Tropical cyclones are forming closer to Southeast Asia’s coastlines, rapidly becoming stronger and lingering longer, according to researchers who say urgent action is needed to protect communities at risk.
Their analysis, published in Climate and Atmospheric Science, shows how climate change is causing cyclone paths to shift towards the north of the region and intensify more quickly, leading to more damage in densely populated coastal areas and in cities such as Bangkok, Vietnam’s Hai Phong, and Yangon, in Myanmar.
It comes as a landslide in Wayanad, in the coastal region of Kerala, southern India, on 31 July, killed more than 360 people and destroyed hundreds of homes. It was triggered by a cloudburst, another type of extreme weather event being driven by climate change.
Tropical cyclones, also commonly referred to in the region as typhoons, which form over warm ocean waters near the equator, intensify with heat and moisture, bringing strong winds and heavy rain.
As sea temperature increases due to global warming, storms will intensify in areas such as the Northwest Pacific, South China Sea, and northern parts of the Bay of Bengal, according to the study.
“As the cyclones travel across warmer oceans from climate change, they pull in more water vapour and heat,” explains Benjamin Horton, an author of the study and director of Singapore’s Nanyang Technological University’s Earth Observatory,
“That means stronger wind, heavier rainfall, and more flooding when the typhoons hit land.”
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Warmer air holds more moisture for longer periods so that we now have long dry periods interspersed with short spells of heavy rainfall, instead of moderate rain spread evenly over many days.
Roxy Mathew Koll, climate scientist, Indian Institute of Tropical Meteorology
Tropical cyclones such as typhoon Gaemi, which lashed the Philippines, Taiwan and southern China in late July, have caused torrential rains and severe flooding, prompting mass evacuations and destroying infrastructure.
Cyclone Remal which hit India and Bangladesh in May at speeds of up to 135 kilometres per hour killed at least 84 people and caused extensive damage to property and power outages.
A year earlier, Cyclone Mocha made landfall on Myanmar’s Rakhine coast, causing widespread destruction and at least 145 deaths.
Asia was the region hit worst by weather, climate and water-related hazards in 2023, according to a World Meteorological Organization report in April. Floods and storms caused the highest number of reported casualties and economic losses, while the impact of heatwaves became more severe, the report said.
“Warmer air holds more moisture for longer periods so that we now have long dry periods interspersed with short spells of heavy rainfall, instead of moderate rain spread evenly over many days,” says Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology, Pune.
Koll led a study on the evolving climate around the Indian Ocean, published April in Science Direct, which showed the region having the highest global risk for natural hazards, with communities increasingly vulnerable to weather and climate extremes.
Cloudburst risks
Heavy rainfall events, extreme cyclones and cloudbursts have been on the increase since the 1950s in South Asia and can be expected to worsen as ocean temperatures rise, says Koll who served as an author for the 2021 Intergovernmental Panel for Climate Change Working Group I report, The Physical Science Basis.
“We are directly witnessing the consequences of warming — monsoon floods, droughts, cyclones, and heatwaves over both land and ocean,” says Koll. “These extreme weather events will amplify in intensity and frequency calling for urgent adaptation and mitigation efforts.”
Kerala, a coastal strip at the southern tip of the Indian peninsula, is particularly vulnerable to erratic monsoon — which lasts from June to September — as it moves inland and is stopped by the Western Ghat ranges, turning the entire state into a giant water slide that drains back into the sea through a system of rivers and backwaters.
Cloudbursts can release more water in a short time than can be quickly drained by the system causing floods and landslides, says E. Shaji, professor of geology at the University of Kerala.
“At Wayanad, an unusually large amount of rain got dumped on top of a hill bringing down large, round, granite boulders measuring about 2 to 3 metres and mixed with loose mud and debris that accelerated down a 40 to 50 degree slope, smashing houses, roads and bridges along the way,” said Shaji.
With erratic, high-intensity rainfall predicted to increase in frequency, thanks to the warming of the Indian Ocean, more landslides are likely to be triggered in the Western Ghats in the future, says Shaji. He says machine learning methods are the best option to identify and predict landslides.
Between 1998 and 2017, landslides affected an estimated 4.8 million people and caused more than 18,000 deaths globally, according to the WHO which says that climate change and rising temperatures are expected to trigger even more landslides in the future.
Following the Wayanad tragedy, the Indian government declared over 56,800 square kilometres of the Western Ghats as ecologically sensitive. The public has 60 days to offer suggestions or objections to planned restrictions on human activities such as quarrying, mining and infrastructural development in the area.
“As with earthquakes, it is buildings that kill people and not landslides,” says Shaji.
“And with the threat of cloudburst events increasing in intensity and frequency, drastic measures to limit developmental activity are being seen as vital to mitigation and adaptation.”
This article was originally published on SciDev.Net. Read the original article.
