Human-caused climate change made April's record-breaking heatwaves in Bangladesh, India, Laos, and Thailand at least 30 times more likely, according to an analysis conducted by a group of leading climate scientists.

The study by World Weather Attribution also emphasises that the region's high vulnerability, known as a heatwave hotspot, exacerbated the impacts of the heatwave.

During April, parts of south and southeast Asia faced an intense heatwave, reaching unprecedented temperatures exceeding 42 degrees Celsius in Laos and 45 degrees Celsius in Thailand.

This extreme heat resulted in widespread hospitalisations, infrastructure damage, wildfires, and school closures. The exact number of fatalities is currently unknown.

Climate change has globally intensified heatwaves, making them more frequent, longer lasting, and hotter.

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To assess the impact of climate change on the Asian heatwave, scientists analysed weather data and computer model simulations, comparing the current climate, with approximately 1.2 degrees Celsius of global warming since the late 1800s, to historical climate conditions using peer-reviewed methodologies.

The analysis focused on the maximum temperatures and heat index over four consecutive days in April in two regions: South and east India, Bangladesh, and all of Thailand and Laos.

The heat index, which considers both temperature and humidity, provides a more accurate understanding of heatwave impacts on the human body.

The findings reveal that climate change made the humid heatwave in both regions at least 30 times more likely.

The realised temperatures during the heatwave were at least two degrees Celsius higher than they would have been without climate change. Unless immediate action to reduce greenhouse gas emissions is not taken, global temperatures will continue to rise, resulting in more frequent and severe heatwaves like this one.

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In the past, such intense heatwaves occurred in Bangladesh and India once in a century, on average. However, now they can be expected approximately every five years. If emissions are not rapidly curtailed, a two-degree temperature increase is projected within the next 30 years, leading to these events occurring at least once every two years.

For Laos and Thailand, the recent humid heatwave would have been highly improbable without the influence of climate change. Even with the impact of climate change considered, this type of heatwave remains extremely rare, happening only once every 200 years.

However, if temperatures rise by 2 degrees Celsius, these heatwaves will become more frequent, occurring approximately once every 20 years, the report said.