Scientists Redefine El Niño Classification Amid Global Warming Surge
In a significant shift, scientists have updated how El Niño and La Niña are labeled to account for accelerating global temperatures. This natural cycle, which distorts weather patterns worldwide, is increasingly influenced by a warming planet, according to meteorologists.
New Study Explains Recent Temperature Spike
A recent study published in Nature Geoscience this month reveals that an unusual twist in the El Niño-La Niña cycle has contributed to Earth's temperature reaching unprecedented levels over the past three years. Japanese researchers found that about three-quarters of the change in Earth's energy imbalance—the difference between incoming and outgoing energy—can be attributed to a combination of long-term human-caused climate change and the transition from a cooling La Niña to a warming El Niño.
From 2020 to 2023, Earth experienced a rare "triple dip" La Niña without an intervening El Niño. Study co-author Yu Kosaka, a climate scientist at the University of Tokyo, explained that during La Niña, warm water remains at deeper depths, cooling the surface and trapping more energy on Earth. "When there is a transition from La Niña to El Niño, it's like the lid is popped off," releasing this heat, said former NOAA meteorologist Tom Di Liberto, now with Climate Central.
Redefining Normal in a Warming World
For 75 years, El Niño and La Niña were defined based on temperature differences in three tropical Pacific regions compared to a 30-year average, updated every decade. However, as global waters warm, this baseline has become obsolete. Nat Johnson, a meteorologist at NOAA's Geophysical Fluid Dynamics Lab, noted that even updating the average every five years proved insufficient.
This month, NOAA introduced a new relative El Niño index, comparing temperatures to the rest of Earth's tropics rather than a fixed normal. The difference between old and new methods has reached up to half a degree Celsius, significantly impacting classifications. Johnson stated that this change will likely result in more events being labeled as La Niña and fewer as El Niño, better reflecting atmospheric interactions.
Implications for Future Weather Patterns
NOAA forecasts the development of an El Niño later this year, which could dampen Atlantic hurricane activity but also drive global temperatures higher in 2027. Jennifer Francis of the Woodwell Climate Research Center warned, "When El Niño develops, we’re likely to set a new global temperature record. 'Normal' was left in the dust decades ago. And with this much heat in the system, everyone should buckle up for the extreme weather it will fuel."
The study also highlighted that approximately 23% of the recent energy imbalance stems from the prolonged La Niña pattern, with over half attributable to greenhouse gases from fossil fuels. This underscores the complex interplay between natural cycles and human-induced climate change, reshaping how scientists understand and predict global weather phenomena.
