A recent study conducted by researchers from IIT-Bombay and ETH Zurich has raised alarming concerns about the increasing occurrence of ‘oppressive heatwaves’ in India, a type of heatwave that combines high temperatures with high humidity. This phenomenon, which poses significant risks to human health, is projected to intensify due to global warming, making it crucial for governments and citizens to prepare for more frequent and severe heatwave events in the future.
Understanding Heatwaves and Their Types
Heatwaves are traditionally defined as periods where temperatures exceed a specific threshold for a consecutive number of days. The India Meteorological Department (IMD) defines a heatwave as three or more days with temperatures above:
- 45°C in plains, and
- 40°C in hilly areas.
However, researchers have now identified two distinct categories of heatwaves based on the combination of temperature and humidity:
- Oppressive Heatwaves: These involve both high temperatures and high humidity levels, creating a suffocating environment that severely impairs the body’s ability to cool down.
- Extreme Heatwaves: These occur with high temperatures but relatively low humidity, posing different health risks but typically allowing the body to cope somewhat better than in oppressive conditions.
Historical Data and Mortality Correlation
The researchers used historical data from 1951 to 2013, sourced from the IMD, NOAA, and other global agencies, to study the changes in heatwave characteristics and their relationship with human mortality in India. They found a strong positive correlation between the number of oppressive heatwave days and increased mortality rates. The data from 1967 to 2007 showed that as oppressive heatwaves became more frequent, the number of heat-related deaths also rose significantly.
Future Projections for Heatwaves
The study analyzed future projections under two global warming scenarios: a rise of 1.5°C and 2°C relative to pre-industrial temperatures. The results were troubling:
- Under 1.5°C warming, the number of oppressive heatwave days is expected to increase five-fold by the mid-century (2035-2065) and end of the century (2070-2100), relative to the historical period (1975-2005). In contrast, extreme heatwave days will remain relatively constant.
- Under 2°C warming, the number of oppressive heatwave days is projected to increase eight-fold by the end of the century, compared to the historical period and the 1.5°C scenario.
This dramatic rise in oppressive heatwaves highlights the increasing health risks, especially in densely populated countries like India, which is already experiencing the effects of climate change.
Health Risks and Mortality
The study underscores the direct health risks associated with oppressive heatwaves. As these events become more frequent, the likelihood of heat-related mortality will increase, particularly among vulnerable populations. The researchers emphasize that the rise in oppressive heatwaves will have a far more significant impact on public health compared to extreme heatwaves, making adaptation measures more critical than ever.
Impact of Limiting Global Warming
The researchers also pointed out that limiting global warming to 1.5°C could have significant benefits:
- It could reduce the likelihood of oppressive heatwaves by 44%.
- It could reduce extreme heatwaves by 25%.
This underscores the urgent need for climate action to prevent the worst effects of global warming, especially in countries like India, where heatwaves already cause widespread damage to human health and infrastructure.
Conclusion: Need for Adaptation Measures
The study’s authors, Naveen Sudharsan, Subimal Ghosh, Subhankar Karmakar of IIT-Bombay, and Jitendra Singh of ETH Zurich, stress the importance of adaptation strategies to mitigate the impacts of oppressive heatwaves. As the frequency of these extreme weather events rises, the risk to public health will escalate. Immediate action, including improved infrastructure, heat action plans, and public awareness campaigns, is essential to reduce mortality and protect vulnerable populations in the coming decades.
By limiting global warming to 1.5°C, we not only reduce the likelihood of these dangerous heatwaves but also safeguard millions of lives across the world. The remarkable increase in oppressive heatwave days highlights the urgent need for proactive measures to protect communities from the looming threat of climate change.
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