Why in News
A University of Oxford study, published in the journal Sustainable Cities and Societies, assessed 205 large cities and ranked 14 Indian cities among the world’s top 50 for urban heat risk. Ahmedabad ranked second globally, with Nagpur and Madurai also among the world’s ten most heat-vulnerable cities; Al Basrah (Iraq) tops the global list. The findings highlight the growing danger of extreme urban heat in India and the urgent need for legally backed Heat Action Plans and heat-resilient cities.
What the Study Found
| Aspect | Detail |
|---|---|
| Study | University of Oxford, in Sustainable Cities and Societies |
| Scope | 205 cities of over a million people worldwide |
| Indian cities in top 50 | 14, with Ahmedabad ranked second globally |
| Top globally | Al Basrah, Iraq |
| Method | Combines hazard, vulnerability and coping capacity |
The ranking is not based on temperature alone. It combines three pillars: the hazard (exposure to extreme temperature), the vulnerability (social and demographic susceptibility, such as age and poverty) and the coping capacity (cooling access, tree cover and response systems), giving a fuller picture of risk than raw temperature.
Understanding Urban Heat
| Concept | What it means |
|---|---|
| Urban Heat Island (UHI) | Cities are hotter than surrounding areas because concrete, asphalt and buildings absorb and retain heat, with little green cover |
| Heatwave | A period of abnormally high temperature; in India it can be a notified disaster in some states |
| Heat stress | The strain on the human body from prolonged heat, which can be fatal, especially for the old, the poor and outdoor workers |
Rapid, unplanned urbanisation, loss of green cover and water bodies, and climate change together intensify urban heat, making cities increasingly dangerous during summer. The Urban Heat Island effect can leave cities 3 to 5 degrees Celsius hotter than their rural surroundings, and rising night-time minimum temperatures deny the body the cooler nights it needs to recover.
The Heat Science Toolkit
| Concept | What to know |
|---|---|
| IMD heatwave criteria | A heatwave is declared in the plains at a maximum of 40 degrees Celsius or more (37 on the coast, 30 in the hills) with a departure from normal of +4.5 to +6.4 degrees; it is severe above +6.4 degrees or at 47 degrees and above |
| Wet-bulb temperature | A measure combining heat and humidity; a wet-bulb temperature of about 35 degrees Celsius is the theorised limit of human survivability, beyond which sweating can no longer cool the body |
| The IMD limitation | India’s heatwave declaration uses dry-bulb temperature and does not factor humidity, so it can understate the danger of humid heat |
Is a Heatwave a “Notified Disaster”?
A crucial governance gap: heatwaves are NOT among the disasters notified under the Disaster Management Act, 2005, which limits access to central disaster-relief funds.
- States may locally notify a heatwave as a “state disaster” and use up to 10 per cent of the State Disaster Response Fund (SDRF) for it, a window opened by the 15th Finance Commission.
- The 16th Finance Commission (2025) recommended adding heatwaves (and lightning) to the notified-disaster list, which would unlock fuller relief and standardised ex-gratia for victims.
- Notification matters because it determines whether heat deaths attract the same official response and compensation as floods or cyclones.
What Can Be Done: Heat Action Plans
| Measure | Detail |
|---|---|
| Heat Action Plans (HAPs) | Early-warning, advisory and emergency-response plans; now across about 23 heat-prone states and 130-plus cities, with 200-plus HAPs in all |
| Ahmedabad | Pioneered South Asia’s first Heat Action Plan in 2013, a widely cited model |
| India Cooling Action Plan (ICAP), 2019 | The world’s first national cooling plan; aims to cut cooling demand 20-25% by 2037-38 |
| Cool-roof policy | Telangana’s Cool Roof Policy (2023) was India’s first state-wide mandatory cool-roof policy |
| Other levers | Mission LiFE, the National Mission on Sustainable Habitat, urban greening and nature-based solutions |
Why Heat Action Plans Underperform
The study strengthens the case for treating heat as a serious, recurring disaster risk, but India’s HAPs have known weaknesses that a strong answer should name:
- Not legally binding. HAPs are advisories, not enforceable mandates, so compliance is uneven.
- Chronically underfunded. Most lack a dedicated budget line, leaving measures unimplemented.
- Generic, not localised. Many are copied across cities and fail to map local vulnerability (slums, outdoor workers).
- Short-term focus. They emphasise warnings and advisories but neglect long-term mitigation (green cover, building norms) and ignore humidity and night-time heat.
The economic and human stakes are large. The ILO estimates India could lose about 5.8 per cent of working hours, equivalent to roughly 34 million full-time jobs, to heat stress by 2030, with agriculture and construction worst hit and the urban poor and outdoor workers bearing the burden.
UPSC Relevance
Prelims
- An Oxford study (in Sustainable Cities and Societies) assessed 205 cities and placed 14 Indian cities in the world’s top 50 for heat risk; Ahmedabad ranked second globally
- Al Basrah (Iraq) tops the global list
- The ranking combines hazard, vulnerability and coping capacity, not temperature alone
- Wet-bulb temperature of about 35 degrees Celsius is the theorised human survivability limit
- IMD heatwave criterion in the plains: maximum of 40 degrees or more with a +4.5 to +6.4 departure (severe above +6.4 or at 47)
- Heatwave is not a notified disaster under the DM Act, 2005; the 16th Finance Commission (2025) recommended adding it
- Ahmedabad pioneered South Asia’s first Heat Action Plan in 2013; ICAP (2019) is the national cooling plan
Mains Angles
- GS3 Disaster Management: “India’s Heat Action Plans are necessary but insufficient.” Critically examine and suggest reforms.
- GS1 Urbanisation: Discuss how unplanned urbanisation and loss of green cover intensify the Urban Heat Island effect.
- GS3 Environment / GS2 Governance: Should heatwaves be a notified disaster under the DM Act, 2005? Examine the case and its implications.
Facts Corner
| Fact | Detail |
|---|---|
| Study | University of Oxford, in Sustainable Cities and Societies (205 cities) |
| Indian cities in top 50 | 14 (Ahmedabad 2nd globally; Nagpur 4th, Madurai 7th) |
| Top globally | Al Basrah, Iraq |
| Method | Hazard + vulnerability + coping capacity |
| Wet-bulb limit | ~35 degrees Celsius (human survivability) |
| IMD heatwave | Plains: 40 degrees-plus, +4.5 to +6.4 departure |
| Disaster status | Not notified under DM Act 2005; 16th FC (2025) recommends adding it |
| First HAP / cooling plan | Ahmedabad, 2013 (South Asia’s first); ICAP, 2019 |
| Economic cost | ILO: ~34 million jobs / 5.8% of work hours lost to heat by 2030 |
Sources: University of Oxford, NDMA, Down To Earth
Source: Oxford Study Places 14 Indian Cities Among the World's Most Heat-Risk Exposed — Ujiyari.com | Free UPSC & State PCS Current Affairs
