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Bengaluru: Heatwaves in India have increased in intensity and frequency over the last 26 years due to global warming, according to a recent study published in the journal Scientific Reports. While this is not new – existing research has shown this before – the study also found that the extent of heat hotspots in the country has increased during these years by 1.5 times. Parts of western India, the southeastern coast and the Indo-Gangetic Plain are among the areas most at risk in terms of health impacts on people.

Recent research predicts that deaths caused by intense heat are likely to increase in the country too. In March, a global report predicted that with current levels of warming caused by climate change, parts of northwestern and central India could witness as many as 24 deaths per every 1 lakh due to hotter temperatures.

More heatwaves, and longer ones

The India Meteorological Department defines heatwaves as periods of unusually high temperatures that occur in an area when compared to what is normally expected over the region during that time. A heatwave is said to occur over a region if the maximum temperature goes above 45 Degrees Celsius, or when temperatures increase from between 4.5 and 6.4 Degrees Celsius above the normal. A severe heatwave is said to occur when maximum temperatures exceed 47 Degrees Celsius, or rises above normal levels by 6.4 Degrees Celsius and higher.

Trends in daily maximum temperatures are one way to assess changes over years. A team of scientists from the Indian Institute of Tropical Meteorology Pune and the National Remote Sensing Centre Hyderabad analysed the daily maximum temperatures for the two hottest months in India – April and May – from 1981 to 2020. 

They found that the average daily maximum temperature increased by ~0.5°C by 2000, and by ~1.0°C by 2020 when compared to 1981 levels due to human-caused warming (activities such as the use of fossil fuels that release carbon emissions into the atmosphere which in turn traps greenhouse gases that increase temperatures globally). North-western and central India and the coast of Andhra Pradesh experienced the most significant increases. The team also found that average daily maximum temperatures are steadily rising in southern India.

The frequency of heatwaves has increased over the past four decades, the study found. Between 1981 and 2000, regions including northwest India, central India and coastal Andhra Pradesh experienced an average of 2.5 to 5.5 heatwave days per year. But over the last two decades (2001–2020), this has risen to 3.5 to 8.5 days per year – and across parts of northern, western, south-central, central-east and peninsular India. 

The duration of heatwaves has increased too. Some parts of India such as central and eastern India and coastal Andhra Pradesh used to experience heatwaves for 2.5-4 days per year from 1981 to 2000. But between 2001 and 2020, this duration has increased to 3–5 days per year, and it has intensified in additional regions too: northern, western, south-central, central-eastern and peninsular India.

“This increase in frequency and duration over the last two decades (2001–2020) indicates a trend towards more severe and prolonged HWs [heatwaves] compared to the previous decades (1981–2000),” the study noted.

A man bathes his horse in the Krishna River amid rising summer heat, in Karad, Maharashtra, Tuesday, April 14, 2026. Photo: PTI.

Impact of global warming, increase in hotspots

The study also analysed the link between rising temperatures and changes in the El Niño-Southern Oscillation phenomenon, which is an interaction between the ocean and atmosphere in the tropical Pacific and known to significantly impact the global climate system by releasing heat into the atmosphere and altering atmospheric circulation patterns. This phenomenon creates warm years in the Indian subcontinent (called El Niño years), neutral conditions, and cool years (or the La Niña). The study found that while global warming drove the higher frequency, duration, and extent of extreme heatwaves, the impact of the El Niño further aggravated these trends in India between 2001 and 2020. 

“This reflects the increasing vulnerability of the region to extreme heat. Moreover, this suggests that we can expect a further increase in HW [heatwave] days under continued global warming,” the study warned.

Using a heatwave hotspot index, the study also identified regions that are particularly sensitive to global warming and vulnerable to heatwaves using satellite imagery. It found that the spatial extent of heatwave hotspots between 1981–2000 and 2001–2020 increased by approximately 1.5 times. 

Between 1981 and 2000, heatwave hotspots were primarily concentrated in the Gangetic plains, central India, coastal Andhra Pradesh and parts of western India per the study. But between 2001 and 2020 this increased drastically to also include parts of northwestern, central and eastern India, as well as large areas of peninsular India. Essentially, hotspots, and their extent, have increased: from 1,190,000 km² in 1981–2000 to 1,810,000 km² in 2001–2020. Under the current global warming scenario, the central plains of India, the southeastern coast, parts of western India, Gangetic West Bengal, and some areas in the central Indo-Gangetic Plain (IGP) region are most at risk in terms of health impacts. 

Increase in temperature-related deaths in India

Hotter temperatures can be fatal – and more so in specific parts of India. 

According to a recent report published in March by the Climate Impact Lab in the Energy Policy Institute at the University of Chicago, US, global climate change will increase the number of premature deaths due to hotter temperatures. It found that the likelihood that a person will die due to a warmer climate depends on where they live – in hotter or cooler climes. Cooler regions (mid-to-high latitudes) across the world are projected to see a decrease in deaths due to extreme cold, while hotter regions (lower-latitudes) such as northern Africa, West Asia, and southwest Asia will likely see more deaths. And this impact of climate change is also highly unequal: more than 90% of deaths due to hotter temperatures will occur in low- and middle-income countries.

A worker carries harvested wheat crop at a farm, in Loharu, Haryana, Tuesday, March 31, 2026. Photo: PTI/Kamal Kishore.

The report predicts that ten times more people will likely die each year in lower-income countries (about 3,91,000 people) than in higher-income countries (about 39,000 people) due to shifting temperatures, despite being expected to have roughly equal populations. The country of Niger in Africa is likely to be hardest hit, as it could witness around 60 deaths per 1 lakh people.

Compared to that, India’s predicted country-level average change in mortality rate is not too high: 2.4 deaths per 1,00,000 people. However, this value belies extremes. For instance, the regions with the largest increase in projected temperature-related mortality are northwest and north-central India. These regions could witness around 23-25 additional deaths per every 1 lakh people, and this change would be on par with the current death rates for tuberculosis and diabetes in India, the report noted.

Karanpur in Rajasthan could witness the largest increase in temperature-caused deaths: 26 deaths out of every 1 lakh. Regions with the largest decrease in projected temperature-related mortality are in the southwest, east, and extreme north (such as Kashmir).

“In general, the areas projected to be most negatively impacted (i.e., largest increases in temperature-related mortality) tend to be those that are already among the hottest and are projected to see increases in the frequency of extreme heat,” Emily Grover-Kopec, one of the authors of the report, told The Wire. “This is particularly true for the northwest (e.g., Punjab, western Rajasthan).”

Conversely, the areas projected to see the most significant decreases in temperature-related mortality tend to be the coolest, particularly those in the extreme north, Grover-Kopec added. “Those areas are projected to see a decrease in temperature-related mortality overall, driven by fewer cold-related deaths. This dynamic plays a key role in the range of projections across India.”

According to the report, 95 cities across Asia will experience an increase in temperature-related mortality of at least 10 deaths per 1 lakh; and that 56 of these cities are in China. Amritsar, the second-largest city of Punjab is part of this list, with an expected 13 deaths per every 1 lakh due to intense heat. 

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