When meteorologists put together seasonal outlooks such as a winter forecast, they often look to the weather of the past, but scientists say history may not be much help with the powerful El Niño unfolding in the Pacific Ocean.
“We're in a bit of uncharted territory,” said Ben Kirtman, dean of the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science.
If this El Niño turns out to be the strongest on record, as many forecast models suggest it will, Kirtman and others say that raises the question: What will a historically strong El Niño look like stacked on top of the planet’s unprecedented warming?
Scientists understand a lot about El Niño, and a lot about climate change, but the unresolved question for this winter is how
the two will interact to influence not only weather in the United States but around the globe, climate scientists told USA TODAY. Will the Southeast and California get their typical rainy winters or super soakers? Could a drought in Indonesia be more severe?
Scientists understand what a strong El Niño means regionally, but not what the impacts of global warming will mean for this event, said Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources and founder of WeatherWest.com.
“We've never experienced an extreme El Nino in a climate as warm as the climate is today,” Swain said. “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.”
'Record after record'
Over 50 years, three El Niño events were considered “extreme”: 1982-83, 1997-98 and 2015-16, said Michael McPhaden, a senior scientist recently retired from the National Oceanic and Atmospheric Administration.
This current El Niño will rival those previous record El Niños, if not exceed them in magnitude, McPhaden said.
"With rising global temperatures because of the heat-trapping greenhouse gases being injected into the atmosphere at ever increasing rates, El Niños today aren’t necessarily like the El Niños that we experienced 40 years ago," he said.
Every year in the decade since 2016 has been among the globe's warmest 10 years on record, according to NOAA and the European Union's Copernicus Climate Change Service.
We're already in "uncharted territory" with how fast the current El Niño “has taken off,” and in terms of how much warmer temperatures are forecast to be by the end of the year, he said. "We're setting record after record already."
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 reported the global average temperature was tied for the second warmest July on record. And El Niño isn’t forecast to reach peak intensity until sometime between October and January.
'Unanswered questions'
Scientists don’t have a clear understanding of how the warming climate will influence El Niño’s relationships with the atmosphere and weather, Kirtman said. “This is an El Nino superimposed on top of a pretty big climate change signal."
“There are some profound unanswered questions,” Kirtman said. “The prediction of El Nino has become so routine, it's easy to sort of forget that we need to do more research."
Unknowns remain in terms of how the climate will react to the El Niño influence over the atmosphere and weather around the globe, said Emily Becker, a research associate professor at the Rosenstiel School, during a joint interview with Kirtman and USA TODAY. “This is a question we’ve been looking at for years, but it’s far from resolved."
For example, climate scientists differ on how the stronger El Niño combined with the warmer climate could influence typical El Niño-driven patterns, such as winter rain across the southern U.S.
Because the atmosphere is warmer, it can hold more moisture, McPhaden said. “In a region where you might normally expect El Nino to produce a heavy rainfall, it now can produce an extreme rainfall just because there's more moisture to wring out of the atmosphere."
That effect already is seen in more intense rainfall events across the nation, and not just during the El Niño or La Niña phases of the El Niño Southern Oscillation, born from changing water patterns along the equator off South America.
Past El Niño events led to severe droughts in various parts of the globe, but in today’s warmer world, higher temperatures can dry out soils and plants more quickly and more thoroughly, McPhaden said. “So it can make an El Nino drought, which would otherwise be severe, into an extreme or an extraordinary drought."
Swain is among the scientists who say El Niño's typical seasonal effects could intensify this winter. The event is shaping up to be so intense that it would be difficult for another influence to produce a different outcome, he said. For example, the southern tier states, in general, have a pretty good shot at a wetter than average or even "much wetter than average" winter, he said. "That's also true in Southern California."
Kirtman is not convinced.
“Do I expect the traditional El Nino signals to happen? I think the answer is yes, without question,” he said. “Do I expect those signals to necessarily be bigger or the impacts to be larger? I don't know the answer.”
“Your assumption would be if the El Nino is bigger, then therefore those signals would necessarily get bigger. And that's not true,” he said. “There's no real reason to expect that those signals will be larger.”
El Niño: A learning opportunity
Scientists fully expect to see things occur during this event that were “completely unanticipated,” Kirtman said.“I would bet dollars to doughnuts that there’s going to be some big surprises,” he said. “The system is pretty well primed for some pretty big effects.”
No two El Niños are exactly alike and each "has its own unique character," McPhaden said.
For example, scientists don’t know exactly where temperatures will be warmest this winter, or how the atmosphere will respond, not just in the tropical Pacific but far afield, he said. “I can't tell you now where the hottest spots are going to be in the tropical Pacific in December."
The surprises won't necessarily be bad, Becker said. "It's that things are not going to happen the way we have seen before."
Because scientists don’t have a great sense of how El Niño interacts with the slowly evolving problem of climate change, Kirtman and Becker said this event presents a huge learning opportunity.
It “might tell us something about what the climate system might look like 15 years from today or 10 years from today,” he said. Those kinds of opportunities are “really powerful.”
Rather than being frightening, Becker said, “more than anything, this is an opportunity to try to understand our future.”
Dinah Voyles Pulver, a national correspondent for USA TODAY, covers violent weather, climate and the environment, among other news. Reach her at dpulver@usatoday.com.
This article originally appeared on USA TODAY: El Niño puts Earth in 'uncharted territory.' Here's what could happen
