The sea surface temperature of the Indian Ocean nearer the equator and south of Sri Lanka has seen a considerable increase of about 1.5 degrees Celsius in the last five decades. This could reduce the strength of the monsoon heat engine - the vertical Monsoon Hadley Cell that drives the monsoon circulation over the Indian subcontinent.
This finding seems to be in line with a certainty included in the 2006 Nick Stern report - "Higher temperatures will increase the chance of triggering abrupt and large-scale changes - warming may induce sudden shifts in regional weather patterns such as the monsoon rains in South Asia or the El Niño phenomenon - changes that would have severe consequences for water availability and flooding in tropical regions and threaten the livelihoods of millions of people."
The period of four months June to September is the south-west monsoon season In India, when the rains are bountiful in South India, with Kerala being the "gateway" and quickly cover the entire subcontinent. The heating of central Indian Ocean, however would mean that this part of the ocean will end up receiving more rainfall. Latent heat released through the condensation of moisture would heat up the atmosphere over that part of the ocean. This would in turn affect the seasonal pressure gradient that usually attracted the moisture-laden winds towards the subcontinent.
The Indian Meteorological Department has recorded not only a decrease in the number of depressions that form over the Bay of Bengal during the monsoon season in recent decades, but also a fall in the strength of the low level monsoon winds over southern India by nearly 20 per cent in this period.
Analysis of data that covers a period of a century has also revealed more changes in rainfall patterns.
- Quantifiable decrease in the state of Kerala, cocooned between the Western Ghats and the Arabian Sea where the rains had been most bountiful
- Abnormal increases in certain other regions such as west-central India.
- Instances of extremely heavy single-day rainfall over parts of the subcontinent.
- Rise in number and severity of tropical cyclones in the seas of the region.
As with all climate change issues anywhere in the world, there is simply no more time for conjecturing and waiting for more evidence. Having said that, let us shed the nagging feeling that policy-makers will act only after the crisis reaches their backyard or porch. Thinking aloud, how is it that no policy-maker seems to hail from affected regions of the world?
Related Reading:
Oceans: The Key to Understanding Our Climate
Where Do Climate Refugees Go When It Rains?
Image Credits:
UCAR.edu
MartinFrost.ws
