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Warming Means Outdoor Laborers Will Work Less in Hot Months

By Stephanie Paige Ogburn, E&E reporter
2/25/2013 12:22:23 PM

By 2050, construction workers will have to spend twice as much time taking respite from the heat as they do now, due to rising temperatures and increases in humidity, according to a study released yesterday in the journal Nature Climate Change.

Outdoor work becomes riskier and more expensive as climate change sets in. Photo courtesy of Flickr.

Researchers from the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory say laborers working outside and in non-air-conditioned settings where heat and humidity affect them, like in kitchens or furnaces, already have to work 10 percent less than normal in hot months, due to heat stress.

By 2050, that reduction in work time will reach 20 percent, even with just a 1 degree Celsius increase from current global temperatures. By 2100, they predict, cities like Washington, D.C., already known for its muggy summer conditions, will begin to feel more like New Orleans, and New Orleans will begin to feel more like the Persian Gulf country of Bahrain.

John Dunne, the lead scientist on the paper, said this study was unique because it looks at the effects of heat stress in normal conditions, versus during specific weather events.

"Previous work looking at heat stress under climate change has focused on conditions to which humans are not well-adapted, such as heat waves. ... What we wanted to do was focus instead on heat stress conditions to which humans are currently adapted," Dunne said in a Friday news conference on the study.

Heat and humidity factors

The measure Dunne and his colleagues used to calculate the effects of heat stress is called the wet-bulb globe temperature, which looks at the combined effects of heat and humidity.

That's a smart way of calculating how climate change will affect the human body, because global warming is projected to increase humidity, said Matthew Huber, director of the Purdue Climate Change Research Center and a professor of Earth, atmospheric and planetary sciences.

"[It] embodies the basic principle that we are all familiar with, 'It's not the heat, it's the humidity,'" Huber wrote in an email.

The researchers projected heat stress impacts on workers out to the year 2200, under two warning scenarios. The first assumes mitigation, where CO2 concentrations begin to stabilize after 2060 to 543 parts per million by 2115. The second scenario assumes CO2 concentrations continue to increase through 2200.

Under that second scenario, worker heat stress is severe; by 2100, the hotter parts of the globe lose 47 percent of worker capacity due to heat stress in hot months, and by 2200, 61 percent of that capacity is lost.

"Only by limiting global warming to less than 3 degrees Celsius or 5 Fahrenheit would we retain labor capacity, as we've defined it, in all areas in even the hottest months," Dunne said.

Heat stress to spread widely

The study modeled projected heat stress impacts across the globe, with maps indicating which areas would see the biggest work reductions due to increased heat and humidity. As expected, equatorial areas are the hardest hit, but under the severe warming scenario, heat stress is a significant factor across a large swath of the globe, except for extreme northern climes, parts of Northern Europe, and California and the Pacific Northwest.

The research did not take into account the effects of urban heat islands, which could increase heat in urban centers, because the science in that area is under debate and thus difficult to put into a model, said Ron Stouffer, a co-author on the study.

A scenario where workers have to rest more to get out of the heat will have significant economic impacts, and the researchers said they hoped economists would use their results to put monetary figures on what the productivity losses could mean.

While they would like to be able to predict how heat stress could affect specific municipalities and regions, their models don't yet have the ability to do this, although it is a goal, Stouffer said.

"The point to be made by the paper is that [in] the future ... the planet will start experiencing heat stress that is unlike anything experienced today," Stouffer said.

Reporter Christa Marshall contributed.

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500. E&E Publishing is the leading source for comprehensive, daily coverage of environmental and energy issues. Click here to start a free trial to E&E's information services.

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