For the past few years, the people of Kerala have been facing a hard time resisting the frequent flash floods. As the years go by, the state may have to rethink its development policies to be able to live with excessive flooding which it will inadvertently face as a result of the climate crisis. Kerala’s southwest monsoon should have retreated by now, to make way for the northeast monsoon. But the state has already received 84% of its share of what should have been the northeast monsoon. Normally the state receives 492mm from Oct 1-Dec 31. But 412.2mm has already been received before the end of October.
What are the possible reasons for these changes in the climate systems along India’s coastline?
Previously, the southwest Indian ocean was known to be cooler than the Bay of Bengal. But over the past few years, sea surface temperatures have become much warmer in the Arabian Sea, increasing the amount of moisture over the area and aiding the formation of low pressure systems. While all low pressure systems do not result in cyclones, they can result in heavy rainfall, as it has happened in Kerala this month.
If we look at the cyclones formed over the Arabian Sea in the last four years, we see that all of them have been intense, with a wind speed of 89-117kmph - including Mekanu(2018), Vayu(2019), Nisarga(2020) and Tauktae(2021). This has made India’s western coast a lot more vulnerable. Moreover, in all the cyclones recorded over the last two decades over the Arabian Sea, there has been an 80% increase in their duration.
While New Delhi received unusual rainfall in September and October, Kerala has been witnessing heavy rainfall across October as opposed to the usual monsoon season (June 1st-September 30th) resulting in 27 deaths, severe waterlogging and landslides. In 2018, the Indian ocean received 7 cyclones out of which 3 were from the Arabian sea. This was because of the warming sea surface temperatures. Similarly in 2019, the Arabian sea contributed 5 out of the total 8 cyclones in the Indian ocean. In 2020, 4 out of 9 cyclones were formed in the Arabian sea. So, the changing climate systems of the Arabian sea are having a direct impact on the rainfall patterns of Kerala.
The IMD predicts that the state is likely to face rainfall for the next 3-4 days as well. From October 20, a fresh spell of rainfall is likely to affect Kerala, south interior Karnataka, Tamil Nadu, Puducherry, Mahe, and Karaikal. There seem to be 2 low pressure systems, over the Bay of Bengal as well as the Arabian Sea which were formed on October 12th. The Bay of Bengal system moved across northern Andhra Pradesh, southern Odisha and Telangana while the Arabian Sea system reached the Kerala coast on 16th October resulting in heavy rainfall. The low pressure systems also interacted with the southwest westerly winds resulting in excessive rainfall.The warming changes in the Arabian sea have also helped the low pressure systems move alongside the coast.
For the future,Kerala will have to prioritise environmental impact assessment while approving development projects such as the Silverline Rail which will cut through ecologically sensitive zones and lead to soil erosion, land degradation and habitat destruction. As cloudbursts and extreme rainfall events leading to flash floods become the new normal, Kerala as well as India will have to pay a heavy price if governments give the nod to infrastructure projects without taking note of climate change.
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