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Climate Change Is Cutting Humans’ Work Capacity

By Lauren Morello

It’s not just the heat, it’s the humidity that gets you.

That’s the conclusion of a new study that finds climate change has reduced humanity’s ability to work by making the planet hotter and muggier.

That one-two punch has already cut the world’s working capacity by 10 percent since humans began burning large amounts of oil, gas, coal and other fossil fuels at the start of the Industrial Revolution, found the analysis, which was published Sunday in the journal Nature Climate Change.

By 2200, heat and increased humidity would hamper people’s ability to work to less than 40 percent of their capacity.

Researchers at the National Oceanic and Atmospheric Administration predict that dive will continue, reshaping daily life in the most populated areas of the planet as climate change intensifies. 

By 2050, a combination of rising heat and humidity is likely to cut the world’s labor capacity to 80 percent during summer months — twice the effect observed today.

“The planet will start experiencing heat stress unlike anything experienced today,” said study co-author Ron Stouffer, a climate modeler at NOAA’s Geophysical Fluid Dynamics Laboratory. “The world is entering a very different environment, and the impact of that on labor will be significant.”

Those calculations don’t take into effect the relief offered by air conditioning. They do assume people will take other measures to beat the heat — working or exercising in early morning, early evening or even nighttime, seeking shade and wearing clothing that helps maximize their ability to stay cool.

The analysis is based on the effect of changes in “wet bulb” temperatures.

Unlike the air temperatures most people are familiar with, wet bulb readings account for humidity and wind speed as well as temperature. That’s important because high humidity can make it harder for people to cool themselves by sweating, increasing the likelihood of heat-related illness.

To determine whether climate change had already affected people’s ability to work the new study’s authors calculated wet-bulb temperature readings for today’s climate and compared them to pre-industrial conditions.

Then, using a NOAA climate model, the researchers projected how conditions would change over the next two centuries for people who are active in environments without air conditioning. 

By mid-century, they found, climate change is poised to cut work capacity during summer months by 20 percent, compared to pre-industrial levels — twice the effect observed in today’s world.

Credit: World Preservation Foundation

Fifty years later, in 2100, that effect would double again if the world does not find a way to reduce its carbon dioxide output. Humans’ work capacity would drop to just 63 percent during the hottest months of the year.

Zoom another 100 years forward, to 2200, and the Earth’s average temperature would be 11°F hotter than it was before the Industrial Revolution. Scorching heat and increased humidity would slash people’s ability to work to less than 40 percent of their full capacity each summer.

Across much of the U.S., a nasty combination of heat and humidity would create “heat stress beyond what is experienced in the world today,” said the study’s lead author, John Dunne, a NOAA research oceanographer. “This illustrates the stark consequences of extreme warming for the tropics and the mid-latitudes, where most people live.”

In the Lower Mississippi Valley, conditions would prevent any safe level of sustained work, the new study found. That’s equivalent to the most severe rating — “black flag” — on the scale the U.S. military uses to determine safe levels of activity for its troops.

In Washington, D.C., conditions would reach the “yellow flag” level on the military scale, the point at which outdoor activities and work “should be curtailed as much as possible,” according to one Navy handout.

Industrial guidelines for preventing heat stress under those conditions recommend working “25 percent on, 75 percent off” — resting three times as long a period as a person labors each hour.

Finding a way to slash the world’s carbon dioxide output later this century would blunt climate’s impact on work capacity but not eliminate the effect, the researchers found.

If society can stabilize the level of CO2 in the atmosphere by early next century, and hold warming to just less than 3°F by 2100, Earth’s tropics and mid-latitudes would experience months each year of “extreme heat stress,” the study said.

The combined heat and humidity in Washington, D.C., would be more stressful than conditions in today’s New Orleans. New Orleans, in turn, would experience more heat stress than Bahrain does now. And in Bahrain — an island in the Persian Gulf where temperatures already hit 120°F in summer months — heat stress would creep close to the limit that humans can endure for more than a few hours at a time.

Even under that “better case” emissions scenario, Washington, D.C., and New York City would both “well exceed” the heat stress of present-day Bahrain by 2200, the researchers found. 

Experts who were not involved with the research praised it as a solid, sobering analysis.

“This is an excellent study that draws upon existing work on heat stress and combines it with climate model projections of the future to bring home the point that ‘global warming’ means, among other things, that it will get quite hot and wet in many places,” said Matthew Huber, a climatologist at Purdue University.

Huber, who has published work examining the limits of humans’ ability to tolerate high heat and humidity, said the study suggests that economic models used to project the economic toll of climate change may be underestimating its financial impacts.

Another researcher who has looked specifically at the effects of climate change on occupational health and productivity, Ingvar Holmér of the University of Lund, Sweden, noted that the wet-bulb globe temperature index the new study's authors used was developed in the U.S. and Europe and has not been extensively tested in Africa and Asia. But it is likely the best of all available options, said Holmer, who called the new study well-written.

The wet-bulb index "forms a reasonably good basis for this type of calculation because it is well-known and simple," he said.

Thomas Bernard, a professor of public health at the University of South Florida, said it’s clear that “you’re going to have a loss of productivity as the temperatures go up.”

“That’s a good, valid, kind of irrefutable message,” said Bernard, who studies heat stress management. “If (the study’s authors) want to argue that there is an economic cost, I think they’re on strong ground.”

Related Content 
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As Climate Change Worsens, Elderly Face Deadly Heat 
As the South Bakes, Is It Too Hot for High School Football? 
Stress + Pollution = Health Risks for Low-Income Kids


By Dave (Basking Ridge, NJ 07920)
on February 24th, 2013

By all accounts, including some that have been reported here, we will be quite ‘lucky’ to keep the mean surface temperature increase due to climate change to within 3 C by 2100. Keeping it instead to within “3 F” (1.7 C) by 2100 seems realistically implausible in view of current emissions, so I read this as a hypothetical optimistic case study – by which even that modest increase has a miserable effect.

BTW: According to one of your examples, I find the concept of Washington DC going slower than it is today an interesting point of view.  Of course, by 2100, maybe they will have moved the capital up to some nice high ground away from the rising ocean, and since they were moving it anyway perhaps someone would have the bright idea of also relocating it to somewhere further north and cooler, as well as higher.  On the other hand, doing that would require long term thinking….

Nice picture of the pooch.

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By David Zetland (Amsterdam)
on February 25th, 2013

I was just in Singapore and Kuala Lumpur. The future will bring permanent air conditioning (and all the ills that come with it).

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By Eric Peterson (Front Royal, VA 22630)
on February 25th, 2013

There’s no analysis of productivity gains during winter.  Also as all mortality studies show, winter mortality from all causes is higher than summer.

If DC’s summer is too stressful then I suggest moving to Miami where the summer heat is tempered by the gulf.  Here’s DC"s normals and records: Here’s Miami: While Miami is 1-2F warmer on average, they lack extreme heat.

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By pyeatte (Everett, Wa 98208)
on February 25th, 2013

Twenty years ago these nitwits predicted climate doom in twenty years…how did that work out? now they make predictions far enough in the future so they will not be alive when the new predictions don’t work out - how convenient.

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By Jim O'Dea
on February 25th, 2013

In the 1890s we were told by newspapers and magazines that we were entering an Ice Age. The NYT reported 4 different climate warnings: 9/18/1924 - “MacMillan reports signs of new Ice Age”, 3/27/33 - Temperature line records a 25 year rise, 5/21/75 - “A major cooling widely considered to be inevitable, 12/27/2005 - Past hot times hold few reasons to relax about new warming.” Time magazine also reported: .... the southward advance of glaciers in recent years have given rise to conjectures of the possible event of a new ice age”, 1/2/39 - men have no doubt that the world at least for the time being is growing warmer”, 6/24/74 - Climatological Cassandras are becoming increasingly apprehensive, for the weather aberrations they are studying may be the harbinger of another ice age”, 4/9/2001 - “scientists no longer doubt that global warming is happening, and almost nobody questions the fact that humans are at least partly responsible’. The Los Angeles Times on 3/11/29 , “Is another ice age coming?” Page 1 in the NYT 10/7/12 reported “Prof. Schmidt warns us of an encroaching ice age”.

So take your pick hot or cold. Weather men who can’t tell you what next year’s weather or even 6 months from now weather will be like can now predict 40 years and 90 years. Oh yeah, oh yeah

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By Pat (Dayton/Ohio/45334)
on February 25th, 2013

But Jim, what about the picture of the bulldog on ice?  I mean who can argue with that?

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By Squidly (Nashville,TN,37214)
on February 25th, 2013

Pffffft .... Send more money!

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By Mark (Calgary,Ab)
on February 25th, 2013

When NOAA using the same climate modeling programs that they use to predict climate 100 years into the future with can finally get one,just one, hurricane season even close to accurate then maybe he might have a point. Apparently, he missed the head of the IPCC say recently that there has been no incremental warming for the past 17 years. So step back from the ledge

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By Doug Springfield MO (springfield mo 65804)
on February 25th, 2013

Gee. I really like it hotter.  Rode my bike in 104 degrees several days last summer, i went down and rode the hottern hell hundred in wichita falls at a finishing temperature of 109 degrees last august.

You just have to drink lots of water.  plus pickle juice.

It’s gotten where I really feel uncomfortable if ambient outside temp is <  80 degrees any more.

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By Matthew Rosenbaum (Australia)
on March 1st, 2013

Dave (Basking Ridge, NJ 07920),

I’m one of those who believe that the chance to keep man-made global warming to less than 2°C (approx. 3.6°F) above pre-industrial levels is now effectively gone.

I base this on the following:

1. ‘Scientists estimate that humans can pour roughly 565 more gigatons of carbon dioxide into the atmosphere by midcentury and still have some reasonable hope of staying below two degrees. (“Reasonable,” in this case, means four chances in five…)”

2. “In fact, study after study predicts that carbon emissions will keep growing by roughly three percent a year – and at that rate, we’ll blow through our 565-gigaton allowance in 16 years.”


Based on this I conclude:

1. As of today we have about 15 1/4 yrs left to stop burning all fossil fuels (eg coal, oil and natural gas) that produce greenhouse gases. Whilst it could be that we could go a bit longer - as we have “four chances in five’ and the estimates may be pessimistic.

2. However we still face the fact that no serious action is planned by the world’s governments till 2020. This is the date set for the implementation of the UN COP global agreement to tax and limit CO2 output. Business as usual is the plan till 2020.

There is doubt that this UN COP global agreement will ever be signed though - as I wrote elsewhere:

The real problem here for global warming is the fact that the imminent election of Tony Abbott in Oz means that there will be no international agreement to limit CO2 in 2015 - as Tony Abbott would never sign such an agreement. President Obama will not be able to sign also, as both houses of the US Congress would never ratify it. I’m sure that there will be other countries that won’t sign either.

3. Even assuming that there will be an international agreement to limit CO2 that comes into effect 2020. We will be left with just over 8 yrs to complete a task that is of such a scale that it is almost impossible to believe it is realistic. We would have to stop (on a global scale) all forms of transport ie cars, motor bikes, buses, trucks, trains, planes etc and all the world’s power plants that run on coal, oil and natural gas etc, etc, etc.

4. Of course the 8 yrs currently left from 2020 could be extended if we quickly started reducing CO2 emissions from 2020. However considering the magnitude of the task in moving everything that currently uses fossil fuels to renewables. Especially as this would have to be done during a time of an ever growing world population. Whose demands for more and more electricity to meet even its most basic needs will only increase whilst the climate is deteriorating markedly makes this the stuff of fairy tales. How long would it take for this transformation? 40-60 yrs I would have thought - assuming we put the entire world on an emergency “war time” footing. I can’t see that we could possibly stretch the “roughly 565 more gigatons of carbon dioxide” equating to 8 yrs of current consumption by 2020 out to 2060-2080.

So a +2°C (3.6°F) world is theoretically still possible, but practically impossible.

And +3°C is what the UN COP is now negotiating for.

Such Is Life Dave (Basking Ridge, NJ 07920).

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By Dave (Basking Ridge, NJ 07920)
on March 1st, 2013

Matthew - down under:  I would tend to agree. The math doesn’t lie. Overall it seems quite clear that a 2C increase is now unrealistically optimistic. +2C in global mean surface temperature is unfortunately also now increasingly seen by some experts as more of a dangerous/extremely dangerous dividing line rather than safe/dangerous as originally viewed 20 years or so ago.  And global emissions have not even peaked yet.

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By Matthew Rosenbaum (Australia)
on March 2nd, 2013


Thks for the reply. You’re correct. Maths doesn’t lie…unfortunately. How - in this case - I wish it would. It is also true that we are already seeing the impact of warming the planet by 0.8°C (1.44°F). And even if we stopped using all fossil fuels and their derivatives today, due to the time delay it takes for CO2 to begin affecting the climate, we would still warm another 0.8°C (1.44°F). So 1.6°C (2.88°F) is inevitable.

My comment “So a +2°C (3.6°F) world is theoretically still possible, but practically impossible” is based on the possibility that humanity may not begin to act before 2020. To avoid such a scenario it all depends on what we do Now. The next 7 yrs will define history in a way that no preceding 7 yrs has. This is why Australia’s Professor Tim Flannery has called this current period to 2020 “The Crucial Decade”.

I’m currently taking inspiration from one of Winston Churchill’s speeches. I’m not sure if it is true, or just an urban legend, but it goes something like this.

Winston Churchill once stood before a group of College graduates and gave them this Leaving Speech. Looking around at the crowd of expectant students. Waiting on words of wisdom from the Master Orator. The man who had lead Britain to what many considered an impossible victory in World War II:

He said the following 10 words - in increasingly louder and firmer tone:

“Never” (a pause)

“Never” (a pause)

“Never” (a pause)

“Never” (a pause)

“Never” (a pause)

“Never” (a pause)

“Never” (a pause)

“Never…Give Up”

And then he sat down.

End of Speech.

It’s not over yet Dave.

I still live in hope.

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