An already powerful El Niño has intensified into “super” territory, crossing a critical threshold at an unprecedented pace for this time of year. The natural climate cycle, officially declared in June, has strengthened at a breakneck speed and is now stronger on this date than any previous event on record. Forecasters warn it is not done bulking up yet.
Key Metric Crosses “Very Strong” Threshold
For months, forecasters predicted El Niño would become “very strong” or “super” by fall. The key measure of its strength—the Niño 3.4 Relative Oceanic Niño Index (RONI)—has now crossed that threshold and is projected to continue soaring.
As a refresher, El Niño is characterized by warmer-than-average sea surface temperatures along the equator in the Pacific Ocean. This warmer water triggers corresponding shifts in the atmosphere, creating a domino effect on weather patterns globally. An active Pacific hurricane season threatening Hawaii, a hurricane-less Atlantic season to date, and overwhelming wildfires in Indonesia are just a few effects already linked to this very strong event.
The stronger an El Niño, the more likely it is to influence these weather patterns, though it does not guarantee more extreme impacts in every location.
How NOAA Measures El Niño Strength
To capture El Niño’s strength, National Oceanic and Atmospheric Administration (NOAA) forecasters measure how far above normal sea surface temperatures are in a specific region of the Pacific using the RONI metric. The latest weekly RONI value hit 2.0 degrees Celsius (3.6 degrees Fahrenheit) above average. This marks the threshold for “very strong,” the highest official category set by forecasters, and the point where El Niño gains its unofficial “super” moniker.
These weekly values provide a reliable real-time snapshot of El Niño’s strength, which is crucial given how fast this event is gaining ground. Just a year ago, a weak La Niña—El Niño’s cool counterpart—was in place. Only a handful of other years have seen such a rapid flip to a potent El Niño, including the strongest event on record from 1982 to 1983.
Weekly vs. Monthly Metrics
Using weekly values is a slight departure from the norm. NOAA’s most widely recognized strength metric is a three-month rolling average RONI. The rolling average smooths out short-term data fluctuations in favor of a cleaner long-term average and updates once a month. This is how a decades-long climate record is built, but the delayed data means it will take weeks for that reading to truly capture how super-sized El Niño is right now.
Record-Breaking Trajectory Confirmed
This is not a normal event. In addition to being the strongest El Niño on record for this date, it is ultimately likely to become stronger than any event before it. By the end of the year, El Niño has a 75% chance of peaking as the strongest event since records began in 1950, according to NOAA’s latest forecast issued last week.
This year’s El Niño is also unfolding in a much hotter world than previous record-setting events due to climate change. A comparison of sea surface temperatures from this year against past record events illustrates how much fossil fuel pollution has rewritten the rules.
Climate Change Alters the Monitoring Metric
Climate change has literally changed the metric used to monitor El Niño. This event is the first to be captured by NOAA’s RONI, which was first implemented in February. The old metric took sea surface temperatures at face value, but RONI subtracts how much warmer the Pacific Ocean is because of climate change to isolate the “true” strength of El Niño. Even with this adjustment, this El Niño continues to clear hurdles in its pursuit of record-breaking strength later this fall or early winter.
Impacts: Past, Present, and Still to Come
Winter is when El Niño is forecast to hit its peak strength and when its influence on global weather is typically most pronounced, but it has already left significant calling cards this summer as it strengthened rapidly.
Hurricane Season Disruption
El Niño has been a major factor in both the Atlantic and Pacific hurricane seasons. In the Atlantic, it has driven storm-killing wind shear to extreme levels and kept it there, even during what should be the busiest time of the season. This created a record-long wait for the season’s first hurricane.
Conversely, El Niño has suppressed that same wind shear over the exceptionally warm Pacific, and activity has exploded. Sixteen storms, including two Category 5 hurricanes, have formed and thrived in the eastern and central Pacific so far. Hawaii alone has faced three tropical systems in less than a month. Fourteen of those storms originated in the East Pacific, which—with two and a half months of the season still remaining—will likely blow past its average seasonal storm total of 15.
Indonesia Wildfires and Global Heat
Elsewhere, Indonesia is battling widespread wildfires, and conditions could deteriorate further. El Niño years make the country drier than usual, leaving plenty of tinder-dry vegetation for blazes to consume and limited rainfall to help fire crews tamp down ongoing activity.
El Niño also raises global average air temperatures above levels already being increased by climate change. It was a factor in making this summer a scorcher around the globe. August was Earth’s hottest on record and could mark the start of a record-breaking warm stretch that would likely culminate in a record-hot 2024—and possibly 2025—globally.
It is clear El Niño is already a major player, but it will hit its full stride in the months ahead, right on time to dictate winter weather across the U.S.
