Experts differ on link between cyclone numbers in India and climate change

While some cite rising sea surface temperature for the frequency in events, others point to negligible deviation in rain, drought and cyclones during the past 100 years

India has been hit by two massive cyclones within a month on both, its western and eastern Coasts. Apart from taking human lives and damaging property the events have also sparked a debate among climatologists and meteorologists about the reasons behind the growing frequency of such extreme weather phenomena.

While the east coast of India has been prone to cyclones and typhoons as the Bay of Bengal is considered to more violent than the Arabian Sea, it is the growing number of cyclones hitting the west coast the past few years that has made experts sit up and take notice.

Data sourced from India Meteorological Department (IMD) shows that between 1891 and 2018, while 126 cyclones were recorded in the Arabian Sea, the number was 3-4 times more in the Bay of Bengal at 520 cyclones.

A new normal in the offing

Climatologists suggest that the Arabian Sea is emerging as the new cradle of cyclones in the world.

Even the IMD in a statement issued sometime back had acknowledged this changing pattern.

"During 2019, eight cyclonic storms formed over the Indian seas. The Arabian Sea contributed five out of these eight cyclones against the normal one per year, which equals the previous record of 1902 for the highest frequency of cyclones over that area. This year also witnessed development of more intense cyclones over the Arabian Sea," the IMD had said in its statement.

So, what is causing this changing pattern?

According to a recent paper by Climate Trends, a Delhi-based agency that works towards bringing awareness around climate change issues and low carbon development, cyclones are fueled by available heat in the water bodies and the conducive temperature for the intensification of the cyclone is 28°C and above.

The Bay of Bengal is usually warmer than Arabian Sea and so hosts more tropical storms.

However, the scenario is now changing, it says, as we have seen Sea Surface Temperature (SST) increasing rapidly in the last century.

In 2021, the average SST over Arabian Sea just before the formation of Cyclone ‘Tauktae’ was 32-33°C, which was above the threshold limit.

The paper said this has led to active convection, torrential rainfall and intense cyclones.

Recent cyclones like Ockhi, Fani, and Amphan have confirmed the trend, as they have intensified from weak cyclonic storms to extremely severe cyclones in under 24 hours due to exceptionally warm SSTs, the paper said.

Dr Roxy Mathew Koll, Scientist at Indian Institute of Tropical Meteorology, and Lead Author, IPCC, Oceans and Cryosphere said that with ‘Tauktae’, this will be the fourth consecutive year of pre-Monsoon cyclones over the Arabian Sea.

This is also the third consecutive year when a cyclone has come very close to the west coast of India.

“Sea Surface Temperatures in Arabian Sea have increased rapidly during the past century and this has led to an increase in the frequency and intensity of cyclones in the Arabian Sea,” Koll said.

He added that climate projections indicate that the Arabian Sea will continue warming due to increasing carbon emissions, causing more intense cyclones in the future.

“Considering that both cyclones and floods due to heavy rains are increasing across the west coast along with a gradual rise in sea level, we need to be prepared,” Koll said.

Reports said Atmospheric scientist Hiroyuki Murakami who had conducted a study of the cyclones originating in the Arabian Sea had concluded that the majority (64 per cent) of cyclonic storms in the region is due to climate change.

The contrarian view

London-based Global Warming Policy Foundation (GWPF) had come out with a report days after Cyclone Amphan struck the Eastern Coast and Nisarga impacted the Western Coast of India in 2020. The study downplayed the impact of climate change over a 100-year period, saying that overall rains, drought and cyclones have not deviated much.

“Scientific evidence simply does not support the idea of any link between drought and climate change. The IPCC (the Intergovernmental Panel on Climate Change) was right to express low confidence in any global-scale observed trend,” GWPF had said in a study, titled Weather Extremes: Are They Caused by Global Warming, authored by Ralph B Alexander.

On tropical cyclones, the GWPF report quotes both, the 2012 and 2013 studies of IPCC that expressed ‘low’ confidence that cyclone activity was increasing over the long term, and that global changes in cyclone activity could be attributed to any particular cause.

This assertion was repeated in the 2019 Special Report on the Global Ocean and Cryosphere, in which the IPCC said, “The lack of confident climate change detection for most tropical cyclone metrics continues to limit confidence in both future projections and in the attribution of past changes and tropical cyclone events.”

The GWPF report also said the frequency of tropical cyclones overall is diminishing.

“However, though the number of major hurricanes (cyclone) of Category 2, 3, 4 or 5 strength seems to show a slight increase over the period (100 years), the trend has been ascribed to improvements in observational capabilities, rather than warming oceans that provide the fuel for cyclones,” GWPF said.

In fact, it said the frequency of land falling hurricanes of any categories 1-5 has not changed in the nearly 50 years since 1970--during a time when the globe warmed by approximately 0.6°C (1.1°F). So the strongest hurricanes today are no more extreme or devastating than those in the past.

“If anything, major land falling hurricanes in the US are tied to La Nin cycles in the Pacific Ocean, not to global warming,” the report said.

Impact of severe cyclones over the west coast

While the Bay of Bengal has been more prone to cyclones, there is a growing number of such events over the Arabian Sea that are greater in intensity because of the sheer economic disruption a big catastrophe is bound to cause.

The west coast is home to some of the richest states in India, which are dotted with factories in almost all major sectors. Repeated disruption in services along this belt is bound to have an effect on the economy as cyclones are known to throw operations out of gear for days on end.

While there are some industries and plants across the eastern coast as well, their number is significantly lower.

Mitigation and risk management strategies

One of the world’s leading providers of reinsurance and insurance, the Swiss Re Group, in a report published some time back titled, ‘Building Resilience in India,’ said that India’s Finance Commission for 2020-2021 has recommended that Indian states set up a mitigation fund, to supplement the existing National and State Disaster Relief Funds and promote local-level mitigation activities.

These are in addition to existing funds set aside for relief activities, and recognises the importance of pre-event (ex-ante) financing.

The Commission also recommended that both central and state governments focus on debt consolidation and comply with the fiscal deficit and debt levels, as per their respective Fiscal Responsibility and Budget Management Acts.

“A well-designed risk transfer solution, or insurance program, can help governments to achieve these twin goals,” the report said.

Meanwhile, reports also said that the Government of India might be re-visiting the idea of establishing a national natural catastrophe insurance pool.

The idea had come up after cyclone Amphan in 2020.

The pool, according to the report, would cover property risks including housing and other dwellings that are exposed to cyclones, floods, earthquakes etc.

The challenge is to identify which insurer should lead the pool.

“Except New India, the other three national non-life insurance companies have weak balance sheets and GIC as the reinsurer is wary of taking on more responsibility like the nuclear pool unless the private sector companies also commit to contribute to the pool,” the report added.

However, analysts at Fitch Rating in another report released in March 2021 believed that natural catastrophe risks could become “less insurable” in future due to the effects of climate change, as well factors like insurance density and economic growth.