Severity of cyclones in Bay of Bengal on the rise, say scientists

The Indian subcontinent, particularly India and Bangladesh, might have to brace for cyclones similar to Fani, termed extremely severe, in the years to come.

The pattern of cyclones over the Bay of Bengal in the last few decades shows that the intensity of cyclones in the region is on the rise. Climate change, leading to higher sea temperatures, is to be blamed for this impending threat, say scientists. 

“Due to global warming, the property of the ocean is changing. The sub-surface water temperature is more than the temperature of the surface water, leading to more conservation of energy and the ability of the sea to form severe cyclones,” said Prasad Kumar Bhaskaran, head of Ocean Engineering and Naval Architecture at the Indian Institute of Technology in Kharagpur.

"The increase in the spatial extent of cyclones can be gauged from the fact that about 20 years ago, the distance between the centre of the cyclone in sea and land used to be in the range of plus, or minus, 70 km, which has now increased to plus or minus 250 km," said Bhaskaran. Thus, more areas are now exposed to the devastation caused by cyclones over the Bay of Bengal.

Meanwhile, a study on the increasing intensity of cyclones in the Bay of Bengal by a team of researchers at the Atmospheric Sciences and Global Change Institute at Pacific Northwest National Laboratory in the US, found that the intensity of storms went from an average classification of Category 3 between 1981-1995 to Category 4f or the 1996-2010 period.

“Climate change has influenced weather patterns over global oceans and at present is a matter of serious concern, as it can have long-term repercussions,” notes Bhaskaran in a study.

In the past, out of 10 recorded cases of very heavy loss of life (ranging from about 40,000 to well over 200,000) in the world due to tropical cyclones, 8 cases were reported in the Bay of Bengal and the Arabian Sea (5 in Bangladesh and three in India), according to a study by All India Disaster Mitigation Institute.

“Almost 5 per cent of the global tropical cyclones form over the Bay of Bengal, with an average occurrence of about 5–6 storms per year in this region. However, the casualties that result from these events are extremely high compared to elsewhere in the world. This region is a low-lying area and is under severe threat from sea-level changes,” according to a study carried out by Bhaskaran.

In 2018, in the six months, starting July 2018, 37 fishermen from West Bengal alone lost their lives while fishing after they were caught in a cyclone in the Bay of Bengal. In the last ten years, the death toll of fishermen from West Bengal due to cyclones in in the area stands at 165, according to data from Kakdwip Fishermen's Association, one of the largest fishermen unions in West Bengal.

Aila, a severe cyclone, which hit India and Bangladesh in 2009, affected nearly four million people in India and Bangladesh.