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Rekha Dixit
Rekha Dixit

MONSOON SERIES-2

Tempestuous and sensitive it may be, but monsoon never fails to keep its date with India

INDIA/ Monsoon has never failed any year, though it has gone through various cycles of strengths | Reuters

Emerging research shows the monsoon is very sensitive; pollution in Europe, rising CO2 levels, just about anything can affect it.

There are a number of uncertainties regarding the Indian Monsoon. It may not arrive on time. It might not shower enough water over the subcontinent. It could come in bursts with long, dry phases stretching to weeks in between. It might not shower its bounty uniformly all over the landscape. This is what makes predicting the monsoon a very challenging task. 

But there is always one certainty. The monsoon has never failed to arrive. 

When we talk about the monsoon failing, we always mean less rain, it is never a no-rain year over the subcontinent. 

Considered the biggest weather phenomenon on the globe, the monsoon dates back to antiquity. The generally held belief is that this phenomenon, in its present form, developed when a chunk of the Gondwana land mass broke off and hit the Asian mainland, causing the lifting of the Tibetan plateau and the creation of the Himalayas. This created a unique pattern. The subcontinental land mass heats up during the summer months, the Himalayas effectively cutting off cooling winds from further north. The low pressure thus created causes the moisture laden clouds, which were building up over the Indian Ocean, to be drawn towards the land, bringing the life giving moisture to a land, which even today depends on the monsoon for over 70 per cent of its water requirement. 

A complex global phenomenon like the monsoon, however, cannot be created with just this school grade physics. There are a number of phenomena which occur across the globe, that influence the behaviour of the monsoon, indeed, even cause it to happen. 

In the last two decades, scientific interest in the Indian monsoon has gone up, and new researches only show the monsoon to be more complex than ever thought, and rather susceptible to climatic events happening in distant parts of the globe. A paper published in Nature traced the antiquity to 40 million years, at the time when the Himalayas were in the process of being formed. It was a time when carbon dioxide levels in the atmosphere were nearly four times the present, and the globe was much warmer. Scientists thus believe that rising carbon dioxide levels right now could have an impact on the behaviour of the monsoon. 

The latest study to hit headlines finds a link with pollution in Europe and the drought in India in 2000, when the monsoon rain was 40 per cent less than normal. The sulfate aerosols in the air have a cooling effect on the atmosphere as they reflect sunlight back to space. This disrupted the heating pattern over the subcontinent, as well as over the sea (where water evaporates and forms clouds), thus causing one of the severest droughts in recent times. 

The monsoon may have never failed any year, though it has gone through various cycles of strengths. One of the theories to explain the sudden fall of the Indus Valley Civilisation is a weakening in monsoon, which dried up the Saraswati and other rain fed rivers. 

Scientists say that climate change is causing changes in how the monsoon sheds water. The general theory is that while the overall seasonal precipitation may remain unchanged, there is likely to be more extreme events, causing natural disasters like the Chennai floods of last year. Have humans tampered enough with global systems to change the behaviour of the monsoon? “This may appear so, but we need to study whether the monsoon is behaving beyond its natural variables,'' says geoscientist Ashok Singhvi. He is working on collating paleontoligical data about the monsoon to analyse whether we can actually say that humans have changed the monsoon beyond its natural behaviour. 

[This article is the second of a three-part series on monsoon in India. Read part 1: The art of monsoon forecast]

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Topics : #monsoon

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