ECONOMY

La Niña expected to intensify global rain and drought after second consecutive year

The La Niña phenomenon has developed for the second consecutive year, with the weather pattern expected to intensify rainfall as well as droughts around the world.

The counterpart to the better known, opposing El Niño phenomenon, La Niña involves the large-scale cooling of the Pacific Ocean’s surface, which drives changes in wind and rainfall with consequences across the globe.

Both the World Meteorological Organization and Australia’s Bureau of Meteorology have in the past week confirmed the back-to-back years of La Niña conditions, with scientific models indicating it will last into early 2022.

The 2021-2022 La Niña would probably be “weak to moderate” and “slightly weaker” than the previous year, said the WMO. Yet it would still be likely to have a continuing effect on agriculture and water supply, as it would cause greater rain in some areas and less in others.

Typical effects of La Niña have included unusually dry conditions in parts of the US and South America, as well as abnormal amounts of rain and more cyclones than normal in countries such as Australia, which has experienced the wettest November in 121 years of records for its most populated state.

“[La Niña’s] impacts can really spread around the world because of the way global circulation works,” said Tim Stockdale, principal scientist at the European Centre for Medium-Range Weather Forecasts.

Maps of the US showing winter precipitation and temperature patterns during the seven strongest second-year La Niña events since 1950

Mike Halpert, deputy director at the US National Oceanic and Atmospheric Administration’s Climate Prediction Center, said La Niña might make certain weather events such as storms more likely, but that it was just one of the factors that contributed to their occurrence.

A severe ongoing drought in Afghanistan was linked to the previous La Niña, while Halpert said parts of the US were likely to experience “another dryer than average winter”.

The International Federation of Red Cross and Red Crescent Societies said this week that the drought in Afghanistan had affected more than 80 per cent of the country, “crippling food production and forcing people from their land”.

According to Stockdale, the occurrence of two consecutive La Niña events, known as a “double dip”, was “actually quite common”. Three in a row was less likely, but “it has happened”, he said.

Map showing difference in rainfall from the long-term average (cm)

In the past month, parts of Australia have been hit by severe storms and flash flooding, prompting evacuation orders by the New South Wales state government. Its emergency service said on Wednesday that it had responded to more than 4,800 requests for assistance since the beginning of the disaster and attended to 153 flood rescues.

Climate change is making extreme weather events more likely and severe, with La Niña and El Niño events anticipated to exacerbate the effects. Temperatures have already risen by 1.1C since pre-industrial times as a result of human activity.

“If you have [a] background of more unusual things happening and then you put more unusual things on top, then the risk of driving extremes becomes higher,” Stockdale said.

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La Niña expected to intensify global rain and drought after second consecutive year

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