One of the most intense El Niños ever observed could be forming
An experimental forecast from scientists at the National Center for Atmospheric Research calls for a ‘super’ El Niño by winter
This time, El Niño is developing alongside an unprecedented surge in global temperatures that scientists say have increased the likelihood of brutal heat waves and deadly floods of the kind seen in recent weeks.
Will that make El Niño’s typical extremes even more dramatic in the winter?
“My answer would be — maybe,” said David DeWitt, director of the National Oceanic and Atmospheric Administration’s Climate Prediction Center.
Whether — and where — this El Niño might produce new weather extremes is difficult to pin down months in advance, scientists said. That’s because research has not clarified any link between human-caused planetary warming and El Niño, or its counterpart, La Niña. Variation among El Niño events also makes weather impacts difficult to predict.
There are signs that rising temperatures could increase El Niño’s capacity to trigger heavy rainfall in some parts of the globe, though, said Yuko Okumura, a research scientist at the University of Texas.
“It’s likely the impact might be stronger,” Okumura said.
An intense El Niño forecast
Climate models have for months suggested the potential for an intense El Niño that could trigger floods, heat waves and droughts.
The phenomenon is marked by a surge of warmth in surface waters along the equator in the eastern and central Pacific Ocean. The warmer those waters become, and the more they couple with west-to-east flowing winds over the Pacific, the stronger the El Niño and its influence on global weather.
NOAA scientists declared the pattern’s arrival in June, by which point there were already signs of unusual warming in the Pacific and other waters around the world.
As global ocean and surface temperatures surged into record territory in the months that followed, official predictions of El Niño’s intensity have solidified. NOAA’s climate forecasters this month estimated the chance of a strong El Niño pattern by winter in the Northern Hemisphere at 71 percent. Its current strength is moderate.
A forecast that the National Center for Atmospheric Research issued Tuesday was even more bullish, using a new prediction system to forecast that the coming winter could bring a super El Niño, with strength rivaling the historic El Niño of 1997-1998. That winter brought extreme rainfall to California and Kenya, and intense drought to Indonesia.
“We might be facing a similar winter coming up,” said Stephen Yeager, a project scientist at the center who helped lead the forecasting. “This is one plausible future.”
The model predicts this El Niño will be a little less intense than the last super El Niño, which occurred in 2015-2016. That El Niño was tied to severe coral bleaching in the Great Barrier Reef, record cyclones in the Pacific, drought and fires in Australia, a historic snowstorm along the Mid-Atlantic coast and disease outbreaks around the world.
Uncertain weather impacts
Though confidence may be high that Pacific waters will remain warm, allowing El Niño to persist for months, that does not mean scientists are sure of what that augurs for weather around the world.
A textbook El Niño includes tendencies toward dry conditions in such places as Indonesia, northern Australia and southern Africa and wet conditions across parts of South America, eastern Africa and along the southern tier of the United States. Signs are already suggesting a hot and dry summer for Australia, for example, where authorities are warning of heightened wildfire dangers.
But that does not mean the same conditions develop with each El Niño.
Peru is where El Niño got its name, signifying the baby Jesus and onset of Pacific Ocean warmth around Christmas. The pattern is known for bringing heavy rain to coastal communities there.
But in the 2015-2016 El Niño episode, that didn’t happen, said Ken Takahashi Guevara, a scientist at the Geophysical Institute of Peru and a former director of the Peruvian meteorological and hydrological service. Now, unlike other past El Niño events, winds that would help drive rainfall are again absent, he said.
“It’s not enough for us to say there is an El Niño or not,” Takahashi said. “This year is particularly hard to say something about.”
DeWitt, of the NOAA climate center, said other short-term weather patterns can make the effects of El Niño harder to detect, or render them altogether absent. Phenomena such as the Madden-Julian Oscillation, which creates unusual rainfall patterns around the Indian and Pacific oceans, and sudden stratospheric warming, when polar regions dramatically warm and frigid air plunges south, can overwhelm the El Niño signal, he said.
Though El Niño is known for bringing moisture flowing to California and the Southwest, for example, that pattern is not yet emerging, he added. When this past winter delivered record precipitation to those areas, it came on the tail end of a lengthy stretch of La Niña conditions — known for a tendency toward drought there.
“The forecasts right now are showing a fairly muted response” to El Niño in the United States, DeWitt said.
Improving future El Niño forecasts
Research is ongoing to better understand any connections between El Niño and global warming, as well as El Niño and its impacts.
Okumura is launching a study using models of atmospheric conditions to explore how El Niño might influence the occurrence of extreme precipitation around the world. Past research has found an increase in such heavy precipitation in California during El Niño.
Scientists have already established a strong connection between planetary temperatures and precipitation intensity, because warmer air is capable of holding more moisture.
And Yeager said the research behind the latest El Niño forecast is part of a broader effort to better predict weather and climate phenomena over scales of one to two years. The research team is looking at whether the current El Niño could be followed in the spring by a rapid transition to La Niña, as has occurred in the past.
Beyond that, scientists are exploring why it may be relatively easier to predict the presence of an El Niño pattern than its impacts, he added.
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