tag:blogger.com,1999:blog-16612221.post4028341853309006635..comments2024-03-19T03:14:04.172-04:00Comments on Rabett Run: CockburningEliRabetthttp://www.blogger.com/profile/07957002964638398767noreply@blogger.comBlogger37125tag:blogger.com,1999:blog-16612221.post-51291756043261932562010-01-20T07:47:24.280-05:002010-01-20T07:47:24.280-05:00Cheers John,
that's fine, though from my view...Cheers John,<br /><br />that's fine, though from my viewpoint of battling denialists* on the net even simpler is best. I'd go for something like this, cutting out the cumulative totaling altogether:<br /><br />"It has been estimated that of 100 molecules of CO2 injected into the atmosphere, 6 molecules will dissolve in the ocean in 1 year; an additional 23 will have dissolved at 10 years; an additional 30 at 60 years; 25 more at 360 years; and the last 16 molecules will take over 1,000 years to dissolve."<br /><br />* Though in my opinion it's a battle that can't be won - the winning is in getting those who would be (in absence of a dissenting voice) swayed over to denialism on the side of science.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-33706082761089286932010-01-10T10:25:56.251-05:002010-01-10T10:25:56.251-05:00We have the old issue, that there is an interchang...We have the old issue, that there is an interchange btw the atmosphere and the ocean, so that when the number of CO2 molecules in the atmosphere increase, they are not the same CO2 molecules. CO2 molecule have no hair as it were. Then you have the problem of how do you explain this to the clown with the large red nose.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-24179244372025163992010-01-10T00:20:45.229-05:002010-01-10T00:20:45.229-05:00Dear yea-mon:
Thanks for the kind words about my ...Dear yea-mon:<br /><br />Thanks for the kind words about my 1998 piece in Monthly Review. <br /><br />You didn't like the arithmetic in one sentence, so let me clarify it [with additions in square brackets].<br /><br />It has been estimated that of 100 molecules of CO2 injected into the atmosphere, 6 molecules will dissolve in the ocean in 1 year; 29 molecules will dissolve in 10 years [including the 6 molecules in the first year]; 59 molecules will dissolve in 60 years [including the 29 molecules in the first 10 years]; 84 molecules will dissolve in 360 years [including the 59 molecules in the first 60 years]; and the last 16 molecules will take over 1,000 years.<br /><br />-John FarleyJohnhttps://www.blogger.com/profile/09575837647825433144noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-71930222120173164622010-01-08T22:50:25.084-05:002010-01-08T22:50:25.084-05:00Hmm. I knew the Kelvin statement of the Second La...Hmm. I knew the Kelvin statement of the Second Law as "no heat engine can be 100% efficient". Meaning, there has to be some energy wasted through transfer to the heat sink at Tc.<br /><br />But nevermind that, I'm with you. If you draw a Carnot cycle on a T-S diagram, the work extracted is the area of the box (Th-Tc)*(S2-S1). If Th = Tc, then the amount of work done is zero. And if Carnot is the best you can do, then absolutely no heat engine can extract work if Th = Tc. <br /><br />I'll do it quantitatively for the phase change example later, to really convince myself.<br /><br />Thank you for the instruction.carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-29340574745940789182010-01-08T21:38:30.989-05:002010-01-08T21:38:30.989-05:00It violates Kelvin's version of the second law...It violates Kelvin's version of the second law - "it is impossible for a heat engine operating in a cycle at a single temperature to do any net work" - if T_h can be made arbitrarily close to T_c (as the paradox assumed.) When you take into account the pressure dependence of the freezing point, T_h and T_c must differ by a finite amount, approximately (dT/dP)(delta p) where delta p is the pressure exerted by the weight.<br /><br />The pressure dependence of the freezing point implies that the heat of fusion also depends on pressure. To lowest order, it's probably ok to assume that the entropy of fusion is independent of pressure, which would give you delta_S/T_h and delta_S/T_c for the heat of fusion at the two pressures. I think that rescues the First Law.Robert P.https://www.blogger.com/profile/16608096675543218433noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-39683544956665358302010-01-08T15:28:48.041-05:002010-01-08T15:28:48.041-05:00Bleh, lost a comment to cyberspace.
Trying again:...Bleh, lost a comment to cyberspace.<br /><br />Trying again: I retract my previous comment. I think this is a PMM1, not a PMM2. Now if Kelvin thinks it's a PMM2, I'm most likely wrong, but can somebody sort me out?<br /><br />You have ice. You bring in heat source at Th and transfer in Qh, Qh = latent heat of melting. The level goes down.<br /><br />You then put a weight on top, and introduce heat sink at Tc. You extract Qc, which is the same latent heat of melting. The level goes up, the weight goes up, and you can extract work from the weight.<br /><br />To me, this is a violation of the First Law. Qh = Qc, but yet there is a W. This cannot be, and the cop-out is the pressure dependence of the phase change.<br /><br />But beyond that, where is the Second Law problem? Heat flows from Th to Tc. Check. Why does the Second Law care that the working fluid is isothermal, in this case with a phase change?carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-40738418156561983042010-01-08T14:17:53.053-05:002010-01-08T14:17:53.053-05:00Bart is right, Eli read his gravity defying post e...Bart is right, Eli read his gravity defying post earlier this morning. <br /><br />As for the Joe Stigliz mouse, surely you have heard of <a href="http://rabett.blogspot.com/2007/12/rabetts-simple-plan-for-saving-world-un.html" rel="nofollow">Eli Rabett's simple plan to save the world</a>.<br /><br />Best recommendation for a climate taxEliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-45850633335334768052010-01-08T11:59:09.430-05:002010-01-08T11:59:09.430-05:00Great pieces by Farley, though in the earlier arti...Great pieces by Farley, though in the earlier article on the case for AGW the piece on CO2 residence time could be a bit clearer:<br /><br /><i>It has been estimated that of 100 molecules of CO2 injected into the atmosphere, 6 molecules will dissolve in the ocean in 1 year; 29 molecules will dissolve in 10 years; 59 molecules will dissolve in 60 years; 84 molecules will dissolve in 360 years; and the last 16 molecules will take over 1,000 years.</i><br /><br />Denialists will just crow: how do you get 194 CO2 molecules from 100?!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-84562442316764808752010-01-08T09:20:43.441-05:002010-01-08T09:20:43.441-05:00Of topic (and rarely even discussed), but probably...Of topic (and rarely even discussed), but probably far more important than anything else at this late date.<br /><br />The elephant in the room: the failure of Copenhagen and the inevitable failure of carbon trading schemes.<br /><br />James Hansen and the economists who invented emissions trading (to deal with a well constrained SO2 problem) are not the only ones who recognize that carbon trading will likely not work and that a carbon tax with dividend is the better approach.<br /><br />Nobel economist Joe Stiglitz also does (<a href="http://host.madison.com/ct/news/opinion/column/article_a43e6c32-ef98-5c38-9a64-ae22b5732127.html" rel="nofollow">Joseph E. Stiglitz: Overcoming the Copenhagen failure</a><br /><br /><br />"Perhaps it is time to try another approach [than carbon trading]: a commitment by each country to raise the price of emissions (whether through a carbon tax or emissions caps) to an agreed level, say, $80 per ton. Countries could use the revenues as an alternative to other taxes -- it makes much more sense to tax bad things than good things. Developed countries could use some of the revenues generated to fulfill their obligations to help the developing countries in terms of adaptation and to compensate them for maintaining forests, which provide a global public good through carbon sequestration."<br /><br />Stiglitz quote end<br />////////////Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-84195826703694454022010-01-08T09:19:38.351-05:002010-01-08T09:19:38.351-05:00My favorite reply to the "only-one-factor-det...My favorite reply to the "only-one-factor-determines-climate-so-it's-not-us" thinking is that observing a bird in the sky doesn't disprove gravity. <br />Longer version here:http://ourchangingclimate.wordpress.com/2010/01/06/a-quick-n-dirty-guide-to-falsifying-agw/<br /><br />BartAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-25315559394111673922010-01-08T01:14:06.200-05:002010-01-08T01:14:06.200-05:00So my gut is OK. What's wrong with my head? ...So my gut is OK. What's wrong with my head? The latent heat for the phase change is being supplied by something, or being released to somewhere. So this can't be a closed system. It's exotic, but I don't see why a heat engine can't have a working fluid that remains at essentially the same temp, but is changing phases due to contact with a heat sink and heat source. <br /><br />I suppose I could draw it on a T-S diagram and/or calculate the entropy changes. But I'm hoping somebody else will do it for me.carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-57737508007303355362010-01-08T00:09:12.899-05:002010-01-08T00:09:12.899-05:00Carrot Eater, you ought to go with your gut - it&#...Carrot Eater, you ought to go with your gut - it's instincts are sound. The pressure dependence of the melting point is indeed the key to the solution - it turns the arbitrarily small ("epsilon") temperature difference into a finite delta T, the difference between the freezing point of water under the pressure of the weight and the melting point of ice after the weight is removed. That difference, while small, is just enough to ensure that Carnot's requirements are satisfied.<br /><br />See: James Thomson, _Theoretical Considerations on the effect of pressure in lowering the freezing point of water_, Cambridge and Dublin Mathematical Journal, Vol. 5, p. 248, 1850.<br />James Thomson was the older brother of William Thomson, who would later become Lord Kelvin. William discovered the apparent paradox, and James came up with the solution. (Moral: if you think you've discovered a way to circumvent the Second Law, run it by your elder siblings before publishing.)Robert P.https://www.blogger.com/profile/16608096675543218433noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-2322142642511500772010-01-07T23:02:37.314-05:002010-01-07T23:02:37.314-05:00ligne: That's the emotional motivation for th...ligne: That's the emotional motivation for them hang on to the MWP, once they've heard of the possibility. I thought the question is more, where did the idea come from in the first place? <br /><br />Looking around, it was a known term in paleoclimate, though it was always ambiguous whether it was a local or global event. It appeared in the IPCC FAR of 1990 and each subsequent report, and it was discussed in MBH99 itself. MBH99 sources it to Lamb, 1965. <br /><br />I'm assuming that nobody in 1975 was walking around feeling very strongly about the MWP. So maybe it became the rallying cry after the appearance of MBH98/99, and anybody reading MBH99 would have become aware of the idea. <br /><br />I wonder why they don't just use the previous interglacial. Sceptic: It was warmer in the previous interglacial, and there were no SUVs then! Response: That may be the case. SUVs aren't the only forcing on earth. So what?carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-9980189322488390202010-01-07T22:21:29.278-05:002010-01-07T22:21:29.278-05:00Well, following Bloom, let's see. Is it real...Well, following Bloom, let's see. Is it really a PMM2 after all? <br /><br />You can say epsilon is really really small, but it's still finite. So you still need an external heat source to raise the temp by epsilon, and an external sink to lower again by epsilon. <br /><br />So really, you aren't extracting work from an isothermal isolated system. By neglecting to tell us how the heating and cooling is done, you tried to trick us into thinking it was an isolated system, but it isn't. (At least, you got me to neglect that, the first time around).<br /><br />You've got a cyclic process with a Th and Qh and Tc and Qc. The heat input is only partially converted to work.<br /> <br />All should be well. <br /><br />I'm also years removed from thinking in this way, so I could still be wrong.carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-75941567457157233902010-01-07T20:17:18.924-05:002010-01-07T20:17:18.924-05:00RP, I'm no perfesser, but isn't the trick ...RP, I'm no perfesser, but isn't the trick that the energy needed to change the temperature plus friction makes for a losing proposition? I'm thinking this has to be way too obvious, though.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-41644851707598068662010-01-07T19:33:24.111-05:002010-01-07T19:33:24.111-05:00anonymous way back up there, and immediately subse...anonymous way back up there, and immediately subsequent carrot eater:<br /><br />i've always assumed the obsession with the MWP was some sort of brain-damaged attempt to counter the "unprecedented warming in $bignum years" point illustrated by the hockey stick.<br /><br />after all, if it was this warm before, and humans weren't responsible then, it can't be our fault this time, can it? and lack of response is clearly due to the undeniable strength of that argument, and not because it's rather hard to type and facepalm at the same time.lignenoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-35295198802687274052010-01-07T17:50:57.042-05:002010-01-07T17:50:57.042-05:00Well, ok, but Eli thinks it does have something to...Well, ok, but Eli thinks it does have something to do with the problem. Modify the set up in the following way, let the separation between the water/ice and the world be a frictionless membrane and the other side of the membrane be a sealed piston. Work is done on the air in the piston by the water when the water freezes and work is done on the water by the piston when it melts. The net work is zero.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-64196888092881517232010-01-07T15:53:55.165-05:002010-01-07T15:53:55.165-05:00That's smart ass, not smart bunnyThat's smart ass, not smart bunnycarrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-13547203057490290682010-01-07T15:21:26.327-05:002010-01-07T15:21:26.327-05:00The smart bunny answer to RP^2 is when you slide t...The smart bunny answer to RP^2 is when you slide the weight onto the water, it falls to the bottom unless the density is less than 1 gm/cm3. Then you don't have a problem.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-59969384726234745482010-01-07T15:20:46.906-05:002010-01-07T15:20:46.906-05:00That would say, "I'd normally neglect...&...That would say, "I'd normally neglect..."carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-88792820605770329082010-01-07T15:19:26.638-05:002010-01-07T15:19:26.638-05:00I love puzzlers.
I'd normally the effect of...I love puzzlers. <br /><br />I'd normally the effect of little differences in pressure on water, but that's got to be the kicker here. Put the weight on top, you change the pressure, and you change the melting point. If even by just a little bit. That's my gut.carrot eaternoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-11841138123611958942010-01-07T13:53:40.278-05:002010-01-07T13:53:40.278-05:00I have taught Thermodynamics to undergraduates for...I have taught Thermodynamics to undergraduates for over 10 years now, and I learn something new each fall when I teach it. I agree with Eli that Fermi's book is good. Another good book is "The 2nd Law" by Henry Bent.<br /><br />Kramm clearly doesn't understand entropy over at Arthur's blog. In fact, he doesn't even show an understand at the level of general physics or chemistry. He sets forth a thought experiment in which he defines the sun as the system and space as the surroundings. Then later, he calls the space "thermodynamically unimportant" The surroundings of an open system are "thermodynamically unimportant"? Even a freshman learns that unless the system is isolated, the surroundings are important.Marknoreply@blogger.comtag:blogger.com,1999:blog-16612221.post-30909334006032038582010-01-07T13:48:50.431-05:002010-01-07T13:48:50.431-05:00Here's a neat little thermodynamics paradox, d...Here's a neat little thermodynamics paradox, due to Kelvin: the "ice heat engine." Start with a column of liquid water at a temperature just an epsilon above the freezing point. Put a weight on top of the column. Lower the temperature by epsilon - the water freezes and lifts the weight. Slide the weight off the column horizontally (for the purposes of this thought experiment we can neglect sliding friction). Now raise the temperature by epsilon, so that the water melts. Lower the weight (thereby extracting work), and slide it back on. This returns us to the original configuration, weight on water. Voila, a perpetual motion machine of the 2nd kind ! It converts heat to work at (within epsilon of) a single temperature. <br /><br />What's the resolution ?Robert P.https://www.blogger.com/profile/16608096675543218433noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-8699735241599947072010-01-07T10:59:43.042-05:002010-01-07T10:59:43.042-05:00Hmm, reminds me that I did TA it. My first intro t...Hmm, reminds me that I did TA it. My first intro to thermodynamics was a book borrowed from my Dad (the chemist) I think when I was still in high school; full of partial derivatives and such that were way beyond me, but I was intrigued. Then I had a rather hopeless undergrad class on thermal physics (from a teacher who probably should have been emeritus by that point, he'd been a dean or something). Then an excellent statistical physics class which resolved everything for me. There might have been one or two in between - I remember a graduate course on critical phenomena which was pretty heavy on the thermo stuff, and I did some undergrad research on related stuff too. And then I was TA and had to actually lecture once a week to a bunch of undergrads on the subject, from yet another book. I guess it's pretty deeply ingrained by now, even though it really wasn't that close to my main subject of study...Arthurhttps://www.blogger.com/profile/06249922708053689717noreply@blogger.comtag:blogger.com,1999:blog-16612221.post-60844137546192483042010-01-06T23:23:17.000-05:002010-01-06T23:23:17.000-05:00Eli really likes Fermi's short book on thermo....Eli really likes Fermi's short book on thermo. Not complicated, but subtle.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.com