Heat stress cost India $9 per tonne of CO2 in lost labour productivity in 2025
A study published in Nature Climate Change estimated that heat-related labour productivity losses in 2025 amounted to $9 for every tonne of CO2 emitted, when calculated for India specifically
Globally, the equivalent figure was $41 in lost labour productivity per tonne of CO2 emitted; other large emitters showed lower country-specific figures — Nigeria ($6), China ($4) and Pakistan ($3) per tonne
Outdoor workers in agriculture, construction and manual-labour roles were identified as facing the greatest exposure, since they cannot access cooling and often lack schedule flexibility
The study frames labour-productivity loss as the second-largest contributor to the overall Social Cost of Carbon, behind heat-related mortality
Researchers called for modified work schedules, improved access to shade/water/rest breaks, better cooling and ventilation, and formal heat-safety protocols to reduce these losses
Social Cost of Carbon (SC-CO2)
The Social Cost of Carbon is an economic metric estimating the total monetised damage caused by emitting one additional tonne of CO2, aggregating impacts across categories such as health, agriculture, ecosystem damage, property loss and — as highlighted in this study — labour productivity.
Key Details
- SC-CO2 is used by governments and multilateral agencies (e.g., US EPA, World Bank) to set carbon prices, evaluate climate policy costs and benefits, and justify regulatory interventions
- It aggregates damages across a long time horizon using a discount rate, making the final figure sensitive to the discount rate chosen — a persistent methodological debate in climate economics
- Labour productivity loss is identified in the study as the second-largest component of SC-CO2, after heat-related deaths, ahead of agricultural and property-damage impacts
The $9/tonne figure for India is a country-specific decomposition of the labour-productivity component of SC-CO2 — it quantifies, in dollar terms, how much of the "cost" of each tonne of carbon emitted shows up as lost work output in India due to heat exposure.
Wet-Bulb Globe Temperature (WBGT) as a Heat-Stress Metric
WBGT is the standard scientific metric for assessing occupational heat stress, used in preference to simple air temperature because it accounts for humidity, wind, and radiant heat — factors that determine how effectively the human body can cool itself through sweat evaporation.
Key Details
- WBGT combines dry-bulb temperature, natural wet-bulb temperature (humidity effect) and globe temperature (radiant heat) into a single index
- International Organization for Standardization (ISO 7243) sets WBGT-based occupational exposure limits for different workloads
- Several Indian states (Maharashtra, Tamil Nadu, Gujarat) have separately notified rules restricting outdoor work when wet-bulb temperature exceeds 30°C, though there is no uniform national WBGT standard
- High humidity regions (coastal and peninsular India) can reach dangerous WBGT levels at lower absolute air temperatures than arid regions, making WBGT a more accurate risk indicator than heatwave declarations based on dry-bulb temperature alone
The productivity-loss estimates in the study are built on WBGT-based occupational exposure modelling — it is this metric, not simple temperature records, that links a given emissions/warming pathway to hours of safe outdoor work lost.
Occupational Safety, Health and Working Conditions Code, 2020 — Heat as a Regulatory Gap
India's labour-code framework, consolidated under the Occupational Safety, Health and Working Conditions (OSH) Code, 2020, currently lacks an explicit, enforceable heat-stress standard, which is relevant to how the productivity losses quantified in this study translate (or fail to translate) into legal protections for outdoor workers.
Key Details
- The OSH Code, 2020 consolidated 13 earlier labour laws (including the Factories Act, 1948 and the Contract Labour Act, 1970) but uses non-specific language such as "reasonable temperature" rather than a defined WBGT-based trigger
- Section 23 of the OSH Code centralises the power to prescribe ventilation, temperature and humidity standards with the central government, superseding earlier state-level flexibility
- The National Disaster Management Authority (NDMA) leads India's Heat Action Plans (HAPs) at the state/city level — a disaster-management response rather than a labour-law entitlement — with a 2025 advisory recognising gig-worker exposure and recommending mandatory heat breaks and work suspension between 11 AM and 4 PM during extreme heat
The study's policy recommendations (schedule changes, mandatory breaks, cooling access) map directly onto this regulatory gap — India currently manages heat-stress risk to workers mainly through disaster-management advisories (NDMA Heat Action Plans) rather than a codified occupational-safety standard, a distinction relevant to any GS3 or GS2 answer on labour welfare and climate adaptation.
- India's 2025 heat-related labour productivity loss: $9 per tonne of CO2 emitted
- Global average: $41 per tonne of CO2 emitted (2025)
- Comparator country figures: Nigeria $6/tonne; China $4/tonne; Pakistan $3/tonne
- Metric used: Wet-Bulb Globe Temperature (WBGT), combining humidity, wind and radiant heat
- Labour productivity loss ranks as the second-largest component of the Social Cost of Carbon, after heat-related mortality
- OSH Code, 2020 consolidated 13 central labour laws but has no defined WBGT-based heat-stress standard
- State-level wet-bulb thresholds (Maharashtra, Tamil Nadu, Gujarat): work considered unsafe above 30°C wet-bulb temperature
- NDMA's 2025 heat advisory recommends suspension of outdoor work between 11 AM and 4 PM during extreme heat events