Duration of heavy work to halve for 800 million people if world warms 2°C: Report provides solutions to tackle heat stress

If Earth warms by around 2 degrees Celsius (°C), around 800 million people will be able to do heavy work for half the duration every day compared to what they can now, according to a review paper published in the journal One Earth on March 1, 2024.

The impacts of increased temperatures and heatwaves on workers in the tropics and their adaptations to the same are understudied, the authors noted in the paper. They outlined possible solutions for adaptation to heat stress at the institutional and individual levels before, and after a heat event.

The best way to mitigate this impact, the researchers noted, is to reduce greenhouse gas emissions from human activities that would slow down global climate change. But many institutional and individual adaptations could also reduce risk of heat stress and help in mitigating the impacts on workers, especially in the tropical regions, they added.

The study comes at a time when many regions around the world are reeling under increased temperatures and early (northern hemisphere) or late (southern hemisphere) heatwave conditions due to general background warming and an ongoing El Nino phenomenon in the equatorial Pacific Ocean. 

El Nino conditions generally lead to warmer than normal temperatures and more heatwaves across many regions of the world. The current El Nino is among the five strongest on record, according to the World Meteorological Organization (WMO). The phenomenon itself is weakening but its impacts shall remain for the time being, WMO observed,

In India, the southern states of Karnataka, Tamil Nadu, Kerala and parts of Andhra Pradesh (Rayalaseema) are also undergoing hot and humid weather. 

The study authors reviewed four sets of literature on: assessing how hot environments impact heat stress and illness, what drives the increase in heat in the tropics, the impacts of humid heat on workers and the adaptation to these impacts at various levels. 

They found that with the 1.1°C warming that has already occurred since the pre-industrial period (1850-1900), a fifth of all hours in the year already exceed the thresholds for the average outdoor worker doing heavy work in the tropical regions. With an additional 1°C of warming, the number would increase to a third of all hours in a year.

The economic losses in terms of Gross Domestic Product (GDP) due to heat stress is projected to be 3-5 per cent in regions such as tropical West Africa, South and South East Asia. 

The study mentioned that with warming of 3°C there may be 10-15 per cent loss of labour productivity in countries such as Bahrain, Cambodia, Pakistan, Qatar and the United Arab Emirates. 

In most of the estimations on the impacts of heat on workers, including the The World Employment Report published by the International Labour Organization, the people engaged in industries such as fisheries and aquaculture have been left out, the authors highlighted in the report. Therefore the estimations may not be accurate. 

The people who work along the coasts or in the oceans also have other compounding events to be careful about, such as storms, algal blooms, shifting and degrading fish stocks, the researchers pointed out. 

Studies in laboratory settings show that there is a 10 per cent reduction in the ability of people to perform physical work under mild heat stress, while there is a 78 per cent reduction in the case of extreme heat stress. 

This is apart from the other health impacts of heat stress from basic dehydration to heat stroke, collapse, long-term impacts on the kidney, brain and heart, which may also lead to inability of individuals to work.  

The study also warned that the experiments conducted in the laboratory often don’t show the real picture of the impacts of heat on human health in the real world, evidenced by epidemiological studies of people who have suffered from heat stress. 

This could happen because of inadequate interpretations of the relationship between temperature and humidity and not taking into account events such as rainfall during a heatwave event. 

The studies have also been mostly conducted in western countries such as the United States and not in tropical countries. Heat indices which give a combined impact of heat and humidity are also mostly based on data from such countries. Separate heat indices for tropical countries are currently unavailable.

Among the many factors responsible for the occurrence of hotter environments, the authors cited background warming, land cover as well as land use changes and various irrigation methods. Among land changes, the conversion of forests to agricultural lands is the most significant factor. 

The impact of irrigation methods is a little more complicated. In places such as urban areas in drier climates, irrigation may lead to cooling. In rural agricultural areas, however, it may add to the atmospheric moisture levels, increasing the chances of humid heat waves. 

In cities, the urban heat island (UHI) effect, which is a phenomenon due to which heat gets trapped in constructed areas adding to the heat, was found to be another factor increasing heat stress. The impact of UHI is the most severe in more moist climates such as forests, less severe in drier climates and the least severe in desert cities. 

In the future, an increase in population in many regions of Africa and Asia would lead to more outdoor workers being exposed to humid heat. 

The solutions suggested for adapting to the predicted increased temperatures, humid heatwaves and their impacts were divided into three categories of solutions: Primary, secondary and tertiary.

The primary solutions need to be implemented before a heatwave has occurred. This could include urban greening, sustainable use of land resources, provisions and training by the government, community-based organisations and employers to reduce worker heat stress and transition of workers to less heat stress work. 

The secondary solutions need to be implemented while a heatwave is ongoing, which are mostly related to reducing heat stress at the workplace such as providing water, shifting working hours to cooler periods and rest breaks. Tertiary solutions include providing monetary and medical benefits and rehabilitation to people adversely impacted by extreme heat. 

The authors concluded that there are also many research gaps that remain, such as regarding understanding how the factors outside a workers’ own needs make adapting to heat more or less difficult. Other aspects that need to be studied further are impacts and adaptations in the context of multiple climate stressors occurring simultaneously or one after the other and maladaptation to heat stress.

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