By dawn in Ahmedabad the air already shimmers. Engines idle, radiating heat the city cannot shed. Factory whistles sound at noon, not to start shifts but to end them. Across the tropics the same routine repeats. Work, once measured in hours, is now rationed by degrees.

The International Labour Organization (ILO, 2025) reckons extreme heat has erased 2.2 percent of global working hours—some 80 million full-time jobs. By 2030 the bill may reach US $2.5 trillion in lost output. Economists call it productivity decline; labourers call it summer.

The economics of overheating

Every extra degree costs twice—once to crops, once to people. The World Bank Climate and Productivity Atlas (2025) finds tropical farm yields drop 4–6 percent per °C above 30. South Asia bears half the global total of heat-related labour losses. India’s rural economy, employing two in five workers, may shed 34 million jobs by 2030. Factories are hardly cooler: in Dhaka’s garment zones wet-bulb temperatures hit 33 °C, brushing the limit of human endurance. Beyond 35 °C the body stops cooling itself; output stops with it. The IMF Regional Outlook (2025) dubs this “thermal drag”—growth that melts before it reaches the ledger.

The biological ceiling

Physiology now defines the workday as firmly as markets do. At 35 °C wet-bulb, even rest is risky after a few hours. The WHO (2025) attributes 480,000 deaths a year to heat stress; kidney failure and dehydration seldom appear in GDP tables. Women fare worst. The ILO Gender and Work Report (2025) shows female fieldworkers lose one-fifth more hours than men because household chores peak at midday—the hottest part of poverty. One Karachi textile worker put it crisply: “We need hours when the sun forgives us.”

Where the mercury rises fastest

South Asia. Average summer temperatures across the Ganges basin and Sindh have risen 1.8 °C since 1980; extreme-day counts have tripled (NASA GISTEMP, 2025). Twenty-three Indian states are now classed “heat-wave-prone”, up from nine a decade ago.

Africa’s Sahel. Planting seasons shorten by a month each decade. The AfDB (2025) expects rural incomes to fall 15 percent by 2035 without new irrigation. Cities like Dakar and Bamako grow denser and hotter: heat islands with rent.

Southeast Asia & the Gulf. Bangkok’s heat index has topped 50 °C. In the Gulf, where migrants build skylines, governments impose midday work bans from June to September—a modest triumph of scheduling over physics.

Adaptation as industry

Some states are learning to engineer shade. India’s Cool Roofs Mission coats rooftops and cuts indoor heat by five degrees. Vietnam tests solar cooling pods for assembly lines. Kenya’s climate labs sync irrigation with satellite forecasts. The private sector has noticed: cooling fabrics, off-grid chillers, heat-hardy machinery—new export lines. The UN Environment Programme (2025) calls it “the adaptation economy”. Capital, unlike climate, adapts quickly.

Politics of the thermometer

Adaptation costs money the hottest countries seldom have. The UNFCCC Adaptation Gap (2025) counts only 11 cents delivered for every dollar of climate loss. The Loss and Damage Fund has released $2 bn of $100 bn pledged—a rounding error beside $1 tn in fossil-fuel subsidies. Laws help; enforcement is patchy. Thailand’s occupational heat limits, Nigeria’s micro-insurance and Colombia’s tax credits for cooled public spaces suggest progress.

Cities that refuse to melt

Urban design is becoming the quiet arm of climate policy. Singapore links tree canopies to wind paths and cools surfaces by two degrees. Medellín’s green corridors shave 2.5 °C off districts. Kigali and Dhaka experiment with bamboo roofs; Riyadh with reflective pavements. Architects call it “thermal democracy”—the right to a liveable micro-climate regardless of income.

When night becomes the new day

At dusk factories reopen; night is the new shift. Economists once measured productivity per hour. Soon they may measure it per tolerable degree. Technology can delay exhaustion; only policy can share relief. In the coming labour economy, success will belong not to those who sweat hardest, but to those who sweat least—and plan early.

Policy takeaway: Make adaptation automatic: codify rest-work ratios at high wet-bulb readings, pre-fund parametric payouts, and bake cool-roof and shade standards into building codes.

Sources. ILO Global Heat Stress Dataset v2.1 (2025); World Bank Climate & Productivity Atlas (2025); IMF Regional Outlook (2025); WHO Global Heat Mortality Review (2025); UNEP Adaptation Economy (2025); UNFCCC Adaptation Gap (2025); AfDB African Climate Resilience Brief (2025).