Funny "debate" about water vapour

[Findthepin1]

I feel like I need to share this. It's funny.

Today my teacher said water has a moderating effect on the climate. I said it's because water vapour is a greenhouse gas, and it traps heat during the night. I was going to mention the fact that the Amazon area is humid, and stays almost the same temperature day or night, and that the Sahara area is dry, and has a very large temperature difference relative to the Amazon, but I didn't get a chance to. They said "Water vapour isn't considered a greenhouse gas." I got somebody to look it up. I was right. It was like:

Me: "It's the greenhouse effect. (blahblahblah explanation)."

Teacher: "Water vapour isn't considered a greenhouse gas."

Me: "Yes, it is. The-"

Teacher: "No."

Me (strained laughing): "Somebody look this up, please."

Person whose name will not be written here for privacy's sake: "It is. He's right. He should be our teacher."

Quiet laughs, murmured agreement

Teacher (smiling): "…No"

I laugh

The teacher ended up not letting me talk for the remainder of the period because they thought I was going to bring the subject up again, while they went on to talk about how chlorofluorocarbons are produced and why they were banned on Earth, without mentioning their extreme role as a greenhouse gas, and about how continental drift is "evidenced" by the fact that people walked across the Bering Strait thousands of years ago. I tried to help, believe me. It was a fun day.

I have heard such statements from my teachers before. A different one once said that primates have been around for 10 billion years, and anatomically modern humans for 20 million. I corrected them by telling them the age of the Earth. Everyone agreed with me. That was another fun day.

P.S. I'm probably wrong about the water vapour holding heat at night thing. Please let me know.

Edited November 4, 2015 by Findthepin1

[Bill Phil]

The atmosphere as a whole holds the heat, including the water vapor.

[GeneralVeers]

The water vapor is much better at it, though. Carbon dioxide is like Imperial Stormtroopers. Only effective in huge numbers, and one all by itself is completely useless.

Water vapor is Chuck Norris.

And also, bonus points to Findthepin1 for conclusively proving teacher wrong. Pretty please with sugar, would teachers PLEASE learn the real truth about stuff before teaching idiocy.......

[NFUN]

At a certain point, it isn't worth it, or at least with some teachers. I regretted putting on a funny look when my Physics teacher said the CMB was caused by supernovae. He is pretty far to the rightt in the d-bag curve, but caution still is important.

[insert_name]

I also belive that waters massive specific heat capacity has a role

[Bill Phil]

I also belive that waters massive specific heat capacity has a role

It is above 4...

[K^2]

Heat capacity is 4.19 J/g for water in liquid state only. It's less for vapor.

But yeah, regardless of whether that's the main effect or not, water vapor absolutely is a greenhouse gas. In fact one of the reasons CO2 doesn't have as big an impact as it could have is because across a wide band of IR atmosphere is already opaque due to all the water vapor.

[KerikBalm]

Is this where you tried to say that human caused global warming is a hoax, and that you know more (as what, a high school student?) than pretty much all climatologists on the planet?

What class had a teacher that was telling you that primates were 10 billion years old? I hope its not your science teacher.

If you're continuously exposed to tripe like that, maybe I can understand why you start to believe a lot of what you are told about science is BS.

Water vapor does have a moderating effect for additional reasons... like raising the albedo of the planet so that more less incoming EM radiation is absorbed.

But if you want to start the global warming debate again... you might as well necro the last thread you participated in...

[Streetwind]

@KerikBalm: He wanted to post something funny. Other posters in this thread are calmly talking to each other and are largely in agreement, only helping each other out with extra info. The only one trying to start a debate here is you... why so angry?

[Claw]

I'd ask you to not skate down the global climate change warpath again. There's only one post I see now that's bringing it up, otherwise it appears that people are discussing water vapor and it's potential as a greenhouse gas (in addition to a personal anecdote).

Cheers,

~Claw

[Rune]

I feel like I need to share this. It's funny.

Today my teacher said water has a moderating effect on the climate. I said it's because water vapour is a greenhouse gas, and it traps heat during the night. I was going to mention the fact that the Amazon area is humid, and stays almost the same temperature day or night, and that the Sahara area is dry, and has a very large temperature difference relative to the Amazon, but I didn't get a chance to. They said "Water vapour isn't considered a greenhouse gas." I got somebody to look it up. I was right. It was like:

Me: "It's the greenhouse effect. (blahblahblah explanation)."

Teacher: "Water vapour isn't considered a greenhouse gas."

Me: "Yes, it is. The-"

Teacher: "No."

Me (strained laughing): "Somebody look this up, please."

Person whose name will not be written here for privacy's sake: "It is. He's right. He should be our teacher."

Quiet laughs, murmured agreement

Teacher (smiling): "…No"

I laugh

The teacher ended up not letting me talk for the remainder of the period because they thought I was going to bring the subject up again, while they went on to talk about how chlorofluorocarbons are produced and why they were banned on Earth, without mentioning their extreme role as a greenhouse gas, and about how continental drift is "evidenced" by the fact that people walked across the Bering Strait thousands of years ago. I tried to help, believe me. It was a fun day.

I have heard such statements from my teachers before. A different one once said that primates have been around for 10 billion years, and anatomically modern humans for 20 million. I corrected them by telling them the age of the Earth. Everyone agreed with me. That was another fun day.

P.S. I'm probably wrong about the water vapour holding heat at night thing. Please let me know.

First, well done for being right. Even better for holding your ground. BUT. Tread carefully! Antagonizing anyone in an argument won't get you anywhere other than feeling smug, doubly so if your grades depend on that person. I know I'm not the best person to say this (made this particular mistake a few times myself), but if you are going to shame a teacher for their lack of knowledge, you'd better do it in private so they can save face with the class. I still remember this min/maxing problem in high school when I hijacked the whole math class... and since I became stubborn, I was never allowed to show the numbers that proved me right, and instead got laughed at, and everybody learned it wrong.

Rune. After all, you don't have to study much to en up teaching, at least in my country...

[KerikBalm]

About the "debate" that "I brought up"... I don't think it takes a lot of reading between the lines to see it was already brought up.

The very first line of the first post:

"Today my teacher said water has a moderating effect on the climate. I said it's because..."

So far the teacher hasn't said anything wrong, and FindThePin interrupted to bring up "greenhouse gas" which is intimately linked to the subject of climate change. He's brought it up many times here, and I'd be willing to bet that he's brought it up in class before. My guess is the teacher was trying to shut him down quickly and prevent him from hijacking the lesson to promote a certain viewpoint on another issue.

After all, he said: "The teacher ended up not letting me talk for the remainder of the period because they thought I was going to bring the subject up again"

My guess is that he causes problems in class whenever something related to this subject comes up

The teacher tried to shut him down poorly and without nuance... that's all I will acknowledge.. and that's not so funny.

That some other teacher says ridiculous things like " primates have been around for 10 billion years, and anatomically modern humans for 20 million" isn't relevant here. I suspect its an attempt to cause some sort of false association of one teacher with another in the minds of readers - so that they don't notice he probably was simply disrupting the lesson.

Antagonizing anyone in an argument won't get you anywhere other than feeling smug, doubly so if your grades depend on that person. .... but if you are going to shame a teacher for their lack of knowledge, you'd better do it in private so they can save face with the class.

Well, even at university level, you can have someone from a nobel prize winning lab giving a lecture, and saying something wrong.

Dr. Micheal Hengartner was teaching a class to us once.... this guy:

http://www.uzh.ch/news/articles/2015/wenn-das-telefon-aus-stockholm-klingelt_en.html

"Although UZH president Michael Hengartner hasn’t won a Nobel Prize himself, for several years he worked at the MIT lab of Robert Horvitz, who earned the Nobel Prize in 2002 for his research into the nematode worm C.elegans. “So at least I had a nose for a Nobel-prizewinning field of research,†grinned Hengartner. "

Anyway, it was a fairly basic (that's a matter of opinion of course) lecture, where he was asking us questions about how you might go about deciphering the genetic code of an organism (they don't all have the same code, assume you found one with a completely different code) - not the sequence but the codon-amino acid mapping...

Then he asked us why there aren't any unassigned codons... and I resisted the urge to be a smartass here...

The answer he was looking for was that an unassigned codon would cause ribosome stalling if there is no tRNA to recognize it, or termination factor to release the mRNA and peptide...

The problem is... there are unassigned codons... at least in one species (surely in more species)... so during the break (it was a two hour class witha break in the middle)... I went up to him in private and told him that there are unassigned codons, at least in the species M. capricolum.

Some quick googling preliminarily convinced him that maybe I was right, and when the class started again, he told the class that you can in fact have organisms with unassigned codons, and credited me with informing him of this.

After the class we talked more, and he thought some more information was needed to confirm it... and by e-mail exchanges I found the papers definitively proving it, and he was satisfied.

There are multiple examples of organisms that don't use all 64 codons, but most have the capability to read all 64, so far its just the one that I know of that can't read all 64.

You may know that some organisms have a highly skewed G-C content... to one end or another... because not all bases are equal. DNA with a high % GC content has a higher denaturing temperature... organisms in hostprings may have high GC content... organisms in low temperature environments may skew towars low GC... then there are also metabolic reasons...

Anyway... M capricolum has a very skewed GC content indicating that selection against certain basepairs is really strong... and because the basepairs are so uncommon, its very very very uncommon to get a spontaneous mutation to produce a codon containing 0-1 of the favored bases... that this organism can dispense with a full set of tRNAs... the detrimental effect of having a very rare spontaneous mutation that causes ribosome stalling is not large enough to offset the benefits to the organism of not mainaining a full tRNA set... apparently.

Anyway.... I'm digressing... I second Rune's statement... if the teacher says something wrong, correct them in private... they will probably appreciate it and make a statement to the class correcting the misinformation.

If the teacher hasn't even made an incorrect statement... don't interrupt.

I can't tell you how many presentations I go to (the department here has weekly meetings where people present scientiic papers or progress reports) where people get interrupted, only to have the question answered in the very next slide.

Wait for the teacher to finish talking about the subject, and then if something still remains unanswered or incomplete, then ask.

From what I read here, it sounds like you interrupted the teacher and tried to bring up a subject that you've brought up before (both in class, and on these forums), and the teacher didn't wan't to put up with it.

[peadar1987]

Water vapour does increase the effective heat capacity of air (mainly by changing phase), and will indeed buffer temperature changes, but the major contributor to the lack of temperature variation in the Amazon is the amount of liquid water around the place. It has a far higher specific heat capacity than sand and rock, as well as also undergoing a phase change, and buffers the temperature changes far more effectively than the relatively small amount of water vapour you will find in the atmosphere. The mass of vegetation (itself containing a lot of water), and the fact that the rainforest prevents mixing of air, trapping heat close to the ground, also has an effect.

The effects are correlated (obviously there will be more water vapour in the atmosphere if there is a source of liquid water to pull it from), but more water vapour in the atmosphere isn't the primary cause of buffered temperature changes.

[PB666]

Amazon lies under the TCZ, its known for moisture production and low end termostability, due tonits diatance to the poles. This explains why there are lots of forest in the ITZ,

Trees have a profound effect on energy, particularly in wetlands.

They transpire, many actually recycle water in the upper canopy.

Block sunlight from hitting the ground. pan evaporations rates give testimony to the profound effect direct sunlight has on thermal conversion at the earth surface. If you take direct solar radiation off the surface youbreduce the ability of the sun to cause diurnal ground temperatue cycles. Without this the ground does not effectively heat up.

Since heat rises all the air between the ground and the upper canopy stays cooler.

Since the canopy soaks up water and the uses it to keep itself cool it stays cooler, and since the acces to air below, cooler wetter, it has a better convection than the grass covered surface. The almost saturated air heats up under the surface of leaves which push water into the air, the heated air picks up the vapor cooling the leaf and spreading the suns heat out as vapor of 1000s of meters of air column and there you have thermostability. Then around 2 to 4 PM the atmosphere takes a dump and releases the heat back to the air in the upper elevations where it gradually radiates back into space.

[Red Iron Crown]

Doesn't water vapor in cloud form help reduce solar gain by raising the Earth's albedo?

[Vaporo]

Eighth grade science: man, that teacher had no idea what she was talking about. According to her, sound travels slower in water than in air, the moon's dark side is always dark while one side simultaneously always faces earth, etc. Luckily, she was willing to listen when I tried to say that she was wrong. Still, though, she obviously only knew what her lesson plans told her about science and not much else.

[peadar1987]

Doesn't water vapor in cloud form help reduce solar gain by raising the Earth's albedo?

Well, clouds aren't technically water vapour, they're an aerosol of liquid water droplets (and/or ice crystals). But yes, increased cloud formation is one of the possible negative feedback loops associated with increased global temperature.

[Jovus]

I thought the primary local effect for water moderation of weather went like this:

1) Sun goes up. During the day, both sun and water get warmer

2) Sun goes down bcause the sun does that. Things start cooling off.

3) Ground cools pretty quickly, because all told rocks have a fairly low specific heat.

4) Water cools more slowly, releasing its heat over time to the air overnight

5) Therefore, places near large bodies of water have less daily (and therefore seasonal) fluctuation in temperature.

6) Temperature gradient is a huge driving factor in weather; therefore, places near large bodies of water have more consistent weather.

Is that not the case? Did I get something wrong? Inquiring minds want to know.

(I'm not disputing that water vapor is a greenhouse gas; it clearly is.)

[YNM]

Fair reasoning ! Good job on that, but I want to correct something :

My teacher said water has a moderating effect on the climate. I said it's because water vapor is a greenhouse gas, and it traps heat during the night. I was going to mention the fact that the Amazon area is humid, and stays almost the same temperature day or night, and that the Sahara area is dry, and has a very large temperature difference relative to the Amazon, but I didn't get a chance to. They said "Water vapor isn't considered a greenhouse gas." I got somebody to look it up. I was right.

Water vapor is indeed a "greenhouse gas" thanks to it's relatively high specific heat capacity, but as soon as it's hot, it moves up (doing work) -> lose heat -> lose even more heat by condensing and freezing (ice is blinding, you know that, and the sun is **** hot thanks to it's heat rays, so heat rays reflected, disaster averted) -> falls down -> water vapor lost from air, rays reach new water surface -> start over.

You might want to apologize to him/her though, as he/she isn't completely wrong. Amazon is full of tree coverage (which, like, reflect the wavelength where the Sun is most intense at), and very wet (full of swamps) so it's not as easily being heated thanks (again) to liquid water high specific heat capacity ; Desert, on the other hand, got no water, and specific capacity of directly exposed rocks is pretty low compared to water. The same reason why you get the sea cool wrt land at day and warm wrt land at night.

That being said, I think I remembered looking at a graph for average content of water vapor in the atmosphere. And guess what - it was like, going up in time...

Edited November 4, 2015 by YNM

[magnemoe]

Water vapour does increase the effective heat capacity of air (mainly by changing phase), and will indeed buffer temperature changes, but the major contributor to the lack of temperature variation in the Amazon is the amount of liquid water around the place. It has a far higher specific heat capacity than sand and rock, as well as also undergoing a phase change, and buffers the temperature changes far more effectively than the relatively small amount of water vapour you will find in the atmosphere. The mass of vegetation (itself containing a lot of water), and the fact that the rainforest prevents mixing of air, trapping heat close to the ground, also has an effect.

The effects are correlated (obviously there will be more water vapour in the atmosphere if there is a source of liquid water to pull it from), but more water vapour in the atmosphere isn't the primary cause of buffered temperature changes.

true, however the amount of water vapour affect temperature changes at one fixed place too, in Europe this is most noticeable during the autumn and winter.

if its humid temperature don't drop so much during the night as then its already cold and dry.

During summer its not so easy to notice as sunny days are far warmer and cloudy days are cool

Else large amount of water at as an heat storage and even out temperatures this is coastal climate, it will also produce humidity.

[PB666]

Doesn't water vapor in cloud form help reduce solar gain by raising the Earth's albedo?

Its self limiting, the more clouds the lower the pan evaporation rate which means lower surface evaporation. Lower evaporation means dynamic equilibrium shifts toward clearing skies. The players in turnover are

1. Diuranal heat cycle

2. +/-Latitudinal cooling - lower incidence angles

3. Coreialis effect and thermal gradients of any kind, doesn't matter.

4. Surface irregularites (e.g. mountains) ..... terrain elements that either accelerate air mass or cause it tobrise quickly.

The combinatio of moisture and the above drives the dynamic toward the clearance of clouds through precipitation, which then favor higher pan evaporation rates.

Unlike CO2 and other greenhouse gases water tends trap heat at low humidities but at saturation prevents heat from reaching trapable layers.

[problemecium]

Heh.

I remember once seeing a quiz question that read, verbatim: "What is the greenhouse gas?"

Of course it was easy to surmise what the poor author meant to be asking, but there is no "the" greenhouse gas. In fact, pretty near EVERY gas can cause a greenhouse effect. Even glass does it (it's where the term "greenhouse" effect came from after all).

Dumb people are dumb.

[Gaarst]

Dumb people are dumb.

Be careful not to mix ignorance and stupidity. Ignorant people can be taught, truly stupid ones are often helpless.

Though in the OP, the teacher insisting on his/her mistake was probably more a matter of pride than anything else, even unconsciously.

[Wesreidau]

Water vapor is indeed a "greenhouse gas" thanks to it's relatively high specific heat capacity, but as soon as it's hot, it moves up (doing work) -> lose heat -> lose even more heat by condensing and freezing (ice is blinding, you know that, and the sun is **** hot thanks to it's heat rays, so heat rays reflected, disaster averted) -> falls down -> water vapor lost from air, rays reach new water surface -> start over.

Am I to understand the Earth "sweats", carrying heat from the surface into the upper atmosphere and space? If so, would higher humidity result in more heat loss?

[Chakat Firepaw]

Am I to understand the Earth "sweats", carrying heat from the surface into the upper atmosphere and space? If so, would higher humidity result in more heat loss?

Not quite. The main way the Earth loses heat is by radiation, (mostly in the far IR band[1]), with only a small amount by 'evaporation', (the loss of lightweight gas molecules). Most of that radiation is generated on the surface and in the lower atmosphere.

While increasing the heat capacity of the atmosphere would increase the amount of radiation that can get out, (a photon generated 10km up is more likely to end up in space than one generated at sea level[2]), adding more water to the atmosphere wouldn't really do anything but create more rain. The atmosphere is just about saturated with water vapour anywhere but right near the surface where the ground warms it.

[1] This is one reason why CO2 is such a big deal, it has an absorption peak that is just about bang on Earth's emission peak.

[2] Well, more likely to result in a photon escaping. In reality most of those photons will be absorbed and re-radiated many times on the way up.