Three El Niño events in the last 50 years were rated “extreme”: 1982-83, 1997-98 and 2015-16. Forecast models suggest the one building in the Pacific now could rival or exceed all of them, and it would arrive in the warmest climate ever recorded.
That combination is what has scientists uneasy. “We’ve never experienced an extreme El Nino in a climate as warm as the climate is today,” said Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources. “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.”
Every year since 2016 has landed among the 10 warmest on record. July was the hottest ever measured in the contiguous U.S., and this El Niño isn’t forecast to peak until sometime between October and January.
A warmer atmosphere holds more moisture, so a region that normally sees heavy El Niño rain could see extreme rain instead, said Michael McPhaden, a senior scientist recently retired from NOAA. The same heat cuts the other way in dry regions, turning a severe drought into “an extreme or an extraordinary drought.”
Not everyone expects the usual patterns to simply get bigger. Ben Kirtman, dean of the University of Miami’s Rosenstiel School, said the classic El Niño signals will show up, but whether their impacts grow is an open question: “There’s no real reason to expect that those signals will be larger.”
What he does expect is to be caught off guard. “The system is pretty well primed for some pretty big effects.”…