A weak La Niña climate pattern has officially developed in the Pacific Ocean, marking a later emergence than initially anticipated. This phenomenon is poised to increase the likelihood of drought and heavy rainfall in various regions, despite contributing to a decrease in global average temperatures.
The eastern tropical Pacific Ocean experiences temperature fluctuations in a cycle known as the El Niño Southern Oscillation (ENSO), with La Niña representing the cooler phase. Typically occurring every three to five years due to strengthened trade winds, this phase results in the upwelling of colder waters off the South American coast.
For several months, sea surface temperatures in this region have been cooler than average, but they did not dip below the threshold necessary to officially declare a La Niña event until recently. Current wind patterns now indicate clear La Niña conditions.
Forecasts suggest that La Niña will persist through April 2025, after which temperatures are expected to return to neutral conditions.
Although categorized as a weak event, the cooler sea surface temperatures are anticipated to impact global weather patterns significantly, heightening the risks of drought in parts of North and South America while triggering intense rainfall in Australia and Southeast Asia.
La Niña typically leads to a decrease in global average temperatures, although the extent of this cooling correlates with the event’s strength. While temperatures have dropped following the warm El Niño phase, they remain above average globally.
The transition to La Niña results in the eastern tropical Pacific being cooler than average; however, global sea surface temperatures still exceed the norm by more than 0.5°C.
The slow cooling of the oceans from their record-high temperatures observed in mid to late 2023 has been noted, indicating a significant climatic shift.
It is not uncommon for La Niña to appear later in the season, even after a robust El Niño event, yet its arrival has occurred months past initial predictions. The reasons behind the discrepancy in forecasts, and whether human-induced climate change contributed to the delay, remain uncertain.
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