La Niña, the cool phase of El Nino-Southern Oscillation (ENSO), is signalling a shift in natural climatic trends around the world. This ocean-atmosphere phenomenon usually lowers global temperatures.
La Niña happens when ocean surface temperatures in the Eastern and Central Pacific Oceans, near the equator off the west coast of South America, are cooler than normal. This result in the trade winds above the sea surface changing character due to a difference in wind pressures. La Niña results in severe rainfall in some parts of the world, while it causes extreme drought in other parts. It can last up to a maximum of two years, unlike El Nino, which usually lasts no more than a year.
It can be recalled that such a long La Niña happened only two times and it was from 1998 to 2001 and 1973 to 1976. According to NOAA, the 1973 – 1976 event lasted 37 months, making it the longest since 1950.
According to the World Meteorological Organisation (WMO), despite the cooling of this naturally occurring climate phenomenon, temperatures in many parts of the world are expected to be above average due to accumulated heat trapped in the atmosphere as a result of record high levels of greenhouse gases. It also stated that there is a 70 per cent chance that the present La Niña will last from June to August 2022 and thereby complete 24 months.
The National Oceanic and Atmospheric Administration (NOAA) on June 6 predicted a 58 per cent possibility of La Nina for August – October and a 61 per cent chance for the winter season.
The changing character of the ongoing La Niña is a source of great concern, rather than its duration. La Nina is known to bring wet and cold winter and spring seasons to India, however this year several parts of the country did not see any spring.
This occurred due to a north – south pressure pattern, which generally develops over India during the winter and dissipates by spring, persisted into March and April this year. Warm waves from the rapidly warming Arctic region coupled with the pattern initiate and sustain heatwaves across the country.
For the third year in a row, India may have a prolonged monsoon season. The monsoon seasons of 2020 and 2021 were also extended, increasing extreme rainfall events, which resulted in floods in many states. Experts even state that this extension was most likely caused by the impact of La Niña.
WMO informed that the ongoing drought conditions across 40 per cent of the United States, as well as the years-long drought conditions in the Horn of Africa and southern South America, will most certainly continue and intensify owing to the continuation of La Niña.
Petteri Taalas, Secretary-General of WMO stated that “Human-induced climate change amplifies the impacts of naturally occurring events like La Niña and is increasingly influencing our weather patterns, in particular through more intense heat and drought and the associated risk of wildfires, as well as record-breaking deluges of rainfall and flooding.”
This effect over the next few months will likely have catastrophic effects in various parts of the world, including India.