A potentially record-breaking El Niño event is underway and we are already seeing its effects. From wildfires in Indonesia to an unusually active tropical cyclone season in the Pacific Ocean, this phenomenon is having a cascading effect on global weather patterns that will peak in the coming winter.
On Thursday morning, the National Oceanic and Atmospheric Administration raised the probability that this El Niño will exceed the intensity of every other El Niño since at least 1950 to 83%, up from 75%, which was already high last month.
Scientists predict and classify El Niño based on warmer-than-normal ocean temperatures in an area called the Niño 3.4 region of the central Pacific near the equator.
When this region of the Pacific Ocean gets warm enough, usually in late summer or early fall, experts declare that an El Niño is occurring. El Niño is a natural climate cycle that occurs once every few years, but this ongoing phenomenon stands out for its unusual intensity.
NOAA’s Climate Prediction Center currently classifies these events based on the Relative Ocean Niño Index (RONI). This index uses the Niño 3.4 regional temperature anomaly and subtracts the average temperature of the world’s tropical oceans. In this way, the index takes into account long-term climate change. Climate change is warming the oceans, effectively amplifying the symptoms of El Niño.
Anomalies that are at least 0.5°C above the mean indicate the presence of El Niño. This season’s El Niño recorded an abnormal temperature of 2°C above average in early September, entering the “very strong” or “super” El Niño region. Experts predict that temperatures will continue to rise, and nearly all computer models predicting the intensity of these events indicate they will set records this fall or winter.
Weekly RONI values indicate the strength of this El Niño. Historical records of El Niño are based on averages over three-month intervals, which has the effect of smoothing out short-term fluctuations. In the past, very strong El Niño events occurred in 2015-2016, 1997-1998, and 1982-1983.
This season has already become a Super El Niño, and based on current trends, it is likely to become the strongest El Niño in recorded history.
