Among other things, there are occupational medical regulations in many countries, which require shorter working hours and more breaks after a certain heat stress. The heat effect is measured with the so-called wet-bulb-globe temperature (WBGT). Humidity, air temperature and the heat absorption of a dark hollow sphere - the black ball thermometer - are measured. Because the dark sphere heats up similarly when exposed to the sun, like the human skin, the heat load in the blazing sun can be read from it. If a certain threshold of the WBGT index is exceeded, appropriate countermeasures must be taken, especially on extremely heat-exposed workplaces.
20 percent less productivity due to heat stress
John Dunne and his colleagues have now used climate data and models to investigate the frequency with which WBGT thresholds commonly used in the United States, for example, in industry and the military today are exceeded in comparison to the time before the Industrial Revolution. However, in their model they also examined how the climate change predicted by the year 2200 will affect the WBGT values and thus the labor productivity worldwide and in individual regions. For their climate models, the researchers took into account a climate protection scenario with a temperature increase of only about two degrees Celsius to 2100 and a worst-case scenario with an increase of 3.4 degrees to 2100 and 6.2 to 2200th Display
"According to our results, the increased heat load in recent decades has meant that global output has fallen in the warmest months to only 90 percent, " the researchers report. Particularly affected are India, Southeast Asia, Central America and North Australia. But by 2100, as the models show, the zones that experience extreme heat and humidity in the summer will expand significantly. The heat stress zone now in India will spread across much of Eurasia, with the Caribbean and the Southeast US also exceeding the WBGT limits more often in the summer, according to Dunne and his colleagues. According to their estimates, this heat stress could reduce global output by around 20 percent by 2050 even in the temperate scenario and by 25 percent by 2100.
Hot and humid like today in Bahrain
Under the scenario of almost unchecked warming, it gets even hotter and smoother, as the models show: Large parts of the tropics and temperate latitudes would then experience extreme heat stress for several months in summer. The climate of the US capital Washington DC would then correspond to that in today's New Orleans, that of New Orleans in the today's Bahrain, as the researchers explain. There is already an extremely high humidity and summer temperatures of near 40 degrees Celsius. This would have fatal consequences for productivity: If climate change is largely unchecked, reductions of up to 40 percent could be expected by 2100, and even by 60 percent by 2200. In the coming decades, climate change could therefore have a serious impact on the world of work, warn Dunne and his colleagues.
However, as the scientists emphasize, their analysis is also subject to considerable uncertainty. For example, it is unclear how well the climate scenarios used actually reflect the climate of the future. Technological and social changes, which also affect the working world, are not taken into account. On the other hand, the study assumes only the effects of heat stress on healthy, well-adjusted individuals, say Dunne and colleagues. The impact on people who have health problems or are unable to adapt well is therefore rather significantly underestimated.John Dunne (National Oceanic and Atmospheric Administration, Princeton) et al. Nature Climate Change, doi: 10.1038 / nclimate1827 science.de - === Nadja Podbregar