WMO predicts first ‘triple’ La Niña this century
“La Niña events for three consecutive years are very rare,” WMO Secretary-General Petteri Taalas said in a press release. The phenomenon is expected to continue to fuel severe weather in far-flung corners of the world.
La Niña usually occurs every two to seven years, usually lasting a year or less. It’s unfolding in the Pacific, but its effects can be felt globally. Along with El Niño, it is one of the extreme phases of the El Niño-Southern Oscillation (ENSO), a recurring climate pattern.
During La Niña, unusually strong trade winds blow warm surface water from the Americas to Asia. Then from the ocean floor, more cold water rises — causing a cooling effect across the central and eastern tropical Pacific. The consequences of this phenomenon vary from region to region and from year to year, but La Niña usually has the opposite effect of El Niño. Australia, for example, tends to get more rain, while East Africa is generally drier than normal.
This particular La Niña event started in September 2020. Since then, Taalas noted, its “signature” has been shown in unusual weather events around the world. This includes the longest drought to hit the Horn of Africa in four decades. Facing five backbone rainy seasons in a row, more than 50 million people across seven countries in East Africa – from Eritrea all the way to Kenya and Somalia – are expected to experience food insecurity this year, according to a UN-backed report. Taalas said the latest La Niña forecast confirmed that the current drought would continue to worsen.
In Australia, on the other hand, La Niña brings record rainfall. Last week, Sydney’s rain gauges recorded more than two metres of rain since the start of the year. It was the first time the city hit that mark earlier this year since records began 164 years ago. Sydney is the capital of New South Wales and severe flooding has plagued parts of the state throughout the year.
Climate change is also at play when it comes to more extreme weather events – whether it’s droughts, floods or La Niña. As global temperatures rise, extreme La Niña and El Niño events will become more frequent by the end of the century — about once every ten years, the study notes.
The World Meteorological Organization predicts that there is a 70 percent chance that La Niña will persist from September to November this year. It has a 55% chance of persisting from December 2022 to February next year.