Rising heat cuts into global worker productivity as emissions climb

Lost labor from warming now ranks as the second largest driver of climate damages, according to economic modeling that puts the cost at $41 per ton of carbon dioxide.

Human muscles generate internal heat whenever a person works, and the surrounding atmosphere determines how quickly that thermal energy can escape. When ambient temperatures and humidity climb together, the cooling power of evaporating sweat falls sharply. Workers facing heavy physical exertion must slow their pace, take frequent breaks, or risk organ damage and fatal heatstroke. That physiological brake on physical exertion does not stay confined to fields and factories. It cascades into the wider economy, depressing output across entire regions where severe heat persists.

Economists and climate scientists have long tried to measure how greenhouse gas emissions translate into monetary damages across the globe. Earlier economic assessments frequently struggled to capture the full physical toll of high temperatures on daily labor, leaving policymakers without a complete estimate of how each additional emission pulse impairs the human workforce. Putting a reliable price on those damages requires linking atmospheric physics to the biological limits of the human body and the practical realities of different occupations, from farming to office work. Determining that link establishes how much society loses when emissions continue unabated.

A study published in the journal Nature Climate Change provides a detailed accounting of that economic toll.¹ Led by Frances Moore, an environmental science and policy professor at the University of California, Davis, the research calculates that each ton of carbon dioxide emitted in 2025 causes $41 in lost labor productivity worldwide.¹ That total places labor productivity losses as the second-largest overall component of the total social cost of carbon, trailing only direct heat-related mortality.¹

How does extreme heat reduce human labor capacity?

Working bodies need a continuous temperature gradient between skin and the surrounding air to shed heat. The human body generates metabolic warmth through movement, and it relies primarily on the evaporation of perspiration to prevent core body temperature from rising past dangerous thresholds. In dry conditions, sweat evaporates quickly into the air. When relative humidity rises, the surrounding atmosphere holds moisture close to saturation, preventing sweat from evaporating effectively. As core temperatures climb, the cardiovascular system redirects blood flow to the skin, straining the heart and draining physical stamina. To avoid debilitating illness, workers must naturally reduce their speed, rest for extended periods, or halt work entirely.

The study measures that environmental stress using the wet-bulb globe temperature.¹ That metric evaluates physical heat exposure by combining air temperature with humidity, wind velocity, and solar radiation, reflecting the actual conditions experienced by an exposed body under the sun.¹² Earlier research published in Scientific Reports by Yann Chavaillaz and colleagues in 2019 similarly demonstrated that cumulative carbon emissions drive linear increases in wet-bulb globe temperature thresholds, requiring laborers in extreme settings to rest between 10 and 40 minutes for every active hour of work.²

Moore and her colleagues combined wet-bulb globe temperature projections with sector-specific data on occupational intensity and outdoor exposure.¹ Agricultural laborers, construction crews, and quarry workers face the greatest direct risk because their jobs demand continuous exertion out in open weather.¹² However, indoor workers without adequate climate control also suffer substantial losses.¹ In uncooled factories, warehouses, and small workshops, indoor ambient heat often accumulates with minimal ventilation, depressing output across manufacturing and processing industries.

Where will the economic toll fall most heavily?

The heaviest economic damages will concentrate in densely populated, tropical, and subtropical nations that already experience high baseline temperatures and elevated humidity. The research identifies India, Nigeria, China, and Pakistan, alongside several nations across the Middle East and sub-Saharan Africa, as the most vulnerable areas.¹ In these countries, large populations work in labor-intensive agricultural and industrial roles, exposing hundreds of millions of people to environmental conditions that exceed safe physical thresholds.

That regional distribution creates an uneven economic burden between wealthy and developing nations. The earlier 2019 analysis in Scientific Reports by Chavaillaz and colleagues estimated that lower-income and lower-middle-income countries face labor productivity losses roughly nine times larger than those borne by high-income nations.² Wealthier countries like Germany, Canada, and the United Kingdom experience minimal labor productivity declines, while developing nations with large farming workforces suffer steep reductions in total national output.²

Disparities in indoor cooling infrastructure amplify that divide. The University of California, Davis team evaluated residential air conditioning adoption across 33 countries and found vast inequalities, with cooling access ranging from zero percent in South Sudan to 90 percent in Japan.¹ Outdoor workers cannot rely on air conditioning during field shifts, but lack of indoor cooling also prevents home recovery between workdays, compounding chronic fatigue and reducing daily performance.

What does this mean for the true cost of carbon?

Evaluating the monetary value of carbon emissions allows governments and institutions to set appropriate regulations, carbon taxes, and infrastructure standards. The economic metric known as the social cost of carbon quantifies the global dollar damage inflicted by releasing one additional ton of carbon dioxide into the atmosphere.¹ The findings by Moore and her co-authors support an overall social cost of carbon of approximately $200 per ton, closely aligning with an estimate calculated by the United States Environmental Protection Agency in 2023.¹

Current federal regulatory guidelines in the United States do not formally incorporate that metric and discourage assigning monetary values to greenhouse gas emissions during administrative analyses.¹ The study directly challenges that practice, stating that the economic evidence confidently rules out a social cost of carbon of zero or lower.¹ By establishing that labor losses account for $41 per ton of carbon dioxide emitted in 2025, the research indicates that omitting workforce impacts substantially underestimates the true cost of fossil fuel combustion.¹

Frances Moore and colleagues Iman Haqiqi, Uris Baldos, Matthew Huber, and Thomas Hertel of Purdue University, alongside Qinqin Kong and Lisa Rennels of Stanford University and Hamsa Ganapathi of the University of California, Davis, emphasize that evaluating these damages provides a necessary foundation for public policy.¹ “Our study contributes to the body of evidence about what the real costs of climate change are,” Moore said in a statement accompanying the research.¹ “Based on these new numbers, labor is the second-largest contributor to the total social cost of carbon, just behind heat-related deaths.”¹

What are the limits of the findings?

The economic estimates represent modelled projections that combine physical climate scenarios with economic vulnerability data, rather than direct tallies of observed workplace output. The research cannot forecast individual business decisions, real-time economic shocks, or unpredictable technological disruptions over coming decades. The underlying calculations also depend on specific assumptions regarding how rapidly societies adopt protective measures such as expanded shade, access to clean drinking water, altered work shifts, and mechanical air conditioning.¹

Furthermore, human physiological resilience has practical biological limits that workplace reorganization cannot fully resolve. While employers can shift certain work hours to early morning or evening periods, high nighttime temperatures and humidity in equatorial regions increasingly limit the cooling window. Expanding air conditioning can protect indoor manufacturing and service staff, but cooling outdoor agricultural fields, open mines, and construction sites remains technologically impossible with current equipment.

“Heat is very dangerous,” Moore noted in the release accompanying the study.¹ “Employers and policymakers need to be treating it as the real health hazard that it is and thinking seriously about ways to mitigate those damages because we’re going to keep seeing more frequent, more intense heat extremes.”¹ As global warming continues to raise average temperatures, the economic durability of international supply chains will increasingly depend on whether governments account for the physiological limits of their human workforce.

What this rests on

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1. 1 E EurekAlert! Document · eurekalert.org The high cost of climate change on worker productivity See the source
2. 2 N nature.com Paper · nature.com Exposure to excessive heat and impacts on labour productivity linked to cumulative CO2 emissions - Scientific Reports Journal article See the source