Asia’s heatwave made 30 times more likely by climate change: study

Following record-breaking heatwaves in Laos, Thailand, India and Bangladesh, experts call on policymakers to prepare heat action plans, especially for vulnerable communities.

India and neighbouring Bangladesh experienced record-breaking heatwaves in April 2023, with schools forced to close and casualties caused by heatstroke. Image: Prabhu B Doss, CC BY-SA 3.0, via Flickr.

The intense heatwave experienced by most of South and Southeast Asia this year was made 30 times more likely due to human-caused climate change, according to the World Weather Attribution group, an international coalition of leading climate scientists.

In April, countries including Bangladesh, India, Laos and Thailand experienced record-breaking heatwaves, with temperatures soaring as high as 45°C in Thailand and 42°C in Laos.

The World Weather Attribution’s latest report revealed that in both the South Asian and Southeast Asian regions, temperatures were at least two degrees Celsius hotter than they would have been without climate change.

“Global temperatures will continue to increase and events like this will become more frequent and severe…until overall greenhouse gases emissions are halted,” the scientists said in a statement.

The researchers analysed weather data and computer model simulations, following peer-reviewed methods, to compare today’s climate, after about 1.2°C of global warming since the late 1800s, with the climate of the past. The analysis looked at the average maximum temperature and maximum heat index for four consecutive days in April across two regions, one covering south and east India and Bangladesh, and a second one including all of Thailand and Laos.

The heat index is a measure that combines temperature and humidity and reflects more accurately the impacts of heatwaves on the human body.

“In Bangladesh and India, events like the recent humid heatwave used to occur less than once a century on average [but] they can now be expected around once in five years now,” the scientists said. If global temperatures rise by two degrees, such events could occur annually, they said.

Meanwhile, the recent humid heatwave in Laos and Thailand “would have been nearly impossible without the influence of climate change”, said the coalition of scientists. 

“It is still a very unusual event that can only be expected around once in 200 years, even with the influence of human-caused climate change. But if temperature rise reaches 2 degrees, it will become much more common, occurring about once in 20 years.”

The heat has already caused widespread hospitalisations, damaged roads, sparked fires and led to school closures but the full human cost of the extreme weather event is still unknown.

“The full impact of a heatwave is often not known until weeks or months later, when death certificates are collected, or when scientists can analyse excess deaths. Many places lack good record keeping of heat-related deaths, therefore currently available global mortality figures are likely an underestimate,” said Anshu Ogra, assistant professor at the Indian Institute of Technology’s school of public policy, ahead of the report’s launch. 

The study also concluded that the high vulnerability in Asia, which is one of the world’s heatwave hotpots, amplified the impacts.

Heat action plans lacking

Heat action plans are crucial in addressing the human and economic impacts of heatwaves, especially when it comes to vulnerable populations, said Ogra. 

The report said that solutions to heat-related harms can also include self-protective action, early warning systems, and passive and active cooling. “They are currently implemented as patchwork, to various degrees, across the countries studied, with India having the most advanced heatwave planning,” the report said.

Vulnerable communities often lack access to complete protection from deadly heat, and policymakers need to consider the different impacts of the extreme heat on these groups of people, such as workers exposed to the sun and those in the informal sector, said Emmanuel Raju, associate professor in the Global Health Section of the University of Copenhagen and member of the Copenhagen Centre for Disaster Research.

“It is important to talk about who can adapt and who has the resources to do that,” he said, adding that vulnerability assessments would produce varying results across different countries, regions and communities. For example, crop productivity failures need to be considered among other invisible factors affecting farmers and agricultural communities.

“Heat is something that we still do not have access to relief or compensation (from). Our action plans need to do more to incorporate that, because it is important to talk about social protection and immediate relief within the context of heat as a disaster,” said Raju.

While India and Bangladesh have formulated heat action plans coupled with advisories from their respective meteorological departments, the study found that Thailand and Laos lacked similar preparedness for extreme heat.

“In Thailand, the Department of Disaster Prevention and Mitigation did give some advisories around heatwaves, but in Laos, we were not able to trace any such advisories,” Orga said. “The case needs to be made to separate heat action plans from disaster management plans.” She said Laos had not issued any heatwave advisories, and recommended that authorities devise proper heat action plans instead of falling back only on disaster management plans, which are more common.

Chaya Vaddhanaphuti, lecturer at the Chiang Mai University department of geography, faculty of social sciences believes that the institutionalisation of a heatwave action plan is necessary in countries such as Laos and Thailand.

“In coming years, we need year-round preparations for a heatwave, and not declare an emergency only when it strikes,” he said.

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