India knows heatwaves well. What is the new threat called heat storm?

India is no stranger to scorching summers, with temperatures soaring above 45°C in parts of the country during severe heatwaves. But climate change is fuelling a bigger, more persistent form of extreme heat that can spread across vast parts of the planet and last for months.A new investigation by news agency Reuters, has labelled these events “heat storms”, a term meant to capture how heatwaves have grown in size and duration. A man takes rest during a heatwave in New Delhi. (Photo: PTI) The investigation analysed hourly global temperature data dating back to 1960 and consulted more than two dozen climate researchers.The findings suggest that extreme heat is no longer just a series of isolated hot spells, and that large heat events can overlap, creating prolonged spells of soaring temperatures across the planet. WHAT EXACTLY IS A HEAT STORM?Reuters, in its analysis, defined a heatwave as five or more consecutive days of unusually high temperatures, and used the term “heat storm” for the largest events, which cover at least 1% of Earth's surface at their peak.This is a new category developed by the news agency, and not an official weather classification. A table showing the strongest heat storms recorded. (Graphic: Reuters) The investigation found that heat storms averaged about five a year in the 1960s, but in the current decade, that figure has risen to around 102 a year.The largest event identified, named Heat Storm Vera, lasted 367 days in 2023 and 2024 and affected nearly 85% of the planet at some point during its lifetime. Unsurprisingly, 2024 broke the record by becoming the hottest year ever recorded.WHY ARE HEAT STORMS BECOMING MORE COMMON?The rise in the sweeping heat was found to be closely proportionate to the increase in greenhouse gases, including carbon dioxide, which trap heat in the atmosphere.Carbon dioxide levels have risen by more than 30% since the 1960s, and over the same period, the average area of the planet covered by heatwaves and heat storms increased more than twelvefold, according to the analysis.Supersized heat waves used to be rare. No longer. A Reuters data-driven examination of global temperatures reveals the emergence of what we call heat storms. They now swarm the planet, upending life around the world. https://t.co/6oOP6jpKYz https://t.co/qbRQbRRPXQ— Reuters (@Reuters) October 20, 2026The investigation also identified a chain of overlapping heat storms that has continued since July 2008, meaning the planet has not had a break from at least one such event somewhere in the world.For India, where heatwaves are becoming a growing concern with each passing year, threatening public health, agriculture and water supplies, the analysis carries a particular significance, and demands attention.The Indian Meteorological Department (IMD) declares heatwave conditions using temperature thresholds and how far temperatures rise above what is normal for a location. People cover their faces to protect themselves from a heatwave in Prayagraj. (Photo: PTI). A “heat storm” is different and doesn't fit into the current mould as it describes the sheer scale of a heat event across the globe, rather than certain thresholds being met.As Earth continues to warm, extreme heat is becoming harder to escape, and is becoming an issue that could define what the future holds for vulnerable nations like India.- Ends