Bangladesh braces for 30-fold increase in humid heat events, alarming climate change impact: Study

The recent intense heatwave affected various parts of Bangladesh, along with India, Thailand, and Lao PDR, has been attributed to human-caused climate change, according to a rapid attribution analysis conducted by World Weather Attribution.

The study emphasises the urgent need for concerted global efforts to mitigate and adapt to the effects of climate change, said a press release.

During the last two weeks of April 2023, Bangladesh experienced extreme temperatures, with Dhaka recording a historic maximum temperature of 40.6°C on April 15th, the highest in decades. These soaring temperatures are consistent with the current climate, which has warmed by 1.2°C since pre-industrial times due to human activities.

The report highlighted in April, parts of south and southeast Asia experienced 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 remains unknown.

Across the world, climate change has made heatwaves more common, longer and hotter. To quantify the effect of climate change on the Asian heatwave, scientists analysed 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 study combined climate models with observational data to estimate the influence of human-induced climate change on extreme heat events. The results revealed a strong increase in the likelihood and intensity of humid heat events, similar to those witnessed in 2023. The probability of such an event occurring in India and Bangladesh has increased at least 30-fold due to human-induced climate change. Moreover, a heatwave that previously had a 20% chance of occurring in any given year is now approximately 2°C hotter in heat index due to human activities.

Concurrent dry weather conditions during the summer season, along with reduced rainfall in southwestern Pakistan, western India, and Bangladesh, have contributed to drought and heatwaves in these regions. People who are most exposed to the sun and vulnerable populations 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.

Chandra Sekhar Bahinipati, Indian Institute of Technology Tirupati, India, said, "Although we have recognized heatwaves as one of the deadliest disasters, particularly in countries like India, Bangladesh, and Thailand, there is a lack of knowledge with respect to who is vulnerable, loss and damage estimation, household coping mechanisms, and the most effective heat action plans. Except for the human casualties, other economic and non-economic loss and damage indicators are not documented. This creates a dearth in assessing the extent of risk, who is vulnerable, and also operationalizing any adaptation planning."

The study highlighted adoption of various coping strategies during the heatwave, such as sitting beside water bodies and adjusting clothing and ventilation. However, discriminatory social and cultural norms in Bangladesh have hindered women's ability to adapt and increased their vulnerability to heat-related risks.

Moreover, presence of Urban Heat Islands (UHI) in cities like Dhaka poses additional challenges. Dhaka ranks among the most affected cities globally, necessitating comprehensive measures to mitigate the adverse effects on living conditions. Bangladesh has responded to these challenges by implementing an Early Action Protocol (EAP) in Dhaka, providing cash transfers to vulnerable residents ahead of heatwave events.

Friederike Otto, senior lecturer in Climate Science at the Grantham Institute for Climate Change and the Environment, said, "We see again and again that climate change dramatically increases the frequency and intensity of heatwaves, one of the deadliest weather events there are. Still, heat action plans are only being introduced very slowly across the globe. They need to be an absolute priority adaptation action everywhere, but in particular in places where high humidity enhances the impacts of heatwaves."

Emmanuel Raju, director of Copenhagen Centre for Disaster Research at the University of Copenhagen, said, "This is another disaster that highlights the need to reduce vulnerability and think deeper about the limits to adaptation. As it often happens, marginalised people are the worst affected. Many of them are still recovering from the pandemic, and from past heatwaves and cyclones, which leaves them trapped in a vicious cycle. It is fundamental to implement mitigation and adaptation strategies to avoid visible and invisible loss and damage".

The study was conducted by 22 researchers as part of the World Weather Attribution initiative, including scientists from universities and meteorological agencies in India, Thailand, Australia, Denmark, France, Germany, Kenya, the Netherlands, the UK, and the United States.