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For the sec­ond con­sec­u­tive year, the weather phe­nom­e­non known as La Niña has devel­oped in the Pacific Ocean and is expected to con­tinue until 2022.

The coun­ter­part of the oppos­ing and bet­ter-known El Niño is expected to inten­sify rain and drought in dif­fer­ent world regions.

While El Niño is linked to abnor­mal warm­ing of the east­ern equa­to­r­ial Pacific Ocean, La Niña involves cool­ing this sig­nif­i­cant sec­tion of the ocean.

The cool­ing effect causes changes in atmos­pheric cir­cu­la­tion or winds, air pres­sure and rain­fall, dis­rupt­ing weather pat­terns across the world.

According to World Meteorological Organization (WMO), the 2021/22 La Niña will be weak or mod­er­ate com­pared to 2020/21.

However, it still car­ries the pos­si­bil­ity of affect­ing sen­si­tive sec­tors such as water sup­ply, health, dis­as­ter man­age­ment and agri­cul­ture because some areas are likely to receive more rain­fall com­pared to oth­ers, with some regions endur­ing pro­longed dry spells.

“[La Niña’s] impacts can really spread around the world because of the way global cir­cu­la­tion works,” Tim Stockdale, a researcher at the European Center for Medium-Range Weather Forecasts, told the Financial Times.

The WMO fore­casts an unusu­ally warm win­ter for the Arctic and north­ern Asia, east­ern North America and Europe. Above-aver­age tem­per­a­tures are also expected in the South Pacific and equa­to­r­ial Africa.

South America, north­west­ern North America, the Indian sub­con­ti­nent, South East Asia and Australia are all expected to expe­ri­ence cooler weather than usual.

“The cool­ing impact of 2020/21 La Niña – which is typ­i­cally felt in the sec­ond half of the event – means that 2021 will be one of the 10 warmest years on record, rather than the warmest year,” said WMO Secretary-General Petteri Taalas. ​“This is a short-lived respite and does not reverse the long-term warm­ing trend or reduce the urgency of cli­mate action.”

La Niña’s effects also include abnor­mally long dry spells in Central Asia and North and South America. Last year’s La Niña has been linked with an ongo­ing drought in Afghanistan. Meanwhile, the north­west­ern United States is expected to expe­ri­ence unusu­ally wet con­di­tions through­out the year.

“Good for [the Northwest], prob­a­bly not so good for cen­tral, south­ern California,” Mike Halpert, the deputy direc­tor of the United States National Oceanic and Atmospheric Administration’s cli­mate pre­dic­tion cen­ter, told ABC News.

The phe­nom­e­non also causes higher-than-nor­mal rain­fall cou­pled with cyclones in South East Asia and Australia, which expe­ri­enced the wettest November 2021 in 121 years of recorded his­tory.

Additionally, more coun­tries are likely to feel the effects of La Niña because vul­ner­a­ble pop­u­la­tions have been hit hard by extreme weather events in recent years and the Covid-19 pan­demic.

According to WMO, there is a 90 per­cent chance that trop­i­cal Pacific sea sur­face tem­per­a­tures will remain at La Niña lev­els until the end of 2021 and a 75 per­cent chance of the tem­per­a­tures stay­ing at La Niña lev­els until the first quar­ter of 2022.

• World Meteorological Organization
• ABC News
• Financial Times