The World Meteorological Organization (WMO) has warned that this year could become the third consecutive episode of the La Niña climate phenomenon.
The United Nations (UN) Meteorological Agency warned that there 70% chance that La Niña will continue in September and November this year.
If this happens, it will be the first time this century that it has a “triple episode” of La Niña.
The current weather phenomenon began in September 2020.
If it continues until the end of the year, it will reach three consecutive boreal winters, which is why it is considered a “triple episode”.
The WMO also estimated that there is a 55% chance of La Niña continuing until February 2023.
What is Nina?
La Niña and El Niño are two opposite phases of the same weather pattern.which is known as the El Niño-Southern Oscillation (ENSO).
ENSO is a natural surface temperature anomaly phenomenon in the equatorial Pacific Ocean that has important implications for the climate around the planet.
El Niño is the warm phaseand usually appears first.
This occurs when atmospheric pressure conditions change, weakening the trade winds in the southern Pacific Ocean.
This is how the winds are known, which generally blow from east to west in this ocean, from the subtropical high pressure regions to the equatorial low pressure areas.
The trade winds carry warm surface water from the equatorial zone off the coast of South America to Asia, on the other side of the ocean.
This causes the waters of the depths, which are colder, to rise in its place.
But when these winds weaken or even reverse, they bring warm water from Southeast Asia to South America.
La Niña occurs when the opposite occurs: when the trade winds are very strong, the upwelling of deep cold waters in the equatorial zone is enhanced and the sea temperature falls below normal.
Because La Niña is considered the cold phase of the phenomenon.
Usually between the two phases there is a period called the “neutral zone” in which neither event is particularly active and temperatures are average.
Climatologist Alfredo “Alpio” Costa, an expert on climate change at the Argentine Antarctic Institute, explained to BBC Mundo that ENSO is quite irregular: from the time a boy starts until a girl ends, and the cycle starts again, usually between two and seven years.
But these two phenomena do not always alternate. Sometimes, as happens now, only one of the phases is repeated several times without the opposite appearing.
“It has been many decades since we have traveled through three consecutive Niñas,” notes the expert.
In this BBC Mundo video, you can see how El Niño and La Niña interact and how they differ:
Costa points out that ENSO has an impact on much of the world because “the extension of the equatorial Pacific Ocean is so large that it ultimately has an effect on climate patterns on a global scale.”
Regarding La Niña, he confirms that it causes changes in the Americas, Asia, Africa and Oceania, “but not so much in Europe”, where the climate is more affected by other meteorological factors.
“Worldwide La Niña effects, called teleconnections, they are very diverse: in the eastern part of Argentina and the southern part of Brazil and Uruguay it causes drought”, he specifies.
“But in northeastern Brazil and northern Australia and Southeast Asia, it generated the opposite, with increased precipitation. And there are areas of China, India and Japan, as well as western Canada and southern Alaska (US), which are affected by colder than normal temperatures,” he says.
“East Africa is also affected by drought,” he warns.
In his report on “the first triple episode of La Niña this century”, WMO Secretary-General Peteri Taalas highlighted the impact it will have on this continent.
“Unfortunately, the latest La Niña data confirms the regional climate forecasts that point to worsening the devastating drought in the Horn of Africathe consequences of which will affect millions of people,” complained Taalas.
It is believed that some 18 million people are facing severe famine as a result of the region’s worst drought in 40 years.
The UN specifies that ENSO are not caused by climate change.
“This is a recurring natural phenomenon that has been occurring for thousands of years,” the agency said.
However, he stressed that “some scientists believe that (El Niño and La Niña) may become more intense and/or more frequent as a result of climate change, although it is not 100 percent clear exactly how they interact .”
“Climate change is likely to affect the impacts associated with El Niño and La Niña in terms of extreme weather events. Further research will help separate natural climate variability from any trends due to human activity.”