The World Meteorological Organisation (WMO) said on Friday it saw unprecedented signs pointing to a looming La Niña, a phenomenon that originates off the western coast of South America but can disrupt weather patterns in many parts of the globe.
In a press release, the Geneva-based agency said temperatures in the central and eastern equatorial Pacific had been between 0,5 and 1,0 °C below normal since the start of the 2006.
”Combined with broader tropical Pacific ocean and atmosphere conditions, this is consistent with the early stages of a basin-wide La Niña event,” it said.
”(…) It is unprecedented in the historical record for a La Niña of substantial intensity or duration to develop so early in the year.”
La Niña, which has the opposite effects to the more notorious El Niño, last occurred from mid-1998 to early 2001.
Under La Niña, the sea-surface temperature in the central and eastern tropical Pacific falls below normal.
This typically brings far dryer weather to the southwestern United States, Florida and western Latin America and above-average rainfall to Australia, Indonesia, Malaysia and the Philippines.
But there can also be a knock-on much further afield, with an increase to monsoon rainfall in South Asia, unusual coolness in tropical West Africa, South East Africa, Japan and the Korean peninsula.
La Niña usually lasts nine to 12 months, although ”some episodes may persist for as long as two years,” the US National Oceanic and Atmospheric Administration (NOAA) says on its website.
The WMO sounded a note of caution.The buildup of this La Niña was so exceptionally swift and intense that it was impossible at the moment to infer what the impact would be, and how long the phenomenon would last, it warned.
”Most models and expert interpretations favour the event dissipating quite rapidly over the next three to six months,” the UN’s weather agency said.
”Nonetheless, neither a continuation of La Niña beyond mid-year, nor the development of El Niño in the second half of 2006, can be ruled out as possible outcomes from the current prevailing situation.”
El Niño, which last ran from 2002-03, occurs when warm water builds up in the western tropical Pacific and creeps eastwards, again causing huge disruption to classic patterns of rainfall and wind.
Both El Niño and La Niña are naturally occurring cycles, although there is much speculation among climate scientists that man-made global warming may make them more frequent and more vicious and that this trend may have already started.
El Niño means ”the little boy” in Spanish. Its name is attributed to fishermen off the coast of South America who noted the appearance of warmer water, often around Christmas. La Niña means ”the little girl”. – Sapa-AFP