Extreme Heat Now a ‘Regular Reality’ in India, Pakistan: Study

Heat on the scale of a recent heatwave in South Asia is now likely to occur once every five years owing to human-induced warming.

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Baking hot temperatures are becoming the norm in many South Asian nations, according to a new study.

A group of researchers with World Weather Attribution analyzed historic observational data and used climate model simulations to quantify the effect of human-caused warming on a heatwave that swept across India and Pakistan in late April and early May. The event brought temperatures exceeding 46C to several cities, killing at least 37 people in India and 10 in Karachi, Pakistan’s largest city.

Such extreme heat, researchers say, is three times as likely to occur on a warming planet compared to pre-industrial climate – now expected once every five years. This makes it no longer an extreme event, but rather a “regular reality,” said Mariam Zachariah, Research Associate in Extreme Weather and Climate Change at Imperial College London and one of the researchers involved in the study.

“Temperatures are being pushed to dangerous levels, making life-threatening conditions more common for hundreds of millions in India and Pakistan,” said Zachariah.

Heat is extremely dangerous for humans as it compromises physiological processes meant to keep the body cool, heightening the risk of heatstroke and other heat-related illnesses. It can be life-threatening if not promptly treated.

The urban and rural poor are often disproportionately exposed to heat due to informal housing arrangements and lack of access to cooling. People with disabilities, older adults, children, unhoused people, and incarcerated people are also more vulnerable.

Outdoor workers like street cleaners and construction workers are another highly vulnerable category. Over 70% of the global workforce – 2.4 billion people – are now at high risk of extreme heat, with as many as 19,000 workers dying from heat-related illnesses each year, according to the International Labor Organization

Hotter and Longer

The increase in extreme heat is a direct result of our warming planet, which is driven by greenhouse gases that trap heat in the atmosphere. This raises Earth’s surface temperature, leading to longer and hotter heatwaves. Every heatwave in the world is now made stronger and more likely to happen because of human-caused climate change. 

That is the case in South Asia, where the hot pre-monsoon period is becoming both hotter and longer. According to the World Weather Attribution analysis, an event like the recent heatwave in India and Pakistan would have been about 1C cooler in a pre-industrial climate.

While a 1C increase might seem negligible on a household thermostat, in the context of global climate, it represents a massive infusion of energy into the atmosphere. This small shift in the average temperature fundamentally alters the frequency of extremes: it pushes the entire distribution of weather events toward the heat, making what were once rare ‘century-level’ events into frequent occurrences.

It is also important to note that for every 1C increase in atmospheric temperature, air can hold about 7% more moisture. In places like India and Pakistan, where heat is rarely dry, this means that one extra degree can push humidity levels past the threshold of human tolerance, turning a manageable heatwave into a lethal health crisis.