Why are the glaciers melting?

[MSimon]

What on Earth have the heat equation and the divergence theorem got to do with the plausibility of an ice sheet putting on mass over the bulk of its upper surface while the edges break up? I'm afraid happyjack27 has produced not a straw man but a red herring...

Typical of the CAGW crowd. At least the Second Law bit was scotched. On to the next Red.

[happyjack27]

What on Earth have the heat equation and the divergence theorem got to do with the plausibility of an ice sheet putting on mass over the bulk of its upper surface while the edges break up? I'm afraid happyjack27 has produced not a straw man but a red herring...

man you guys get confused so easily. it is someone else who made a straw man of what i was saying about the heat equation before. can you get that straight in your heads please? to say a person made a straw man of their own argument doesn't even make any sense -- it's not even meaningful. and please don't tell me i have to explain the meaning of straw man to.

as to why the heat equation was brought up, well way back in the beginning peopel weere talking about change in surface area of glaciers. htat sway back in the beginning. it took me this long to explain to them how heat works. all the time they were mocking and ridiculing like small poorly behaved children, unaware of their own ignorance.

really thought this was an older crowd. anycase hope that clears up those confusions.

[happyjack27]

What on Earth have the heat equation and the divergence theorem got to do with the plausibility of an ice sheet putting on mass over the bulk of its upper surface while the edges break up? I'm afraid happyjack27 has produced not a straw man but a red herring...

Well who can blame him? Every time a piece of an ice shelf breaks off, we get video and people claiming this is AGW. How often does the media explain the ice itself is thickening and growing?

This is why politics has no place in science.

as i explained in the comment i just posted 93413's comment isn't even sensical.

[MSimon]

Unhappy,

OK. I'll buy it. You brought a straw man to the argument (the second law) and I corrected you. Fair enough?

now you're just being silly.

Are you saying the second law is the essence of your argument? I distinctly remember you saying that is was not central.

Could you clarify please?

[MSimon]

...it's easy to see how you'd apply it to glaciers and global temperature. to get a fair reading you have to consider that crushed ice melts at a different rate than whole ice, and why that is.

So icebergs melt faster than glaciers? Or? Ice cubes melt faster than icebergs? Or my slurpee is going to melt faster than my iced drink (shaken not stirred)?

From the wiki:

The second law of thermodynamics states that the entropy of an isolated macroscopic system never decreases, or, equivalently, that perpetual motion machines are impossible.

Which is to say you can't get a transfer of Q without delta T. And the Q flows from hot to cold. Unless you are doing work on the system. Carnot had a few words on the subject (very few if you read equations).

[happyjack27]

Unhappy,

OK. I'll buy it. You brought a straw man to the argument (the second law) and I corrected you. Fair enough?

now you're just being silly.

Are you saying the second law is the essence of your argument? I distinctly remember you saying that is was not central.

Could you clarify please?

????

"You brought a straw man to the argument". that is just being silly. it doesn't even make any sense.

and now you're making even less sense. i have no idea what you are talking about anymore.

please just look up the meaning of straw man argument finally. (i feel i've been very patient.) i'lll even do a google search for you. here, top result of "straw man" in google search is: http://en.wikipedia.org/wiki/Straw_man i just did half the work.

read that and maybe then things will be a bit clearer to you.

[MSimon]

now you're just being silly.

Are you saying the second law is the essence of your argument? I distinctly remember you saying that is was not central.

Could you clarify please?

????

"You brought a straw man to the argument". that is just being silly. it doesn't even make any sense.

and now you're making even less sense. i have no idea what you are talking about anymore.

Wait. I thought you said that the second law determined heat transfer across the surface?

And I thought you brought the second law up first. And now you don't want to talk about it? OK. Don't. You first.

[happyjack27]

Are you saying the second law is the essence of your argument? I distinctly remember you saying that is was not central.

Could you clarify please?

????

"You brought a straw man to the argument". that is just being silly. it doesn't even make any sense.

and now you're making even less sense. i have no idea what you are talking about anymore.

Wait. I thought you said that the second law determined heat transfer across the surface?

And I thought you brought the second law up first. And now you don't want to talk about it? OK. Don't. You first.

please just look up the meaning of straw man argument finally. (i feel i've been very patient.) i'lll even do a google search for you. here, top result of "straw man" in google search is: http://en.wikipedia.org/wiki/Straw_man i just did half the work for you. maybe you can do the other half?

read that and maybe then things will be a bit clearer to you.

[93143]

The ice caps are shrinking in surface area only. They are thickening and the ice is growing, not shrinking.

firstly, the second law of thermodynamics works across surfaces not volumes, so surface area change is what you'd look for, not volume change.

The above was your first post. I don't care what happened afterwards; that first post was a complete non sequitur.

the volume of say ice will grow or shrinks in proportion to the spatial temperature differential between the water/ice and the air times the _surface area_ , NOT the volume.

Right, and that volume change is indicative of the conditions seen at the surface.

How does this contradict anything anyone said?

Maybe you should explain what exactly you think the relevance of glaciers to Earth's climate is; I suspect there's a hidden logical disconnect around here somewhere.

...

Basically, if you're worried about the "glaciers melting" you're worried about them getting smaller, ie: losing mass. That mass would then go into the oceans and raise global sea levels. If a land-borne ice sheet is gaining volume, then whether or not its extent is shrinking (which there could be a number of mechanisms for), it is not raising sea levels - quite the opposite.

If it is merely "thickening", that statement is not sufficient to specify mass gain at a rate sufficient to offset the loss at the edges. Under these circumstances more data is desireable to determine whether the ice mass is going up or down.

...

Your example with crushed ice is completely irrelevant as far as I can tell, and it's not like anyone misunderstood it (it's pretty trivial). I really don't see that harping on it accomplishes anything.

Also, you have a really weird definition of the Second Law of Thermodynamics if you think the term is interchangeable with "the heat equation". Have you ever actually studied thermodynamics? Do you know why it is that a heat engine can never exceed the Carnot efficiency? Ever heard of the Clausius-Duhem Inequality?
...

Finally, your reading comprehension is terrible. I did NOT accuse you of anything relating to a straw man.

If it makes you feel any better, I too feel that MSimon is misusing the term.

[MSimon]

????

"You brought a straw man to the argument". that is just being silly. it doesn't even make any sense.

and now you're making even less sense. i have no idea what you are talking about anymore.

Wait. I thought you said that the second law determined heat transfer across the surface?

And I thought you brought the second law up first. And now you don't want to talk about it? OK. Don't. You first.

please just look up the meaning of straw man argument finally. (i feel i've been very patient.) i'lll even do a google search for you. here, top result of "straw man" in google search is: http://en.wikipedia.org/wiki/Straw_man i just did half the work for you. maybe you can do the other half?

read that and maybe then things will be a bit clearer to you.

So was your bringing up the second law a straw man argument? I can accept that.

[happyjack27]

Wait. I thought you said that the second law determined heat transfer across the surface?

And I thought you brought the second law up first. And now you don't want to talk about it? OK. Don't. You first.

please just look up the meaning of straw man argument finally. (i feel i've been very patient.) i'lll even do a google search for you. here, top result of "straw man" in google search is: http://en.wikipedia.org/wiki/Straw_man i just did half the work for you. maybe you can do the other half?

read that and maybe then things will be a bit clearer to you.

So was your bringing up the second law a straw man argument? I can accept that.

i was giving you the benefit of the doubt. but i can only extend that so far. now it's clear that you really are just trying to be an ass.

[MSimon]

93413,

If it makes you feel any better, I too feel that MSimon is misusing the term.

But I didn't use the term first. Unhappy said my calling into question the relevance of his use of the second law in his argument was a straw man. You can look it up.

But you just did the same. Was it the same straw? Or same straw different man. Or different straw same man?

If Unhappy wants to keep discussing semantics I'm fine with that. If he would prefer thermo I'm fine with that.

I'm at ease in either realm. I blog every day. I get lots of practice.

[MSimon]

i was giving you the benefit of the doubt. but i can only extend that so far. now it's clear that you really are just trying to be an ass.

Of course. Succeeding I might add.

Now answer the question. Was your bringing up the second law a straw man argument?

[happyjack27]

The ice caps are shrinking in surface area only. They are thickening and the ice is growing, not shrinking.

firstly, the second law of thermodynamics works across surfaces not volumes, so surface area change is what you'd look for, not volume change.

The above was your first post. I don't care what happened afterwards; that first post was a complete non sequitur.

it doesn't seem to me like you know what non sequitur means. what i said was clearly logically related. he was looking at change in volume as if ti wasnt dependent on surface area. but as we know ice of the same volume will melt faster if it has a larger surface area. so the situation isn't really that simple. so you see that logically relates. non sequitur means that the response does not logically relate.

the volume of say ice will grow or shrinks in proportion to the spatial temperature differential between the water/ice and the air times the _surface area_ , NOT the volume.

Right, and that volume change is indicative of the conditions seen at the surface.

yes, over a long time, you can look at stored energy vs ambient energy and what not. i'm just saying its a more complex process and you really have to include surface are in your calculations to get them to come out right.

How does this contradict anything anyone said?

i never said it did contradicted anything directly. i just wanted to point out that there may be a danger in oversimplifying things to much.

Maybe you should explain what exactly you think the relevance of glaciers to Earth's climate is; I suspect there's a hidden logical disconnect around here somewhere.

...

Basically, if you're worried about the "glaciers melting" you're worried about them getting smaller, ie: losing mass. That mass would then go into the oceans and raise global sea levels. If a land-borne ice sheet is gaining volume, then whether or not its extent is shrinking (which there could be a number of mechanisms for), it is not raising sea levels - quite the opposite.

If it is merely "thickening", that statement is not sufficient to specify mass gain at a rate sufficient to offset the loss at the edges. Under these circumstances more data is desireable to determine whether the ice mass is going up or down.

...

Your example with crushed ice is completely irrelevant as far as I can tell, and it's not like anyone misunderstood it (it's pretty trivial). I really don't see that harping on it accomplishes anything.

Also, you have a really weird definition of the Second Law of Thermodynamics if you think the term is interchangeable with "the heat equation". Have you ever actually studied thermodynamics? Do you know why it is that a heat engine can never exceed the Carnot efficiency? Ever heard of the Clausius-Duhem Inequality?
...

Finally, your reading comprehension is terrible. I did NOT accuse you of anything relating to a straw man.

If it makes you feel any better, I too feel that MSimon is misusing the term.

...

While I'm at it:

actually i tend to test pretty highly on reading comprehension. and your reading comprehension is clearly worse than mine since you added a whole bunch of sh*t i didnt say and therefore ended up misunderstanding me entirely even when what i said was very simple and i stated it very simply.

i haven't read your whole comment and i'm not sure i'll get around to it.

also, positive feedback in the case you suggest would just be absurd - it would violate the conservation of energy.

The scenario is thus: Water vapour traps solar energy and causes the Earth to heat up, releasing more water vapour, which then traps more solar energy, leading to more heating, releasing more water vapour, until the oceans have boiled and the Earth's net emissivity is a tiny number due to all the atmospheric absorption (I believe Venus' net emissivity is about 0.03). This does not violate conservation of energy; the energy source is the Sun and the only way for the energy to leave is via radiation, which is strongly influenced by atmospheric absorption (ie: the so-called "greenhouse effect"). The lower the net emissivity, the higher the surface temperature has to be for the planet to remain in equilibrium under solar irradiation.

The only way this would stop short of the oceans boiling completely away would be if the atmospheric pressure were so high that further evaporation would raise the remaining water's boiling point faster than it would raise the planet's surface temperature. I'd try to figure out if this ever happens, but it's not exactly a trivial calculation, and I really need to get to school and take a look at a two-phase turbulent mixing layer simulation I'm trying to run... Even if such a point exists, we're obviously nowhere near it now...

On a somewhat related note, according to my calculations, if the oceans boiled completely the mean surface pressure would be 27 MPa (about triple that of Venus). Water's critical point is 22 MPa and 647 K, so in this scenario the lower atmosphere would be a supercritical fluid, and would blend smoothly into any "ocean" that was left...

you know you guys are both using the term positive feedback a little loosely here.

No, no they aren't. Have you ever studied dynamic systems and control thereof? This system is obviously nonlinear, but in the regime the planet is currently in, it is reasonable to state that the feedback appears to be negative. (At least, I am not aware of any mechanism that could be holding the climate stable in the face of a positive water vapour feedback.) If it were reasonably warm and very dry, that would not be the case, and the feedback would be positive, but of course it would eventually hit the point of forming clouds, and that would halt the runaway greenhouse effect from water vapour...

positive feedback requires an orthogonal energy source. take for instance an audio amplifier. it can amplify the sound in a positive feedback loop only because it has a source of power _other than_ the sound its amplifying. another example is in the ecosystem - the energy source for positive feedback there is ultimately the sun (or volcanic energy from way back when the earth formed, but you get the idea). so unless you're implying nuclear fusion is going on in the water vapor, thus using the atomic mass as an energy source, the system cannot do that. maybe you're talking about approximate behavior on a short time scale. in which case stored enegy would be your energy source. but really what you have to look at when you're considering something like the atmosphere is is equilibrium or in any case long-term behavior.

in any case the original "positive feedback" usage here seemed to imply a runaway process in which more energy came out than was put in, and that's where the apparent contradiction came in.

as you see the equilibirum results turn out to be vastly different than reasoning from "positive feedback" because e.g. what looks exponential close up really turns out to be sinusoidal, etc. the positive feedback model here is really just an approximation of a certain paramter regime and at a certain scale, which turns out to be something of a more statistical phenomenon that really doesn't have the same qualitative properties. e.g. the phase space / topology ends up being vastly different when you zoom out.

this is what i mean when i say you're using the term loosely.

aslo you're talking about things like reflection and scattering. (no? you guys really haven't given enough information to imply otherwise.) , which are passive things, not active.

[happyjack27]

i was giving you the benefit of the doubt. but i can only extend that so far. now it's clear that you really are just trying to be an ass.

Of course. Succeeding I might add.

Now answer the question. Was your bringing up the second law a straw man argument?

i already told you that's not even a sensible question. look up straw man. please! either that or just stop talking, 'cause this nonsensical crap is really kind of starting to bore me.