Cause and Effect | El Nino may make a bad situation worse

A new update issued by the World Meteorological Organisation (WMO) last Wednesday said that global temperatures are likely to surge to record levels in the next five years, with an El Nino turbocharging the warming being caused due to GHGs.

“A warming El Niño is expected to develop in the coming months and this will combine with human-induced climate change to push global temperatures into uncharted territory,” WMO Secretary-General Professor Petteri Taalas said in a press release. In technical terms, the United Nations agency’s Global Annual to Decadal Climate Update, said there was a 66% likelihood of exceeding the 1.5°C threshold in at least one year between 2023 and 2027.

During normal conditions, winds (typically, the Pacific Jet Stream — a current of strong, high-altitude winds that occur over the Pacific Ocean) blow west along the equator, also taking warm water from South America towards Asia. To replace this warm water, cold water rises from the depths, a process called upwelling.

El Nino and La Nina are opposing climate patterns that break these conditions. Together, they form the ENSO cycle. An El Nino event often begins in the middle of the year, with unusual warming of surface water in the eastern equatorial Pacific.

The warm water is pushed back east, towards the west coast of Americas, instead of the South America-to-Asia movement, with a lower quantity of cold water rising to the surface — thus the sea surface temperatures become higher than usual.

As the water warms, it creates an area of low pressure.

The Pacific Jet Stream, now weakened, moves south and spreads further east. The phenomenon has a high correlation with warmer summers and droughts in some areas. In India, it has disrupted monsoon rains in the past.

In 2015, an El Nino year, India recorded a 14% deficiency in monsoon rain.

El Nino peaks during November-January, and decays in the first half of the following year. La Nina, on the other hand, is associated with cooler weather globally on an average and excess rainfall. But, despite a prolonged three-year run of the last La Nina (a triple dip), which ended earlier this year, the last eight years were the warmest ever recorded – virtually a testament to how potent GHGs alone have become in raising the global temperature.

According to WMO predictions, released in April, there is a 60% chance for the onset of El Nino during May-July, with the probability likely to rise to 60-70% during June-August, and 70-80% in autumn, with no probability of a La Nina.

“Typically, El Niño increases global temperatures in the year after it develops – in this case this would be 2024," the WMO release last week said.

In India, as in some other parts of south and southeast Asia, temperatures have already risen to 45°C, and a further rise is expected as the summer takes hold.

Beyond the temperature rise (expect real impact next year), the El Nino this year also poses a threat to India’s rural economy.

A good monsoon is critical for the kharif (or monsoon) crop. According to India’s agriculture ministry, 51% of India’s farmed area, accounting for 40% of production, is rain-fed, making the monsoon critical. About 47% of the country’s population depends on agriculture for their livelihood.

And to make matters worse, an El Nino year also has a higher number of western disturbances.

A western disturbance (WD) is a low-pressure area (or an area of disturbed air pressure) that is created due to the warming of the water, and it moves from west to east (hence, western) from over the Mediterranean sea. The movement itself is an attempt to restore the equilibrium of the pressure upset because of the La Nina warming the water.

WDs typically bring rain, snow and fog to India.

As an El Nino sets in, the frequency of WDs increases. This year, that has caused moody weather which on one hand, has kept the country’s summer milder than usual, but, on the other, has brought unseasonal rain that has hit farming.

A coastal El Nino may already have set in, climate scientist at the Indian Institute of Tropical Meteorology, Roxy Mathew Koll said in a Twitter thread on May 17. “A sea surface temperature anomaly of 0.5-0.8 degrees Celsius for the central-east Pacific is often used as a threshold to identify an El Niño,” he said.

“Niño 3 index indicates that the east Pacific temperatures are warmer than usual and have crossed the threshold,” he said, sharing a time series of the temperature anomalies. The last reading on the series, on May 16, showed a reading of 1 degree Celsius.

Warming of the water due to El Nino presents another dire possibility, that of rise in sea surface temperatures, and marine heatwaves.

According to a time series of daily mean sea surface temperatures from the National Oceanic and Atmospheric Administration’s Optimum Interpolation SST, the average temperature for world’s ocean surfaces has oscillated seasonally between 19.7°C and 21°C since record keeping began in 1980.

On April 1, this temperature was 21.1°C and it stayed there for the next four days – in other words, breaking the records. Hotter oceans would not only increase the frequency of storms, they would also cause further shrinking of the ice sheets and rising of global sea levels.

Marine heatwaves, meanwhile, would make it near impossible for marine wildlife to survive, accelerate coral bleaching, and alter the food chain.

“We all know that our climate is warming – but I imagine that most people first think of warmer air temperatures. In fact, our oceans have been soaking up much of this extra heat, keeping the atmosphere relatively cool. This has come at a cost, and we are now seeing the temperature of our oceans at their hottest since records began,” On May 17, European Space Agency’s lead ocean scientist, Craig Donlon, said in a report, Our oceans are in hot water.