What’s causing tropical cyclones

A POWERFUL cyclonic system, Tauktae, which made landfall in Gujarat after barrelling up the Arabian Sea in the Indian Ocean, is the equivalent of a Category 3 hurricane in the Atlantic and East Pacific Ocean basins. Reports said it could be the biggest to hit western India in three decades.

What is a tropical cyclone?

Cyclones are low-pressure systems that form over warm tropical waters, with gale-force winds near the centre.

The winds can extend hundreds of kilometres from the eye of the storm. Sucking up vast quantities of water, they often produce torrential rains and flooding resulting in major loss of life and property damage. They are also known as hurricanes or typhoons, depending on where they originate in the world, when they reach sustained winds of at least 119 kilometres per hour (74 miles per hour).

Tropical cyclones (hurricanes) are the most powerful weather events on earth, according to NASA.

Why is climate change fuelling them? Oceans soak up more than 90 per cent of the heat generated by greenhouse gases, leading to rising water temperatures. As cyclones draw their energy from warm waters, the rising temperatures are causing intense storms to become more common, experts say.

“Now what is happening – the Arabian Sea temperatures, the ocean’s surface temperatures – are warming rapidly,” climate scientist Roxy Mathew Koll of the Indian Institute of Tropical Meteorology said.

Rising sea levels could also boost storm surges from cyclones, making them even more deadly and destructive.

Why are there more in the Arabian Sea?

Scientists say historically, the Arabian Sea averaged two or three cyclones, that were typically weak, in a year. The Arabian Sea also previously experienced fewer severe cyclones than the Bay of Bengal off India’s eastern coast.

But rising water temperatures because of global warming is changing that, they said. This is the first time since the start of satellite records in 1980 in India that there have been four consecutive years of pre-monsoon cyclones in the Arabian Sea.

“One of the reasons that we are seeing more and more storms and cyclones in the tropical regions, especially regions like Arabian Sea and all, is because of ocean warming, rapid ocean warming,” Koll said. “The Arabian Sea is one of the fastest warming basins across the global oceans.”

Cyclones have been relatively rare in Gujarat, but they can be destructive and dangerous. The worst was in 1998 when more than 4,000 people died.