Vicious cycles of extreme heat, and where they can be broken
21 vicious cycles in which extreme heat feeds itself, traps people or overwhelms institutions, with where each one plays out in Asia, the evidence, and the actions that could break it.
Open the cycles on the interactive mapLoops that feed the heat itself
The global cooling loop
Cooling powered by fossil fuels adds to the warming that makes us need more cooling.
The summers feel longer, so she buys a second air conditioner for the shop. It keeps her customers comfortable, and the power that runs it adds a little more to the warming that made her buy it.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (World): 3×. The energy used for cooling could triple by 2050 as air conditioners grow from 1.6 billion to 5.6 billion, unless they become more efficient. International Energy Agency, 2018
In Southeast Asia (Southeast Asia): 40m → 300m. air conditioners in Southeast Asia between 2017 and 2040, half of them in Indonesia, unless efficiency improves. Cooling could then make up as much as 30% of the region’s peak electricity demand. International Energy Agency, 2019
Where it plays out: Fast-growing cities across South and Southeast Asia, where air-conditioner ownership is rising quickly.
Where it breaks: Clean, efficient cooling
Solutions to try: Minimum energy performance standards for cooling appliances (cuts the electricity each air conditioner needs, so the same cooling adds less warming); Transition to purpose-designed low-GWP room AC (moves to refrigerants that warm the planet far less when they leak); Solar-reflective roof coatings (keeps buildings cooler without power, so less cooling is needed at all); National cooling action plans and cross-sector implementation roadmaps (plans the country’s cooling demand as a whole, so efficiency and clean power keep pace with growth). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Southeast Asia’s air conditioners could rise from 40 million in 2017 to 300 million in 2040, half of them in Indonesia. Without more efficient units, cooling could drive as much as 30% of the region’s peak electricity demand. International Energy Agency, 2019
- The world’s stock of air conditioners is set to grow from 1.6 billion to 5.6 billion by 2050, and the energy they use to triple, unless efficiency improves. International Energy Agency, 2018
The dry-soil loop
Heat dries the soil. Dry soil can’t cool itself, so the land heats up faster.
After weeks without rain, the soil in his fields cracks and the afternoons feel hotter than they used to. Without moisture to cool it, the ground bakes faster each day, and the next dry spell starts sooner.
A composite, drawn from the evidence for this cycle. Not a real person.Where it plays out: Rain-fed farmland on the Indian subcontinent and in mainland Southeast Asia during the hot, dry pre-monsoon months.
Where it breaks: Deep emission cuts, Keep water in the soil
Solutions to try: Organic residue mulch for cooler crop root zones (keeps moisture in the soil, so it can keep cooling itself); Shade-tree agroforestry for crops (shades the ground and holds water in the land); Permeable pavements retaining rainfall for evaporative surface cooling (in towns, lets rain soak in instead of running off, so the ground stays moist longer). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Reviews the evidence that dry soils amplify hot temperatures: with less water to evaporate, more of the sun’s energy goes into heating the air. Seneviratne et al., Earth-Science Reviews, 2010
The melting-ice loop
Heat melts ice. Darker ground and water absorb more sunlight, and the melting speeds up.
The snowfield her family has used for generations shrinks a little each year. The bare rock that replaces it holds the sun’s heat, and the edge of the ice retreats faster than she remembers.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Hindu Kush Himalaya): 30–50%. of the region’s glacier ice could be gone by 2100 at 1.5–2 °C of warming, after melting 65% faster in the 2010s than the decade before. ICIMOD, 2023
In Southeast Asia (Papua, Indonesia): 99%. of the glacier area on Puncak Jaya, Southeast Asia’s last tropical ice, has gone since 1850. Only about 0.17 km² was left in 2024, and it will very likely disappear around 2030. Ibel, Mölg and Sommer, The Cryosphere, 2025
Where it plays out: The Hindu Kush Himalaya, whose snow and ice feed rivers such as the Indus, Ganges and Brahmaputra.
Where it breaks: Deep emission cuts, Cut black carbon
Solutions to try: Only cutting the warming slows this loop. These cut cooling’s own share of it; nothing local stops the melting. Minimum energy performance standards for cooling appliances (cuts the electricity, and so the emissions, each air conditioner needs); Transition to purpose-designed low-GWP room AC (moves to refrigerants that warm the planet far less); National cooling action plans and cross-sector implementation roadmaps (plans cooling growth so it adds as little warming as possible). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Puncak Jaya’s glaciers, the last in Southeast Asia, have lost more than 99% of their area since 1850 and about 65% since 2018. About 0.165 km² remained in 2024, and they will very likely be gone around 2030. Ibel, Mölg and Sommer, The Cryosphere, 2025
- Glaciers lost ice 65% faster in the 2010s than in the decade before. At 1.5–2 °C of warming, glaciers across the region lose 30–50% of their volume by 2100. ICIMOD, 2023
The wildfire loop
Heat dries forests into fuel. Fires release carbon and strip away the trees that cool the land.
The undergrowth he walks through each morning is drier than it used to be. When a fire comes, it takes the trees that kept the valley cool, and the land beneath them dries out further.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (World): +50%. more extreme wildfires are projected by the end of the century, and up to 14% more by 2030. UNEP and GRID-Arendal, 2022
In Southeast Asia (Indonesia): US$16.1 billion. was the cost to Indonesia of the forest and peatland fires of June to October 2015. World Bank, 2016
Where it plays out: The dry-season burning belt of northern Thailand, Myanmar and Laos, and Indonesia’s peatlands.
Where it breaks: Deep emission cuts, Fire-smart landscapes
Solutions to try: Breaking this loop needs forest and fire management, which this library does not yet cover. These protect people while it turns. Locally calibrated impact-based heat-warning triggers (warns people early, based on what the heat will do locally, not just the temperature); Pre-agreed heat anticipatory action and forecast finance (releases agreed money before the worst days, rather than after); Pooled pre-arranged finance for heat action (shares the cost of bad years across places, so one disaster does not empty a budget). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Indonesia’s forest and peatland fires of June to October 2015 cost the country an estimated US$16.1 billion. World Bank, 2016
- Climate change and land-use change are making wildfires worse. Extreme fires are projected to rise by up to 14% by 2030 and 50% by the end of the century. UNEP and GRID-Arendal, 2022
Loops that break the systems we rely on
The cooling trap
Air conditioning heats the street, and a hotter city needs even more air conditioning.
Air conditioners hum above her stall, blowing their heat into the lane where she works. The hotter the lane gets, the more of them switch on, and the afternoon becomes harder to bear.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Singapore): Up to 7 °C. warmer: how much hotter Singapore’s commercial centre has measured than its outskirts on calm, clear nights. Cooling Singapore, citing Chow and Roth, 2006
Where it plays out: Dense, high-rise city cores such as Hong Kong, Bangkok and Metro Manila.
Where it breaks: Cool by design, Green, cool cities
Solutions to try: Solar-reflective roof coatings (keeps rooms cooler without power, so less air conditioning runs); Street trees and retained mature canopy (shades and cools the street the air conditioners heat); Efficient BLDC ceiling fans (gives comfort for a fraction of the power and waste heat of air conditioning); Coordinated fans and higher-setpoint air conditioning (lets air conditioning run at a higher setting with a fan, cutting its load). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- In a Phoenix heatwave, waste heat from air conditioners raised night-time air temperatures by more than 1 °C in parts of the city. Salamanca et al., Journal of Geophysical Research, 2014 (summary by Arizona State University)
- China, India and Indonesia are expected to account for half of the world’s air conditioners by 2050. International Energy Agency, 2018
- Chennai’s built-up area more than doubled between 2000 and 2020, and night-time land surface temperatures in its urban areas run about 2 °C higher than on its peri-urban edges. Tamil Nadu State Planning Commission, 2024
- Singapore’s commercial centre has measured up to about 7 °C warmer than its outskirts on calm, clear nights. Cooling Singapore, citing Chow and Roth, 2006
The energy–water loop
Water systems need power and power plants need water. In a heatwave, each failure deepens the other.
During a heatwave the power fails, so the pumps stop and taps run dry. Meanwhile the power station upstream is short of water to cool itself, and the cuts come more often.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (India): 14 TWh. of electricity lost in India in 2016 because thermal power plants ran short of water. World Resources Institute, 2018
In Southeast Asia (Vietnam): US$1.4 billion. was the World Bank’s early estimate of what northern Vietnam’s power cuts cost in May and June 2023, about 0.3% of GDP, after heatwaves pushed up demand and dried hydropower reservoirs. World Bank estimate, reported by AFP via The Manila Times, 2023
Where it plays out: Coal-fired power plants along water-stressed rivers in India.
Where it breaks: Power that doesn’t need water, Backup power for water
Solutions to try: Solar/hybrid pumping with water storage for resilient water service (keeps water pumping on solar or stored power when the grid fails); Heatwave grid-readiness planning and emergency resource coordination (prepares the grid and its water supply before the heat season); Demand response and scheduled flexible loads to relieve heat-period peaks (moves flexible loads off the peak, so the grid is less likely to fail); Minimum energy performance standards for cooling appliances (lowers the peak itself, by making every air conditioner use less). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Heatwaves in May and June 2023 pushed up demand while hydropower reservoirs ran low, and rolling blackouts hit northern Vietnam. The World Bank’s early estimate put the cost at about US$1.4 billion, roughly 0.3% of GDP. World Bank estimate, reported by AFP via The Manila Times, 2023
- 14 of India’s 20 largest thermal utilities shut down at least once for lack of water between 2013 and 2016. Water shortages cost 14 TWh of power in 2016. World Resources Institute, 2018
The groundwater loop
Dry fields need more water, so farmers pump harder, aquifers fall and the shortage deepens.
As the fields dry, he pumps for longer each season. His neighbours do the same, the water table drops, and the well has to be dug deeper just to keep the crop alive.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (India): 109 km³. of groundwater lost from Rajasthan, Punjab and Haryana in six years (2002–2008), mainly to irrigation, while rainfall stayed close to normal. Rodell, Velicogna and Famiglietti, Nature, 2009
In Southeast Asia (Mekong delta, Vietnam): 2.5 cm+. a year: how fast parts of the Mekong delta are sinking as its aquifers are pumped down. Minderhoud et al., Environmental Research Communications, 2020
Where it plays out: Punjab and Haryana in northwest India, where groundwater tables have been falling for decades.
Where it breaks: Smart irrigation and groundwater rules
Solutions to try: Organic residue mulch for cooler crop root zones (keeps water in the root zone, so fields need less pumping); Shade-net structures for crop microclimate protection (cuts the heat and water stress on crops); Shade-tree agroforestry for crops (shades crops and soil, so less water is lost). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Groundwater pumping has sped up the sinking of the Mekong delta, to more than 2.5 cm a year in some areas. Minderhoud et al., Environmental Research Communications, 2020
- Satellites show Rajasthan, Punjab and Haryana lost 109 km³ of groundwater between 2002 and 2008, mainly to irrigation, while rainfall stayed close to normal. Rodell, Velicogna and Famiglietti, Nature, 2009
The dying-green loop
Heat and drought kill city trees. Without their shade the streets get hotter, and hotter streets kill more trees.
She waters the street trees she planted years ago, but a hot, dry summer still kills some of them. Without their shade the pavement heats up, and the trees that remain struggle even more.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (164 cities worldwide): 76%. of urban tree and shrub species in 164 cities could face temperatures beyond their natural range by 2050, up from 56% today. Risk is highest in cities such as New Delhi and Singapore. Esperon-Rodriguez et al., Nature Climate Change, 2022
Where it plays out: Hot, fast-growing cities such as New Delhi and Singapore, where every urban tree species studied is at risk from rising heat.
Where it breaks: Keep city trees alive
Solutions to try: Street trees and retained mature canopy (protects mature canopy and plants trees that can survive the heat); Community maintenance arrangements backed by public/service support (pays for watering and care through the dry season, when young trees die); Blue-green river corridors and naturalised drainage landscapes (keeps water in the city’s landscape, so trees are not left dry); Permeable pavements retaining rainfall for evaporative surface cooling (lets rain reach tree roots instead of draining away). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Of 3,129 tree and shrub species in 164 cities, 56% already face temperatures beyond those in their natural range, rising to about 76% by 2050 under a mid-range warming scenario. Risk is highest in low-latitude cities such as New Delhi and Singapore. Esperon-Rodriguez et al., Nature Climate Change, 2022
- Drought stops urban trees from cooling through transpiration. In one Berlin park more than 500 of 870 new trees died within ten years despite watering, and Berlin cut about 44,000 street trees between 2012 and 2019 while planting about 18,000. Hansen et al., chapter 10 in Nature-Based Solutions for Cities, 2023
- Tree shade sharply lowers the radiant heat people feel by day, which is the cooling lost when trees die. Middel et al., Bulletin of the American Meteorological Society
The overwhelmed-clinic loop
Heat illness floods clinics. Overwhelmed clinics treat people later, and more cases become severe.
On the hottest days the waiting room fills with people who are dizzy, vomiting or confused. With so many waiting, some are seen late, and by then their illness has become more serious.
A composite, drawn from the evidence for this cycle. Not a real person.What breaking it saves (Ahmedabad, India): 1,190. deaths a year were estimated to be avoided after Ahmedabad’s heat action plan prepared hospitals and warned the public. Hess et al., Journal of Environmental and Public Health, 2018
Where it plays out: District and city hospitals during South Asia’s pre-monsoon heatwaves.
Where it breaks: Heat action plans, Heat-ready health services
Money arranged before heat: 13 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Heat-ready clinic protocols and staff capability (prepares staff and protocols to treat heat illness early, before it turns severe); Heat surge staffing, triage and referral coordination (adds staff, triage and referral for heat surges); Resilient power for health-facility cooling and cold-chain loads (keeps the clinic cool and its medicines safe when the power fails); Locally calibrated impact-based heat-warning triggers (warns ahead, so fewer people reach the clinic already severely ill). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Heat-related deaths among people over 65 reached a record 167% above the 1990s level in 2023. Lancet Countdown, The Lancet, 2024
- After Ahmedabad’s heat action plan prepared hospitals and warned the public, an estimated 1,190 deaths a year were avoided. Hess et al., Journal of Environmental and Public Health, 2018
Loops that trap people
The poverty–heat trap
People who can’t afford to stop working fall ill. Illness costs income, and lost income makes stopping even less affordable.
He knows the midday sun is dangerous, but stopping means losing a day’s pay. When the heat makes him ill, he loses several days instead, and the next week he cannot afford to rest at all.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Bangladesh): US$1.78 billion. Heat-related illness cost Bangladesh 250 million workdays in 2024, about 0.4% of its GDP. World Bank, 2025
In Southeast Asia (Bangkok, Thailand): 75%. of home-based workers in Bangkok lost at least a day’s work a month to their own or a family member’s heat illness. Nearly 80% of informal workers surveyed cut their hours because of heat. WIEGO and HomeNet Thailand, 2025
Where it plays out: Construction sites, brick kilns, farms and street markets across South and Southeast Asia.
Where it breaks: Heat-safe work, Income protection in heatwaves, Social protection floors
Money arranged before heat: 24 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Paid rest, shade and drinking-water protocols (gives paid rest, shade and water, so stopping does not cost a day’s income); Reschedule work and reduce peak-heat task exposure (moves heavy work away from the hottest hours); Parametric heat insurance for income shocks (pays out when heat crosses a set level, replacing lost income); Scale up existing social protection for heat risk (tops up existing payments in a heatwave, so families are not forced to work through it). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- In a survey of informal workers in Bangkok, nearly 80% had cut their hours because of heat, and 75% of home-based workers lost at least one day of work a month to their own or a family member’s heat illness. WIEGO and HomeNet Thailand, 2025
- Across 2.7 million firms in 23 advanced economies, including Japan and Korea, ten extra days above 35 °C cut yearly labour productivity by 0.3%, and over 1.5% above 40 °C. Very humid places lost 0.75%, more than double the average. Korea has already lost about 0.15% of productivity to added heat since the early 2000s. OECD Economics Department, Working Paper No. 1828, 2024
- Up to three-quarters of India’s workforce, about 380 million people, depend on heat-exposed labour, work that produces nearly half of the country’s GDP. World Bank, 2022, reported by Down To Earth
- Heat stress is projected to cost 2.2% of all working hours by 2030, equal to 80 million full-time jobs. South Asia is among the worst hit, losing about 5% of working hours. International Labour Organization, 2019
- Heat exposure put a record 512 billion potential labour hours at risk in 2023, with potential income losses of US$835 billion. Lancet Countdown, The Lancet, 2024
- Heat-related illness cost Bangladesh 250 million workdays in 2024, worth up to US$1.78 billion, about 0.4% of GDP. Since 1980 the ‘feels-like’ temperature has risen by 4.5 °C. World Bank, 2025
The medical-debt trap
Treatment costs push families into debt. Debt removes any option to rest, and working through the heat brings more illness.
Treatment for heat illness costs more than they had saved, so they borrow. Repaying the loan means everyone works longer hours through the hot months, and someone else falls ill.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (India): 29 million. Indian households faced catastrophic spending on medicines alone in 2011–12. This is the scale of the trap from all illness, not heat alone. Selvaraj, Farooqui and Karan, BMJ Open, 2018
In Southeast Asia (Cambodia): US$5,800+. was the average microloan in Cambodia in 2024, over four times the median income per person. This is all borrowing, not heat alone, but it is the debt families draw on when illness or a lost harvest strikes. Human Rights Watch, 2025
Where it plays out: Households without health insurance, where most medical costs are paid out of pocket.
Where it breaks: Heat-safe work, Free care for heat illness
Money arranged before heat: 9 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Reduce financial barriers to heat-related care (removes the cost of heat-related care, so treatment does not create debt); Heat-triggered cash outside an insurance contract (pays cash when heat strikes, so families need not borrow); Scale up existing social protection for heat risk (uses existing social payments to reach families quickly in a heatwave); Community-health-worker heat education and referral (helps people spot heat illness early, before treatment becomes expensive). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Cambodia’s average microloan was over US$5,800 in 2024, more than four times the country’s median annual income per person. Human Rights Watch, 2025
- Medicine costs alone were catastrophic for 11.2% of Indian households in 2011–12, about 29 million households. Selvaraj, Farooqui and Karan, BMJ Open, 2018
- In a survey of more than 2,000 residents of five cities, heat harmed health, cut incomes and working hours, and pushed some households towards high-interest loans. Women and people with disabilities faced the hardest trade-offs between health, work and care. American Red Cross, Red Cross Red Crescent Climate Centre, Nepal Red Cross Society and Bangladesh Red Crescent Society, 2026
The energy-poverty trap
People who can’t afford to cool fall ill. Illness brings debt, and debt puts cooling even further out of reach.
She has a fan but rations it to keep the electricity bill down. On a hot night she falls ill, the cost of care adds to what she owes, and next summer she can afford to run the fan even less.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (World): 1.12 billion. of the world’s rural and urban poor are at high risk because they lack access to cooling. Sustainable Energy for All, 2023
Where it plays out: Tin-roofed informal settlements in cities such as Dhaka, Karachi and Mumbai.
Where it breaks: Free care for heat illness, Affordable cooling for the poorest
Money arranged before heat: 2 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Prevent heat-period electricity/water disconnection for inability to pay (stops electricity and water being cut off in a heatwave because a bill is unpaid); Solar-reflective roof coatings (cools the home without power, at low cost); Efficient BLDC ceiling fans (gives cooling for a fraction of the running cost); On-bill financing and tariff-based cost recovery for efficient cooling (spreads the cost of efficient cooling across bills, so poorer households can afford it). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- 1.12 billion of the rural and urban poor are at high risk because they lack access to cooling. Sustainable Energy for All, 2023
The displacement loop
People forced to move often land in heat-trapping housing, fall ill, lose income, fall further behind, and are forced to move again.
Pushed from their village by failed harvests, they rent a tin-roofed room that traps the heat. Illness costs them work, the rent falls behind, and they move again, to somewhere hotter and cheaper.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (South Asia): 40 million. people in South Asia could be forced to move within their own countries by 2050 without action, of up to 216 million worldwide. World Bank, 2021
In Southeast Asia (East Asia and the Pacific): 49 million. people in East Asia and the Pacific could be forced to move within their own countries by 2050 without action. World Bank, 2021
Where it plays out: Migrant settlements on the edges of fast-growing cities such as Dhaka.
Where it breaks: Income protection in heatwaves, Cool, affordable housing
Solutions to try: Independent over-roof shade, including ventilated PV shade (shades the hot tin roofs common in the housing people move into); Public air-conditioned cooling centre or shared refuge (gives a cool place to go when home is too hot); Multilingual heat information and routes for migrant workers (reaches newcomers in their own language, with routes to help); Heat-vulnerability mapping linked to beneficiary targeting (maps who is most exposed, so help reaches new arrivals). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Without action, as many as 49 million people in East Asia and the Pacific could become internal climate migrants by 2050. World Bank, 2021
- Without action, climate change could force up to 216 million people to move within their own countries by 2050, including about 40 million in South Asia. World Bank, 2021
The lost-schooling loop
Children pulled out of school earn less as adults, and poorer families pull more children out of school.
When heat closes her school for weeks and money is tight at home, she starts helping her mother instead. She falls behind, and each year it becomes harder for her family to send her back.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (World): 171 million. students had their schooling disrupted by heatwaves in 2024. South Asia was the most affected region. UNICEF, 2025
In Southeast Asia (Philippines): 3.6 million. students in the Philippines lost classroom learning in early April 2024, when 5,288 schools switched to remote learning as the heat index reached danger levels. AFP via Malay Mail, April 2024
Where it plays out: School systems that closed classrooms during the 2024 heatwaves, including in the Philippines and Bangladesh.
Where it breaks: Keep children in school
Solutions to try: School heat operating plans, water access and escalation (keeps schools open safely, with water, plans and clear steps to escalate); Closure decisions with offline learning continuity (keeps children learning when schools have to close); Schoolyard greening, depaving and shade as a coordinated retrofit (shades and cools school grounds); Heat-responsive school timetables and activity changes (moves the school day and activities away from peak heat). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Without air conditioning, each 1 °F hotter school year cuts that year’s learning by about 1%, and the losses fall hardest on disadvantaged students. Park, Goodman, Hurwitz and Smith, American Economic Journal: Economic Policy, 2020
- Heatwaves disrupted schooling for an estimated 171 million students in 2024. South Asia was the most affected region. UNICEF, 2025
- In early April 2024, 5,288 schools across the Philippines switched to remote learning as the heat index reached danger levels, affecting more than 3.6 million students. AFP via Malay Mail, April 2024
- Bangladesh closed schools for about 33 million children in its April 2024 heatwave, and Cambodia cut the school day by two hours. NBC News, 2024
The sleepless-nights loop
Hot nights wreck sleep. Poor sleep frays mental health, and stress makes sleep harder still.
Her room never cools down, even after midnight, so she sleeps in short, restless stretches. Tired and anxious, she finds sleep harder to come by, and each night feels longer than the last.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (India): 70%. of India’s districts gained five or more very warm nights each summer over the last decade. Mumbai gained 15. Council on Energy, Environment and Water (CEEW), 2025
In Southeast Asia (Singapore): 76 → most nights. Singapore has averaged 76 warm nights a year, above 26.3 °C, over the last 40 years. By the end of the century such nights could come on most nights of the year. National Environment Agency, Singapore, 2024
Where it plays out: Tropical cities whose nights stay hot, such as Bangkok, Chennai and Ho Chi Minh City.
Where it breaks: Cool nights and support
Solutions to try: Night flushing / night-purge ventilation (lets cool night air flush out the day’s heat); Solar-reflective roof coatings (stops the roof soaking up heat that it gives off at night); Efficient BLDC ceiling fans (gives cheap air movement through the night); Night-time and round-the-clock outreach with heat escalation (checks on people at risk after dark, when hot nights do harm). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Singapore averaged 76 warm nights a year (above 26.3 °C) over the last 40 years; by the end of the century such nights could occur on most nights of the year. National Environment Agency, Singapore, 2024
- Data from 47,628 people in 68 countries shows hot nights shorten sleep, with bigger losses for older people and in lower-income countries. Minor et al., One Earth, 2022
- A review of 114 studies links higher temperatures with poorer mental health, including higher suicide rates. Thompson et al., The Lancet Planetary Health, 2023 (summary by Imperial College London)
- Over the last decade, nearly 70% of India’s districts gained five or more very warm nights each summer, while only about 28% saw a similar rise in very hot days. Mumbai gained 15 very warm nights a summer, and Bengaluru 11. Council on Energy, Environment and Water (CEEW), 2025
- Tamil Nadu’s summer minimum temperatures have risen by about 0.75 °C since the 1980s, and about 56% of its people now live where summer nights are warmer than the 1981–2011 average. Tamil Nadu State Planning Commission, 2024
The green-displacement loop
Green space follows wealth. When greening reaches poorer districts without protection, rents rise, residents are pushed into hotter housing, and the gap grows.
The new park brings shade and cooler evenings to her street. It also brings higher rents, and she moves to a hotter part of the city with fewer trees than the one she left.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (28 cities in North America and Europe): 17 of 28. cities studied saw greening in the 1990s and 2000s strongly linked to gentrification between 2000 and 2016. Anguelovski et al., Nature Communications, 2022
Where it plays out: Riverbanks, canals and old inner-city sites turned into parks, as studied in Bangkok and Seoul.
Where it breaks: Green without pushing people out
Solutions to try: Greening helps only if residents can stay. Protection for tenants is not yet in this library, so pair these with it. Women-led co-design and worker governance (lets residents shape where greening goes and who it serves); Heat-vulnerability mapping linked to beneficiary targeting (puts shade where heat risk is highest, not where land values are); Community maintenance arrangements backed by public/service support (keeps greening in residents’ hands, with public support). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Across 28 cities in 9 countries, greening in the 1990s and 2000s was strongly linked to gentrification between 2000 and 2016 in 17 of them. Anguelovski et al., Nature Communications, 2022
- Green space tends to favour wealthier neighbourhoods, and new parks meant to fix that can raise housing costs and displace the residents they were meant to help. Small, local projects are more likely to reach those who need them. Wolch, Byrne and Newell, Landscape and Urban Planning, 2014
- Fieldwork on how recent gentrification in Bangkok, including green urban renewal, affects the city’s lower-income residents. Endo, The Developing Economies, 2026
- Nature-based solutions can deepen injustice when benefits flow to some and costs, including displacement, fall on others; procedural, distributional and recognition justice all need attention. Chapter 3 in Nature-Based Solutions for Cities, 2023
The heat credit squeeze
Heat empties shops and small firms miss repayments. Banks tighten credit, so firms can’t afford to adapt, and the next heatwave hits harder.
In a long heatwave, customers stay indoors and sales fall, so she misses a loan repayment. The lender is more cautious next time, and she cannot borrow to buy a cooler or shade for the shop.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Delhi, India): 49%. of 721 Delhi street vendors surveyed lost income in the 2024 heatwaves, and 80% saw fewer customers. Greenpeace India and National Hawkers Federation, 2024
Where it plays out: Market towns and city high streets in heat-exposed districts, and lenders whose loans are collected door to door, as in microfinance across northern and central India.
Where it breaks: Heat-smart lending
Money arranged before heat: 2 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Heat-relevant housing and cooling credit with technical appraisal (offers credit for cooling and heat-proofing, with a check that it will work); Public shade structures, sails and market/queue canopies (shades markets and queues, so customers keep coming); Parametric heat insurance for income shocks (pays out when heat crosses a set level, so repayments are not missed); A fallback funding layer when an index misses real harm (covers the harm an index misses, so a missed payout does not become default). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Across 2.7 million firms in 23 advanced economies, heat cut the productivity of small firms while medium and large firms showed no loss, and the largest grew revenue about 0.6 points faster than small firms after hot years. Losses lasted up to two years. Restaurants and hotels were hit hard, partly through lower demand. OECD Economics Department, Working Paper No. 1828, 2024
- Loan-level bank data from Mexico show that ten extra days of extreme heat in a quarter raise small-business loan delinquency by about 4%, mainly among firms that depend on local customers. Banks then raise rates, ask for more collateral and lend less for two to three quarters. Aguilar-Gomez et al., summarised in VoxEU, 2024
- India’s microfinance industry body said loan quality worsened in April–June 2024, partly because heatwaves cut borrowers’ incomes and lenders’ collections. Sa-Dhan, reported by Business Standard, 2024
- A caution for lenders: in Cambodia, researchers found that borrowing to get through climate shocks often delayed the harm rather than removing it, leaving households more indebted for the next shock. King’s College London, 2023
- Of 721 Delhi street vendors surveyed in April and May 2024, 80% saw fewer customers during heatwaves and 49% lost income. Greenpeace India and National Hawkers Federation, 2024
- Car dealers said heat cut showroom footfall by about 15% in June 2024, leaving them with 62–67 days of unsold stock against a recommended three weeks. A sign of where to look; the link to their loans is not yet measured. Federation of Automobile Dealers Associations, reported by Orissa Post, 2024
The farm-debt loop
A failed harvest pushes farmers into debt. Debt leaves less for seed, water and fertiliser, so the next harvest fails more easily.
A heatwave at the wrong moment shrinks the grain, and the harvest does not cover what he borrowed. With the loan still open, he buys less seed and fertiliser, and the next crop is more fragile.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Philippines): −10%. rice yield for each 1 °C rise in growing-season night temperature, at the International Rice Research Institute’s farm in the Philippines. Peng et al., PNAS, 2004
Where it plays out: Rain-fed farming districts of India, Pakistan and Bangladesh, where a failed season often means borrowing from moneylenders.
Where it breaks: Crop insurance and fair credit
Money arranged before heat: 2 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Shade-net structures for crop microclimate protection (protects crops from heat damage); Organic residue mulch for cooler crop root zones (keeps crop roots cooler and moist); Parametric heat insurance for income shocks (pays out after a heat-hit season, so farmers need not borrow for seed); Pre-agreed heat anticipatory action and forecast finance (releases money before the damage, while it can still protect the harvest). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Heat raises suicide rates in India only during the growing season, when it also cuts crop yields, pointing to farm income losses. The findings have been debated. Carleton, PNAS, 2017
- Days above 34 °C make wheat in northern India age early, and crop models may underestimate yield losses at +2 °C by as much as 50%. Lobell, Sibley and Ortiz-Monasterio, Nature Climate Change, 2012
- At the International Rice Research Institute’s farm in the Philippines, rice yields fell by about 10% for each 1 °C rise in growing-season night temperature, while daytime highs had little effect. Peng et al., PNAS, 2004
Loops inside institutions
The invisible-deaths loop
Heat deaths go uncounted, so heat protection goes unfunded, so more people die uncounted.
She knows that heat played a part in many deaths this summer, but few were recorded that way. With so few counted, it is hard to make the case for next year’s heat budget.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (India): 48,385 vs 185. suspected heatstroke cases against confirmed heatstroke deaths in India in 2024, up to 28 July: most of the toll goes uncounted. Ministry of Health and Family Welfare, reply in India’s Rajya Sabha, 2024
Where it plays out: Much of Asia, where death certificates rarely record heat as a cause.
Where it breaks: Count every heat death, Cooling centres and check-ins
Solutions to try: Timely heat-illness and death surveillance (counts heat illness and deaths as they happen); All-cause and excess-mortality analysis for heat attribution (measures the full toll by comparing deaths with a normal year); Heat-death investigation and consistent certification (records heat as a cause of death consistently); Dedicated and traceable heat operating budgets (turns the counted toll into money set aside for protection). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Suspected heatstroke cases rose from 4,481 in 2022 to 48,385 by 28 July 2024, while confirmed heatstroke deaths rose only from 33 to 185. Ministry of Health and Family Welfare, reply in India’s Rajya Sabha, 6 August 2024
- In 2020, India’s crime records bureau recorded 530 heatstroke deaths while the disaster agency recorded four. Different systems count differently, which makes the full toll hard to see. Associated Press via PBS NewsHour, 2024
- Death certificates usually record only the immediate cause, such as heart failure, so heat as the trigger goes unrecorded. Down To Earth, 2024
- Between 1 March and 26 July 2026, India’s heat surveillance, covering more than 51,000 reporting units, logged 4,853 heatstroke cases but only 20 heatstroke deaths. Ministry of Home Affairs, reply in India’s Lok Sabha, reported by Down To Earth, 2026
- Monitors at 24 indoor and outdoor workplaces in Singapore found workers could face more heat stress than nearby national weather stations reported. NUS Project HeatSafe, 2024
The reactive-spending loop
Stretched budgets skimp on prevention. Emergencies multiply, and costly emergency response stretches budgets further.
With money stretched, the cooling shelters and water points she planned are cut back. When the heatwave arrives, emergency spending takes even more of the budget, and prevention is cut again.
A composite, drawn from the evidence for this cycle. Not a real person.What breaking it saves (Developing countries): US$3–16 billion. in losses could be avoided every year by spending US$800 million on early warning systems in developing countries. Global Commission on Adaptation, 2019
In Southeast Asia (Bangkok, Thailand): Up to 0.7%. of Bangkok’s economy is what heat deaths cost, an estimated 593 a year in 2016–18. The upper estimate is more than the city’s whole public health budget for 2020. Park and Rubinyi, World Bank working paper, 2026
Where it plays out: Disaster budgets designed for floods and cyclones rather than heat.
Where it breaks: Dedicated heat budgets, Anticipatory action
Money arranged before heat: 27 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Dedicated and traceable heat operating budgets (sets aside and tracks money for prevention); Pre-agreed heat anticipatory action and forecast finance (agrees in advance what money is released, and when); Heat action plans with a seasonal responsibility matrix (assigns who does what before each heat season); Recognise heat in disaster-funding rules and eligibility (lets disaster funds be spent on heat). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- About 593 deaths a year in Bangkok in 2016–18 were attributable to heat. Valued at 0.1–0.7% of the city’s economy, the upper estimate exceeds the city’s 2020 public health budget. Park and Rubinyi, World Bank working paper, 2026
- US$800 million spent on early warning systems in developing countries could avoid US$3–16 billion in losses every year. Global Commission on Adaptation, 2019
- Direct response typically gets over half of wildfire spending, while planning and prevention get less than 1%. UNEP and GRID-Arendal, 2022
- Of 37 heat action plans reviewed, 11 discussed funding, and 8 of those simply asked departments to find their own money. Only two included a vulnerability assessment. Centre for Policy Research, 2023
- In August 2026 India added heatwaves to its notified natural calamities, so national and state disaster response funds can pay for heatwave relief. Before, states could spend only up to 10% of their response fund on locally declared disasters such as heat. Heat mitigation projects are funded separately, from disaster mitigation funds. Ministry of Home Affairs, reply in India’s Lok Sabha, reported by Down To Earth, 2026
The protection-gap loop
As insurers retreat, public budgets absorb the losses, protection is cut, and the risk drives insurers further away.
After several bad years, insurers no longer cover heat losses for businesses like hers. When a heatwave hits, she turns to public relief, which strains the budget meant for protection.
A composite, drawn from the evidence for this cycle. Not a real person.What this cycle costs (Asia): 92%. of Asia’s US$65 billion in natural catastrophe losses in 2025 was uninsured, falling on households, businesses and governments. Swiss Re Institute sigma, reported by Global Reinsurance
Where it plays out: Fast-growing Asian economies where few households or small businesses carry insurance.
Where it breaks: Dedicated heat budgets, Shared risk pools
Money arranged before heat: 27 kinds of insurance, pooled funds, credit and forecast-based finance name this cycle. Paying when heat strikes asks of each whether it paid, and when.
Solutions to try: Pooled pre-arranged finance for heat action (shares heat risk across places, so no single budget carries it alone); Targeted premium support and renewal finance (helps those most at risk keep their cover); A fallback funding layer when an index misses real harm (backs up index cover when it misses real harm); Recognise heat in disaster-funding rules and eligibility (opens public disaster funds to heat losses). A suggested match, not a measured effect on the cycle. Business ideas for this cycle.
- Only about 8% of Asia’s US$65 billion in natural catastrophe losses in 2025 was insured. The rest fell on households, businesses and governments. Swiss Re Institute sigma, reported by Global Reinsurance
- In developing markets with low insurance cover, the protection gap is driven by unaffordable premiums, limited awareness and weak distribution, and heat’s drag on growth and household incomes could shrink the customer base further. Global Asia Insurance Partnership, 2026