Here Comes Trouble
Avinash Celestine
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El Niño could lead to a weak monsoon, posing the most serious challenge yet to the new government
The first big challenge to Narendra Modi's prime ministerial skills is now possibly in plain sight -and it's developing not in India but thousands of miles away off the coast of Peru, South America. The now-notorious El Niño weather phenomenon is not yet fully developed -it will reach its full fruition around September and October, but already it is being linked to a weak monsoon, soaring prices of vegetables and the possibility of poor agricultural output. The BJP fought this election around the inability of the previous government to rein in inflation and the rising prices of essential commodities. Now it is faced with the very real possibility that inflation could well head higher in the coming months.The signs are hardly positive. The monsoon shortfall is currently around 42% and with land temperatures high and little sign of rain in a number of regions, crop planting is delayed. During the 2009 drought, one of the worst India faced in many decades, rainfall deficit in June was running at similar levels. Delayed planting of key crops such as onion has already forced prices upward.
What is El Niño and how will it affect the monsoon? The big problem here is one of uncertainty -about the future path of the monsoon, about the extent of any weakness in rainfall and even the extent of the El Niño phenomenon. “It has been, and still is, very difficult to predict the monsoon and the effect of the El Niño on it,“ points out Balaji Rajagopalan, professor at the University of Colorado in Boulder (US), who has researched the links between the Indian monsoon and the El Niño.
The El Niño Cycle Indeed El Niño, and the role it plays in periodic droughts which hit the Indian subcontinent, was one of the foundational questions that drove modern weather research.
In his book on Victorian famines, writer Mike Davis calls the El Niño Southern Oscillation (or ENSO to give it its full name) the “elusive great white whale of tropical meteorology for almost a century“. And despite more than a century of research, it still, in a sense, remains that way.
El Niño arises in the eastern Pacific, along the coast of South America. In `nor mal' years, there exists both a temperature and air pressure difference between the oceans there, and the western Pacific, thousands of miles on the other side, near Indonesia and Southeast Asia. The waters of the eastern Pacific near South America are colder, and are associated with higher atmospheric air pressure over them, as compared with the waters of the western Pacific which are warmer, and are associated with lower atmospheric pressure.
As we learnt in high school geography, wind always blows from a region of high pressure to a region of low pressure, and this is what happens over the Pacific, with winds blowing from the east to the west. In turn, the air over the western pacific rises into the atmosphere and then cycles back east, and the whole process starts again.
During El Niño, the sea temperatures off the coast of South America are much warmer than in other years. Along with this, the air pressure over it is much weaker as well. This sharply narrows the difference between the western and eastern Pacific, making the cycle much weaker. In a sense the region of low pressure moves away from Asia and towards South America. The Indian monsoon too is affected by this movement of low pressure air away from the Asian region into the middle of the Pacific and is `dragged' away from the Indian land mass. The result: rains and winds over India which are far lower than normal. Indeed, large parts of South and Southeast Asia become drier. Conversely, the Pacific coasts of South America, including countries such as Peru, become much wetter and see much higher rainfall.
This, very broadly, is how El Niño works. In actual fact though, it's hardly that simple.
An Old Puzzle As the chart on the next page (El Niño and the Indian Monsoon...) shows, strong El Niño conditions (the shaded region to the right) usually occur along with a weak monsoon. But note that there have been cases, most notably in 1997, when a very strong El Niño was accompanied by a normal monsoon. “We were anticipating a major disaster in 1997, as El Niño developed, but nothing happened,“ says K Krishna Kumar, a meteorologist currently consulting with the meteorological department in Qatar, but who has been with the Indian Institute of Tropical Meteorology since 1982. Kumar and Rajagopalan were co-authors on a paper in 2006 which pointed to a simple fact: “...severe droughts in India have always been accompanied by El Niño events. Yet El Niño events have not always produced severe droughts“.
The reasons for this complex relationship are still unclear. In 1997 for instance, one possible reason for the normal mon soon, despite a strong El Niño, was another phenomenon, which occurred independently of El Niño.
The mechanism involved was similar to El Niño (a difference in pressures and temperatures between two different parts of the ocean which sets up a cycle of wind movement), except that this time, the cycle didn't occur in the Pacific, but between the western and eastern Indian Ocean. This so-called `Indian Ocean Dipole' (IOD), effectively acted as a counterweight to El Niño, dragging the Indian monsoon back towards the Indian landmass.
This tug-of-war between the El Niño phenomenon, and other separately occurring weather phenomena, makes the complex problem of forecasting a monsoon's strength much more so. “A positive IOD [such as that which occurred '97] can nullify the impact of El Niño,“ points out a senior government scientist. “Forecasters will be looking to see how the IOD will behave this time around as well.“
The 2006 paper pointed to another possible indicator of how strongly El Niño affects the Indian monsoon. It argued that Indian droughts are much more likely to occur in years when the warming effect of El Niño in the Pacific ex tends far beyond the eastern Pacific and into the central Pacific Ocean as well. If true, this means that just knowing the existence of an El Niño phenomenon isn't enough -it's also important to understand exactly which parts of the Pacific Ocean are getting unusually warm.
“However, currently our El Niño prediction models don't have the ability to account for this factor,“ says Kumar.
Adding to the problem is that El Niño doesn't occur before the monsoon -it evolves along with it.
“El Niño is not a predictor of the monsoon,“ says the government scientist. “It co-evolves along with it. They are not two independent systems interacting apart from each other.“
Rajagopalan says: “El Niño is firmly established around September and that's when the correlation between Indian monsoon patterns and El Niño is the strongest.“
Unfortunately of course, govern ments and farmers don't have the luxury of waiting till then to understand the nature of the effect.
Reading the Signs So what will scientists be looking at in the coming weeks? Apart from the direct indicators of the drift in El Niño, as captured through various indices and measures, they will also look for possible phenomena like the IOD that could counteract the adverse effects of El Niño. On that front, the news isn't good -earlier this week Japanese weather forecasters pointed to the possibility of an IOD which could actually reinforce the impact of El Niño, and force monsoon winds and rain away from the Indian subcontinent. “I would also look at incidents like the occurrence of rainfall over the eastern Pacific,“ says Kumar. “Once that happens, it disturbs the monsoon circulation which gets displaced away from the Bay of Bengal. However this has not happened as yet.“
Ultimately though, as Rajagopalan points out, there is no getting away from the complexity. “I don't see monsoon forecasting getting much simpler any time soon. We will have to learn to manage our risks much better in this context.“
The stakes are high enough. As Sulochana Gadgil and Siddhartha Gadgil pointed out in a paper some years back in the Economic and Political Weekly, despite agriculture's share in GDP declining substantially over the past several decades, the impact of severe droughts has remained between 2% and 5% of GDP. The 2002 drought they found, lead to a 15% impact on food grain production. And ironically, they found that while the adverse effects of a drought on GDP remained relatively unchanged, the positive impact of a good monsoon on GDP had actually declined since 1980.
The new government has its work cut out.
What is El Niño and how will it affect the monsoon? The big problem here is one of uncertainty -about the future path of the monsoon, about the extent of any weakness in rainfall and even the extent of the El Niño phenomenon. “It has been, and still is, very difficult to predict the monsoon and the effect of the El Niño on it,“ points out Balaji Rajagopalan, professor at the University of Colorado in Boulder (US), who has researched the links between the Indian monsoon and the El Niño.
The El Niño Cycle Indeed El Niño, and the role it plays in periodic droughts which hit the Indian subcontinent, was one of the foundational questions that drove modern weather research.
In his book on Victorian famines, writer Mike Davis calls the El Niño Southern Oscillation (or ENSO to give it its full name) the “elusive great white whale of tropical meteorology for almost a century“. And despite more than a century of research, it still, in a sense, remains that way.
El Niño arises in the eastern Pacific, along the coast of South America. In `nor mal' years, there exists both a temperature and air pressure difference between the oceans there, and the western Pacific, thousands of miles on the other side, near Indonesia and Southeast Asia. The waters of the eastern Pacific near South America are colder, and are associated with higher atmospheric air pressure over them, as compared with the waters of the western Pacific which are warmer, and are associated with lower atmospheric pressure.
As we learnt in high school geography, wind always blows from a region of high pressure to a region of low pressure, and this is what happens over the Pacific, with winds blowing from the east to the west. In turn, the air over the western pacific rises into the atmosphere and then cycles back east, and the whole process starts again.
During El Niño, the sea temperatures off the coast of South America are much warmer than in other years. Along with this, the air pressure over it is much weaker as well. This sharply narrows the difference between the western and eastern Pacific, making the cycle much weaker. In a sense the region of low pressure moves away from Asia and towards South America. The Indian monsoon too is affected by this movement of low pressure air away from the Asian region into the middle of the Pacific and is `dragged' away from the Indian land mass. The result: rains and winds over India which are far lower than normal. Indeed, large parts of South and Southeast Asia become drier. Conversely, the Pacific coasts of South America, including countries such as Peru, become much wetter and see much higher rainfall.
This, very broadly, is how El Niño works. In actual fact though, it's hardly that simple.
An Old Puzzle As the chart on the next page (El Niño and the Indian Monsoon...) shows, strong El Niño conditions (the shaded region to the right) usually occur along with a weak monsoon. But note that there have been cases, most notably in 1997, when a very strong El Niño was accompanied by a normal monsoon. “We were anticipating a major disaster in 1997, as El Niño developed, but nothing happened,“ says K Krishna Kumar, a meteorologist currently consulting with the meteorological department in Qatar, but who has been with the Indian Institute of Tropical Meteorology since 1982. Kumar and Rajagopalan were co-authors on a paper in 2006 which pointed to a simple fact: “...severe droughts in India have always been accompanied by El Niño events. Yet El Niño events have not always produced severe droughts“.
The reasons for this complex relationship are still unclear. In 1997 for instance, one possible reason for the normal mon soon, despite a strong El Niño, was another phenomenon, which occurred independently of El Niño.
The mechanism involved was similar to El Niño (a difference in pressures and temperatures between two different parts of the ocean which sets up a cycle of wind movement), except that this time, the cycle didn't occur in the Pacific, but between the western and eastern Indian Ocean. This so-called `Indian Ocean Dipole' (IOD), effectively acted as a counterweight to El Niño, dragging the Indian monsoon back towards the Indian landmass.
This tug-of-war between the El Niño phenomenon, and other separately occurring weather phenomena, makes the complex problem of forecasting a monsoon's strength much more so. “A positive IOD [such as that which occurred '97] can nullify the impact of El Niño,“ points out a senior government scientist. “Forecasters will be looking to see how the IOD will behave this time around as well.“
The 2006 paper pointed to another possible indicator of how strongly El Niño affects the Indian monsoon. It argued that Indian droughts are much more likely to occur in years when the warming effect of El Niño in the Pacific ex tends far beyond the eastern Pacific and into the central Pacific Ocean as well. If true, this means that just knowing the existence of an El Niño phenomenon isn't enough -it's also important to understand exactly which parts of the Pacific Ocean are getting unusually warm.
“However, currently our El Niño prediction models don't have the ability to account for this factor,“ says Kumar.
Adding to the problem is that El Niño doesn't occur before the monsoon -it evolves along with it.
“El Niño is not a predictor of the monsoon,“ says the government scientist. “It co-evolves along with it. They are not two independent systems interacting apart from each other.“
Rajagopalan says: “El Niño is firmly established around September and that's when the correlation between Indian monsoon patterns and El Niño is the strongest.“
Unfortunately of course, govern ments and farmers don't have the luxury of waiting till then to understand the nature of the effect.
Reading the Signs So what will scientists be looking at in the coming weeks? Apart from the direct indicators of the drift in El Niño, as captured through various indices and measures, they will also look for possible phenomena like the IOD that could counteract the adverse effects of El Niño. On that front, the news isn't good -earlier this week Japanese weather forecasters pointed to the possibility of an IOD which could actually reinforce the impact of El Niño, and force monsoon winds and rain away from the Indian subcontinent. “I would also look at incidents like the occurrence of rainfall over the eastern Pacific,“ says Kumar. “Once that happens, it disturbs the monsoon circulation which gets displaced away from the Bay of Bengal. However this has not happened as yet.“
Ultimately though, as Rajagopalan points out, there is no getting away from the complexity. “I don't see monsoon forecasting getting much simpler any time soon. We will have to learn to manage our risks much better in this context.“
The stakes are high enough. As Sulochana Gadgil and Siddhartha Gadgil pointed out in a paper some years back in the Economic and Political Weekly, despite agriculture's share in GDP declining substantially over the past several decades, the impact of severe droughts has remained between 2% and 5% of GDP. The 2002 drought they found, lead to a 15% impact on food grain production. And ironically, they found that while the adverse effects of a drought on GDP remained relatively unchanged, the positive impact of a good monsoon on GDP had actually declined since 1980.
The new government has its work cut out.
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