La Nina cycle peaks

The 2020-2021 La Nina phenomenon has passed its peak, the United Nations weather agency said yesterday, but its impact on temperatures, rain and storm patterns is set to continue.

La Nina refers to the largescale cooling of surface temperatures in the central and eastern equatorial Pacific Ocean, occurring every two to seven years.

The effect has widespread impacts on weather around the world – typically the opposite impacts to the El Nino warming phase in the southern oscillation cycle.

Besides the cooling effect, La Nina is usually associated with wetter conditions in some parts of the world and drier conditions in others.

La Nina conditions have been in place since August-September last year, according to atmospheric and oceanic indicators.

“La Nina appears to have peaked in October-November as a moderate strength event,” said the World Meteorological Organisation (WMO). It said there was a 65% likelihood that La Nina would persist from February through April. The odds shift rapidly thereafter, with a 70% chance that the tropical Pacific will return to neutral conditions in the cycle by April-June.

“El Nino and La Nina are major drivers of the earth’s climate system,” said WMO secretary-general Petteri Taalas. “But all naturally occurring climate events now take place in the context of human-induced climate change, which is increasing global temperatures, exacerbating extreme weather, impacting seasonal rainfall patterns and complicating disaster prevention and management.”

The temporary global cooling effects of La Nina were not enough to prevent last year from being one of the three warmest on record.

“Despite the general cooling influence of La Nina events, land temperatures are expected to be above normal for most parts of the globe in February-April 2021,” the WMO said.