A powerful El Niño is building in the Pacific Ocean, and scientists say it may become the strongest on record just as it enters a climate unlike any they have studied before. That combination, they say, leaves them in a bit of uncharted territory.
People in the United States are searching for what that means now because El Niño is not expected to peak until sometime between October and January, when its influence on winter weather is usually strongest. The question is not whether it will matter, but how the extra heat already in the system will change the result.
Ben Kirtman said scientists do not fully know how a warming climate will alter El Niño’s relationship with the atmosphere and weather, even though forecasting the event itself has become routine. “This is an El Nino superimposed on top of a pretty big climate change signal,” he said, adding that there are “some profound unanswered questions.”
The uncertainty matters because if this El Niño turns out to be the strongest on record, it would be judged against a short list of extreme events that Michael McPhaden said includes 1982-83, 1997-98 and 2015-16. He said the current event will rival those previous record El Niños, if not exceed them in magnitude, while also arriving after a decade in which every year has ranked among the globe’s warmest 10 years on record, according to NOAA and the European Union’s Copernicus Climate Change Service.
That is why scientists are asking a different question than the one they usually ask in a winter forecast. Instead of simply looking back for guidance, they are asking whether the Southeast and California will get their typical rainy winters or super soakers, and whether a drought in Indonesia could become more severe. Daniel Swain said, “We’ve never experienced an extreme El Nino in a climate as warm as the climate is today,” and compared the effect to an elevator rising floor by floor: “If El Nino gets us to the 8th or 9th floor, that plus global warming is going to get us to the 10th or 11th floor.”
The friction is that El Niño itself is no longer mysterious in the way it once was. Scientists can track it, forecast it and compare it with past episodes, yet the backdrop has changed so quickly that old examples may not hold. Sea surface temperatures are warmer than normal and in some cases have been record-warm for this time of year, July temperatures in the contiguous United States were record warm, and NOAA said the global average temperature was tied for the second warmest July on record.
McPhaden said the field is already “in uncharted territory” because of how fast the current El Niño has taken off. That is the practical answer to the question now: the event is here, it is strengthening, and the climate around it is warmer than the climate that produced the past extremes. What happens between October and January will show whether this super El Niño behaves like the ones that came before it, or like something new.
