El Nino set to return in Pacific Ocean after 7 years, NOAA issues warning

Nino 3.4 index value jumped from minus 0.2° Celsius to 0.8° Celsius between March and June this year; meteorologists say such accelerated rates of warming were unusual

El Nino is back in the Pacific Ocean after seven years, the National Oceanic and Atmospheric Administration (NOAA), US, said on Thursday.

El Nino is a climate pattern that develops along the equatorial Pacific Ocean after intervals of around two to seven years. During El Nino, the ocean water sees unusual warming in a band, straddling the equator in the central and east-central Pacific. When El Nino Southern Oscillation (ENSO) is in its neutral phase, the trade winds blow west along the equator and take the warm water from South America towards Asia. However, during El Nino, these trade winds weaken and can turn into westerlies.

As the winds blow from the west to east, they cause warm water to move into the central and eastern equatorial Pacific Ocean, and reach the coast of western America. During such years, there prevails warmer-than-average sea surface temperatures along the equatorial Pacific Ocean.

Impact of El Nino

El Nino has been associated with severe heatwaves, floods, and droughts across the globe.

Michelle L’Heureux, climate scientist at the Climate Prediction Center, NOAA, said, "Depending on its strength, El Nino can cause a range of impacts such as increasing the risk of heavy rainfall and droughts in certain locations around the world."

Severity of El Nino this year

This year's El Nino is the fifth since 2000.

At the start of this year, an El Nino was predicted to emerge by August, but this did not happen. Sea surface temperatures along the equatorial Pacific Ocean are showing signs of much more rapid warming than had been predicted by weather models.

The Nino 3.4 index value — the vital indicator confirming an event of El Nino — jumped from minus 0.2° Celsius to 0.8° Celsius between March and June this year. The threshold value of this index is 0.5° Celsius.

Meteorologists have warned that such accelerated rates of warming, following three years of La Nina that ended in February this year, were unusual, according to a report in The Indian Express.

Impact on India

Over the last hundred years, India has witnessed 18 drought years and 13 of these were associated with El Nino. Between 1900 and 1950, there were seven El Nino years, but during the 1951-2021 period, there were 15 El Nino years. This shows that the frequency of El Nino events has been increasing over time, according to the Indian Express report.

Of the 15 El Nino years in the 1951-2021 period, nine monsoon seasons in India recorded deficient rain by more than 90 per cent of the long period average (LPA).