90 per cent of India, entire Delhi in 'danger zone' of heatwave impacts: Study

The study, conducted by the University of Cambridge, also revealed that Delhi is particularly vulnerable to severe heatwave impacts

Representative image of a hot day in India (Getty Images)
Representative image of a hot day in India (Getty Images)


Heatwaves in India are becoming more frequent and severe due to climate change, with over 90 per cent of the country in the "extremely cautious" or "danger zone" of their impacts, according to a new study.

The study, conducted by the University of Cambridge, also revealed that Delhi is particularly vulnerable to severe heatwave impacts, despite its recent state action plan for climate change failing to reflect this fact.

It suggested that heatwaves have impeded India's progress towards achieving the United Nations' Sustainable Development Goals (SDGs) more significantly than previously thought, and that the current assessment metrics may not fully capture the impacts of heatwaves linked to climate change on the country.

To assess India's climate vulnerability and the potential impact of climate change on SDG progress, researchers conducted an analytical evaluation of the country's heat index with its climate vulnerability index.

The heat index (HI) is a measure of how hot it feels to the human body, taking into account both temperature and humidity. The climate vulnerability index (CVI) is a composite index that uses various indicators to account for socioeconomic, livelihood and biophysical factors.

The researchers accessed a publicly available dataset on state-level climate vulnerability indicators from the government's National Data & Analytics Platform to classify severity categories. They then compared India's progress on the SDGs over 20 years (2001–21) with extreme weather-related mortality from 2001 to 2021.

The study showed that more than 90 per cent of India is in the "extremely cautious" or "danger" range of heatwave impacts because of the HI, though otherwise considered "low" or "moderate" vulnerability in terms of their CVI.

States that were categorised as "low" in the CVI rankings were found to be in "danger" HI categories, indicating that heatwaves put more people at extreme climate risk across India than estimated by CVI.

The authors concluded that the use of the CVI may underestimate the actual burden of climate change with respect to heat, and suggested that India should consider reassessing its climate vulnerabilities to meet the SDGs.

They warned that if India fails to address the impact of heatwaves immediately, it could slow progress towards achieving the SDGs.

The study also highlighted that the current heat action plans designed and implemented according to the Delhi government's vulnerability assessment do not include HI estimations, which is concerning since even the areas of "low" climate vulnerability in Delhi are at high risk for heatwaves.

The high intensity of development in the central, east, west, and north-east districts can further elevate the HI risks through heat island formation, the study noted.

The authors said that some of the critical variables in Delhi that aggravate heat-related vulnerabilities include concentration of slum populations and overcrowding in high HI areas; lack of access to basic amenities like electricity, water and sanitation; non-availability of immediate healthcare and health insurance; poor condition of housing; and dirty cooking fuel (biomass, kerosene and coal).

The threshold for a heatwave is met when the maximum temperature of a station reaches at least 40 degrees Celsius in the plains, at least 37 degrees Celsius in coastal areas and at least 30 degrees Celsius in hilly regions, and the departure from the normal temperature for the season and zone is at least 4.5 degrees Celsius.

Earlier this month, the India Meteorological Department (IMD) predicted above-normal maximum temperatures for most parts of the country from April to June, except parts of the north-west and the peninsular regions.

Above-normal heatwave days are expected in most parts of central, east, and north-west India during this period.

In 2023, India experienced its hottest February since record keeping began in 1901. However, above-normal rainfall in March kept temperatures in check.

March 2022 was the warmest ever and the third driest in 121 years. The year also saw the country's third-warmest April since 1901.

In India, about 75 per cent of workers (around 38 crore people) experience heat-related stress.

A report by the McKinsey Global Institute warns that, if this continues, by 2030 the country could lose between 2.5 percent to 4.5 percent of its Gross Domestic Product (GDP) per year.

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