Researchers find future temperatures could exceed livable limits

May 4, 2010 by Elizabeth K. Gardner, Purdue University
This map shows the maximum wet-bulb temperatures reached in a climate model from a high carbon dioxide emissions future climate scenario with a global-mean temperature 12 degrees Celsius (21 degrees Fahrenheit) warmer than 2007. The white land areas exceed the wet-bulb limit at which researchers calculated humans would experience a potentially lethal level of heat stress. Credit: Purdue University/Matthew Huber

Reasonable worst-case scenarios for global warming could lead to deadly temperatures for humans in coming centuries, according to research findings from Purdue University and the University of New South Wales, Australia.

Researchers for the first time have calculated the highest tolerable "wet-bulb" temperature and found that this temperature could be exceeded for the first time in human history in future climate scenarios if greenhouse gas emissions continue at their current rate.

Wet-bulb temperature is equivalent to what is felt when wet skin is exposed to moving air. It includes temperature and atmospheric humidity and is measured by covering a standard thermometer bulb with a wetted cloth and fully ventilating it.

The researchers calculated that humans and most mammals, which have internal body temperatures near 98.6 degrees Fahrenheit, will experience a potentially lethal level of heat stress at wet-bulb temperature above 95 degrees sustained for six hours or more, said Matthew Huber, the Purdue professor of earth and atmospheric sciences who co-authored the paper that will be published in Thursday's (May 6) issue of the .

"Although areas of the world regularly see temperatures above 100 degrees, really high wet-bulb temperatures are rare," Huber said. "This is because the hottest areas normally have low humidity, like the 'dry heat' referred to in Arizona. When it is dry, we are able to cool our bodies through perspiration and can remain fairly comfortable. The highest wet-bulb temperatures ever recorded were in places like Saudi Arabia near the coast where winds occasionally bring extremely hot, humid air over hot land leading to unbearably stifling conditions, which fortunately are short-lived today."

The study did not provide new evaluations of the likelihood of future climate scenarios, but explored the impacts of warming. The challenges presented by the future climate scenarios are daunting in their scale and severity, he said.

"Whole countries would intermittently be subject to severe heat stress requiring large-scale adaptation efforts," Huber said. "One can imagine that such efforts, for example the wider adoption of air conditioning, would cause the power requirements to soar, and the affordability of such approaches is in question for much of the Third World that would bear the brunt of these impacts. In addition, the livestock on which we rely would still be exposed, and it would make any form of outside work hazardous."

While the Intergovernmental Panel on Climate Change central estimates of business-as-usual warming by 2100 are seven degrees Fahrenheit, eventual warming of 25 degrees is feasible, he said.

"We found that a warming of 12 degrees Fahrenheit would cause some areas of the world to surpass the wet-bulb temperature limit, and a 21-degree warming would put half of the world's population in an uninhabitable environment," Huber said. "When it comes to evaluating the risk of carbon emissions, such worst-case scenarios need to be taken into account. It's the difference between a game of roulette and playing Russian roulette with a pistol. Sometimes the stakes are too high, even if there is only a small chance of losing."

Steven Sherwood, the professor at the Climate Change Research Centre at the University of New South Wales, Australia, who is the paper's lead author, said prolonged wet-bulb temperatures above 95 degrees would be intolerable after a matter of hours.

"The wet-bulb limit is basically the point at which one would overheat even if they were naked in the shade, soaking wet and standing in front of a large fan," Sherwood said. "Although we are very unlikely to reach such temperatures this century, they could happen in the next."

Humans at rest generate about 100 watts of energy from metabolic activity. Wet-bulb temperature estimates provide upper limits on the ability of people to cool themselves by sweating and otherwise dissipating this heat, he said. In order for the heat dissipation process to work, the surrounding air must be cooler than the skin, which must be cooler than the core body temperature. The cooler skin is then able to absorb excess heat from the core and release it into the environment. If the wet-bulb temperature is warmer than the temperature of the skin, metabolic heat cannot be released and potentially dangerous overheating can ensue depending on the magnitude and duration of the .

The National Science Foundation-funded research investigated the long-term implications of sustained on climate extremes. The team used climate models to compare the peak wet-bulb temperatures to the global temperatures for various climate simulations and found that the peak wet-bulb temperature rises approximately 1 degree Centigrade for every degree Centigrade increase in tropical mean temperature.

Huber did the climate modeling on supercomputers operated by Information Technology at Purdue (ITaP), Purdue's central information technology organization. Sherwood performed the wet-bulb calculations.

"These temperatures haven't been seen during the existence of hominids, but they did occur about 50 million years ago, and it is a legitimate possibility that the Earth could see such temperatures again," Huber said. "If we consider these worst-case scenarios early enough, perhaps we can do something to address the risk through mitigation or new technological advancements that will allow us to adapt."

Explore further: Errors in the Measurement of Global Warming Corrected

More information: Paper: … /0913352107.abstract

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2.4 / 5 (37) May 04, 2010
Can someone stop paying those retarded researches and use the money for more useful science?
3.7 / 5 (36) May 04, 2010
Can someone stop posting their retarded comments and make some constructive and factual entries?
3.7 / 5 (25) May 04, 2010
It's not retarded nor useless. After all it's a bunch of simulations on how the climate could evolve. Even if the initial conditions and/or the rules used to build it are somehow wrong and approximate, this kind of model can always teach you something.
2.5 / 5 (22) May 04, 2010
I loaded a picture of Earth into Photoshop and, after a full hour of paintbrushing, have a representation of our planet one hundred years from now. The seas have all turned purple, the land masses have smiley faces, and the whole globe has a rather mean-looking leather jacket.

Everything's going to hell in a handbasket here, people! Run for the sleeves!
3.5 / 5 (25) May 04, 2010
This propaganda stuff is becoming a liability for you as I am now obliged to add a disclaimer any time I endorse your site.

Let me guess, you use the Kruger-Dunning effect to say that you're on the high end, right?

Would you like to actually add something to this, such as questionable methods or proof that the study is flawed, or do you just like to sit there and case dispersions with nothing like facts to back you up?
3.9 / 5 (28) May 04, 2010
Can someone stop paying those retarded researches and use the money for more useful science?

Most people thought the scientists that worked on the first cathode ray displays were retarded and useless. Same goes for cat whisker transistors (tubes were obviously better), not to mention the first mechanical cultivators. Expressing Luddite thinking on a scientific site is likely to earn nothing but scorn. Particularly using such ill-stated and abusive language.
2.6 / 5 (10) May 04, 2010
I think I posted too many negative reviews in this section. Here is positive one, for a change.

It is too early to tell, but this study bears all the signs of groundbreaking research. The problem the affects of high temperature on human (and animal) body has a long history. A noteworthy predecessors Dr. James Kettle, and Samantha Hot built a graph of animal lifespan depending on the ambient temperature. (The notorious "Reverse Hockey Stick"). Unfortunately, their research was had a major flaw: they used microwave oven as a heat source, so it was unclear if subjects die of the heat or microwave radiation. The current paper advances the previous study in two directions:
1. It uses computer models rather than microwave oven
2. It explores the much wider range of temperatures.
For example, it predicts that under conditions of the surface of the sun (6000C) the living thing would evaporate in 0.15 sec...
2.5 / 5 (8) May 04, 2010
That's why air conditioning was invented and why AC is enabling more people to live in FL and other tropical locations around the world.

The point is maybe their research would lead somewhere and inspire other more advanced computer models? Perhaps, these models would predict some previously unknown physical effect that would be leveraged on industrial scale and result into something as useful as AC?
4.8 / 5 (12) May 04, 2010
I might suggest that our ablilities to adapt to our environment may one day prove our worthiness in space.
3.2 / 5 (13) May 04, 2010
Good article, and a good idea introducing the wet-bulb concept into the AGW discussion.

Ignore the barkers, they're just enjoying the small notice their jerk comments produce.

"The dogs bark, the caravans move on."
3.2 / 5 (13) May 04, 2010
Wet bulb of 95 degrees in high humidity is lethal after 6 hours? BS! A couple of years ago, I went camping in the Midwest, and it exceeded 100 in the shade far more than 6 hours in a row. Humidity was very high. Several thunderheads formed nearby, but unfortunately didn't hit the campsite so we got no relief from rain and no shade from overhead clouds. The last 2 days of a 4 day camping trip, we easily exceed the so-called lethal wet bulb limit. I'm still here.

Places like Georgia exceed that limit all the time during the summer, and Georgia didn't have air conditioning in the early 1800s when slaves were sweating in the cotton fields. Yeah, I expect more than a few died from heat stroke, but Georgia was hardly uninhabitable.

Even if you believe these wild predictions (which no one should given the track record of previous wild predictions) there's no reason to believe significant parts of the world will be rendered uninhabitable by global warming.
4.3 / 5 (6) May 04, 2010
I think that any problem like this can be solved by engineering a technological solution. All it needs is investment.
3.3 / 5 (9) May 04, 2010
Azpod: did you happen to have a glass-bulb thermometer with a wet cloth wrapped around it to measure the wet-bulb temperature? How often did they do this in 19th century Georgia? Even a slight breeze will lower the wet-bulb temperature significantly. The point of wet-bulb temperature, as I understand it, is to take sweat into consideration. If your sweat can't take away enough body heat, you die. 95 degrees wet-bulb temperature after 6 hours is simply a quantization of this effect. Obviously, on your camping trip, your sweat took away enough body heat to allow you to survive and misunderstand things that are written on the internet.

As for the 'wild predictions' and the world becoming uninhabitable due to global warming, it all depends on how much global warming we get. This research looks at how much warming is needed to make places uninhabitable, and says 21 degrees F will be enough. It also says there's only going be 7 degrees by 2100. Don't jump to ideological conclusions.
2.2 / 5 (13) May 04, 2010
I am getting totally sick of these stories in support of the big lie...otherwise known as global warming.
3.5 / 5 (13) May 04, 2010
And just like everything you've ever posted on this site, jonnyboy, you've added nothing except total BS. Congratulations, you're running at 100% efficiency.
3.2 / 5 (6) May 05, 2010
Wet bulb is measure of humidity - when wet bulb and dry bulb show same temperature we are in 100% humidity.

So why introduce new terminology? Humidity as a standard measure has been around for a very long time.

So what this article is saying in old-speak is that if Global Warming continues unabated for another 2 hundred or 3 hundred years then large parts of the tropics may reach temperatures that are close to 38 degrees C and humidity close to 100% and will therefore become unlivable.

Given that people are not that stupid - I think that if temperatures increase by about 10 degrees C we might notice.

Especially given the fuss we are currently making over a possible 0.5 degree increase in global temperature that may take place in next 10 years or so.
2.6 / 5 (10) May 05, 2010
7 degrees! 12 degrees! 25 degrees!!!!!
Who are all these clowns throwing such preposterous numbers around? Have they even bothered to read the actual IPCC report (assuming at least that one has any validity)? Have they bothered to check and see that the past 100 years have seen no more than +0.8 degrees of warming (physically measured and confirmed by now, not just "modelled")?

I swear, it's like a contest of "who forecasts the most scary Climate Apocalypse" for the press lately. Or like someone derives physiological pleasure from pulling numbers our of their rear.
4.8 / 5 (5) May 05, 2010
... eh, we'll all be living in under-ground / -water cities by then.
Well, not us, we'll be dead...
3.4 / 5 (7) May 05, 2010
Human resiliency is far greater than the wet bulb concept suggests.

We did raise two multicentenial civilizations with high astronomy, engineering, and world knowledge within a tropical rainforest running in temps averaging from 70-90 degrees during hte lifetime of their empire. Second, the areas that are marked as being "unlivable" are primarily desert today with the exception of South America.

We'll simply migrate closer to the poles as we have in times past.
3.7 / 5 (6) May 05, 2010
If this article worries you, I've got some nice cool farmland in Antarctica to sell you. Twenty-four hours of sunlight during the growing season, and a few thousand years worth of irrigation water already present. ;-)

Or you could visit Philadelphia, Atlanta, or Memphis in August to see if you can survive in the conditions they are predicting here. Those cities have 90-90 days. These are days where both the temperature and humidity are over 90 for a significant part of the day.* Offices and businesses without air conditioning (are there any left?) close for the day, and quite often some elderly woman is hospitalized for heat stress after ignoring warnings and working in her garden. (I always wondered if it was the same one every time. ;-)

*Obviously, the wet bulb temperature can be below 95 degrees on one of these days. On the other hand I remember one where the temperature reached 103 with 98% humidity--and no wind to speak of.
4.3 / 5 (4) May 05, 2010
There seem to be a number of people who do not understand wet bulb temps. To put it in "every day speak", it is the dew point. Any meteorologist worth his salt can tell you that the humidity may be 98%, but the dew point can be much lower. I live in the south east and the highest dew point I've seen was around 90 degrees. I used to work for eight hours a day in an enviornment that had temps of 140 degress all day long, but the dew point in that area was amazing low.

All of that said, I didn't see the reasoning behind the predicted rise in dew point along with actual temp. What is the rationale for this? I would think dew points would remain basically the same.
3 / 5 (8) May 06, 2010
Anthony Watts' House of Waffles and Fruitcake? You think that is reputable? The guy that thinks snow is an rebuttal against AGW? The guy with no degree, with no scientists backing him and a forehead the size of Maryland? He's a laughingstock, a moron and a nothing. Go away, you aren't serious about a discussion, you just identified yourself as a pathetic uneducated twit.
1 / 5 (2) May 06, 2010
with no scientists backing him and a forehead the size of Maryland?

Michael Mann?
1 / 5 (4) May 06, 2010
I haven't read the comments above, but let me add this: the weather channel can't even predict what the weather will be like tomorrow. Usually off by at least 50%.
3.7 / 5 (7) May 06, 2010
I haven't read the comments above, but let me add this: the weather channel can't even predict what the weather will be like tomorrow. Usually off by at least 50%.

When viewed over extended periods of time the chaos of weather is a fairly smoothed line of climate. It is easier to predict long term as opposed to regional short term in this case.

Think of it this way, on the quantum scale, the particles that make up an atom appear, disappear, teleport, cease to be, pop into existence, etc. But when you look at the atom, it exists and appears stable.
3.3 / 5 (7) May 06, 2010
Actually, marjoke, I do pay attention to Lindzen. I also pay attention to the other experts that have pointed out where he is wrong. He does have the credentials, but that doesn't mean that he is automatically correct.

Here is a quote from Lindzen: "And if we had warming, it should be accomplished by less storminess."

Lindzen is limited to Lindzen. He shows a clear lack of acknowledgement of the accomplishments of others and thinks that he alone holds all of the cards.
5 / 5 (1) May 07, 2010
The record high dew point (wet bulb temp) was 95 degrees. It occured in Dubai. As I stated earlier, I live in the southeast and the highest dew point I've seen was close to 90 degrees. It is very difficult for the dew point to rise above that which is why I question the prediction of increased dew points for the future just because the air temps rise.
May 07, 2010
This comment has been removed by a moderator.
3 / 5 (2) May 07, 2010

Dew point is relative humidity. The dew point when it rains is 100%. Where are you getting your evidence for Dubai being the highest Dew point, especially since it's a desert.

Are you referring to Dewpoint Temperature?
1.7 / 5 (6) May 09, 2010
ALGORE-ISM: A multibillion dollar faith based, global hoax to redistribute wealth, install global governance, grab power and money, and levy social justice by warning of a nonexistent, impending, major, global catastrophe, invoking the god of “Science”, claiming a consensus, and refusing debate.

Anthropogenic Global Warming (AGW) is preached as the next global catastrophe.

For basis of definition, see: “The Reason” about 5/9 down at:
5 / 5 (1) May 09, 2010
I haven't read the comments above, but let me add this: the weather channel can't even predict what the weather will be like tomorrow. Usually off by at least 50%.

On the contrary, the Nat'l Weather Service is accurate 100% of the time. I suggest you look up just how they predict the liklihood of precipitation: it will surprise you, cuz their method is always correct. Zero error rate.

email me with subject: WEATHER ERROR and i'll explain , for those who can't find the info by themselves.
5 / 5 (1) May 09, 2010
hmmm... trolls keep talking about socialism as if vladmin putin is coming to invade alaska and the only stopping him is sarah "drill baby, drill" palin.

i was a teenage socialist and i will concede that i believe that some intense socialistic projects may be necessary for human survival. all are welcome to please rebut...

my question is; if at some point in the future oil runs out (as we (most of us) are not devotees of a religion of oil as god) as it is a finite resource, where will the energy to BUILD and MANUFACTURE the power system infrastructure that will be needed to serve a world population larger than at present?
5 / 5 (1) May 09, 2010
that, is, where do we expect the energy to come from?

as well, why is it that many seem willing to risk the welfare of the planet and its people against their oil stock or their petro-chem. engineering job to propagandize against taking action?

so, i assert, some socialism is necessary. petro-industry should be appropriated for the good of the people and the energy used to build power system infrastructures of the future, primarily geothermal and solar with hydrogen and electric transportation.

the only problem i see with this is that people are rabidly consuming the propaganda of left vs right that allows for neglect of collective responsibilities. this is no different than the attitude that it is "too expensive to educate the poor, provide excellent healthcare for all, have industries that don't poison everyone" etc.

these arguments for collectivist industry fly in the face of short-term wall-street profiteering.
not rated yet May 09, 2010
well, marjon, nothing coming out of mexico has been good for their people.

here in the u.s. of a. we have gone to war one way or another and trounced every socialist or commie in this hemisphere. why are we not taking out chavez? one reason may be that he is making leftist, oil socializers look really really bad by clamping down on civil rights. so i would hypothesize that he is part of the problem and doing a very good job at it too as the logical conclusion is that what he is doing is "wrong" and can never work.

how are dirty industries working for us?
Expert panel: Carcinogenic chemicals in environment threaten Americans
not rated yet May 09, 2010
Their not retarded they know exactly how to milk the the people for more money.
1 / 5 (1) May 09, 2010
Actually this generation of American, starting with "X", is working harder for less gains than any other previous generation.

The smacktalk in the media about X being lazy was specious drivel.
3.5 / 5 (4) May 09, 2010
Actually this generation of American, starting with "X", is working harder for less gains than any other previous generation.

The smacktalk in the media about X being lazy was specious drivel.

I think it has something to do with corporate and government corruption. The average CEO makes 13 million per year, the average household in America makes ~44k per year. The average government employee makes nearly double the average private sector household's combined income.

Basicly, government and capitalism in general in America have degenerated into a "politically correct" form of fuedalism, or even a pyramid scheme. "Hey everyone, work for us and you'll get the best pay and benefits." But the only people who really benefit are the top 10%.

The price of energy has gone up 300% in the past 10-12 years, and most other goods and services are double the price, but the minimum wage has only gone up 40%, while the average income has hardly gone up at all. CEOs got it all.
1 / 5 (2) May 09, 2010
It's not retarded nor useless. After all it's a bunch of simulations on how the climate could evolve. Even if the initial conditions and/or the rules used to build it are somehow wrong and approximate, this kind of model can always teach you something.

Like how not to use a model to predict anything.
3.3 / 5 (3) May 09, 2010

Compared to what?
"Oil hasn't become expensive this decade; rather the dollar has become very cheap.

In case you didn't know this, people get paid in the fake currency commonly known as "dollars".

Now since minimum wage has only gone up slightly, and average incomes have only gone up slightly, but many goods and services have doubled and tripled in cost, this means the average buying power of the American worker is only about half what it was 10-12 years ago.

So where did the remainder of the inflated dollars go, since they didn't go to wages? It went to CEOs and governments.

So the CEOs end up gaining a disproportionate amount of money compared to average people as the dollar "inflates".

Since lawmakers get to vote themselves a raise every year while normal folks typically cannot do so, it means the rich and powerful continue to get richer and more powerful, while most normal people actually end up worse off than before, even if they work longer hours.
5 / 5 (2) May 09, 2010
Invest in Vault-tech today!
5 / 5 (2) May 10, 2010
One of the primary effects of inflation is to make currently held debt less expensive.

If the worth of money halves, and all incomes and bank accounts stay the same, then the amount of money that workers and savers have is half of what it was. But the amount of money that debtors owe also halves.

Because of this inflation is an (effective) tax on savers, bond holders, and wage earners, but not debt owers or stock holders - those two groups are on the receiving end of the wealth transference.

This is both the strength and the weakness of fiat monetary systems. In a standards based monetary system adaptation and expansion are extremely limited. This has several effects, but one of the biggest is that it means that any largescale mismanagement of money by a government is not a recoverable situation. Fiat monetary systems are flexible enough to allow for gross mismanagement... but at the cost of both standard of living and longterm economic growth.

Both systems have their flaws, reall
not rated yet May 10, 2010
I still think that 1200 characters would be better than 1000;).
1 / 5 (1) May 10, 2010
And now, thanks to Physorg's championing of this trash, it becomes a laughing stock.
I can no longer endorse it as the attached disclaimers and qualifiers are now the body of the text and the good reporting but a footnote.
It's official. Physorg sucks too much.
Sadly, I will now close my account. I can't be associated with morons.

This is the reponce when when stomping your feet like a child. A true intelligent person would be in a Panic to post his views to educate not run away. I do not agree with him but that is not the reason I do not like his post. He gave up or failed to use logic or reason to win the debate.

The facts is that we affcet the world much less than a single volcano. What about the March like weather in May caused by the Iceland Volano. This is a reverse temporary magnitude change in weather predicted by GL.WRM computer models in a few weeks.
not rated yet May 10, 2010
The facts is that we affcet the world much less than a single volcano.

Absolutely wrong. Localized changes due to natural events are pretty minimal as global drivers. I'd ask you to provide proof of your claim, but on this forum that seems to be a pretty rare thing.

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