Waste heat, the hidden source of rising temperatures in modern cities

As North India heads into another punishing summer, Punjab is already feeling the strain. Farmers worry about heat stress on wheat, residents brace for spending longer afternoons indoors and cities prepare for rising electricity demand, worsening traffic congestion and heat radiating from concrete. When we talk about climate change, we usually focus on greenhouse gases (GHGs). Yet another form of warming affects urban residents every day, but rarely receives much attention: anthropogenic heat, or waste heat.Waste heat is the heat released by vehicles, air-conditioners, factories, power plants, diesel generators and countless machines that keep modern life running. GHGs remain the main source of global warming, but waste heat makes local conditions worse, especially in dense urban areas where buildings, roads and human activity are tightly packed. Climate change is heating the planet, while waste heat is making cities even harder to live in.This is not a minor issue in a rapidly urbanising and energy-hungry country like India. Every time we burn fuel, run machinery or cool a building, much of that energy eventually escapes into the surrounding environment as heat. Thermal power plants lose a substantial portion of their energy during electricity generation and many industrial processes, from steel-making to oil refining, do the same. Conventional vehicles are also inefficient: much of the fuel they burn becomes heat rather than motion.At the same time, concrete, asphalt and glass absorb solar radiation during the day and release it slowly after sunset. This is the familiar urban heat island effect. Waste heat adds another layer. The result is that cities often remain warmer than nearby rural areas, particularly at night, when relief should normally come.Chandigarh, with more registered vehicles than residents, illustrates how transport itself becomes a generator of heat. Ludhiana's industrial activity, Mandi Gobindgarh's furnaces and the expansion of commercial and residential cooling across urban Punjab all add to the heat burden. Even when the source goes unnoticed, its effects are felt in hotter streets, warmer nights and greater outdoor discomfort.Air conditioning is perhaps the clearest example of this paradox. Air-conditioning is increasingly essential, especially for the elderly, children, patients and those working indoors. But while an AC cools one room, it releases heat outside. When thousands of such units run at once in a dense neighborhood, they can make surrounding streets and building exteriors even hotter.The same is true of transport. India now has well over 40 crore registered vehicles, most powered by internal combustion engines. In heavy traffic, engines idle, exhaust systems run hot, brakes generate frictional heat and crowded roads radiate warmth back into the air. You can feel it while standing near a busy junction in summer. It is a lived reality.Our digital lifestyles also carry a hidden thermal cost. Data centres, server rooms, telecom infrastructure and their cooling systems consume large amounts of electricity and release much of it as heat. As India's digital economy expands, this footprint will grow. Punjab too is becoming more integrated into this infrastructure through IT parks, commercial expansion and rising demand for uninterrupted digital services.The public-health consequences are serious. Higher temperatures increase the risk of heat exhaustion, dehydration, cardiovascular stress and sleep disruption. Outdoor workers, street vendors, delivery workers, traffic police, construction labourers and factory workers bear the brunt. Poorer households suffer disproportionately because they often have less access to cooling, shade, reliable electricity and healthcare. When nights remain hot, the body has less chance to recover, making prolonged periods of heat more dangerous.This is why waste heat deserves greater attention in public discussion. It is not separate from development; it is one of the hidden costs of the way we develop. Unless cities begin to plan for it, the problem will grow alongside rising incomes, traffic, industrial growth and increasing demand for cooling.Denmark, Sweden and Finland already use waste heat from power plants, industries and data centres to warm homes, while some Indian industries use waste heat to generate electricity.Punjab has an opportunity to respond early and intelligently. Industrial waste-heat recovery can help factories reuse energy instead of releasing it as waste heat into the environment. Better building design, insulation, reflective roofs and efficient appliances can reduce the need for excessive cooling. More trees, shaded bus stops, ventilated public spaces and water access points can make summer streets safer. Stronger public transport and less dependence on private vehicles would reduce both emissions and heat on the roads.The state can also link heat management to broader environmental priorities. Rooftop solar and canal-top solar can reduce dependence on thermal power. Cleaner biomass use would be far preferable to open burning of crop residue. Local governments can incorporate heat risk into building rules, transport planning and summer preparedness instead of treating heat as merely a seasonal inconvenience.The larger lesson is simple. Energy does not disappear after it powers our homes, vehicles and industries. Much of it returns to the environment as heat. In crowded cities that heat accumulates around us: in the air we breathe, on the roads we walk, and in nights that no longer cool down enough. If Punjab wants its cities to remain livable in the decades ahead, it must pay attention not only to the invisible gases warming the planet, but also to the heat building up around us. Waste heat may receive less attention than climate change, but for millions of urban residents, it is one of the most immediate ways climate stress is felt.Recognising and managing this hidden heat may prove essential if our cities are to remain habitable in a warming world.

Waste heat, the hidden source of rising temperatures in modern cities

It is the heat released by vehicles, ACs, factories, power plants, diesel generators and machines that keep modern life running.

SS Sekhon

Waste heat, the hidden source of rising temperatures in modern cities

It is the heat released by vehicles, ACs, factories, power plants, diesel generators and machines that keep modern life running.

SS Sekhon

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