Multiple studies show that increased temperatures result in drops in productivity. As the world warms and workers are more likely to be subjected to high heat levels, this is becoming an increasing problem.

Commuters walk to work over London Bridge in London, England. (Photo by Scott Barbour/Getty Images)

A typical worker in Riyadh, the capital and largest city of Saudi Arabia, may have lost as much as the equivalent of 932 hours of productivity due to high heat – 117 days in total – from the beginning of January to 8 November 2020.

Riyadh is located in the middle of the an-Nafud desert and has always experienced hot weather. However, a surge in urban activity and rising temperatures as a result of climate change have led to a significant increase in temperatures in recent years.

The temperature in Saudi Arabia shot up from an annual average of about 24.6°C at the beginning of the 1990s to about 26.4°C in the years to 2019 – an increase of 1.8°C in less than 30 years.

Due to this increase, workers in Riyadh are now estimated to have lost the equivalent of an additional 92 hours of productive working hours from January–November compared with the same time period in 1990.

To work out exactly how high temperatures are impacting productivity, Energy Monitor analysed 14 million temperature records from 324 cities around the world and applied a model that estimates how much productivity is lost at different temperatures.

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By GlobalData

Our analysis shows that another Saudi city, Dhahran, has lost the equivalent of about 868 hours of productivity so far this year, 125 hours more than in 1990.

In Manama, the capital of Bahrain, workers lost an estimated 716 hours of productive time from January–November this year, 170 hours more than in 1990, the biggest increase in our analysis.

Cairo (+139 hours), Phoenix (+108), Taipei (+81) and Las Vegas (+76) were also among the cities that saw the biggest increases in potential hours of productive work lost due to an increase in heat in the past 30 years.

On average, the cities in our analysis lost the equivalent of an additional nine hours of productivity from January–November 2020 compared with the same months in 1990. While one work day may not seem like much, this represents a 58.2% increase in productivity loss over a 30-year period.

And this lost productivity is not just affecting cities in the desert or those used to living with extreme heat. 

Take Madrid, the capital of Spain. It is among the Western cities most affected by heat stress this year. While our analysis doesn’t account for the famous Spanish siesta, a typical 9am–6pm worker in Madrid would have lost 192 hours of productivity so far this year, the equivalent of around 24 days. This is an increase from 128 hours of productivity – or 16 days – lost in 1990.

Workers in Hong Kong spent an additional 45 hours not working compared with 1990, while even those in London have seen their productivity decrease by an estimated ten hours in 30 years.

In August, parts of the UK experienced temperatures reaching 34°C for a long run of days and several “tropical nights” where night-time temperatures did not drop below 20°C.

All workers who do their job in a hot environment are at risk of heat stress. Extreme versions of it can lead to illness and injuries, and temperatures of over 39°C can even lead to death.

A 2018 study found that around 2.7% of all occupational injuries in Spain recorded between 1994 and 2013 could be attributed to non-optimal ambient temperatures, a big part of them being the direct result of heat stress.

However, even at lower temperatures, heat can lead to a significant decline in how productive a worker is. This is particularly true for a growing number of people in vulnerable groups, such as older workers, those with underlying health conditions, essential workers, pregnant women, and even those who have or are recovering from Covid-19.

Worldwide, 2.2% of the total working hours will be lost every year from 2030 onwards, estimates the International Labour Organisation (ILO). This amounts to 80 million full-time jobs.

In southern Asia and western Africa, where temperatures are already high and are expected to increase at a faster rate than in the rest of the world, workers could lose 5% of their productivity each year.

The ILO believes the accumulated loss from heat stress could amount to $2.4trn in 2030 even if global heating is limited by the end of the century to 1.5°C above pre-industrial levels. The bill will be even higher if governments fail to speed up the transition to a clean energy economy. Current policies to tackle climate change would lead to heating of around 3°C.

Farmers and construction workers will likely be the most affected, with the agricultural sector accounting for an estimated 60% of all global working hours lost due to heat in 2030. Construction workers will suffer 19% of the lost productivity.

That doesn’t mean office workers are not affected by high temperatures. One study found productivity in call centres decreased by 5–7% when the air temperature exceeded 25°C.

The ILO report confirms these findings. It notes that temperatures of above 24–26°C are associated with reduced labour productivity and that temperatures of 33–34°C lead to a 50% loss in work capacity.

While academic sources use different models to calculate the extent to which heat affects work productivity, they mostly paint the same picture.

Excessive heat doesn’t just mean a few hours of idleness at work every year. Without significant change, 143 million people could be forced to leave their homes by 2050, shows a World Bank report.

Jobs are also threatened beyond it being simply too hot to work. Many jobs, particularly in the most vulnerable countries, rely on the ecosystem in which they exist. Any disruption to local environments is likely to have serious implications for those working in farming, fishing and forestry and, indirectly, for the wider society.

So what can be done to reduce the effects of excessive heat? The ILO suggests that countries should ratify and implement better labour standards to ensure that workers and businesses are less likely to be affected by rising temperatures.

Maximum temperatures to which workers are exposed should be set by regulations. Employers must also be made to provide ways to protect workers from heat and dehydration. Buildings and other types of infrastructure should also accommodate rising temperatures.

Ultimately, limiting the effects of climate change will also have a big impact on the extent to which heat will make us less productive. Our analysis shows that productivity loss increased by 57.7% in just 30 years. Even under the most optimistic scenarios, productivity will continue to decline, but ditching fossil fuels in favour of renewables and energy efficiency will help restrict that decline.

How we worked out the numbers

For this analysis, we used temperature records from National Oceanic and Atmospheric Administration’s National Centers for Environmental Information, a US government agency that provides access to one of the largest public environmental databases.

We limited our research to a list of weather stations in 157 US and 167 non-US cities compiled by the University of Dayton. Since records may not be consistently available for each city for the years 1990 and 2020, we cut the list to 209 cities with reliable data.

For each city, we collected temperature readings for each hour between (and including) 9am and 5pm of each week day, while leaving a gap at 1pm, when many workers would have a lunch break. Where we didn’t have on-the-hour temperature records, we used the closest available record.

We then applied a combination of the Sahu and Wyndham models that estimate how much work capacity is reduced for each hour at different temperatures for work of moderate intensity.

While this method doesn’t account for differences in work hours around the world, differences in the ways people cope with heat or for inconsistencies in where weather stations are located, it nonetheless shows that the negative impact of heat has clearly risen in just 30 years from 1990.