Cooling La Niña is on wane, but temperatures set to rise: UN weather agency

It noted that above-normal temperatures in the next three months are expected in western, central and eastern Asia and over the southern half of North America, and that there is a moderate likelihood (65 per cent) that the La Niña event will continue into April.

Above-normal temperatures are also likely over most northern high latitudes – except northwestern North America – southern, central and eastern parts of South America, and equatorial and northern Africa.

Below-normal temperatures are more likely for northern South America.

‘Unusually wet’

Turning to rainfall, WMO said that there were “increased chances of unusually wet conditions” that were consistent with La Niña’s effects on regional climates, over much of South East Asia, Australia and northern South America and islands in Melanesia.

Southern Africa may also see above-normal rainfall, the agency continued, along with “an increased probability of above-normal precipitation (possibly as snow) over much of the Northern Hemisphere north of about 45 degrees North”, although WMO credited the “ongoing negative Arctic Oscillation” climate driver for this trend, which has been observed since December, rather than La Niña.Drier-than-normal conditions are however likely over much of western and central Asia “and along about 30 degrees North in

East Asia, as well as parts of the Greater Horn of Africa, parts of Central Africa, sub-tropical latitudes of North America, islands in Polynesia and some parts of southeastern South America” says WMO’s Global Seasonal Climate Update (GSCU).

Cooling off

La Niña refers to the large-scale cooling of ocean surface temperatures in the central and eastern equatorial Pacific Ocean, along with changes in winds, air pressure and rainfall in the tropics.

It has been in place since August 2020, WMO said, “but this was not enough to prevent 2020 from being one of the three warmest years on record”.

La Niña usually has the opposite impact on weather and climate to El Niño, which is the warm phase of the so-called El Niño Southern Oscillation (ENSO).

Human factor

Although El Niño and La Niña are major drivers of the Earth’s climate system, so too is “human-induced climate change, which is increasing global temperatures, exacerbating extreme weather, impacting seasonal rainfall patterns and complicating disaster prevention and management”, said WMO Secretary-General, Professor Petteri Taalas.

The WMO chief added that it was thanks to the agency’s ability to predict La Niño and El Niño events in advance that just-in-time interventions can be carried out to protect communities and countries in climate-sensitive regions sectors.

Other climate drivers include the North Atlantic Oscillation, the Arctic Oscillation, the Indian Ocean Dipole and other teleconnection patterns.

East Africa

According to WMO data, East Africa’s short but important rainy season from October-December saw generally drier conditions in the north and east, with wetter or nearer normal conditions in the south and west. Similar mixed rainfall patterns are forecast between now and April.

Southern Africa

Many parts of southern Africa have seen above-average rainfall, WMO noted, with a significant exception being parts of Mozambique and Madagascar, which have seen little or no rainfall.

Central Asia

Central Asia generally receives most of its annual rainfall in the first half of the year, but the past three months have seen many parts of Central Asia experiencing below-normal rainfall. The outlook for the next three months indicates that below-normal rainfall is again likely.

South East Asia

Large parts of South East Asia have seen “significantly above-normal” rainfall totals in the last few months. This trend is likely to continue, particularly to the east of the region.

Central Pacific Islands

The islands of the Western Central Pacific, including Papua New Guinea, Kiribati, Tuvalu and Northern Cook Islands have experienced extremely dry conditions over the last few months.

South America (North of the equator)

Rainfall has been very mixed, with eastern equatorial areas seeing well above-normal totals, while western equatorial areas have had less rain than normal. Looking ahead, forecasts highlight above-normal rainfall from February through to April for much of the region.

South America (South of the equator)

Much of the region has seen below-normal rainfall in the last few months, but the situation has been “significantly” worse in Uruguay, central Brazil and northern Argentina. WMO’s latest seasonal global seasonal forecast indicates that this trend is likely to continue.