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Asia's risk of humid heat waves rises 30 times with climate change

Human-induced climate change has significantly increased the probability of extreme heatwaves in Bangladesh, India, Laos

By Ground report
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Temperature over all ice-free oceans for May 2023 was highest on record

Human-induced climate change has significantly increased the probability of extreme heatwaves in Bangladesh, India, Laos and Thailand by up to 30 times, according to a rapid attribution analysis by a team of renowned climate scientists associated with the Attribution Group of the World Climate.

The study also emphasized the high vulnerability of the region to heat waves, which are among the most severe in the world, which amplifies the negative impacts.

Heat wave experienced in parts of South and

A webinar was held on Wednesday to discuss the report's findings. During the event, Fredrik Otto, Senior Lecturer in Climate Science at the Grantham Institute for Climate Change and the Environment, Emmanuel Raju, Director of the Copenhagen Center for Disaster Research at the University of Copenhagen, and the authors of the report, Chhaya Vadhanaphuti, Mariam Zakaria and Anshu Ogra provided information on various aspects of the study.

The reality on the ground reflects the severity of the heat wave experienced in parts of South and Southeast Asia in April. Record temperatures of 42°C in Laos and 45°C in Thailand caused widespread shocks. The heat wave led to numerous hospitalizations, damaged roads and scattered fires, leading to the closure of schools. Tragically, a significant number of deaths occurred, although the exact number is unknown.

Climate change has contributed to the increase in the frequency and intensity of heat waves around the world. To assess the specific impact of climate change on the Asian heat wave, the scientists conducted a comprehensive analysis using meteorological data and computer model simulations.

They compared current weather conditions with those of the late 19th century, focusing on a 1.2°C increase in global warming. The study underwent a peer review process to ensure its scientific rigor.

Fredrik Otto, Senior Lecturer in Climate Science at the Grantham Institute for Climate Change and the Environment, said "We are witnessing a dramatic increase in the intensity and frequency of heat waves due to climate change. These waves of heat are among the most destructive weather events".

He added "Despite this, the implementation of heat action plans is progressing slowly around the world. There is now an urgent need for comprehensive adaptation plans, especially in areas where the impact of heat waves is amplified by higher humidity."

Climate Change: 30-Fold Increased Risk

The study focused on analyzing the mean maximum temperature and heat index over a four-day period in April within two regions. One region covered southern and eastern India and Bangladesh, while the other covered Thailand and Laos. The heat index, which takes temperature and humidity into account, was used to provide a more accurate assessment of the impact of heat waves on human health.

The study findings revealed that both regions experienced a significantly higher probability of humid heat waves, with at least a 30-fold increased risk due to climate change. Temperatures have increased by a minimum of 2°C compared to a scenario without climate change. Unless there is a complete cessation of greenhouse gas emissions, global temperatures will continue to rise, resulting in more frequent and intense heat waves and other extreme weather events.

In the past, humid heat wave events in Bangladesh and India occurred infrequently, occurring less than once per century. However, due to climate change, these events are now projected to occur approximately once every five years. If global temperatures continue to rise and exceed a 2°C increase, a humid heat wave is expected to occur at least once every two years. Without rapid reductions in greenhouse gas emissions by governments, global temperatures could exceed the 2°C threshold in the next 30 years.

Heat waves most devastating disasters

Chandrasekhar Bahinipati, from the Indian Institute of Technology, Tirupati, said "Although we have identified heat waves as one of the most devastating disasters, especially in countries like India, Bangladesh and Thailand, information is lacking on which communities are vulnerable."

He added "There is a lack of information on loss and damage assessment, national response mechanisms and the most effective heat action plans. Documentation of economic and non-economic indicators of loss and damage, beyond the mere loss of life, is also insufficient. creates difficulties in assessing the scope of risk, identifying those at risk, and implementing an effective adaptation plan."

Emmanuel Raju, director of the Copenhagen Disaster Research Center at the University of Copenhagen, said "This is another disaster that emphasizes the need to reduce vulnerability and think deeply about constraints and adaptability. Often, it is the communities that are marginalized. those who are disproportionately affected by these weather events, who are still recovering from the impacts of the COVID-19 pandemic and previous heat waves and cyclones, thus being caught in a complex cycle, for what is now essential to implement mitigation and adaptation strategies to mitigate both visible and invisible damage".

India fall into extreme danger category

Chhaya Vaddhanaphuti, one of the report's authors, said: "Our study found that the heat index levels in all four countries - India, Bangladesh, Laos and Thailand - fall into the extreme danger category, ranging from 41 to 54. degrees Celsius Particularly in urban areas temperatures can reach up to 54 degrees Celsius which is highly dangerous Understanding the full impact of heat waves is challenging and can take some time All four countries have better provisions for warnings "Weather-related early warnings. Heat action plans have been developed and are being implemented, especially in India and Bangladesh, but more significant work is still needed on these plans."

Mariam Zakaria, another author of the report, explained that the study used heat index as a variable. She highlighted the fact that humidity and temperature have an impact on human health. Based on estimates, it was found that the heat index value exceeds 41 degrees Celsius in both regions, falling into the dangerous category. It has been observed that this is not unexpected under current climatic conditions. If assessments and models are combined, incidents of high-humidity heat waves will increase.

Anshu Ogra, a member of the team that prepared the report, said: "Vulnerability is an important factor in preparing for heat waves. Vulnerability varies in different countries and even within regions. Various factors, such as social and economic factors, occupation, gender and physical ability are responsible for vulnerability. Assessing vulnerability is a crucial aspect of preparedness in heat action plans".

He added "there are currently state and district-level heat action plans in India, but it has become a challenge to find similar initiatives in Thailand and Laos. While Thailand talks about heat waves, there is no talk about it in Laos."

Unprecedented humid heat

The study found that the recent waves of unprecedented humid heat in Laos and Thailand were highly unlikely to have occurred without the influence of climate change. Although still rare, these events are predicted to occur about once every 200 years. However, if global temperatures rise to the 2°C level, such events may become more common, occurring once every 20 years.

While South and Southeast Asia frequently experience extreme heat waves, the rapid onset of a heat wave like the one observed would be particularly devastating. Communities that are highly exposed to prolonged periods of intense heat, as well as other vulnerable groups, continue to bear the brunt.

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