Relevance: GS-3: Conservation, environmental pollution and degradation, environmental impact assessment

Key phrases: Wind speed, Global Terrestrial Stilling, Panchamrit Pledges

Why in News?

• Recently, many reports have highlighted that the wind speed in major Indian cities has been slowing down consistently and significantly over several decades.
• On mapping wind speeds during the years 1958 to 2015 in the country’s fastest urbanizing cities (2011 census), it is found that there is an alarming and surprisingly consistent decline.
• The average wind speed has fallen by 47% in Hyderabad, 47% in Bengaluru, 46% in Kolkata, 34% in Ahmedabad and 25% in Pune.

What are the major highlights of the article?

1. Agri-research institute ICRISAT’s data on annual variations in wind speed for each month collected in situ district stations for near-surface wind speeds.
   • For each city, ICRISAT collected monthly data, removed a few outliers (that likely indicated storms), and estimated average annual wind speeds over 10 cities of India characterized by the fastest urbanization.
2. There are considerable variations in wind speed across months (May, June and July have suffered the biggest drop in wind speeds), but the annual average is highly variable.
3. Surely, the measurement indices (including the height of the wind-speed measurement devices) simulated weather models, and more granular data on such patterns will reveal the exact nature of this phenomenon.
4. Even the simplest of metrics offers findings that call for a larger investigation of this urban wind slowdown.

What are the key implications of declining Wind Speed?

1. Disproportionate impact on Atmospheric Parameters: Small changes in average wind speeds can have a large influence on atmospheric parameters.
   • For instance, slow winds cannot carry moisture for long, resulting in altered rainfall patterns.
   • Agriculture depends crucially on transpiration (a plant’s exhalation of water vapour), which in turn needs evaporation that is a function of wind speed.
   • Wind-dispersed plant species also depend on wind speeds for survival. There are studies showing the impact of wind speed on natural disasters and ocean dynamics.
2. Phenomenon of cities as 'Gas Chamber' further compounded:
   • Lower urban wind speeds also mean that air pollution in cities takes longer to get dispersed, making these places a toxic gas sink (Delhi comes to mind) and exacerbating public-health problems.
3. Greater setback to Greener and Cleaner Energy:
   • Falling wind speed also has huge implications for the wind-energy sector.
   • Typically, a 5% fall in wind speed can lead to an almost 17% fall in wind energy in an average turbine.
   • Falling wind speeds can thus blow away the promise of 'Panchamrit Pledges' by the Indian government.
4. Phenomenon of 'Global Terrestrial Stilling':
   • Interestingly, scientists have found (not too long ago) that wind speeds have been declining globally since the 1960s.
   • Scientists call this “global terrestrial stilling”. The average fall has been 0.5km per hour every decade, studies note.
   • It may not seem like much of a drop, but over long periods of time, it can meet humanity with a 'tryst of disaster’.
5. Case Study of Europe:
   • The decline has been as high as 15%.
   • Scientists have claimed that this ‘stilling’ may not be reversed.
   • Due to such observations, the issue has become important globally.
   • Most wind speed related studies focus on Europe and North America. Such investigations in India, unfortunately, have been scanty.

How is wind speed going to impact India?

1. Data and research shows causes for concern in India:
   • While the exact explanation of why wind speeds are falling is not clear, some scientists say it is happening (along with other atmospheric changes) as a result of an increase in surface roughness, attributed to land-use changes. This can be due to urbanization, or even forest growth.
2. 'Unplanned and Top-heavy Urbanization' in India:
   • Studies revealed that wind speeds are negatively correlated with population density.
   • For instance, wind speeds in Korea have decreased more in urban areas, and by more than they increased in rural regions, during 1993-2015.
   • Studies in China indicate that urbanization is one of the major factors that can explain weakening winds in urban regions.
   • Other studies show that increasing vegetation (due to agriculture and afforestation) would best explain the falling wind speeds, but these are outweighed by those studies where urbanization is put forth as the main culprit.
3. Urbanization affects the local climate through increased human intervention and the resultant complexity in airflow.
   • Characterized by urban ‘heat islands’, altered rainfall patterns, increased fog, haze and reduced evaporative cooling, urbanization may well be the main driver of falling wind speeds.
   • Given the dramatic reduction in wind speed in urban pockets of India, the hypothesis is the same. The wind speed fell in some of the less-rapidly urbanizing districts, and noticed a relatively slower rate of change viz a viz heavy populated cities.

What is the way ahead for India?

• Data collection strengthening: The reliability of studies on urbanization’s effects on wind speed depend crucially on the methods adopted, but, by and large, it is likely that urbanization has a big effect.
• Inclusion of 'Wind Speed' as major determinants in climate related policies: India is urbanizing at an unimaginable rate, and even though scholars have considered various implications arising from it, changing wind speed has not gained much attention.
• Wind speed and associated parameters are important atmospheric variables that deserve appropriate scrutiny in India.
• Urbanization is certainly a compounding factor. Non-urban areas may have other reasons, such as differing climatic conditions, geographical vulnerabilities, etc. that could result in changing wind speeds.

Conclusion:

• Natural phenomena need to be scientifically investigated for their implications to broader socio-economic and cultural outcomes.
• India’s meteorological data-gathering infrastructure is admirable. What we need is an interdisciplinary engagement of that data to distil an informed understanding of these winds of change so that we can formulate adaptation strategies

Source: Live-Mint

Mains Question:

Q. Explain the emerging trends of wind speed in urban India. Discuss its implications on the phenomenon of climate change. (10 marks).