As global temperatures rise due to climate change, extreme heat events are becoming more frequent and intense, particularly in regions like India. Increasing greenhouse gas emissions have led to unprecedented temperature levels, which, when combined with high humidity, create hazardous conditions. One crucial metric for understanding these dangers is the Wet Bulb Temperature (WBT), which accounts heat and humidity to reflect how well the human body can cool itself through sweating. Unlike standard temperature readings, WBT accounts for the moisture in the air, affecting how efficiently sweat can evaporate and cool the body. It’s measured by wrapping a thermometer bulb in a wet cloth and allowing the water to evaporate, providing a more accurate representation of how the body responds to hot and humid conditions. As WBT rises, it becomes increasingly difficult for the human body to maintain a safe core temperature. Once a critical threshold is crossed, the body can no longer regulate its heat effectively, leading to dangerous health conditions such as heat stress, dehydration, and even heatstroke. Prolonged exposure to high WBT levels can be fatal, even for healthy individuals, particularly if they are resting or staying hydrated. Post-Monsoon Heat: An Underestimated Challenge: In many parts of India, the post-monsoon weather can be deceiving. Even though temperatures might not seem extreme, high humidity levels make the heat feel much worse. For example, in cities like Delhi, temperatures might be around 32°C, but with humidity above 75%, it can feel like 44°C or higher. This is when Wet Bulb Temperature becomes critical. When the WBT rises above 31°C, the body can no longer cool itself effectively, even at moderate temperatures. Initially, researchers believed that a WBT of 35°C was the maximum a human body could endure. However, new studies have revised this limit downward. Research conducted at Penn State University found that the critical WBT threshold is closer to 31°C, especially when humidity exceeds 50%. In controlled environments, participants performing minimal physical activity were unable to maintain a safe core body temperature even at these lower WBTs, which challenges earlier assumptions about human heat tolerance.
Climate Change and WBT: A Rising Concern: The frequency of extreme WBT events is increasing due to climate change. Historically, WBT events exceeding 31°C were rare. Between 1979 and 2017, there were only about 1,000 such instances worldwide. However, in recent years, several countries, including India, Pakistan, and Saudi Arabia, have recorded WBT levels exceeding 35°C, highlighting that this isn’t just a future concern—it’s happening now. The 2022 heatwave in India and Pakistan, for example, was found to be 30 times more likely due to climate change, underscoring the importance of understanding and mitigating the effects of extreme wet-bulb temperatures in the future. As global temperatures rise, particularly in tropical regions, scientists estimate that Wet Bulb Temperatures will increase by 1°C for every degree of global warming. This means that limiting global warming to 1.5°C above pre-industrial levels is essential to prevent vast areas of the tropics from becoming uninhabitable due to extreme heat stress. Without urgent action, millions of people living in these regions could face unprecedented heat exposure, where even the most basic daily activities become life-threatening. Preparing for the Future: India’s Path to Resilience: India’s vulnerability to heatwaves and extreme Wet Bulb Temperatures highlights the urgent need for comprehensive adaptation strategies. The Indian Meteorological Department (IMD) has already initiated efforts like the Har Ghar Mausam campaign, which issues local heat index-based warnings to raise public awareness about heat waves. However, integrating Wet Bulb Temperature into these warnings is essential for a fuller understanding of the risks, particularly in the post-monsoon season. SEEDS (Sustainable Environment and Ecological Development Society), a humanitarian organization with three decades of experience, focusses on community-centered adaptation: Addressing the risks of Wet Bulb Temperatures requires community-level efforts. Raising awareness about high WBT is crucial; individuals must understand the dangers and necessary precautions. Initiatives like educational workshops can equip community members with vital knowledge. By fostering preparedness, we can enhance community resilience against the health threats posed by extreme Wet Bulb Temperature conditions. Beyond public awareness, India must also invest in sustainable infrastructure and climate resilience. Heat-resilient infrastructure, such as buildings designed to reduce heat absorption through reflective materials, green spaces, and water features, can help cool urban areas. Establishing community cooling centers in densely populated cities will provide immediate relief for those most at risk. Moreover, affordable, energy-efficient cooling solutions need to be made accessible to lower-income families to reduce heat-related mortality without overburdening the energy grid. Strengthening public health systems is equally crucial, with a focus on training healthcare workers to recognize and respond swiftly to heat-related illnesses to prevent fatalities.
In 2020, in collaboration with Microsoft, SEEDS developed ‘Sunny Lives’, an AI model that enhanced community preparedness and aided governments plan better for extreme weather at a hyper-local level. Developed under Microsoft’s global programme ‘AI for Humanitarian Action’, the model processes large volumes of data to provide risk information at a hyper-local (building cluster) level. The roof of a building reveals the condition of a house, and the model uses high-resolution satellite imagery to detect and assign vulnerability scores to buildings according to their roof types. Other location and hazard-specific attributes are also used in calculating the vulnerability scores. It’s tools such as these when used diligently that can help scale impacts and save lives. Conclusion: As India faces the dual challenges of rising temperatures and increasing humidity, the implications of Wet Bulb Temperature on public health cannot be overstated. The growing frequency of extreme heat events, exacerbated by climate change, poses significant risks, especially for vulnerable populations. It is crucial to recognize that maintaining a healthy environment is not merely about infrastructure but also about empowering communities with the knowledge and resources necessary to adapt. By integrating Wet Bulb Temperature data into heatwave alerts and investing in sustainable solutions, India can take meaningful strides toward protecting its citizens. Collaborative efforts between government agencies, non-profits, and local communities will be essential in fostering resilience against extreme heat. Only through proactive measures and a commitment to adaptation can India safeguard the health and well-being of its people in an increasingly uncertain climate.