Mint Explainer: How a strong El Nino would hamper India’s monsoon & agriculture

The formation of an El Nino is likely to affect the production of key crops and could even alter trade routes for their markets. What does this mean for India and how will it affect the southwest monsoon, cyclone formation, and agriculture? Mint takes a look.

What are the differing predictions by the Indian Meteorological Department and the Australian Bureau of Meteorology?

El Nino, which is associated with warming of equatorial Pacific Ocean waters, often hampers the June-September monsoon. India’s met department has said that El Nino could emerge in the monsoon season starting from June, although the sea surface temperature (SST) over the Pacific Ocean may not exceed 1.5°C in the entire season. The rise in SSTs is currently at 0.9°C. A rise of up to 1°C is considered a weak El Nino and a rise of 1°C to 1.5°C is classified as moderate. The Australian Bureau of Meteorology on the other hand predicts El Nino will pick up pace, increasing SSTs by 3°C by October and 3.2°C by November.

What if the Australian Bureau of Meteorology’s forecast proves correct?

Indian meteorologists do not see SSTs increasing by more than 2.5°C. However, as El Nino is stronger this year, there is a high chance India will experience slightly below-normal rain. During El Nino, monsoon winds are weak and air sinks over India's mainland, suppressing cloud formation and rain. If rainfall remains unevenly distributed in July, a crucial month for Kharif crops sowing, their yields may be affected.

The prediction of a ‘super El Nino’ could further fuel high inflation and slow down growth with increased weather fluctuations in the form of heatwaves and unseasonal rains. Prices of key crops such as rice, wheat and pulses are already high and a failed monsoon would push food inflation even higher.

How’s the track record of the Australian Bureau of Meteorology?

Australia’s met department has had the most extreme and accurate forecasts of developing El Ninos. It correctly predicted the super El Niño that peaked at 2.6°C in November and December of 2015. Another accurate prediction was in 1997, when El Niño caused SSTs to rise 2.4°C. The latest prediction – that the SST will rise by more than 3°C by November.-- will break all records if it proves correct.

How would an extremely strong El Nino affect rainfall and Indian agriculture during the Northeast monsoon in October-November?

The Northeast monsoon nourishes India’s soil for Rabi crops (mainly wheat, barley, gram, and mustard). Climate scientists say this winter rainfall cannot be predicted with high confidence right now. However, historical data indicate that in an El Nino year, north India typically receives above-normal rain during winter months due to above-normal western disturbances. These western disturbances are low-pressure areas that originate in the Mediterranean and move eastwards, bringing rain to north India in winter. Other factors also come into play here, apart from El Nino. Ocean-atmospheric conditions over the Atlantic Ocean can also change the frequency of western disturbances.

How does El Nino affect the formation of cyclones?

El Nino had no role in the formation of the recent Cyclone Biparjoy. Such cyclones usually emerge in the Arabian Sea between April and early June. In October-December, El Nino suppresses cyclone activity in the Bay of Bengal. Both the frequency and intensity of cyclones in this basin are below normal in an El Nino year. In a La Nina year, cyclones are more frequent and intense than normal after the monsoon. There is also no connection between the El Niño-Southern Oscillation (ENSO) and cyclones.