Three Places In India Emerge As New Heatwave Hotspots, Human Population At Risk: What It Means

Northwestern, central and south-central India have emerged to be new hotspots of intense heatwave over the past 50 years, a study has said.

The study said climate change and consequent increase in heatwave trends would put a larger population at risk. The study also highlights the need for developing effective heat action plans in the three heatwave hotspot regions with a focus on different vulnerabilities among the inhabitants.

Researchers analysed monthly, seasonal and decadal variations along with long-term trends of heatwaves and severe heatwave events for pre-monsoon (March May) and early summer monsoon (June July) season between 1951 and 2016.

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What is a heatwave?

For the plains, a "heatwave" is declared when the maximum temperature is more than 40 degrees Celsius, and at least 4.5 notches above normal. A "severe" heatwave is declared if departure from normal temperature is more than 6.5 degrees Celsius, according to the IMD.

Published in the journal International Journal of Climatology, the study links heatwaves with greater concerns for human health, agriculture and the natural ecosystem.

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How will it affect humans?

Heatwaves have emerged as a deadly health hazard, claiming thousands of lives across the globe in recent decades, with episodes strengthening in frequency, intensity and duration in the past half-century in India as well. This has caused severe impact on health, agriculture, economy and infrastructure. In such a scenario, it is extremely important to identify the most heatwave vulnerable regions of the country to prioritise immediate policy intervention and stringent mitigation and adaptation strategies, the Department of Science and Technology said.

The study suggests a way forward to assess climate performance and uncertainty in extreme weather analysis in future projections.

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Led by Professor RK Mall of Mahamana Centre of Excellence in Climate Change Research (MCECCR) at Banaras Hindu University (BHU), the researchers studied the changes in spatial and temporal trends in heatwaves and severe heatwaves over the past seven decades.

What did the study find?

They found a shift in the pattern of heatwave events with an increasing trend in three prominent heatwave prone regions in northwestern, central, and south-central India, the highest being in West Madhya Pradesh.

A significantly decreasing trend was observed over the eastern region in the Gangetic plains of West Bengal. The trends are continuously changing in the eastern region of Gangetic West Bengal and Bihar to north-western, central and south-central regions of India.

¡°The research also observed an alarming southward expansion and a spatial surge in severe heatwave events in the last few decades that may put a greater population at additional risk of heat stress in a region already characterised by low Diurnal temperature range (DTR), or the difference between the maximum and minimum temperatures within one day, and high humidity,¡± the Ministry of Science and Technology said in a release.

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Importantly, the heatwave and severe heatwave events were found to be positively correlated with mortality in Odisha and Andhra Pradesh, highlighting that human health is highly susceptible to severe heatwave disasters.

With an ever-increasing extreme-temperature threshold, a heat resilient future is the need of the hour. Dense population with an intensive outdoor work culture calls for equitable heat resilient mitigation and adaptation strategies covering each section of the society depending on their vulnerability, it said.