Hyderabad: Rapid human-induced climate change acted as a trigger for April's record-breaking humid heatwave in India, Bangladesh, Laos and Thailand and the trend is likely to continue at least 30 times more, climate scientists warned.
The rapid attribution analysis, which was done by an international team of leading climate scientists as part of the World Weather Attribution group, also sounded a grave warning for the region. The high vulnerability in the region, which is one of the world’s heatwave hotpots, speeded up the impacts, findings said.
The report is based on findings of 22 researchers as part of the World Weather Attribution initiative from universities and meteorological agencies in India, Thailand, Australia, Denmark, France, Germany, Kenya, the Netherlands, the UK, and the United States. In April, parts of south and southeast Asia reeled under an intense heatwave, with record-breaking temperatures that passed 42ºC in Laos and 45°C in Thailand. The heat caused widespread hospitalisations, damaged roads, sparked fires and led to school closures. The number of deaths, however, remains unknown.
Across the globe, climate change has made heatwaves more common, longer and hotter. To analyse and quantify the impact of climate change on the Asian heatwave, scientists pieced together weather data and computer model simulations to compare the climate as it is today, after about 1.2°C of global warming since the late 1800s, with the climate of the past, following peer-reviewed methods.
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 heat waves on the human body.
In both regions, the researchers found that climate change made the humid heatwave at least 30 times more likely, with temperatures at least 2°C hotter than they would have been without climate change. Until overall greenhouse gas emissions are halted, global temperatures will continue to increase and events like this will become more frequent and severe.
In Bangladesh and India, events like the recent humid heatwave used to occur less than once a century on average; they can now be expected around once in five years, and if temperature rise reaches 2°C - as will happen within around 30 years if emissions are not cut rapidly - events like this will occur, on average, at least once every two years.
In Laos and Thailand, the scientists found that an event like the recent humid heatwave would have been nearly impossible without the influence of climate change, and 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 the temperature rise reaches 2°C, it will become much more common, occurring about once in 20 years.
While high temperatures are the norm in south and southeast Asia, early heatwaves such as this one are particularly damaging. People who are most exposed to the sun and vulnerable population are routinely the worst impacted. The current patchwork of heatwave solutions must be improved to account for inequalities and existing vulnerabilities, the scientists said, adding that heat action plans should be inclusive and comprehensive, and ensure access to basic services, such as water, electricity and health care.
