Hotter, wetter climate slashes labor capacity by 10 percent – ‘We project that heat stress-related labor capacity losses will double globally by 2050 with a warming climate’

By Environment Correspondent Deborah Zabarenko
24 February 2013

WASHINGTON (Reuters) – Earth’s increasingly hot, wet climate has cut the amount of work people can do in the worst heat by about 10 percent in the past six decades, and that loss in labor capacity could double by mid-century, U.S. government scientists reported on Sunday. Because warmer air can hold more moisture than cooler air, there’s more absolute humidity in the atmosphere now than there used to be. And as anyone who has sweltered through a hot, muggy summer knows, it’s more stressful to work through hot months when the humidity is high. To figure out the stress of working in hotter, wetter conditions, experts from the National Oceanic and Atmospheric Administration looked at military and industrial guidelines already in place for heat stress, and set those guidelines against climate projections for how hot and humid it’s likely to get over the next century. Their findings were stark: “We project that heat stress-related labor capacity losses will double globally by 2050 with a warming climate,” said lead author John Dunne of NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton. Work capability is already down to 90 percent during the most hot and humid periods, Dunne and his co-authors wrote in the journal Nature Climate Change. Using a middle-of-the-road projection of future temperature and humidity, they estimate that could drop to 80 percent by 2050. A more extreme scenario of future global warming, which estimated a temperature rise of 10.8 degrees F (6 degrees C), would make it difficult to work in the hottest months in many parts of the world, Dunne said at a telephone briefing. Labor capacity would be all but eliminated in the lower Mississippi Valley and most of the United States east of the Rocky Mountains would be exposed to heat stress “beyond anything experienced in the world today,” he said. Under this scenario, heat stress in New York City would exceed that of present-day Bahrain, while in Bahrain, the heat and humidity could cause hyperthermia – potentially dangerous overheating – even in sleeping people who were not working at all. Humans are endothermic creatures, which means they give off heat. If they can’t get rid of it faster than they create it, they go into hyperthermia. Typically, humans cool off by doing less heat-producing activity, but it may get so hot and humid that even a sleeping person wouldn’t be able to dissipate heat fast enough. “This planet will start experiencing heat stress that’s unlike anything experienced today,” said Ronald Stouffer, a co-author of the study. The only way to retain labor capacity, Dunne said, is to limit global warming to less than 5 degrees F (3 degrees C). [more]

Hotter, wetter climate slashes labor capacity by 10 pct – U.S. study

ABSTACT: A fundamental aspect of greenhouse-gas-induced warming is a global-scale increase in absolute humidity1, 2. Under continued warming, this response has been shown to pose increasingly severe limitations on human activity in tropical and mid-latitudes during peak months of heat stress3. One heat-stress metric with broad occupational health applications4, 5, 6 is wet-bulb globe temperature. We combine wet-bulb globe temperatures from global climate historical reanalysis7 and Earth System Model (ESM2M) projections8, 9, 10 with industrial4 and military5 guidelines for an acclimated individual’s occupational capacity to safely perform sustained labour under environmental heat stress (labour capacity)—here defined as a global population-weighted metric temporally fixed at the 2010 distribution. We estimate that environmental heat stress has reduced labour capacity to 90% in peak months over the past few decades. ESM2M projects labour capacity reduction to 80% in peak months by 2050. Under the highest scenario considered (Representative Concentration Pathway 8.5), ESM2M projects labour capacity reduction to less than 40% by 2200 in peak months, with most tropical and mid-latitudes experiencing extreme climatological heat stress. Uncertainties and caveats associated with these projections include climate sensitivity, climate warming patterns, CO2 emissions, future population distributions, and technological and societal change.