Why recent heat waves are a consequence of man-made climate change

By Vikas Meshram* 

Recent data from the global air quality organization IQAir has presented an alarming picture: nineteen of the world's twenty hottest cities are located in India. This is a serious warning about the country's environmental future. While climate change is the primary driver of rising temperatures, the indifference of governments and citizens toward environmental protection has compounded the crisis. The continuous shrinking of forest cover and rising carbon emissions from changing lifestyles are further fuelling the surge in heat.

This April, a few days of relative coolness were followed, within days, by a massive heat wave. Such sudden seasonal shifts are extremely dangerous for human health, and the number of people falling ill as a result underlines the gravity of the situation. According to the meteorological department, a heat wave is declared when temperatures cross 40 degrees Celsius — a threshold that many cities across the country had already breached by the fourth week of April. States such as Maharashtra, Bihar, Uttar Pradesh, West Bengal, and Odisha are bearing the worst of it. The situation has grown so dire that school schedules have been revised in several states, the duty hours of traffic police altered in Maharashtra and Chhattisgarh, and workers prohibited from outdoor labour during peak afternoon hours. Water sprinklers have been deployed on roads, at bus stands, and at railway stations in an effort to provide relief.

The causes are multiple and reinforcing. Harsh pre-monsoon sunlight, reduced snowfall in the Himalayan region, rising sea surface temperatures, and the weakening of wind systems that once brought seasonal cooling have all contributed. Dry winds are obstructing cloud formation, reducing the likelihood of rain. With no signs of pre-monsoon showers in sight, intense heat may persist well into the coming weeks.

This is not merely a natural fluctuation in weather. It is a direct consequence of man-made climate change. The Climameter report, which analysed heat waves from 1950 to the present using data from the European meteorological organisation Copernicus, found that the current heat wave is four degrees Celsius hotter than historical ones — a difference attributed entirely to human activity, with natural causes playing a negligible role. In the last 80 years, the number of extremely hot days in major cities worldwide has tripled. In the 1940s, roughly 15 days of extreme heat were recorded annually on global sea surfaces; today, that figure has multiplied many times over.

The consequences for human life are devastating. More than 150,000 people die worldwide each year due to heat waves, and more than one-fifth of those deaths occur in India. China and Russia follow, each accounting for approximately 14 percent of heat-related fatalities. A study by ETH Zurich has warned that if adverse weather conditions continue to worsen, the death toll could climb steeply — over the last two decades alone, the figure has approached one hundred thousand. The effects on the human body range from dehydration and heat stroke to death. Young children, the elderly, women, those with chronic lung conditions, and outdoor labourers are at greatest risk. It is estimated that 80 percent of India's population and 90 percent of its land area could come within the range of intensifying heat waves. If this challenge is not addressed in time, India will face serious obstacles in achieving its sustainable development goals.

A research paper from Harvard University's Salata Institute for Climate and Sustainability makes clear that the worst of India's heat crisis still lies ahead. Scientists at Columbia University have warned that if fossil fuel companies continue emitting at current rates through 2050, heat could reach lethal levels by 2100, claiming millions of lives. Every additional million tonnes of carbon released is estimated to trigger 226 more heat wave incidents worldwide. The United Nations Climate Committee has stated that a 43 percent reduction in carbon emissions by 2030 is necessary to limit global warming to 1.5 degrees Celsius. Failing that, the Earth's temperature could rise by four degrees Celsius by the end of this century.

This, then, is not the story of a difficult summer. It is a signal of a catastrophic long-term trajectory. The monsoon will bring temporary relief, but the underlying intensity of heat will only grow. Immediate measures are necessary but insufficient. Reducing carbon emissions, expanding forest cover, accelerating the shift to renewable energy, and embedding green spaces into urban planning are no longer optional — they are imperatives. The fact that nineteen of the world's hottest cities are in India is a record of shame, and reversing it will require coordinated action from government, industry, and citizens alike. The cost of inaction will be borne not by us alone, but by every generation that follows.

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*Independent writer