Previously we had thought that El Niño would be unaffected by climate change. Tropical rainfall conditions such as those experienced in extreme El Niños have a dramatic influence on the world […] the impact therefore on mankind is substantial."

El Niños, which essentially disturb global rainfall patterns, causing extreme drought in some regions and massive flooding in others, are ultimately "an 'irreversible' climate change phenomenon," said Collins. 

"It would take a dramatic reduction in greenhouse emissions over a number of generations to reduce the impact," he said. "It is even more evidence that cutting emissions would be a good idea."

Such extreme and fast-acting changes to weather patterns could have "profound socio-economic consequences" around the world according to the report.

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