Impact of Weak El Nino conditions

Context:

• The Indian Meteorological Department (IMD) from Ministry of Earth Sciences has declared that weak El Nino conditions are prevalent in equatorial Pacific Ocean.
• These conditions are likely to persist in early part of summer season and weaken thereafter.
• The preliminary impact of a weak El Nino can already be seen with the rising temperatures and heat waves across the country. In early March, the heat wave season began in many areas of Tamil Nadu, coastal Andhra Pradesh and Rayalaseema.

El Nino

• El Nino (Spanish for Christ Child) is the occasional development of warm ocean surface waters along the coast of Ecuador and Peru. Recently this development has been used for forecasting of climatic conditions in different parts of the world.
• The El Nino normally occurs around Christmas, roughly every 2 to 7 years and lasts usually for a few weeks to a few months.
• El Nino event is related to two important atmospheric circulation systems:
  • Hadley Circulation:It features air rising near the Equator, flowing pole ward at a height of 10 to 15 kilometres above the earth’s surface, descending in the subtropics, and then returning equator ward near the surface.
  • Walker Circulation:There is a stable low-pressure system above the western Pacific near South East Asia and a high-pressure system in the central Pacific. This results in a constant westward flow of the air masses from the area of high pressure to the area of low pressure. At higher altitudes this air then flows directly eastward, oblique to the Hadley Circulation.
• Due to the combined components of Walker Circulation and Hadley Circulation, there is a strong prevailing wind toward the west in the lower layers of the atmosphere, which maintains the stable coastal upwelling system off the coast in western South America.
• La Nina is the condition opposite of an El Nino. In a La Nina, the tropical Pacific trade winds become very strong and an abnormal accumulation of cold water occurs in the central and eastern Pacific Ocean.

Impact of El Nino around the world:

• It causes flooding in Peru and Equador.The earlier cool water off the coast was rich in nutrients and fish, providing rich pickings for the Peruvian fishing industry.During El Nino, the warm water sloshes back towards South America, which hides the nutrient-rich cold waters and ensures fish are in short supply.
• The lack of fish is the reason that El Nino was first discovered by the Peruvian fishermen. They noticed that every three to seven years, there would be virtually no fish in the seas. The reduction in fish caused by El Nino can be dramatic; an event in 1972-1973 almost brought the complete collapse of the Peruvian fishing industry.
• The severe El Nino had also caused massive coral bleaching in the Great Barrier Reef and droughts in parts of Africa, South East Asia and South America.
• Last year, Australia underwent its worst drought in living memory — in regions like the New South Wales the drought was the worst in 400 years.
• It also brings drought in Indonesia and Australia.

 Impact of El Nino in India:

• El Nino and the Indian Monsoon rains are inversely related:
  • Trade winds coming from South America normally blow westward towards Asia during Southwest Monsoon. Warming of the Pacific Ocean results in weakening of these winds.
  • Therefore, moisture and heat content gets limited and results in reduction and uneven distribution of rainfall across the Indian sub-continent.
  • In the 135 years between 1880 and 2014, around 90 per cent of all evolving El Nino years have seen below normal rainfall.
• It leads to drought conditions:
  • The most prominent droughts in India, six of them, since 1871 have been El Nino triggered droughts, including the recent ones that occurred in 2002 and 2009.
  • Drought has negative bearing on crop production leading to very serious consequences on the livelihood of farmers especially the poor and marginal ones.
  • In addition, the drop in agricultural production destabilises the food security framework of our country, leading to increased prices for the food products and push the lower economic class to hunger and starvation.
• Hotter than usual summers:
  • Whenever there is an El Nino during summer, temperatures tend to rise, with increased chances of stronger or more severe heat waves.
  • The last El Nino event that ended in 2016 had lasted for two years and caused heat waves in India. The heat waves in 2015 and 2016 killed more than 2,500 people in India.

Disease outbreaks by El Nino:

• Major diseases like chikungunya, dengue, malaria, Hantavirus, rift valley fever, cholera, plague and zika are affected by the weather events induced by El Nino.
• The scientists analysed certain disease outbreaks and tried to correlate them with higher temperatures and erratic rainfall patterns characteristic of the El Nino.They found that in regions like Southeast Asia, Tanzania, western United States and Brazil — which are generally affected by the El Nino — the spread of diseases came after shifts in rainfall, temperature and vegetation.
• There was either excess of droughts or floods which created the environmental conditions that favoured the growth and propagation of disease causing microorganisms and their carriers.
• The study’s analysis indicates that the intensity of disease activity increased by 2.5-28 per cent during El Nino events than in other periods in the affected regions. For instance, plague in regions like Colorado and New Mexico and cholera in Tanzania were impacted by above normal rainfall.
• Similarly, excess land surface temperatures in Brazil and Southeast Asia aided the spread of dengue. El Nino, in itself, is a difficult phenomenon to track and study, which makes its consequences even more difficult to understand.

El Nino and Global warming:

• El Niño contributes to an increase in global temperatures:
  • The United Nations has declared 2015 the hottest year since record keeping began. It was also a year marked by the occurrence of a “super” El Niño.
  • Even without El Niño, 2015 would have been a record warm year, but climate scientists believe El Niño was responsible for 8 percent to 10 percent of the warming. Scientists estimated that El Niño accounted for 0.07?C of the above average warming that occurred in 2015.
• But does rising temperature, in turn, intensify El Niño:
  • Study suggests that super El Niño events could double in the future due to climate change. Using 20 climate models to examine possible changes in El Niño over the next 100 years, the scientists projected that extreme El Niño events could occur roughly every 10 years instead of every 20.

Way forward:

El Niño, the weather phenomenon which is devastating the livelihoods of tens of millions across the world, demands immediate attention to development solutions to mitigate the impact of its inevitable return.

• Scientists should make mathematical models to predict El Nino events. The most completemodels should aim to represent as wide a range of physical processes as possible. The results thus far, though by no means perfect, give a better indication of the climatic conditions that will prevail during the next one or two seasons.
• Developing risk map and adaptive plan for climate smart agriculture.
• Increase the water storage capacities by building more reservoirs, recharging the ground water, reducing the run-off by streams and rivers, managing the water allocation to every sector, covering the soil layer with straw to reduce the moisture evaporation.

Practice question:

Discuss the consequences of weak El Nino conditions with reference to India. Also suggest measures to mitigate its impact.