Scientists at the National Oceanic and Atmospheric Administration (NOAA) have announced that La Nina, a cool weather phenomenon, has officially arrived.. Now researchers say the weather model is finally in progress, although they warn that the event will likely be significantly weaker and shorter than usual, Live Science writes..
La Nina is the cold phase of the natural climate pattern known as the El Nino-Southern Oscillation (ENSO) cycle, which is a pattern of atmospheric and sea temperature changes in the tropical Pacific Ocean. The phases of this cycle are also known to influence global weather and Earth's climate.
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During a La Nina event, the northern U.S. and Canada tend to experience colder and wetter winters, while the southern U.S. gets warmer and drier, according to researchers.. It is also known that La Nina tends to increase hurricane activity over the Atlantic.
Observations show that this year La Nina came later than researchers expected, and therefore simply did not have time to gain strength before the start of winter. Scientists believe the conditions of this unusual cool event began in December last year and are likely to persist until April. NOAA said in a statement that scientists had been expecting La Nina since last spring, but all the necessary conditions did not come together until December 2024..
Note that ENSO is a multi-year cycle that causes a warm El Nino, and then a colder event - La Nina. This change of cycles occurs approximately every 2-7 years, and each of the phenomena usually lasts up to a year. It is known that El Nino contributed to the incredible heat in 2023 and 2024, and therefore scientists believed that its retreat would be followed by La Nina.
It's still unclear why La Nina developed so slowly, but scientists believe warmer average global ocean temperatures may have played a role..
NOAA has a flowchart for determining when La Nina officially begins: Tropical Pacific surface temperatures should fall 0.5 degrees Celsius below the long-term average. Observations show that since April last year the average temperature in this part of the Pacific Ocean has remained within 0.5 degrees Celsius and only fell below the threshold in December.
Scientists now believe there is a 59% chance of La Nina continuing through February-April, followed by a 60% chance of neutral conditions continuing into March-May.. Temperatures must remain below the threshold for five consecutive seasons—any three-month period—for this La Nina to be included in NOAA's official historical record.
Alas, scientists believe that this will not happen if La Nina fades away by March-May.
At the same time, scientists recognize that ENSO events are difficult to predict, and therefore the situation can change dramatically at any moment. Researchers will continue to monitor surface temperatures in the tropical Pacific Ocean to see how long La Nina lasts.
Previously, Focus wrote that something that scientists had previously overlooked was found in the ocean: a new Earth climate switch.