Cyclones Tauktae and Yaas left trails of destruction after sweeping in from the Arabian sea on May 14 and from the Bay of Bengal on May 26 respectively and brought heavy rainfall and flash floods to areas along the coasts of different states. Apart from causing caused widespread infrastructure and agricultural damages, the storms killed many and displaced many others along the eastern and western coasts. Cities experienced their highest ever recorded wind gust.

The cyclones made landfall as India was in the grip of a devastating second wave of the coronavirus pandemic which claimed thousands of lives. Millions worldwide watched tragedy unfold on their television screens and realising the humanitarian cost of the disaster, were obviously in search of the causes of frequent tropical cyclones because these two provided a flashback of the 2020 cyclone (Amphan) that devastated West Bengal. The accounts of widespread damage to property and loss of life have made this season one that we will forget.

As global warming gathers pace, intense cyclones from the Bay of Bengal and the Arabian Sea are making landfall with greater frequency every year. Almost exactly a year ago, cyclone Amphan formed over the Bay of Bengal and travelled at great speed towards the Bengal coast, turning into a super cyclone in 24 hours. It was supercharged by gathering energy from the anomalously high sea surface temperatures in the Bay of Bengal. About a week after Amphan caused widespread havoc in West Bengal, cyclone Nisarga formed over the Arabian Sea and struck the Maharashtra coast as a destructive storm front. In the post-monsoon season, cyclone Nivar hit the Coromandel coast at Puducherry.

Tropical cyclones can have devastating economic consequences. Globally they are among the most destructive natural hazards. From 1980 to 2018, tropical cyclones were responsible for nearly half of all natural disaster losses worldwide, with damage amounting to an aggregate of US$ 2111 billion. The overall damage and the number of people affected by tropical cyclones has been increasing since the 1970s. The vulnerability to cyclones has been increased due to factors including population growth, urbanisation, increasing coastal settlement, deforestation, destruction of mangrove forest and global warming. Also non-compliance of Coastal Regulation Zone notifications is one of the causes for damages of natural resources in the Coastal zone. Tropical cyclones, also known as typhoons and hurricanes, have caused an estimated 1.33 million deaths since the beginning of the 20th century and affected more than 629 million people in this timeframe.

A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterised by low atmospheric pressure and strong winds followed by heavy rainfall. Tropical cyclones always have an eye, a central region of clear skies and warm temperatures. The proportion of severe tropical cyclones (category 4 & 5) has increased, possibly due to anthropogenic climate change. The influence of climate change on cyclones has been notoriously difficult to separate from natural variability. But an increasingly consistent picture is emerging that suggests human activities are probably influencing some aspects of these extreme weather events, although the exact extent of the human influence is still difficult to determine in today’s observations. Many of the observed trends in tropical cyclones are at least qualitatively consistent with expectations from a warming climate. If the globe warms by 2 degrees Celsius, it will cause a roughly 5 per cent increase in maximum wind speeds.

Since satellite records began in India in 1980, this is the first time that pre-monsoon cyclones have been recorded in the Arabian Sea for four consecutive years. It is now a well known fact that the global ocean has absorbed 90 per cent of the excess heat generated by greenhouse gas (GHG) emissions since 1970. This has led to anomalous ocean warming, which in turn makes cyclones intensify rapidly. This proportion of intense tropical cyclones is projected to increase further, bringing a greater proportion of storms having more damaging wind speeds, higher storm surges, and more extreme rainfall rates.

According to researchers, cyclones are also intensifying so rapidly because of unprecedented high temperatures over the Indian Ocean (Bay of Bengal and the Arabian Sea). It is explained in the way that heat is energy, and cyclones intensify rapidly by turning the potential energy stored in the ocean to kinetic energy. The energy of a cyclone is proportional to the mass of the air and its velocity squared. An index of the cyclone energy, known as the Accumulated Cyclone Energy has been developed. Tropical storms are caused by warm moist air over the rising seas. As the air rises it draws in more warm air which feeds the storm. As the hot air rises it also cools and condenses. When it condenses it gives up the latent heat of vaporisation which gives more energy to the storm. When storms reach land, or cold water, they lose energy due to friction and also because warm, moist air supply from the oceans is cut off. The western tropical Indian Ocean has been warming for more than a century, at a rate faster than any other region of the tropical oceans, and turns out to be the largest contributor to the overall trend in the global mean sea surface temperature (SST).

A panel comprising 13 countries, including India, Bangladesh, Myanmar, Pakistan, the Maldives, Oman, Sri Lanka, Thailand, Iran, Qatar, Saudi Arabia, the United Arab Emirates and Yemen, name cyclones in the region. In 2020, a new list of names was released that had 169 names of cyclones, having 13 suggested names each from 13 countries. The cyclones are named to identify the storms to send out warning notifications about their development. As the technical names could be difficult for common people to remember and in order to spread awareness, naming them gives a unique identifier to these cyclones and makes it easier for the media and various authorities to disseminate information on them.

Cyclone Tauktae (pronounced as Tau’Te) that intensified into an “extremely severe cyclonic storm” made a landfall on Gujarat coast late on 14 May 2021 with windspeed between 150 kmph and 160 kmph leaving a trail of destruction behind. The cyclone had been given the name by Myanmar. The name comes from the Burmese language and means a ‘gecko’ or a very hitch-pitched lizard. The cyclone in the Bay of Bengal was called ‘Yaas’, a name given by Oman meaning Jasmin in English, while next cyclone will be called ‘Gulab’ as recommended by Pakistan. At present the first list is in use. Once the names in the first list are exhausted, the second list of names in the table will be used, and so on.

In this piquant situation there is emergent need to identify the most vulnerable areas of our nation and prepare a national policy with international support for implementation. The nation must provide specific goals and timelines to achieve these goal. The actions to be implemented include reforestation, preparing local emergency shelters, building of levees and dams, creation of early warning systems, reinforcing existing communication infrastructure, finding new sources of fresh water, promoting and subsidising the proliferation of renewable energy, improving irrigation techniques to promote sustainable agriculture, increasing public education efforts on sustainable measures, and lobbying internationally for the increased use of renewable energy sources.

In addition to these, some ecosystems, such as marshes, mangroves and coral reefs, must be preserved as these serve as a natural obstacle to coastal erosion, storm surges and wind damage caused by hurricanes. These natural habitats are seen to be more cost-effective as they serve as a carbon sink and support biodiversity of a region. Although there is substantial evidence of natural habitats being the more beneficial barrier for tropical cyclones, built defenses are often the primary solution for government agencies and decision makers.

If the people of the coastal and mangrove areas were more aware of the ocean’s vulnerability and ecological fragility of their coastal homes, they would surely force more compliance of laws and regulations to protect it.

The writer is former Senior Scientist, Central Pollution Control Board.