Talk:Wet-bulb temperature

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Is it the same as dew point temperature[edit]

Is it the same as dewpont temperature User:Tikai 13:20, 23 May 2007 (UTC)

Generally not. It is at 100 percent relative humidity. If the air is less than saturated, the wet bulb temperature is higher than the dew point. - Ac44ck (talk) 02:25, 25 March 2008 (UTC)
Should this explanation be added to the article? At the very least, wet-bulb temperature and dew point seem to be related terms. Vagary (talk) 03:22, 25 March 2008 (UTC)
I inserted an explanation of this point into the article, because I had the same question.
Here is more: in dew-point, you decrease the temperature till you get 100% relative humidity. In wet-bulb, you decrease the temperature and use the released heat to evaporate water into the same parcel of air. The difference is that in wet-bulb temperature, the evaporated water not only lowers the temperature of the air but also raises its (absolute) humidity, so the temperature at which 100% relative humidity is reached is higher (i.e. sooner) than for dew-point.
In any cases, when one discusses dew-point, wet-bulb, etc., it is clear that the system is not in equilibrium regarding water evaporation. Equilibrium corresponds to 100% relative humidity, and then all 3 temperatures (dry-, wet-, dew-) coincide. But nonequilibrium is the typical case in normal everyday weather situations. While there will be an equilibrium right at the evaporating surface -- it will be at dew point, all 3 temperatures will coincide, and it has 100% humidity so to speak -- these values will diverge as one moves away from the surface. This disequilibrium is possible because it takes time both for the temperature and for water vapor to spread out (diffuse) their changing values on the evaporating surface.
What I wonder about, though, is why the relative humidity is not closer to 100% more often, since after all, it is the equilibrium. A related question is why 100% relative humidity is not exceeded more often. This must have to do with further dynamics of weather -- i.e. the equilibrating mechanism for when the relative humidity exceeds 100% (condensation and rainfall) is far faster than the ones for when it's less than 100% (evaporation, heat diffusion, convection). (talk) 17:40, 13 September 2014 (UTC)

Meaning of "Saturated"[edit]

Ac44ck, are you responsible for the wording of the main article ? If so I would like to point out to you that in thermodynamics 'saturated' means 'in thermodynamic equilibrium with the liquid phase'. In this topic, it is not the air which becomes saturated, but the water vapour which is present in the air. The use of phrases such as "If the air is less than saturated..." here and in the main article suggest a lack of understanding of the topic which undermines the usefulness of the article. Saturated air is air in equilibrium with liquid air, and this is not the meaning that you intend (I think). I hope that you will revise the article and correct these errors; I have done this in one place, but it is not my article, so I do not feel that it is appropriate for me to undertake this task.

Is it a fundamental error, and a false way of thinking to imagine that air mops up water vapour and eventually becomes 'saturated' in the usual sense of the word. According to Dalton's Law of partial pressures, the behaviour of water vapour does not depend in any degree on the presence of air, but soley on the volume which the vapour occupies; the presence of any other gas in that volume is irrelevent. To be based on sound theoretical principles, this article should take cognisance of this basic fact, and should be worded accorddingly. Andrew Smith — Preceding unsigned comment added by (talk) 15:14, 7 February 2013 (UTC)

You will find yourself "correcting" many people whose work is in HVAC. It is not my article, either. Feel free to embark on a mission to bring rigid purity of language to this article. I doubt it would make the article more useful. I suspect you will encounter less than appreciation if you attempt to force the HVAC industry to change its terminology.
You may be surprised to learn that I do not endorse the concept of air "holding" water: Talk:Psychrometrics#Inappropriate_editorialization.
I think the one "correction" you made to this article is not clear. What do you mean "water vapour in the air becomes saturated?" Do you mean the pressure of the water vapor in the air reaches the saturation pressure for water at the same temperature as the air? If so, your "correction" does not say it clearly. Can you phrase what you mean in a way that uses rigidly pure language and is concise enough to maintain a reader's interest? -Ac44ck (talk) 06:37, 8 February 2013 (UTC)

WikiProject class rating[edit]

This article was automatically assessed because at least one WikiProject had rated the article as stub, and the rating on other projects was brought up to Stub class. BetacommandBot 10:05, 10 November 2007 (UTC)


This article explains how to measure wet-bulb temperature and one particular use of that measurement, but doesn't say what the wet-bulb temperature could be interpreted to mean, which should be the first priority in a general-purpose encyclopaedia. Based on my lay reading of this article and dry-bulb temperature, as well as usages at deep lake water cooling and snow cannon, I could conclude that it is one of:

  • An intermediate measurement in the calculation of humidity.
  • A "climate variable" that might be important for "human comfort and building energy efficiency"
  • The temperature that water evaporates at under other environmental conditions
  • The temperature of something with water evaporating off it under other environmental conditions
  • The temperature at which water produces ice crystals under other environmental conditions

The article should explain what the impact of wet-bulb temperature is and how it varies relative to the more commonly-understood dry-bulb temperature. Vagary (talk) 03:34, 25 March 2008 (UTC)

Thanks for elaborating.
  • The article on psychrometrics contains more info on how close a wet bulb thermometer might be to reporting an adiabatic (or, more technically, isobaric) wet-bulb temperature.
  • The details to calculate the dew point from the wet-bulb temperature (as opposed to the other way around) seem amiss here.

-Ac44ck (talk) 05:16, 25 March 2008 (UTC)

The practical considerations section is exactly what I was talking about, great job writing it! I rearranged the lead so readers aren't hit with terms like "adiabatically" right away. Vagary (talk) 16:59, 28 March 2008 (UTC)

Changed isobaric to thermodynamic[edit]

The term "isobaric wet-bulb" seems to be used mostly by meteorologists.

Results 1 - 10 of about 134 for "isobaric wet-bulb temperature"

The term "thermodynamic wet-bulb" seems to be more popular:

Results 1 - 10 of about 894 for "thermodynamic wet-bulb temperature".

-Ac44ck (talk) 22:26, 7 April 2008 (UTC)

Tw as a function of T and Td[edit]

Dr. Eric A Anderson (1968) gives an equation for estimating wetbulb temperature (Tw) from drybulb (T) and dewpoint (Td) temperatures, all in degrees F:

Tw = T - (T - Td)*(0.12 + 0.008*T)

source link: —Preceding unsigned comment added by (talk) 20:04, 7 May 2008 (UTC)

Empirical Tw equations derived by late Julius F Bosen[edit]

"Wet-bulb temperatures are computed based on empirical equations derived by Julius F Bosen and revised by J. N. Johnson in Naval Weather Service Technical Note #7 (1963). Temperatures must be input in degrees Fahrenheit.

For Fahrenheit temperatures equal to or greater than 0-degrees;

TW = T - (0.034A - 0.00072AB)*(T + TD - 2D + 108)

For Fahrenheit temperatures below 0-degrees;

TW = T - (0.034A - 0.006A2)*(0.6(T - TD) - 2D + 108)

where: T = dry-bulb temperature, degrees-F; TD = dew-point temperature, degrees-F; A = (T - TD)/10; B = (A - 1); D = P/33.8639; P = pressure in mb."

source link: —Preceding unsigned comment added by (talk) 21:07, 21 November 2008 (UTC)

Formula for dew point temperature[edit]

*Do we want to show how to calculate dew point temperature in an article on wet bulb temperature?

  • The formula seems overly complex. Is it calculating the dew point temperature at sea level as opposed to at the measuring station? That value may be useful on a national weather map, but it may not be the value usually sought.
  • Shouldn't be "wet-bulb at station pressure" and not "wet-bulb at saturation pressure"?

-Ac44ck (talk) 01:58, 21 December 2008 (UTC)

I moved it to the article on dew point temperature. -Ac44ck (talk) 19:38, 21 December 2008 (UTC)

Cooling adiabatically to saturation[edit]

When asked for a definition of Wet Bulb Temperature I quoted from the article: "the temperature a volume of air would have if cooled adiabatically to saturation at constant pressure by evaporation of water into it, all latent heat being supplied by the volume of air."
Unfortunately the professor of atmospheric physics didn't agree and gave the following feedback:

"Evaporating water into the air parcel isn't an adiabatic process as it involves heat transfer from air to water. This is a semantic point since the system (water+air) is indeed adiabatic but we use the term adiabatic in atmospheric science to refer to the gaseous part of the atmosphere only."

Perhaps it would be worth making the clarification. Zebas (talk) 14:27, 20 January 2010 (UTC)

Wet-bulb temperature and Human Health[edit]

This section seems to be more about a hypothetical "global warming" scenario than a discussion of "Wet-bulb temperature and Human Health."

"The study did not provide new evaluations of the likelihood of future climate scenarios."


Predictions, speculation, forecasts and theories stated by reliable, expert sources or recognized entities in a field may be included, though editors should be aware of creating undue bias to any specific point-of-view.

- Ac44ck (talk) 17:13, 30 May 2011 (UTC)

The section as I originally added it contained three paragraphs.

I assume there is no neutrality dispute with parapgrah #1, which is, after all, simply an introduction to human health issues from heat stress in general and is supported with a direct citation from the (US) Center for Disease Research.

Likewise, I assume there is no neutrality dispute with parapgrah #2, which simply states the medical processes that allow people to survive at ambient temps above human mammalian body temp, and describes how the wet bulb limit puts a bio-medical cap on that process (e.g., if wet bulb temps rise to the point that evaporative cooling becomes impossible).

So far this section is purely a review of human health and biological principles.

So you must be taking issue with paragraph 3, which as I wrote it states:

"There have been very few instances where the wet bulb temperature approached the human limit for a brief time. If global warming raises average temperatures by 12°F it would cause some areas of the world to surpass the human wet-bulb temperature limit, and a 21°F warming would put half of the world's population in an uninhabitable environment."

I assume you have no problem with paragraph 3 sentence 1, since that is based on the historical meteorological record and supported with citations to both science journalism and peer reviewed literature.

Therefore, you must be alleging a neutrality dispute with the last sentence of the last paragraph, talking about global warming. Well, what's the problem? Even if YOU believe in global cooling, the sentence merely states what will happen if you happen to be wrong, and most important for wikipedia's rules, the last sentence is reporting what is stated in the peer reviewed literature without addition or spin.

You seem to feel that the global warming thing is a just a hypothesis. I will rely on scientific opinion on global warming as grounds to consider the neutrality allegation resolved. NewsAndEventsGuy (talk) 20:43, 31 May 2011 (UTC)

I think it reads even more like hell-fire, fear-laced propaganda now. Do you see a neutral point of view there? I don't. - Ac44ck (talk) 01:29, 1 June 2011 (UTC)
Maybe we can compromise. I deleted the potentially offensive cross link to global_warming. But I stick to my guns that (A) the historic record regarding wet bulb temperature as applied to human survival is a relevant topic for "wet bulb temperature". Likewise, a peer reviewed calculation of how the climate system would have to change before humans have a survival issue with wet bulb temperature is relevant to "wet bulb temperature". None of that says anything about whether global warming is a hoax or a threat. It simply states a historic fact about wet bulb temp, and states what the literature says about our climate safety margin in light of wet bulb temp. I can understand that two minds might quibble over the neutrality of one's writing style, but its hard to imagine any neutral editor casting the substance as not RELEVANT.NewsAndEventsGuy (talk) 13:35, 2 June 2011 (UTC)
This seems like an improvement; still, the example is contrived and hypothetical. When has anyone stood naked in a shower with a fan blowing on them in a room that has a wet-bulb temperature of 95°F? The time frame is decades hence. It says portions of the world would become "uninhabitable." Would they all be uninhabitable year-round? Or only for six hours per day on certain days of the year? Except for traditional Eskimos, parts of Alaska are "uninhabitable" for part of the year due to cold. That doesn't stop people from vacationing there in the summer.
If one wants to address "Wet-bulb temperature and Human Health," why not focus on real-world, present-day situations. For one: steam room. Based on the assertions in the referenced article, six hours in a steam room may be fatal.
The readings may not be conincident, but a skim of this article
may suggest people can get into trouble working in 38°C air at at humidity between 67 and 72 per cent.
A graph of endurance vs. wet-bulb temperature may be interesting.
After discussing situations that readers could reasonably encounter in the present day, then it *might* be of interest to discuss a decades-out projection by a scientist who presumably makes money by promoting fear about global warming.
WP:SOAP comes to my mind. - Ac44ck (talk) 23:46, 2 June 2011 (UTC)
Given the scientific opinion on global warming and traffic stats for global warming registering in excess of 10k per day, the research into potential problem should global temps rise is clearly of interest to a number of readers. Plus, its a verifiable reference. For both reasons, it belongs here. NewsAndEventsGuy (talk) 00:06, 3 June 2011 (UTC)
Noted: No acknowledgement that the other three (and perhaps more) facets of the purported topic, "Wet-bulb temperature and Human Health," are of more practical use in the here-and-now to most readers. A theory that is famous for being famous deserves priority over discussing the danger of staying too long in a steam room? - Ac44ck (talk) 00:19, 3 June 2011 (UTC)
Per wiki guidelines I'll assume good intentions by assuming your goal is to improve the article instead of just picking a
fight. To do that, I suggest you go hunt up some verifiable citations about steam rooms and wet temp, and then add
that information also. NewsAndEventsGuy (talk) 01:19, 3 June 2011 (UTC)
"I think it reads even more like hell-fire, fear-laced propaganda now. Do you see a neutral point of view there? I don't. " -- Which shows that you're taking an ideological, not scientific, approach. Merely stating scientific facts and projections is not "hell-fire" or "fear-laced" -- that is purely projection on your part. And the claim that it is "propaganda" is likewise contrary to fact. NPOV does not require that science be countered with anti-science. -- (talk) 23:04, 10 January 2013 (UTC)

I have issues wth the WBGT part of this paragraph. Specifically, the bullet saying 'measurement of solar radiation' should be changed to measurement of radiant heat. This is the transfer of energy from a difference in heat from any two unobstructed, nearby objects. Solar radiation is only one possible source. A furnace, asphalt, even humans also emit this and are applicable to WBGT. As explicitly noted, in the citation already in place. Secondly, again as written in the citation, that formula is wrong. WBGTi is NOT 0.7WB+0.3DB. I'll have to mull over it for a minute but I also think there is a better spot for the last paragraph in the section, if at all.BarrenAvalanche (talk) —Preceding undated comment added 23:03, 5 September 2011 (UTC). .

The first sentence of the second paragraph is incorrect and is not supported by the reference provided. Heat transfer is driven by a difference in temperature and flows from the higher temperature to the lower temperature; this part shouldn't be up for debate. Typical human body temp is 98.6°F skin might be 2°F lower is ambient is typical. 95°F is not hot enough to transfer heat to the body. Even as ambient gets to 97°F and 98°F heat will still not be transfered to the body. Skin will get warmer because the heat coming from the core will not be lost to ambient as quickly. Heat will not be transfered to the body until ambient wet bulb exceeds core temp. "... A sustained wet-bulb temperature exceeding 35 °C (95 °F) is likely to be fatal even to fit and healthy people, unclothed in the shade next to a fan; at this temperature our bodies switch from shedding heat to the environment, to gaining heat from it

..." . BGriffin (talk) 10:59, 5 July 2017 (UTC)BGriffin

Likelihood of environmental conditions approaching wet bulb survival limit[edit]

I think we have resolved the major problems with the sub section on wet bulb temp and human wealth. The remaining issue is whether to say ANYTHING about the likelihood that this will be an issue EVER.

Option 1: Say nothing. That's the current version as I write this.

Option 2: Use the lead authors quote from the news article which in its entirety is:

Although we are very unlikely to reach such temperatures this century, they could happen in the next.

Option 3: Use the author's text from the peer reviewed literature. That paragraph in its entirety (minus internal cites) says:

Recent studies have highlighted the possibility of large global warmings in the absence of strong mitigation measures, for example the possibility of over 7 °C of warming this century alone. Warming will not stop in 2100 if emissions continue. Each doubling of carbon dioxide is expected to produce 1.9–4.5 °C of warming at equilibrium, but this is poorly constrained on the high side and according to one new estimate has a 5% chance of exceeding 7.1 °C per doubling. Because combustion of all available fossil fuels could produce 2.75 doublings of CO2 by 2300, even a 4.5 °C sensitivity could eventually produce 12 °C of warming. Degassing of various natural stores of methane and/or CO2 in a warmer climate could increase warming further. Thus while central estimates of business-as-usual warming by 2100 are 3–4 °C, eventual warmings of 10 °C are quite feasible and even 20 °C is theoretically possible.

If you want to include a reference to the authors statements on liklihood, then we should say something that faithfully reports the authors complete statement without altering its meaning by selective truncation. Or we could just say nothing, which is my current preference for this article. NewsAndEventsGuy (talk) 10:02, 5 June 2011 (UTC)

Still looks like a long-winded way to make a plug for global warming to me. Whether atmospheric temperatures rise or not is about ... atmospheric temperature, not "human health." Where and how wet bulb temperature goes "too high" is meteorology, physics or engineering, not health science. In my experience, the global warming crowd is nothing if not tenaciously tendentious. I may revisit this later. As far as I am concerned for now, I have other things to do and this paper (it isn't yours by chance, is it?) gets cite points for having footnotes in Wikipedia. I would still favor omitting the dire forecast and the emphasis on a criterion that no one else uses. - Ac44ck (talk) 09:18, 6 June 2011 (UTC)


Is User:NewsAndEventsGuy asserting ownership of this article by his last edit summary?

if its repetitive edit or point repitition and I will fix

Is he claiming others must submit edit proposals to him? And, as arbiter and Editor, he claims sole right to make changes?


Also see WP:SOAP.

User:NewsAndEventsGuy tries to make much hay claiming the reference is "peer reviewed" and "carefully cited." Neither are related to WP:NPOV.

To see POV pushing, one need only refer to this edit:

The editor who saw fit to mention "global warming" in the first clause of a section purportedly about "Wet-bulb temperature and Human Health" describes himself as "a climate science friendly guy" here:

This article is about wet-bulb temperature, a thermodynamic property. It is not particularly about meteorological wet-bulb temperature, and nowhere else is it about global warming, prognostications a century hence, or novel criteria.

The "carefully cited" reference is about heat stress. Wet-bulb temperature is only one factor in heat stress. The article also used the value 35°C as a threshold value. Why isn't the reference "carefully cited" in the 35 (number) article? Why isn't it "carefully cited" in the temperature article?

My proposed edit referenced the wet bulb globe temperature article for "Wet-bulb temperature and Human Health" and left it at that.

Repeating information from the wet bulb globe temperature article is redundant.

Positing "a naked person resting in gale force winds" is an unrealistic and novel criterion. Wikipedia is not a platform for promoting the adoption of novel criteria.

Speculating about dire consequences a century hence is POV pushing in an article which is about a thermodynamic property. - Ac44ck (talk) 16:44, 18 June 2011 (UTC)

A. NewsAndEventsGuy (that's me) believes in cleaning up his own messes, that's all I meant.
B. Ad hominem attack is a poor basis for a POV challenge. As they say in legal circles, if the facts are on your side argue facts, if the law is on your side argue the law, and if neither is on your side, pound the table. AC44CK first pounds the table by smearing me personally. Next he tries to argue the law. See Wikipedia:Wikilawyering.
C. An example of wikilawyering is when one individual suppresses information by (a) ignoring WP:Scope to unilaterally demarcate an article's scope and then (b) hyping WP:own with a nasty and false ad hominem spin, both for the purpose of excluding material they find disagreeable. If one wants to look at article history to see about the scope, not so long ago AC was advocating this subsection include a discussion of heat stress and steam rooms.
D. Because there are several explicit references to meteorological concerns in this article and its annotations (and even more implicit ones) the suggestion that the scope excludes meteorological wet bulb temp falls a bit short.
E. Contrary to AC's suggestion, there are four (not one) carefully cited sources in this subsection. Each supports precisely what I wrote in the text. AC's POV challenge is premised on a false characterization of the current text.
F. AC believes "a naked person resting in gale force winds" is a novel and unrealistic criterion. First, that's not my creation but instead the scenario at the heart of Sherwood's paper. Second, I view the colorful language as the scientists' attempt to make the concept of wet bulb temperature and human health instantly accessible to a lay audience. They set out to contemplate the absolute worst circumstances, and then calculate what humans can survive. AC may not like this paper, however see WP:I_just_don't_like_it
G. AC may want to undercut Sherwood's methodology by saying its pure speculation as opposed to a plausible scientific quantification but without some verifiable citations isn't that a POV on his part?
H. Finally, and this is the most ironic of all, articles can overlap. This articles overlap with wet bulb globe temperature was created because NewsAndEventsGuy made a good faith effort to accommodate one of AC's earlier objections! If the Sherwood paper had referenced wet bulb globe temperature instead, the information could go on that page. But Sherwood et al only discussed "indexes", of which wet bulb GLOBE temperature is just one. The article now includes Sherwood's explanation as to why they looked at JUST wet bulb temperature (not wet bulb GLOBE temp). Seems like this is one time that overlap is a necessary evil to clearly explain that line of reasoning, and again, it arose as part of a good faith response to some of AC's earlier criticism.
Thanks for not just deleting it this time. On that we agree. NewsAndEventsGuy (talk) 22:59, 18 June 2011 (UTC)
What did I say that wasn't a fact? In what way do you disagree with the characterization that this article is about a thermodynamic property?
Someone whose recent edit history deals overwhelmingly with climate-change related issues and describes himself as a "a climate science friendly guy" dropped the "we're all gonna die" party line in an article that is about a thermodynamic property. I suppose one might argue that there is "balance" because the reference cited talks about only half the population dying. The hype "half of us are gonna die a century hence if ..." is still speculation and fear mongering.
I did not say this article "excludes meteorological wet bulb temp." I said it isn't about such in particular. Mine was an accurate statement. Your characterization my statement was not.
I suggested other areas where wet-bulb temp is an issue (steam rooms, etc.) because the original text was so skewed to be a pro-global-warming scare piece; the title "Wet-bulb temperature and Human Health" seemed like a farce. I tried to suggest balance, for which I am now criticized.
So the references are "carefully cited." All references should be carefully cited. A cite for the purpose of POV-pushing remains such even if it is done with precise, artistic flair in calligraphy. I didn't say there was only one cite.
Who created a novel criterion is unimportant. The facts are that no one else uses it, and people who are naked in gale-force winds have more immediate problems than "half of us are gonna die a century hence."
I saw WP:I_just_don't_like_it, which includes the converse: "I just like it," as well as the following:
To decide what should be in it purely on the basis of what is merely popular or interesting to whatever small group of editors happens to be around at the time that a discussion is had, is to head down the road towards chaos and confusion.
Based on the multitude of climate-science related edits by NewsAndEventsGuy in recent weeks, it would seem that "I just like it" is apropos.
The "we're all gonna die" hype is "climate science friendly" POV pushing in an otherwise unrelated article.
Did you read the WP:Scope essay you invoked? While it is not a policy, as implied by your invocation of it, the lead of that essay supports my view:
The scope of an article is a description of the article subject which identifies the range of material that belongs in the article, and thus also determines what does not belong (i.e., what is "out of scope").
The lead, ideally the introductory sentence or at least introductory paragraph, of an article, should make clear what the scope of the article is.
Do you disagree that it is possible that a "peer reviewed" statement "does not belong" here no matter how "carefully cited" it might be?
The lead of this Wet-bulb temperature says it is about a measurement, not prognostication. A speculation of the "we're all gonna die a century hence" variety is something that "does not belong" here. - Ac44ck (talk) 08:01, 19 June 2011 (UTC)

PROGRESS! We agree that the article's scope does include some meteorlogical aspects of wet bulb temperature after all.
I don't know about you, but I haven't spent much time in the poorest, hottest, and most humid places in the world. Nonetheless, I am aware that a great many people do live there without air conditioning, and for them, whether they know how scientists do this measurement or not, its role in the weather that rules their daily lives is a major issue. Therefore, the safety margin we humans enjoy is a relevant meteorlogical reason as to why anyone should care about this measurement. Applying your reasoning to the article on penicillin, we should purge that article of any discussion how we use that drug or why care about it. I doubt most folks would agree.
To accomodate your global warming skepticism, the article now makes zero mention wether we're warming, cooling, or staying the same. It simply reports the safety margin these researchers quantified. Would that research be more palatable if it had come from some meteorlogical journal, with no mention of global warming and the "spin" that there is a large safety margin? If a given reader thinks we're warming a great deal they can extrapolate that there's a reason to be concerned. If they think we're cooling, they can feel reassured that this really isn't a problem. It couldn't be more neutral, not even if its deleted, because the deletion proposal is driven by your own POV. If you still have problems with the article feel free to add to the health section and expand it! Deletion because you don't like it is not the answer.
In sum, you're still attacking this research by (a) trying to restrict the article scope to the sterile mechanics of this measurement and excluding any discussion of why anyone should care about the measurement, and (b) continuing to build your case by assailing me personally.
In other words, we're repeating all our prior arguments. May I suggest we both chill out for a bit to see if anyone else wants to chime in?NewsAndEventsGuy (talk) 11:57, 19 June 2011 (UTC)

Wet Bulb and Human Health Considerations (Third Opinion)[edit]

Forgive me, I'm not quite sure of wikipedia's protocol so I'm just going to comment here. As I mentioned above I have several issues with the paragraph as it is currently written. First, it's not solar radiation. It is all types of radiation, as the citation states. Secondly, the formula for WBGTi is wrong.

The whole paragraph is also sort of written stragely, as it sort of seems all over the place.

In order for the human body to function properly (Enzymes and all that good stuff to work), the body must be regulated at ‘normal’ temperature. Hyperthermia or Heat Stress occurs if the body’s internal temperature rises above this normal temperature (~>38C). Thermoregulation of the body occurs through evaporative cooling. Evaporative cooling is where the body secretes sweat, which then rests on the skin. In order for this liquid to evaporate, energy is needed. This energy is taken from the surrounding area by lowering the temperature which cools it – hence evaporative cooling.

Some factors affect the body’s ability to perform this. Exercise or extensive physical activity, heats up the body internally which makes it more prone to heat stress. Fortunately, after exposed to similar work regimens for several consecutive days (4-5 work days) the body begins to acclimatize and work more efficiently.

Externally, the body can be affected by the conventional big three of heat transfer: convection, conduction and radiation. These heat the body. Clothing can also affect this as it can hold the liquid to one’s skin and limit moisture evaporation which obviously impairs the cooling.

Since the rate of moisture evaporation is so important with heat stress, I measure several parameters which affect this ability. While there are different standards to do so, (Humidex and Heat Index are sort of simplified versions), OSHA, CCOHS (the ones I’m familiar with) as well as many other different countries use WBGT. This is also an international standard; I’ll have to double check the number though (ISO ____).

WBGT uses a combination of wet bulb, dry bulb and globe temperature to calculate (as well as coefficients for clothing worn and varying threshold limit values for activity levels / acclimatization). From this, ACGIH publishes TLV which outline how much rest is needed per hour. This allows for us to consider other factors such as humidity (water more readily evaporates in drier conditions, once saturated evaporation becomes difficult), wind (if there is wind it’ll better distribute the evaporated water instead of concentrating it in area while it diffuses), and radiation (every single object emits / absorbs heat energy through thermal radiation, colder object obviously emit less and absorb more. Solar radiation is a portion but not the only means of).

Two different methods are used to calculate this based on the presence of radiant heat sources, known as WBGT outdoors. This can be slightly confusing as the sun is a radiant heat source, but being outdoors and in the shade eliminates this (the two objects are obstructed so there isn’t a radiative transfer between them) so WBGT indoors is used. Likewise, while indoors a radiant heat source such as a furnace or hot machinery, WBGTo is to be used. This is done to better model how the body feels the heat, as skin’s emissivity is very high so it does absorb a lot (WBGTo uses a dry bulb to sort of lower the WBGT reading as a globe temperature is the highest value and raises it so much more on the comparative scale – hence making the TLVs have to be higher).

But I don’t really understand why this can’t all be said in the WBGT wiki article (which I intend to update as it’s also factually incorrect).

I can’t comment on the environmental impact aspect in the last as I come from an engineering / HSE background. However, I’d suggest it could still be shortened significantly, or push it either into the heat stress wiki or WBGT wiki.

Wet Bulb temperature operates through evaporative cooling like the human body. In order for the evaporative cooling to work in humans, the wet bulb temperature has to be lower than the internal human body temperature because it is trying to lower the temperature. As with heat transfer, there also has to be a slight temperature difference for it to occur at a level or reasonable efficiency (e.g. a heat exchanger will typically have a difference of no less than 5C between the hottest cold stream temperature and coolest hot stream temperature – depending on direction of flows.).

Therefore it is plainly obvious that the maximum temperature the wet bulb temperature can be is internal body temperature if evaporative cooling is to occur. The maximum temperature is also going to be slightly lower than that to allow for the evaporative cooling to occur at a reasonable rate. 35C makes sense. The quip about gale like winds, naked, and in the shade is just for testing purposes to eliminate other factors (removes the evaporative cooling affects that wind, clothes and radiation have on the body). 100% humidity just makes for saturation again to keep its focus just on wet bulb temperature. This obviously would never happen and those other factors would actually lower the ‘lethal’ temperature to a lower value. I’ll have to refer to my books but I think there’s a better indicator to determine a lethal temperature, then arbitrarily using just wet bulb on its own.

I guess from my standpoint, that whole section is just stating a whole lot of nothing. It partly explains things and tries to randomly connect to make a point. If anything, I’d just say:

“In order for [evaporative cooling] to efficiently occur in humans, the wet bulb temperature must be slightly below the internal human body temperature at a temperature of 35C.(7)(8) To date, this temperature is not known to occur naturally (for 6 consecutive hours), and researchers believe this would only occur if the average global temperature excessively rises. ((Aside: if the average global temperature is ~15C, a 7C increase is HUGE))

Death or [Hyperthermia] may still occur at temperatures lower than this as the wet bulb temperature is only one component of the body’s ability to [thermoregulate]. To account for these various factors, industrial hygienists, armed forces, and athletes most prominently use the [Wet Bulb Globe Temperature]. This international standard takes into account the wet bulb temperature as well as the [dry bulb temperature], and [globe temperature].”BarrenAvalanche (talk) —Preceding undated comment added 01:58, 6 September 2011 (UTC).

Thanks for input. IMO, various prior versions of the paragraph on human health were better written, flow-wise. What you see on that score is the result of extreme compromise. Point about non-solar radiant heat source is well taken. I can live with your alternative wording, except for characterizing a 7C temp rise as "excessive" and I don't like that because it is subjectively ambiguous. On one hand, 7C increase in earth's average surface temperature would (of course) be a an "excessive" change in the sense of being huge. On the other hand, characterizing that much rise as "excessive" could be misinterpreted as meaning there's no way our climate could ever possibly change that much. However, plenty of geologic evidence suggests 7C more has happened before, and some current climate models running out beyond 2100 agree. Other than that quibble, I can live with the alternative wording. Thanks for caring. NewsAndEventsGuy (talk) 03:33, 7 September 2011 (UTC)
First, can I propose if nothing else that the correct formula be put into that section quickly. It should be 0.7 Wet Bulb + 0.3 GLOBE, not dry. And again, the hyperlink should be to radiant heat not solar (and wording).
I'd also suggest that we don't need the science daily citation unless I’m missing a piece of unique information - as far as I can tell it’s a news article summarizing the other paper cited, but I'd yield to you if you believe it is contributing the other one isn't.
Excessive, is probably poor wording, yes. I'd agree to that for sure, but I couldn't think of a more suitable word.
From my point of view, an excessive temperature jump would have to occur in that it’s well past the point of just a significant change. Most if not all of the world's population would already be dead.
We're talking about a temperature that has NEVER been recorded in the history of humanoids. Let alone for 6 hours. I have been unable to find any record of a wet bulb temperature above 31C.
I'm uncomfortable of using an exact number such as 7C temperature as per my understanding of the article its modelling the likelihood that it is plausible somewhere on earth will reach that temperature. It isn't until 12C in the model that half the population becomes exposed to the possibility. To me there is a lot more ifs involved with that number then the 35c, and the article EXPLICITLY states that 35C is a hypothesized number (for the same reasons I previously listed as being reasonable) it is not the be all, end all and as per the article could be wrong. Furthermore, using that number to me sensationalizes it a bit as it makes it seem like a viable way for mass death. At a glance, it seems like just a small difference.
Global warming is a threat, yes. There is a maximum temperature that humans can survive in if every single other factor is removed - 35C, yes. But that lethal limit won’t be the lethal cause of global warming.
As anyone in an area where that temperature could be reached will be long dead. For that to be the culprit, you'd have to be physically floating in the air to avoid conduction, in the shade to avoid solar radiant heat, away from every single object that emits radiant heat at a similar or hotter temperature (other people, rocks, metal...), and be directly exposed to constant hurricane wind (and no metal fans, as that would give off radiant heat). For 6 hours. That's just to survive at that heat, if any of those don’t occur the 35C drops to a lower value. Without any protection from the elements you'd have to be constantly protecting yourself from flying debris as obtaining cuts would be lethal. With the air temp getting limited relief at night, there isn't a huge time margin for it to even occur daily. It'd also have to be a sudden jump, as humans would otherwise have long moved out of that region as the area would not be viable to support life due to lack of sufficient food, infrastructure and such. Other factors more commonly associated with doomsday in global warming also become a factor - such as the widespread global flooding.
As per the articles, a jump in 5C would have already set in motion other doomsday issues. Those issues don't rely on reaching the maximum temperature in the summer months under 'optimum' meteorological conditions.
You'd also likely have hyperthermia, long before that too.
For instance, above 54C Humidex (I believe thats the threshold for heat index as well) heat stroke is considered imminent by regulatory agencies. 55C Humidex correlates to 40C with a relative humidity of 50% (among values). As per psychrometric charts, that correlates to 30.5C Wet Bulb. In some regions today, heat based death is one of the leading causes of weather related death. People are dying from the heat and we’re nowhere near that 35C threshold.
The more I look at it the more I think the Wikipedia article should just state that its one of the measures used by regulatory agencies and in WBGT to monitor for potential heat stress / hyperthermia, seeing as how the lethal limit of 35c is simply just severe hyperthermia. So I guess I’m in favour of removing all reference to global warming as well. This isn’t a heat stress article and in industry it would be unconventional to use only wet bulb temperature as the health element. As it stands there is no reference to this in hyperthermia or thermoregulation – which is the direct culprits for this. I don’t understand why it is in a topic on the thermodynamic property of value.
To me, It’s like putting a paragraph in the article for ocean on the health hazards of drowning from flooding due to global warming. Where it’s replacing ocean with wet bulb temperature, drowning with hyperthermia/heat stress, and flooding with ambient air temperature.BarrenAvalanche (talk) 16:41, 8 September 2011 (UTC)
Thank you for your informed opinion, BarrenAvalanche. The human health section did not exist until it was used as a mechanism to include a reference to global warming. *How* the wet-bulb temperature comes to have a given value is not important; that is why wet-bulb temperature is a thermodynamic property, a state function. The "how" is important in a thermodynamic process. The doom and gloom global warming scenario is out of place in an article on a thermodynamic property. - Ac44ck (talk) 03:14, 11 September 2011 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── my guess is you two will have no objection to the change I just made in the article. I'm neither agreeing nor disagreeing with comments in this thread, but I can live with the change I just made in the article, and I bet you can too. Of course, please let me know if I'm mistaken. NewsAndEventsGuy (talk) 14:49, 11 September 2011 (UTC)

Global Warming[edit]

This article is not a suitable venue for speculations about global warming. This recent edit is out of place:

although detailed analysis predicts that a large degree of global warming ...

And if a "large degree of global warming" does not happen, then the statement is irrelevant to the thermodynamic property which is the subject of this article. -Ac44ck (talk) 03:28, 9 July 2012 (UTC)

"As of 2010 wet-bulb temperatures only very rarely exceeded 30 °C anywhere although detailed analysis predicts that a large degree of global warming can take wet-bulb temperatures over the human heat-stress limit in many parts of the world."

I like the inclusion of the human health effects, and data on what could potentially be deadly, as well as the highest limits currently reached. But the mention of global warming doesn't exactly make sense to me. The phrasing in this wiki makes it seem like was a question of whether global warming has the ability to affect wet-bulb temperature - this question being extensively analyzed and the study came back in the affirmative. But the sources aren't actually considering that a question, it is a given, only the exact ratio of how wet-bulb increases with global temperatures is studied. If it can be easily assumed that with global warming, wet-bulb goes up, then to say that with "a large degree of global warming" that the wet bulb temperature would similarly raise at least significantly almost seems like begging the question, or some sort of fallacious reasoning. If the question was whether global warming led to an increase in wet-bulb temperature, or whether any degree of global warming would be able to raise the wet-bulb temperature by just a few degrees, it might be relevant. Like one of the citations mentions "I knew just from basic physics that there would be a point at which heat and humidity would become intolerable" all the final phrase is really saying is- if global warming occurs, cause and effect and the basic laws of physics will still be in effect. The last sentence is at best a bad representation of the citations, and worse might even be saying something that the articles themselves don't say. If global warming is to even be mentioned it should read more like "but a large degree of global warming would have to occur for these wet-bulb temperatures to be reached" which is what the sources are saying, and what the wiki isn't, at least not to me Awhislyle (talk) 07:53, 6 December 2012 (UTC)

The article currently say "a large degree of global warming can ..." ... this is quite uncontroversial. And while global warming itself is controversial, it is not controversial that a large number of climate scientists -- certainly the most vocal ones -- as well as much of the media, is saying that a large degree of global warming will occur, and a large fraction of the population believes that it will. Since this scenario is well within the realm of possibility, it is perfectly valid to say what the consequences of it would be.

Those who have vociferously objected that the language isn't neutral have had over a year to repair it but have not done so. As there does not appear anywhere on this page a valid argument that this section violates neutrality nor a coherent suggestion to add material to make it neutral (only calls to remove mention of global warming by people who are clearly ideologically opposed to it), I'm removing the tag. -- (talk) 23:18, 10 January 2013 (UTC)

It isn't appropriate to fix something that doesn't belong. It should simply go away. - Ac44ck (talk) 05:16, 24 July 2014 (UTC)

Vandalism - Jun 11 2013[edit]

I just noticed some idiot wanting attention vandalized "temperature" to "shitty".. I reverted it, but.. there may be other hidden vandalism - can someone who's worked with this article look it over to make sure I didn't miss anything? Thanks, Jimw338 (talk) 23:52, 11 June 2013 (UTC)

Comment on "General" Section[edit]

1) Cooling of the human body through perspiration is inhibited as the wet-bulb temperature (and absolute humidity) of the surrounding air increases in summer.

Good point but should be said mire directly: presumably what is meant is that the wet-bulb temperature is considered a better measure of discomfort than either the dry-bulb temp or the relative humidity alone. But I don't have a source for this.

2) Other mechanisms may be at work in winter if there is validity to the notion of a "humid" or "damp cold."

I appreciate the curiosity about this point (since "damp chill" will not caused by evaporative cooling, could it be by enhanced heat conduction?) but this sounds like a private opinion or a call for research.

3) Lower wet-bulb temperatures that correspond with drier air in summer can translate to energy savings in air-conditioned buildings due to:

Reduced dehumidification load for ventilation air

Increased efficiency of cooling towers

Interesting but perhaps belongs later in the article? (talk) 16:42, 13 September 2014 (UTC)

4) The upper limit for heat stress humans can adapt to is called into question with a 7 °C temperature rise, quantified by the wet-bulb temperature, regions of Earth would lose their habitability.

Is this an inserted political opinion or is global warming really better quantified by wet-bulb temperature readings as opposed to normal temperature readings? In any case this belongs later in the article. (talk) 16:42, 13 September 2014 (UTC)

Okay, looking around the web I can see the crucial difference between typical high dry-bulb and wet-bulb temperatures and their effects on humans. But 3) and 4) should come only after presentation of that essential information. (talk) 16:57, 13 September 2014 (UTC)

External links[edit]

The link marked "Indirect evaporative cooler cools below wet-bulb" seems interesting and relavant, but it appears to be broken. Does anyone know where this should point? --Aj537 (talk) 15:50, 1 May 2015 (UTC)

I changed the link marked "Shortcut to calculating wet-bulb" to what appears to be the same calculator, but at NOAA instead of NOAA seemed a bit more of an authority on meterology. --Aj537 (talk) 15:54, 1 May 2015 (UTC)

External links modified[edit]

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