The city of Churu, Rajasthan, recorded 47.0°C at 10:32 AM local time on Tuesday. By noon, the mercury had climbed further. This is not an isolated event. Heatwaves across India and Pakistan have become the norm rather than the exception, and British climate experts are now raising urgent warnings that the entire diurnal cycle is being disrupted.
Dr. Anjali Mehta of the Grantham Institute at Imperial College London described the situation as a fundamental breakdown of the planet’s thermal regulation. “Mornings and nights no longer exist in the way we understood them. The residual heat from the day carries over into the night, and the sun rises onto already scorched ground. There is no respite.”
Data from the India Meteorological Department confirms this. Minimum temperatures in cities like Delhi and Jaipur have risen by 2.5 to 3.0°C over the past three decades. The number of tropical nights, where the temperature does not fall below 20°C, has increased by 40% in the last decade alone. When night offers no cooling, the human body cannot recover. The result is a spike in heat stroke cases, cardiovascular stress, and mortality.
The physical mechanism is straightforward. Carbon dioxide and other greenhouse gases trap longwave radiation that would otherwise escape to space. This energy accumulates in the lower atmosphere and ocean. During a heatwave, the boundary layer becomes superheated and the usual cooling from nocturnal radiative loss is suppressed by the increased downward infrared flux from the warmer, moister air. The planet is effectively wrapped in an extra blanket that never fully lifts.
British scientists from the Met Office Hadley Centre have been monitoring the unfolding crisis. Their latest projections show that, under current emissions trajectories, parts of South Asia will exceed the threshold of “physiological survivability” for humans within two decades. The wet bulb temperature, a measure of heat and humidity combined that indicates the body’s ability to cool itself through sweating, is expected to regularly exceed 35°C. At that point, even healthy people in the shade with unlimited water and no clothing can die within six hours.
“We are seeing changes that should be decades away,” said Professor Tim Palmer of Oxford University. “The models are catching up with reality, and it is grim. The loss of the diurnal cycle in these regions is a clear signal that the Earth system is shifting to a new, hotter state. It is not an exaggeration to say we are watching the habitability of one of the most populous regions on Earth being stripped away in real time.”
The implications for agriculture are severe. Cereal crops and pulses rely on cool nights to minimise respiration losses. Without that cooling, grain yields drop precipitously. India’s wheat harvest in 2022 was already affected by an early heatwave, and this year will be worse. Food prices are climbing, and malnutrition will follow.
The response from policymakers remains inadequate. While the Indian government has introduced heat action plans, these are bandages on a haemorrhage. The root cause is the continued burning of fossil fuels. The only meaningful solution is a rapid, just transition to a zero-carbon energy system. Every fraction of a degree of warming we can avoid reduces the severity of these events.
I ask you to listen to the data. This is not a story about politics or opinion. It is about the physical reality of a planet that is warming, and about the people who are already paying the price. We have the technology to change course: solar, wind, storage, and efficiency. What we lack is the collective will.
The sun will rise tomorrow over Churu, and it will be hot. But it does not have to be this hot, and it does not have to be this way forever. The window to act is closing, but it is not yet shut.
