Current El Niño dubbed 'unprecedented' by UK and Japan, but US agencies remain cautious. Climate change complicates measurements and historical comparisons.
El Niño called unprecedented by UK and Japan
The UK Meteorological Agency has called the current El Niño "unprecedented," while Japan's agency has labeled it "the most powerful ever observed." However, American forecasters suggest it has not yet surpassed past extreme El Niño events.Differing measurement criteria
The varying assessments stem from different measurement criteria. Some agencies focus on surface water temperatures, while others look at deviations from a defined "norm," which can be calculated in multiple ways.El Niño's impact on ocean currents
Normally, winds blow from east to west along the equator in the Pacific, pushing warm waters toward Asia. El Niño disrupts this pattern, weakening the winds and allowing warm water to remain or return to the center and east of the Pacific, affecting global weather patterns.UK's assessment based on temperature
The UK's assessment of El Niño as "unprecedented" is based on the temperature of the water in the Pacific Ocean. They observed that sea surface temperatures in the central equatorial Pacific have now exceeded those recorded during previous El Niño episodes.Japan's measurement method
Japan's Meteorological Agency declared the current El Niño the most powerful based on the deviation between sea surface temperatures and the normal in the Niño3 region. Their calculations show this episode surpasses the 1997 event in observations dating back to 1949.US measurement and criteria
The United States monitors a slightly different region, called Niño3.4, and declares an El Niño episode when temperatures there exceed the normal by at least 0.5°C, with a weakening of surface winds and a shift eastward of tropical rains.New index for measuring El Niño
To determine "the normal" temperature for comparison, the NOAA and WMO use an index comparing the Pacific region's temperature to a 30-year average. The RONI index now measures how much the central-east of the Pacific is warmer or cooler than the rest of the tropics.Threshold for record-breaking El Niño
For this El Niño to surpass all previous episodes in American data, its RONI anomaly must reach at least 2.5°C for three months. This would place it above the episodes of 1982-83 and 2015-16, though the NOAA considers this possibility "high" but not certain.Scientific opportunity
Climatologist Emily Becker emphasized that regardless of its ranking, the current El Niño is an exceptional opportunity to study and understand this powerful phenomenon in the context of a warming world.
