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Comments 129001 to 129050:

129001. Quietman at 08:46 AM on 18 January 2009
        Christmas cartoon on melting North Pole
        Sorry, Are we in another La Nina now?
129002. Quietman at 07:11 AM on 18 January 2009
        Volcanoes emit more CO2 than humans
        Spencers argument is specifically about sensitivity to CO2. Look under Arguments, the Pacific Decadal Oscillation (at this site). I posted a link to a draft he did that they have refused to publish. I would prefer to be wrong about all this as I much prefer a warmer world but I fear that Spencer may be right. I am sure that Fairbridge was as the last two winters have been showing. The test is 2007 through 2011. Halfway there.
129003. Quietman at 07:00 AM on 18 January 2009
        Christmas cartoon on melting North Pole
        John and Phillipe In all honesty, I sincerely hope that I am wrong and that you are correct. I have lived in temps up to 140F and down to -60F and believe me I prefer heat to cold. But I simply can't believe all that science pointing to another glacation is wrong and that we are attempting to encourage it's start. La Nina is not affecting this winter and that article was posted yesterday. I have not personally experienced any warming since the Plains Blizzard of 1996. 1998 was a freak rewarming due to El Nino. The warming trend was just a weather cycle IMO, the true trend is cooling, hopefully slight.
129004. Patrick 027 at 12:17 PM on 17 January 2009
        Volcanoes emit more CO2 than humans
        In that work of Spencer we've discussed, his argument was not abotu CO2 forcing but about climate sensitivity. There is no flaw in the fundamental sense. There is uncertainty. Spencer's argument seemed ill-concieved to me - the logic isn't quite there.
129005. Patrick 027 at 12:10 PM on 17 January 2009
        Volcanoes emit more CO2 than humans
        "the average length of an interglacial BTW" Average, perhaps. Not all. Once every few interglacials, one is longer - although this is too long of a pattern to have been repeated much in the last several hundred thousand years, but there was at least one extra-long interglacial. Based on astronomical forcings, this interglacial could be one of the extra-long ones, perhaps lasting another 20,000, 30,000, or 50,000 years, even without AGW. "t won't cause a rise in sealevel because it is expanded (frozen) water that is also displacing sea water at present. " Yes, of course. Yet, the sea level is rising; Greenland is losing land-based ice (potential point of confusion: the base of the ice is below sea level in many parts, and in Antarctica too (West Antarctica in particular), but the height of the surface of the ice is such that most of the weight of the ice is not supported by the water - it will raise sea level when it melts). Antarctica may also be losing ice in total even though some parts may be gaining ice mass. "Sea level rise is within the Fairbridge curve; ie. normal or "expected"." But if it is expected, what is the expectation based on? (Fairbridge's argument about Solar jerk was based on cycles dominated by Jupiter and Saturn, but the actual forces (tides on the sun) would be dominated by Jupiter and Venus, then Earth and Mercury, before any other gas giants - and I showed earlier these would be exceedingly exceedingly small effects.) I'm really not at all convinced that the Fairbridge curve was/is based on a solid body of evidence. "I like the way you calculate out the CO2 forcing" Thank you - but actually, I only explained how it is calculated, and the physical principles on which it is based, which are as sound as the inverse square law. "but I still agree with Spencer." Spencer doesn't really make a durable point, though.
129006. Patrick 027 at 11:50 AM on 17 January 2009
        Volcanoes emit more CO2 than humans
        Regarding the P/T extinction: The concept as I understood it: There was a long ice-house period (with some significant ice, sometimes more (ice ages)) in the late Paleozoic. I've not been clear just when that ended, whether that was part of the P/T extinction or not. If it had ended but only just recently, that might have left species more vulnerable to any further warming. It was a time of continental collision - the formation of Pangea. One version: So then this Siberian trap flood volcanism starts up and persists for ~ a million years (more?), pumping CO2 into the air at a faster than typical rate. (Aerosols too, but those don't accumulate.) Eventually there is a lot more CO2. The Earth warms - maybe 5 degrees C - some extinctions occur (more on land??) The warmth causes CH4 release from the oceans. Sudden burst of warming. A total of 10 deg C more than before the flood volcanism? More extinctions. Oxygen doesn't dissolve as well in the oceans because of higher temperatures. Anaerobic bacteria that produce H2S become more commonplace. H2S in oceans, maybe some in the air. More extinctions.
129007. Philippe Chantreau at 10:40 AM on 17 January 2009
        Christmas cartoon on melting North Pole
        People have become so used to not have a winter that they're surprised when there is one.
129008. Philippe Chantreau at 10:39 AM on 17 January 2009
        Christmas cartoon on melting North Pole
        There is no such thing as weather anymore?
129009. Quietman at 09:46 AM on 17 January 2009
        A Great Science Fiction Writer Passes - Goodbye Dr. Crichton
        An interesting piece with a little insight: Scion of Frankenstein Michael Crichton, novelist and policy provocateur Ronald Bailey | February 2009 http://www.reason.com/news/show/130852.html
129010. Quietman at 09:36 AM on 17 January 2009
        Christmas cartoon on melting North Pole
        1-16-2009, MSNBC News: By Friday morning, cities and towns in 13 states reported temperatures well below zero, among them: -50 in Big Black River, Maine, in what could be a new state record -46 in Embarrass, Minn. -42 in Island Pont, Vt. -42 in Necedah, Wis. -39 in Berlin, N.H. -38 in Monticello, Iowa -36 in Sterling, Ill., possibly tying a state record -35 in Paradox, N.Y. -26 in Stambaugh, Mich. -20 in Valparaiso, Ind. -19 in Lawton, Pa. -16 in Snowshoe Mountain, W.Va. -14 in Dayton, Ohio In upstate New York, meteorologist Dave Sage said areas near Lake Erie were walloped by snow, with 2 inches falling per hour in some areas on Friday morning. As Ricky would say - Splain This Lucy
        Response: The question of specific instances of cold weather is answered here. More generally, recent cooling across 2008 was due to the cooling effect of La Nina and to a lesser extent, the solar minimum.
129011. Quietman at 07:17 AM on 17 January 2009
        Volcanoes emit more CO2 than humans
        Sea level rise is within the Fairbridge curve; ie. normal or "expected". The Arctic is the obvious problem which is why I did not mention it. But outside of Greenland it won't cause a rise in sealevel because it is expanded (frozen) water that is also displacing sea water at present. Add to that the increased sea and glacial ice in Antarctica despite the small area near S.A. and there is no reason for additional sea level rise. The planet went through a brief warm spell, a large part caused by ocean cycles but some was abnormal. The anomally clearly shows which areas and they are decidely not global. I like the way you calculate out the CO2 forcing but I still agree with Spencer. There is a fundamental flaw somewhere. Be the one to find it.
129012. Patrick 027 at 06:37 AM on 17 January 2009
        Volcanoes emit more CO2 than humans
        Here's the thing(s) about that: " Eastern Canada and the N.E. U,S, are not the only places on earth that have cooled while population centers warmed and it is from population centers that most data comes from. Why was this cooling ignored? " No, not really. The Arctic has warmed, the oceans have warmed (Aside from other data, sea level has been rising - that has to be mainly a combination of melting or temperature inceases - melting involves some of the heating occuring without temperature changes, of course). "South America, Antarctica and Africa have not experienced the same changes as Europe and PARTS of Asia. " ... " South Atlantic and Antarctic deep water is notably getting colder." The point being, you have to put all those together. It's still global warming, in the sense that there is more heat coming in then going back into space. "Glaciers in sunny california are GROWING because of the extra moisture off the Pacific." And why is that happening? "All of this climate change can easily be explained without super powerful CO2 forcing that historically does not seem to very powerful at all." It could be explained without CO2, but with strain and guessing. Much or most can be explained very very very very very very very very easily with a net forcing that is the sum of contributions from the changes in CO2, somewhat smaller from the rest of GHGs, a sizable likely negative aerosol contribution, rather small contributions from episodic volcanoes and solar radiation, and also, some other effects of ozone depletion (that doesn't explain the general global warming, etc, but it has effects). Etc.
129013. Philippe Chantreau at 16:07 PM on 16 January 2009
        Arctic sea ice melt - natural or man-made?
        You need to stop insinuating that the cites are some ploy to try to convince people of something or some way to establish a "consensus." It is a tool that researchers can use to access more information. Accessorily, it helps to determine the relevance and usefulness of a paper. The example I gave in post #394 is about diabetes and genetic, no suspicious consensus problem in this now, is there? You've spent too much time reading conspiracy BS on so-called skeptic sites,IMO.
129014. Quietman at 09:09 AM on 16 January 2009
        Arctic sea ice melt - natural or man-made?
        Phillippe Actually I do spend a lot of time at both PLos Biology and PLos ONE. Granted I am only lookong at Paleontology and Evolution related papers. I check the references but I have never noticed a "number cited" but you may be right, I may have overlooked it as I don't consider consensus important. I look to see WHO is referenced as there are authors I trust and others I do not.
129015. Quietman at 08:49 AM on 16 January 2009
        Volcanoes emit more CO2 than humans
        Also you might want to read Peter Ward's work on the PT extinction (not the media coverage that assume CO2). While Ward does not recognize the importance of the Antarctic impact, he does cite the Siberian Traps that it created as releasing METHANE and poisionous gas. While the gas may have caused a GH condition, the GHG did not cause the extinction event, which (as he points out in Gorgon and elsewhere) was a two stage extinction. First the oceans died (90% of all ocean species) and was followed by land species (70%). What most forget when reading about the PT extinction is that the Pennsylvanian-Permian Ice Age had just closed and the planet had warmed (naturally) prior to the extinction event, just like right now after 12000 years of interglacial (the average length of an interglacial BTW).
129016. Quietman at 08:38 AM on 16 January 2009
        Volcanoes emit more CO2 than humans
        ps Glaciers in sunny california are GROWING because of the extra moisture off the Pacific. I have posted links to all of these articles that describe what I have said. All of this climate change can easily be explained without super powerful CO2 forcing that historically does not seem to very powerful at all.
129017. Quietman at 08:35 AM on 16 January 2009
        Volcanoes emit more CO2 than humans
        Patrick You may recall that when we started talking about Bertha we took note that tropical storms had been forming farther east, meaning a change in air currents. Eastern Canada and the N.E. U,S, are not the only places on earth that have cooled while population centers warmed and it is from population centers that most data comes from. Why was this cooling ignored? South America, Antarctica and Africa have not experienced the same changes as Europe and PARTS of Asia. In fact, it has been noted that most warming has been on the western coasts of the Americas and Europe. If you check the ocean threads here you will see that overall the oceans have not warmed but there ate definate warm currents and hot spots. South Atlantic and Antarctic deep water is notably getting colder. Referring to this as "climate change" is quite accurate, but it is by no means "global warming".
129018. Philippe Chantreau at 18:44 PM on 15 January 2009
        Christmas cartoon on melting North Pole
        Sure, he's OK if you carefully pick what years to compare with. NSIDC put things in perspective: http://nsidc.org/arcticseaicenews/ Of course, we're not considering volume here...
129019. Tanuki at 12:45 PM on 15 January 2009
        Water vapor is the most powerful greenhouse gas
        Help please! I have not be able to find the paper disclosing the physics of the carbon dioxide and water interactions. Here I see only references to climate models and empirical studies, I would prefer to see the description of the actual phyical chemistry.
129020. Mizimi at 01:32 AM on 15 January 2009
        Water vapor is the most powerful greenhouse gas
        Chris; the paper is Santer 2007 noted above. And you didn't answer the question....how do climate models incorporate the heat emitted from life which is independant of IR ? Also, as you have previously averred, the WV content of the atmosphere is dependent on P~T, (subject to availability)so when it is removed during photsynthesis it is readily replaced..returning to "equilibrium"; so WV emitted by air breathers adds to the atmospheric content.
129021. Patrick 027 at 15:44 PM on 14 January 2009
        Arctic sea ice melt - natural or man-made?
        EP Flux AND SSWs - TOGETHER AGAIN (FIXED EARLIER PROBLEM - corrections to comments 403-405): If the zonal wind is slowing down in geostrophic balance, this implies decreasing stability (warming below, cooling above) on the poleward side and the opposite on the equatorward side. Deceleration by u'v' flux, taken in isolation, first causes an ageostrophic decrease in u (the zonal wind), which is then acted on by the coriolis effect, causing poleward displacement, which is balanced by adiabatic sinking below and rising above on the poleward side (vertical stretching) and the opposite on the equatorward side, which causes an adiabatic temperature change pattern as described in the last paragraph; it reduces the initial change in u but balances the remainder with a change in the mass distribution. The meridional circulation is the momentum-flux forced adiabatic MMC; the coriolis acceleration of the poleward part of the MMC increases u; thus reducing the initial change in u. A similar MMC (the VMC) would occur in response to a reduction of u forced directly by friction. In contrast, for the eddy thermal fluxes that would cause a decrease in the geostrophic u, taken in isolation, they first cause an increase in the ageostrophic u (by directing the temperature changes in the same direction as described two paragraphs previously). The adiabatic MMC caused by this is in the same direction as that described by the previous paragraph. It reduces the temperature changes but the coriolis acceleration of the equatorward part of the MMC causes a decrease in u to balance the remainder of the temperature changes. ----------- The two MMCs are in the opposite direction. For the mechanism of SSWs, the adiabatic MMC forced by the u'v' flux divergence must be dominant, or else the DMC caused by the temperature changes must be able to act fast enough to have a 'sudden' effect. (The changes in temperature tend to shift radiative fluxes so as to diabatically cool the adiabatically-warmed areas, etc, and the adiabatic circulation which occurs in response to the diabatic processes would cause poleward drift at the level of the EP flux convergence. However, I'd guess this process isn't fast enough for something 'sudden' (how sudden is sudden? - will report back).) THIS is because, while if both u'v' and v'T' make contributions to EP flux convergence, the resulting temperature changes are correct for an SSW, an SSW also involves poleward drift at and around the level of the EP flux convergence. ----------- Seperating the DMC from it's adiabatic MMC response: The diabatic process doesn't by itself cause any vertical motion in x,y,p coordinates. It just moves the isentropes. In x,y,q coordinates, this looks like vertical motion relative to fixed isentropes. The adiabatic MMC response to the diabatic changes reacts by moving the isentropes part-way back (but not all the way back) to their earlier positions, but in so doing requires vertical motion in x,y,p in the same direction as that which occured in the DMC in x,y,q. Vertical stretching and compression in x,y,p change the stability part way, but not all the way, back to the pre-DMC values, while the corresponing horizontal convergence and divergence, while conserving the DMC-generated IPV changes, cause changes in AV and thus RV (tending to be in the same direction as the diabatic IPV change) so as to balance the remaining portion of the pressure, temperature, and stability changes. ----------- A question that may come up - as the EP flux convergence propagates downward in response to changing wave-propagation properties (more later on why that happens), shouldn't the temperature changes that occured below the EP flux convergence reverse themselves as the level of EP flux convergence shifts downward? I don't know - apparently it doesn't, at least not fully. Perhaps it has something to do with changes in pressure and stability with height? -------------- What is the EP flux and what isn't it? I think the adiabatic MMC response to diabatic processes must be included in the DMC, or else it wouldn't make sense to show a DMC (residual MMC) circulation on the graph in Holton (in log-p coordinates - not isentropic coordinates) However, a long term average for a stable climate must assume there is no net movement of isentropes, so the vertical motion of diabatic processes must automatically appear in log-p coordinates, although this includes the adiabatic response AND something else... Holton doesn't explicitly note a VMC but that may just be because it's small. Or maybe it is included by approximation with the DMC just because the DMC was calculated by assuming VMC = 0 (an approximation). All adiabatic MMCs (inluding those in response to diabatic and viscous processes) also produce momentum, temperature, and IPV fluxes directly by advection, but they are, as I understand it, small in comparison to those fluxes in the EP flux and the sources and sinks directly from diabatic and viscous processes. Since additional MMCs would have to react to such processes, it is useful approximation to set them aside (at least for the purposes in Holton Ch. 10). Ealier I described how it would be possible to have (at least over a shorter time period ??) adiabatic zonal average vertical motion without vertical displacement of average q. However, in that case, there would be zero average adiabatic cooling or warming. Just something to keep in mind.
129022. David Horton at 12:32 PM on 14 January 2009
        Climate's changed before
        This The_skeptic_who_came_in_from_the_cold.html is an attempt to answer, for a skeptic (not denialist) friend, his proposition that since climate had changed before there was nothing to either explain or worry about. It is an attempt to distinguish between genuine skepticism and malign, planet-hating, denialism. The comment from tommybar "even if C02 is contributing, which it may have/be, a lot has been shown that it's 'greenhouse' ability is a logarithmic function, and that it has already contributed as much as it can" is interesting because it has suddenly started cropping up, in blogs around the world almost simultaneously. Could it be the latest talking point provided for the denialist anti-environment lobby? Funny how they all sing to the same tune (ice caps on Mars, Antarctic ice growing, planet now cooling) at the same time with each new attempt to stack the card deck, shuffle the pea, while distracting the punters.
129023. Patrick 027 at 12:13 PM on 14 January 2009
        Arctic sea ice melt - natural or man-made?
        "author A cites author B on a point, checking the citation you find B hasn't done the experiment and is instead citing author C. Checking author C you discover that like author B he has not done the experiment but is instead citing another author but this time it is author A from an earlier paper." That could actually make sense many times. If C had some insight about A's earlier work that A and B did not have by themselves, and B did some more work on it or commented about it and made some key point in the process, than it makes sense that A would reference those points in additional work if it applied... Note that additional work is not necessarily an experiment. There's math and logic, analysis, etc, to do, and also, comparing multiple experiments to each other...
129024. Wondering Aloud at 09:20 AM on 14 January 2009
        Arctic sea ice melt - natural or man-made?
        A circular citation is very common, though it depends on the field and the publisher,it works like this author A cites author B on a point, checking the citation you find B hasn't done the experiment and is instead citing author C. Checking author C you discover that like author B he has not done the experiment but is instead citing another author but this time it is author A from an earlier paper. The circles tend to have 3-5 members but I've learned if I don't find the original actual experiment in the first 2 or 3 steps the author is faking. Peer review is only one step in the scientific method, I've seen it work well and I've seen it fail totally. If for instance you have failed to isolate the variable than the fact that the reviewer doesn't notice either is not a great help. I think you were trying to make a different point and I was picking on you for something minor but as you already know I think poor scientific method, especailly drawing conclusions too broad for the data available is a large problem. Unless you want it privately I really don't want to enter into specific examples our legal system is not the same as yours and this is a public forum and I am not really anonymous.
129025. Quietman at 06:45 AM on 14 January 2009
        There is no consensus
        ps I'm not a believer in consensus. The greatest minds in history all went against consensus. It just happens to be the topic of this thread and John wants us to try and stay on topic, hence most of my arguments and links are in the appropriate threads. Just click on "arguments" for the full list.
129026. Quietman at 06:41 AM on 14 January 2009
        There is no consensus
        Yes I do have something better. Tree farming. CO2 is doing as much as a GHG it can right now. But it can do more if we let it. Better management of our forrests will help make the planet more productive. Unfortuantely most states have no green acreas laws. If you wan't to help the environment get your state to pass one. Those states with green acres laws make it a minimum of 2 acres of property per house. Even if they only grow grass it's better than asphalt. This produces O2 and frees up nitrates which combined with CO2 aids in plant growth. One visable truism about past periods of high CO2 concentrations is giganticism. Plants and animals grew much larger than today and covered the entire earth. We don't have much chance of achieving this kind of growth but we could at least increase food production and free up land that is currently incapable of supporting life.
129027. usa1 at 05:00 AM on 14 January 2009
        Christmas cartoon on melting North Pole
        Looks like Santa is OK. http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png Ice coverage is above the levels in 2005, 2006, 2007, and 2008. I wonder if we will hear about this in the media... don't count on it. Now if the levels were low... look out!
        Response: I'll direct you to the page that poses the question Is Arctic ice-melt manmade or a natural cycle?
129028. Tanuki at 04:59 AM on 14 January 2009
        Water vapor is the most powerful greenhouse gas
        Chris: I have difficulty some points you have mentioned. "Water Vapour as a positive feedback" If this were true, then what prevents the water from providing it's own feedback into what is essentially a thermal runaway? As well, it's a well documented fact that carbon dioxide dissolves in rain water, resulting in a typical pH of 6.5. So how can the lifetime of CO2 be so large if it's readily washed out by rain fall?
129029. Risky at 22:12 PM on 13 January 2009
        There is no consensus
        Re: #121 Quietman, where is that well-honed skepticism you keep telling us about? You can be quite dismissive of the IPCC ("Sorry, but my view of anyone who has not left the IPCC by this point is someone that can not think for themselves. Sheep going along for the ride with what they view as "the winning team". Lots of BS and outright lies fudging numbers and skewing results to get funding. "). Yet you uncritically post a link to a story that is no more than the annual reheating of that old chestnut, the Leipzig Declaration. I am sure there are some genuine scientists in climate-related fields are among the additional 250. Some of them might even be climate scientists, with published, peer reviewed science to back their skepticism, but the liberal padding of the numbers with T.V. weather reporters and other interlopers does not inspire confidence. If the skeptics genuinely feel they have a good basis for refuting scientific consensus here, why would they need to pad out the list? Obviously they don't feel their scientists are reputable enough, or the science is strong enough. Your basis for skepticism seems to change depending on the discussion - one minute, a believer in CO2 emissions as the only way to forestall a catastrophic ice age, the next minute dismissive of the very idea of ACC (see above 'BS and outright lies fudging of numbers blah blah blah...'). This is not skepticism, it's advocacy. Any argument to avoid deep cuts to emissions will do - even contradictory ones. Any skeptical scientist will do, even the ones who are not scientists, or not even skeptics. As for the story itself: "In fact, the total number of scientists represented in the report is 12 times the number of U.N. scientists who authored the official IPCC 2007 report." A bit of a nothing statement. Kind of like saying that all of our scientists outnumber some of theirs. The site posted does not list an author, but if you are interested, look up Marc Morano. Quietman, as a genuine skeptic, surely you have something better than that?
129030. Patrick 027 at 14:47 PM on 13 January 2009
        Arctic sea ice melt - natural or man-made?
        "VMC" - actually, Holton identifies the friction itself as a direct forcing of the zonal wind. Which makes some sense, of course. But the result by itself won't be a balanced wind (then again, near the surface, the wind is generally less (subgeostrophic) and directed partly from high to low pressure...
129031. Patrick 027 at 12:28 PM on 13 January 2009
        Arctic sea ice melt - natural or man-made?
        "But that is what happens. So I must have goofed-up something before...(?)***" Well, after "SO, I think this is essentially what's happenning.", I forgot that the EP-flux related zonal wind accelerations were due to the sum of the coriolis effect acting on the adiabatic MMC AND the momentum flux convergence. Still, however, the result should be in geostrophic balance with the IPV rearrangement, so I'm still missing something...
129032. Patrick 027 at 12:21 PM on 13 January 2009
        Arctic sea ice melt - natural or man-made?
        ... Those diabatic effects: relative to isentropes, there will be upward motion where there is heating and downward motion where there is cooling. Where there is heating above cooling, air is being pulled out of isotropic layers - the stability is increasing, tending to produce cyclonic IPV; by itself this leaves an ageostrophic wind shear such that there is a vertical minimum in cyclonic ageostrophic RV; thus there will tend to be a vertical maximum in convergence (or minimum in divergence), increasing cyclonic RV the most at that level and decreasing the stability until the horizontal variation in stability and vertical variation in vorticity are balanced for the new IPV. And so on for the opposite: cooling above heating. Thus the diabatic vertical motion across isentropes drives horizontal motion; diabatic vertical stretching tends to drive horizontal convergence (or a vertical minimum in divergence), etc...(it is because of geostrophic or gradient wind adjustment that this would occur, as opposed to vertical stretching in pressure coordinates, which, in a hydrostatic approximation, requires horizontal convergence because of conservation of mass, regardless of whether horizontal forces are balanced or not.) **PS NOTE THIS PARAGRAPH FOR LATER (REMINDER: 2AGEO1). This diabatic circulation is the residual meridional circulation (Holton, p.323) (For here, RMC for short). The coriolis effect acts on the horizontal part of RMC to produce acceleration in a perpendicular direction (this is part of the geostrophic (or gradient-wind or whatever) adjustment just described, which conserves IPV while bringing horizontal variations in S into geostrophic (or gradient wind) balance with vertical variations in RV). For zonal averages, seen in the y,z* plane, the coriolis effect acts on northward RMC to cause zonal wind acceleration (westerly). This is in addition to zonal wind accelerations caused by EP flux divergence (which is proportional to an IPV flux - which only redistributes IPV that exists: it is an adiabatic process, as I understand it) AND viscous forces (which are strongest near the surface, and can create or destroy IPV - near the surface, this generally tends to bring it toward f*S*g (that is, tending to bring RV toward zero). (PS the RMC is weak enough that one can approximate IPV fluxes without actually including IPV advection from the RMC; but RMC, although diabatically driven, can adiabatically advect IPV as well as be related to the diabatic creating and destruction of IPV). And the Ferrel cell?: The total MMC (mean meridional circulation) is the superposition of the RMC, which is necessarily thermally direct everwhere, with the adiabatic component of the MMC (mean meridional circulation), and a part due to friction (I'll just refer to that as VMC for now). The adiabatic component of the MMC could be divided into two components: one driven by eddy heat fluxes (v'T') and one driven by eddy momentum fluxes (u'v'). The first is thermally direct relative to the horizontal convergence and divergence of eddy heat fluxes (the temperature CHANGES driven by eddies), although it can be thermally indirect relative to the actual temperature distribution (as it typically is in midlatitudes). The second is thermally direct where the vertical variation in the convergence in the momentum flux (WHICH is equal to the vertical variation in the RV flux (v'RV') - see Holton p.320) is in the opposite direction of the geostrophic wind shear; otherwise it is thermally indirect. My understanding is that Both of these, and the sum of the two together, can be seen as the ageostrophi secondary circulation that is necessary to maintain nearly geostrophic balances between pressure gradients, temperature gradients, and horizontal stability variations, AND wind , wind shear, and vertical vorticity variations. So the adiabatic eddy-flux driven portion of the MMC is the process by which the eddy-driven adiabatic rearrangements of zonally-averaged IPV are brought back toward geostrophic balance. **PS NOTE THESE TWO PARAGRAPHS FOR LATER (REMINDER: 2AGEO2). The vertical motion of adiabatic MMC moves WITH isentropes, not across them. (continual transport of isentropes cannot occur indefinitely, of course. If the MMC is taken as averaged motion in the y,z plane, averaged over x along constant y and z* (or z or p), then it is not averaged along isentropes. The vertical part of the adiabatic MMC is the average of all adiabatic vertical motions - **if, on average, downward vertical motions occur where the stability is greater than where upward vertical motion occurs, then the average change in q could be zero while the average adiabatic vertical motion is upward, etc**. Of course, over any given time period, there could be some change in q, and then, diabatic processes could act to cancel the change in some places and times. SO, I think this is essentially what's happenning.: Increasing Rossby wave amplitude at a given position** (not to be confused with amplitude changes following propagation to different places, although the two could happen at the same time and place sometimes) tends to involve an adiabatic flux of IPV that is down gradient. Other waves can also cause IPV fluxes although some will not depend on IPV gradients to exist so much (gravity waves, for example). (PS the analogy for gravity waves is that increasing amplitude at a given location** corresponds to a downgradient flux of q - a vertical maximum in increasing amplitude corresponds to an area-average decrease in S at that level.) ** - well, actually it is at a location that moves with the air...but not too important a distinction, I think, for the following: For zonal averages: Divergence of the EP flux corresponds to a northward IPV flux; the resulting adiabatic rearranging of IPV drives a secondary ageostrophic circulation - in this case, the adiabatic MMC. The coriolis effect acting on the horizontal part of that MMC produces the acceleration of the zonal wind that is 'caused' by the EP flux divergence. The vertical and horizontal parts of the adiabatic MMC together move the temperature and wind fields toward geostrophic balance in response to the changed distribution of IPV. Although there is a way for the vertical part of the adiabatic MMC not to always result in an average change in isentrope positions, the change in IPV distribution may require (I think) some average change in q as well as changing atmospheric winds. The diabatic RMC is air rising across isentropes where there is heating and air sinking across isentropes where there is cooling, and the resulting adiabatic ageostrophic secondary circulation (although actually I'm not sure if the vertical part of that adiabatic circulation is included in the RMC ... it isn't included in the adiabatic MMC, though). The coriolis effect acts on the horizontal part of the RMC to cause a zonal (westerly) acceleration of the wind; this combined with adiabatic vertical motions act to bring the wind and temperature back toward geostrophic balance with the IPV changes caused by diabatic processes. The VMC could be described similarly. For long-term stable atmospheric circulation, for the averages over time, the coriolis accelerations acting on the RMC and VMC must cancel the accelerations 'caused' by the EP flux divergence (the coriolis acceleration of the adiabatic MMC), and the q changes and IPV changes must cancel. The VMC is of course driven by friction ((vertical) mixing of momentum and exchange of momentum with the surface). (I think the VMC is weak compared to the rest of the MMC.) The RMC is driven by radiational heating and cooling and latent heating and cooling (much or most (?) of the later occuring at the surface, and not cooling the air directly). Some of the RMC is determined by variations in atmospheric and surface properties (albedo, opacity, temperature) and the stimulation of latent heating in the presence of moisture (fronts, cyclones, ITCZ, ...). BUT some of the RMC can be driven by the EP flux if/when the EP flux is not balanced by an RMC (or VMC) to begin with... (? I was about to describe sudden stratospheric warmings (SSWs here) but the description doesn't quite make sense given what I just wrote. An SSW can occur when an planetary waves (kind of Rossby wave) propagate up into the stratosphere but slow and stop and some point. EP flux convergence continues to occur there; IPV is moved southward. The westerly wind decelerates. AS I had just described it, the deceleration of the wind is due to the maintenance of near geostrophy by the coriolis effect acting on the adiabatic MMC which is in response to the IPV rearrangement - that MMC would involve rising air below poleward and above equatorward and sinking air below equatorward and above poleward. If that were the case, the following wouldn't happen: The coriolis effect acts on the deceleration, causing poleward drift, and a meridional circulation with sinking below poleward and above equatorward, and rising below equatorward and above poleward. The adiabatic changes in temperature CAUSE diabatic heating and cooling that act to reduce the temperature change - the rising air diabatically heats and the sinking air diabatically cools - the RMC in response to EP-flux (but the diabatic temperature changes, at least in the case of a SSW, do not completely offset the adiabatic temperature changes; the air that sank still has higher T). But that is what happens. So I must have goofed-up something before...(?)*** What happens after that: The changes in the state of the atmosphere around the level of the initial EP flux convergence change the way planetary waves can propagate; they block their upward propagation at a lower level. This causes EP flux convergence at a lower level. And so on - the EP flux convergence, deceleration of westerlies, adiabatic warming of the air on the poleward side only partially reduced by diabatic cooling, etc. - all propagates downward leaving changes in it's wake. There is some connection between this kind of phenomenon and AO/NAM and SAM.)
129033. chris at 10:15 AM on 13 January 2009
        Water vapor is the most powerful greenhouse gas
        All that grade school "numerology" isn't going to get you very far Mizimi. re #48 and "water vapour emitted by air breathers". Remember that every molecule of water vapour returned to the atmosphere by metabolic respiration was a water molecule pulled out of the atmosphere by photosynthesis: nCO2 + nH2O ------> (CHOH)n + nO2 photosynthesis where (CHOH)n is generic carbohydrate (CHOH)n + nO2 ------> nCO2 + nH2O respiration re #49 and atmospheric relative humidity. Remember that the bulk of the atmosphere is much colder than 15 oC and so the water content at 50% relative humidity is far lower rather quickly as one ascends re #47/#49 Which paper are you talking about (mizimi: "just re-read that paper....")? You should really give your sources when you start expounding numbers. You make so many mistakes that it would be helpful if you could simply state where you obtained your numbers/ideas from so that we could assess them ourselves. Otherwise it's hardly worth addressing many of your points since they are based on series of unattributed numbers which very often turn out to be incorrect...
129034. tommybar at 06:50 AM on 13 January 2009
        It's the sun
        I've wasted a lot of my free time over the past year trying to make myself come to a conclusion of all the AGW debate. This argument, that the TSI correlation ended in 1975 doesn't prove CO2 is the driver, or disprove it either. If you look at the ENSO variations since 1975--totally dominated by warmer El Ninio events--there could definitely be a correlation there. So trying to limit the "it's the sun" argument to only TSI is misleading, because that is only one aspect of the sun's relationship with climate. Furthermore, it may be but one forcing--the oceans another, and greenhouse gasses another, and perhaps others as well. Fact is, it doesn't seem that past climate changes are very well understood, so it's fair to be skeptical that trace gasses are the primary reason for this climate change.
129035. Patrick 027 at 06:47 AM on 13 January 2009
        Arctic sea ice melt - natural or man-made?
        MORE EP FLUX: "(at least where RV variations are not significant relative to beta - I think)" Strike that - I think it includes RV variations. I took another look at the math (Holton p.326-327 in particular) and I understood much better the derivation of the relationship: (zonal (x) average of IPV'v')/g*S0) ~= zonal average of (quasigeostrophicPV)'*v' = divergence of EP flux / density. Where the quasigeostrophic potential vorticity = IPV/(g*S0), where S0 is a basic state S that is constant over x; the division is to give IPV in terms of vorticity AV while still accounting for variations in S. (Holton doesn't actually give the relationship as such but I conclude that this must be the case - ). One key thing to remember is that some of the variations over x can be dropped from the equations because the average over x, of the variation over x, taken along a closed loop (lines of latitude) must be zero. And for such a zonal average, net fluxes of IPV in the zonal direction obviously can't be accounted for; one would have to divise some regional EP flux averaged along the direction of one's choosing, etc. for that... BUT ANYWAY, at least in the quasigeostrophic beta-plane approximation in log-p coordinates, the zonal average of the northward eddy flux of IPV is proportional to (the divergence of the EP flux) / density (or the southward eddy flux is proportional to the convergence, etc.). So when the IPV gradient is to the north (which is the general tendency), EP flux convegence corresponds to increasing Rossby wave amplitudes, etc. PS other waves and eddies can contribute to a IPV fluxes and EP fluxes The meridional (y direction) variation in the EP flux divergence thus corresponds to a net depletion or accumulation of positive IPV (or the reverse for negative IPV), for increasing or decreasing divergence northward, respectively. The same variation in wind can be due to vorticity variation over a short distance with large vorticity maxima and minima magnitudes, or over a large distance with small vorticity maxima and minima magnitudes; wind is proportional to vorticity times length. In an analogous way, for a given magnitude of EP flux divergence (at a given y, z* location), whether it is spread out over y or concentrated, the same total amount of IPV*mass must be passing through that point; the same IPV * length scale of IPV must apply for the areas of IPV flux convergences and divergences; so the effect on the zonal wind is about the same. EP flux divergence accelerates the zonal wind to the east (more westerly), as can be understood from the changing PS since EP flux divergence and converge result in horizontal fluxes of IPV, and since there is only a finite distance from south pole to north pole, the IPV distribution (and the average zonal winds) has to change as a result, unless diabatic and viscous processes destroy and create IPV and transport it vertically across isentropes (which, without diabatic effects, otherwise act as material surfaces that air can't cross) in such a pattern as to balance the EP flux's effects.
129036. Ian Forrester at 05:02 AM on 13 January 2009
        Latest satellite data on Greenland mass change
        Mizimi could you please tell me where you got your information that Iceland has an estimated 250 x 10E6 km3 of ice? That seems rather unusual since Greenland only has 2.85 million km³ of ice. Also can you explain where the missing 17 Gtonnes of H2O disappears to when 179 Gtonnes of ice melts? I would have thought that a ton of ice would melt to give a ton of water.
129037. chris at 04:32 AM on 13 January 2009
        What does CO2 lagging temperature mean?
        Re #38

        Yes chris, CO2 can cause a small temperature rise because it's a GHG.

        CO2 can cause a large temperature rise. It depends on the atmospheric concentrations of course.

        We also know that it can not prevent an Ice Age as shown by the historical record...

        The evidence indicates that it can indeed prevent an Ice Age. The evidence from paleoproxies for temperature and atmospheric greenhouse gases indicates that Ice Ages in the deep past were associated with the reduction of atmospheric greenhouse gas levels below thresholds required to maintain the Earth in a non-ice age state. In other words atmospheric CO2 has prevented Ice Ages for long, long periods of the Earth's deep past. (see for example: D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675.)

        ...and it can't cause catastrophic global warming because life still exists on this planet even though CO2 reached levels in the Mesozoic over three times the proposed "tipping point" and never tipped.

        It certainly can cause catastrophic global warming. Global warming can obviously be catastrophic even if it doesn't eliminate life in its entirety. If, for example, global warming was to occur to an extent that resulted in widespread breakdown of the structures of our societies, we'd consider that catastrophic. Or if mankind were to succumb while a denuded life on Earth went on without out us, that would be catastrophic, wouldn't it? The latter scenario is rather more consistent with those resulting from the extinctions associated with the Early Jurassic, the end Permian, the end Cretaceous, the Paleo-Eocene Thermal Maximum and so on. P.S. what do you mean by "proposed tipping point"? No one has mentioned "tipping point" on this thread have they?
129038. Mizimi at 22:55 PM on 12 January 2009
        Latest satellite data on Greenland mass change
        Sorry..that .62m should have been 6.2 including differences in water/ice volumes. To melt that amount of ice would require an enormous amount of energy..around 950 x 10E21joules and I don't see where that excess energy is going to come from in a time frame of a few hundred years.
129039. Philippe Chantreau at 19:58 PM on 12 January 2009
        Arctic sea ice melt - natural or man-made?
        I don't care whether you agree with my definition or not, quite frankly. However, I care a little that you don't misunderstand what I say. I said that expertise usually implies an advanced degree. Not always, and it is not a requirement. However, that's the most common situation. Recognition as an expert is not nearly as important as genuine expertise, which stems from sincere pursuit of understanding through the scientific process. However, chances are that, if you are a genuine expert, you will get recognition. The scientific process involves peer-reviewed publications. I dont' care what you or anybody else says, peer-review publishing guarantees a minimum level of quality without which science would not be the successful enterprise that it is now. Everybody has anecdotes relating flaws in any system. So what? And please be more specific: "some fields" or "well known experts" does not tell me much. What exactly are you talking about? Why don't you cite these terrible dissertations, so we can see for ourselves? Furthermore, having references and cites listed actually enables anyone to verify things, so it is a good thing from that point of view also. I've read countless lines of BS about how the peer-review process is all wrong. Still not convinced and not about to be. This site is about peer-reviewed science, if you don't trust it, you shouldn't waste your time commenting about it. In the business and financial world, they operate differently. Their "standards" are about to cost us 800 billions, bar a complete collapse. Science does not do so bad in comparison. Lastly, I don't understand your circular thingy. I'm writing a paper and doing my research. I cite an article. How can that article reference another that will then reference the one that I haven't even finished writing?
129040. Wondering Aloud at 13:37 PM on 12 January 2009
        Arctic sea ice melt - natural or man-made?
        I just came here because there were so many posts but Phillipe I could not disagree more with you on your definition of what a scientist is. A scientist is someone who uses scientific method. Compared to this one requirement, advanced degrees and "expert" recognition are just trivia. Also how often a paper is cited is not an indication of accuracy though it may be an indication of popularity. At best it may tell you who had an idea first. If you want an ugly experience spend a few days tracing references in papers and find out how many are fake, misquoted, unrelated or describe other "experiments" so badly done they were meaningless. See how long it takes you to find a circular citation. (A cites B who sites C who was citing A in the first place) In some fields 50% bs is fairly common, I've seen PhD disertations from well known "experts" that when you eliminate the fake references and the unrelated ones didn't have anything left.
129041. Patrick 027 at 13:12 PM on 12 January 2009
        Arctic sea ice melt - natural or man-made?
        EP flux clarification (Holton p.323): EP stands for Eliassen-Palm The y component: - (u'v' averaged over x) * density The z component (R and H in particular are not the same R and H I had referred to earlier.): (v'T' averaged over x) * density * f0 * R / (N^2 * H) I think f0 is a representative f over a band of latitudes; the variation in f is taken into account in another way using a quasigeostrophic approximation. In this context, H and R are NOT than the height scale of a particular phenomenon and the Rossby radius of deformation. H is the scale height of the atmosphere, which is the height over which density and pressure decrease by a factor of e (Holton, p.253 - in actuality these can be different and H can vary over height and space due to temperature variations, but the purpose here is to use "log-pressure coordinates", where vertical distance is "z*" - where z* = H * ln(p/ surface pressure) (ln = natural logarithm) which is an approximation of the actual geometric height z. R is just the ideal gas constant given in terms of mass rather than moles (which means it varies depending on composition). I had initially described the EP flux convergence as being in the Northern Hemisphere; the point here is that EP flux convergence should always imply a net flux of IPV down gradient (at least where RV variations are not significant relative to beta - I think). Note f and typical IPV values are negative in the Southern Hemisphere; in the Southern Hemisphere, cyclonic RV is negative... _____________________ Anyway EP flux divergence acts to increase the zonal average zonal (westerly) wind speed, while EP flux convergence slows it down or makes it more easterly, which makes sense given the change in IPV distribution it is associated with.
129042. Patrick 027 at 16:44 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        Fronts - Fronts can be/are very important mesoscale aspect of baroclinic waves (in extratropical cyclones in particular) and jets. The most familiar fronts (seen on TV weather maps) are strongest at the surface, but some upper-level fronts occur, too; I think they are associated with jets; they can be extrusions of stratospheric air into the troposphere (frontal zones have higher S, although they may occur in larger environments of relatively smaller S). Fronts can develop from quasigeostrophic mechanisms, but there are faster mechanisms (with greater ageostrophic effects) that allow faster frontal development - there is a kind of instability in that a strong temperature gradient can act to intensify itself (but quasigeostrophic processes can and do produce the seeds of fronts). In the vertical, frontal surfaces (at least the lower level ones or the portions within the troposphere (?) slope over their colder sides going upward. Air trajectories don't cross frontal surfaces much (at least for lower level fronts (?)), so fronts generally move with the wind. ... I'm not going to spend more time on Fronts here. --------------- While a fixed forcing may produce some Rossby wave whose phase lines are stationary, the wave activity can spread with the group velocity. For a northward vorticity gradient, the group velocity, depending on wavelength and direction, can be to the east or west, but it can never keep up with the phase lines in their direction of propagation relative to the air as blows through them. Thus, wave activity spreads downstream along a westerly flow; westerlies continue to meander after passing just a single forcing (mountain range, etc.). In contrast, easterlies can (at least in an idealized setting) respond with just one displacement at the forcing and resume straight flow. **Extensive teleconnection patterns due to the forcing of Rossby waves by, for example, deep convection over a tropical SST anomaly (ENSO or what-have-you), require (as far as I know) that the winds in that region are westerly (to the east). ______________________ Wave Mean interaction: If the basic state has a constant IPV gradient and the Rossby waves are constant in amplitude along the gradient, then, the average IPV over an integer number of wavelengths is unchanged by the presence of the wave. If, however, this is not the case - for example, if the Rossby wave amplitude decreases or increases along the IPV gradient, then the average over wavelengths of the IPV can change. There will generally be a net shift of IPV down gradient, as if the Rossby waves have mixed the IPV (although without wave breaking or some other things, the mixing is reversable because there has been no mixing on the scale of the waves). In so far as this contributes to a net change in RV, this means the presence of the wave has caused an average increase in RV toward lower original IPV and the opposite in the opposite, which thus requires some change in the average wind in between. This is related to the EP flux of the waves. It makes sense that an average over wavelengths of vorticity flux (i.e. or e.g. - average of v'RV') must occur with convergence or divergence of the momentum flux (u'v'), because concentrating momentum in one place tends to produce a new RV' gradient across that place. vertical variation of thermal fluxes v'T'(vertically differential temperature advection) suggests a change in S. Considering averages over x and looking at the EP flux in the vertical plane y,z (taking the default of y being toward the north for convenience): The upward component of the EP flux is proportional to the average of v'T' - it is proportional to the eddy temperature flux (but also depends on N, H, f, and density - see Holton, p.323). Convergence of this component thus implies that stability S is increasing more to the south and/or decreasing more to the north, which suggests a decreasing northward IPV gradient. The northward component of the EP flux is proportional to the negative of the average of u'v' (and also density - Holton, p.323) - it is proportional to a northward eddy easterly (westward) momentum flux. Convergence of this component thus implies a decrease in the northward RV gradient, which would tend to contribute to a decrease in the northward IPV gradient. Of course, each variable is not seperately conserved - but in the process of geostrophic adjustment, the effect on IPV should be at least qualitatively the same, and Holton p.326-327 proves mathematically (not that I was able to follow every step, but at least it makes sense qualitatively) that a southward eddy flux of IPV (multiplied or divided by constants ** so as to be the quasigeostrophic potential vorticity, given in units of vorticity) is equal to the convergence of the EP flux, divided by density. Given the prior description of the effect of a maximum in Rossby wave amplitude, for a basic state northward IPV gradient, EP flux convergence should correspond to increasing wave amplitude, while divergence should correspond to decreasing amplitude. Which suggests that the wave energy and activity moves with the EP flux.
129043. Patrick 027 at 15:55 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        ... In reality, the westerly jets that increase in strength toward the upper troposphere reach a maximum near the tropopause as a consequence of a general reversal of the temperature gradient going into the stratosphere (Although in winter, the temperature gradient is not reversed everywhere, and there is another westerly jet at higher levels at high latitudes (the polar night jet, I believe). PS the tropopause generally slopes downward toward the poles, with breaks at jets. (climatological seasonal zonal (over all longitudes) averages of the zonal wind shows only one westerly jet maximum in each hemisphere (outside the stratosphere) - but there can be two such jets at any one time and longitude: the polar-front jet is associated with strong thermal gradients generally at mid to high latitudes, while the subtropical jet is associated with thermal gradients over the subtropics in the upper troposphere that are not so strong at the surface (perhaps associated with converging meridional winds from the Ferrel and Hadley cells? - and also perhaps due to a reduced dry static stability (S) toward the tropics due to the effect of higher temperature on the moist adiabatic lapse rate). The subtropical jet's vertical wind shear can be stronger for it's associated thermal gradient because the coriolis effect (magnitude of f) is weaker at lower latitudes. Of course, at any one time, jets can merge and branch and break off into closed loops and have confluent entrance and difluent exit regions, etc.) Static stability, in winter in particular, increases within the lower troposphere from midlatitudes toward polar regions; geometrically this allows the equatorward temperature gradient to decrease with height. ... Imagine instead the case of an easterly jet at some level, with a westerly jet at some level above it, implying an equatorward thermal gradient in between. No such gradient (or a weaker or opposite gradient) below requires an increase in S toward the equator at the level of the easterly jet (although just having a much reduced gradient could be accomplished just by a reduction of S going downward). The easterly (= westward) jet has anticyclonic RV on the poleward side and cyclonic RV on the equatorward side. These combined may be able to overcome the beta effect, so that there could be an equatorward cyclonic IPV gradient at the level of the easterly jet. Then there could be baroclinic instability away from the surface. Actually, it need not be an easterly jet; it could just be a relative minimum (in the horizontal) in the westerlies. Moist processes: Cyclones generally have precipitation and latent heating, so they are not dry adiabatic; isentropes are not reliably material surfaces even if radiational heating and cooling can be set aside for short periods of time. What could be used instead where latent heating occurs are surfaces of equivalent potental temperature (pseudoisentropes?), and the Rossby waves within such regions would depend on arrangements of equivalent-IPV. Alternatively, one can account for the creating and destruction of IPV by diabatic processes (and viscous processes, too, as long as we're at it). IPV is generally created beneath a maximum in heating and destroyed above it (while diabatic heating will transport it upward across isentropes). (The relationship is not 100% precisely so because the same heat causes essentially the same change in Temperature T at all levels, but the change in q, while proportional to T, also depends on pressure p. An evenly vertically-distributed increase in T would cause greater increases in q at lower p, thus reducing S). Using the IPV perspective may help in trying to understand how climate change would alter storm track activity (again, see also comment 76 at http://www.skepticalscience.com/volcanoes-and-global-warming.htm ). __________________________
129044. Patrick 027 at 14:51 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        "(Eddies can be shed from meandering jets and currents - see Cushman Roisin p.250)." - and also, Bluestein p.211-213. "the eddy momentum flux " Another way (I think?) to visualize that is that when a wave is tilted, the wind coming around the bend has to leave the bend with some momentum that is different than it had before, and something has to provide the acceleration, and there must be some equal and opposite reaction somewhere (distributed, of course). Of course, the distinction between streamlines and trajectories alters this picture but I think in the case of the transport of u' by v' between shear of u in the y direction, it still works out... ------------- Barotropic waves: Wavelength dependence of instability - without counteracting wind shear, the longest wavelengths are the most likely to escape phase locking and not be amplified; For a given wind shear of the same sense as the IPV maximum or mimum, the shortest wavelengths will be the most easily pulled away from phase locking. However, the range of unstable wavelengths could be shifted a bit toward longer wavelengths because the wind fields of longer wavelengths penetrate farther across the reversal so that the waves on opposite sides can interact more strongly. Also, as wavelength increases, the phase speeds increase up to a point and then approach a maximum value due to the effect of divergence to maintain near geostrophy; so in some conditions, perhaps there is not a long-wave cutoff for instability. Of course, this is all altered by S, because AV = IPV/(S*g). Also, unless there is an actual gap with no IPV gradient in between two regions of constant IPV gradient, there is no obvious set distance to use between the two sets of waves, so it could be more complicated. Cushman-Roisin p.250 suggests critical wavelengths (I assume this means unstable or most unstable in this context) scale with the width of a jet. I'll have to go back to Ch. 7 to check out how that works. Bluestein p.211 suggests the midlatitude region in between the subtropical and polar-front jets (a relative minimum in westerly winds has anticyclonic RV on the poleward side and cyclonic RV on the equatorward side) could be a place where there is barotropic instability (taking into account beta (the gradient of planetary vorticity (f)), which is always increasing cyclonic vorticity poleward.). More wave-mean interaction: as the contours of IPV deform and the band of minimum or maximum IPV breaks up into vortices, there is a net (averaged across wavelengths) transport of IPV down-gradient - toward a minimum and away from a maximum in the basic state. ------------- Baroclinic Instability: -- (NOTE basic state is assumed to be near geostrophic balance or gradient wind balance - this implies that a vertical wind shear (typically, increasingly westerly (to the east) with height) is proportional to a horizontal temperature gradient (toward the equator for the case of the just-described westerly vertical shear). The temperature gradient, for other given conditions, is proportional to the slope of isentropic surfaces (in terms of isobaric coordinates in particular) multiplied by S (the static stability).) -- The IPV gradient being considered is in the 'horizontal' (actually along isentropic surfaces, which can and do slope where there is a horizontal temperature gradient). Thus there isn't generally an IPV maximum or minimum at a reversal of the IPV gradient over vertical distance. For a non-IPV non-isentropic (not in x,y,q coordinates but rather x,y,p) perspective, see (Quietman already saw this) comments 76 and 77 in particular at: http://www.skepticalscience.com/volcanoes-and-global-warming.htm (And also Holton Ch.8, and Martin, Bluestein, etc.) By some nice clear reasoning, Bluestein discusses how instability is related to wavelength and basic state characteristics on p.208-211 (p.210-211 in particular). Small S and large wavelength L increase the interaction of two sets of waves across a vertical distance (via the vertical penetration of an RV anomaly and hence the wind field from an IPV anomaly); S does this both by increasing the vertical spread of RV from it's maximum (at the level of it's source IPV anomaly)and the value of RV at all levels (because AV is proportional to IPV/S, etc...). However, these effects also increase the self-propagation speeds that would tend to pull the two wave sets out of any phase locking. Larger f (actually, larger basic state AV and f_loc) increases the interaction across a vertical distance. The interaction is stronger also if the vertical distance is smaller. Larger vertical wind shear (in the opposite sense of the vertical variation of phase propagation) can help overcome the effect of self-propagation. Bluestein concludes that there is a range of wavelengths that can amplify by baroclinic instability, and the range can shift toward longer wavelengths L if S is large and/or the basic state vertical wind shear is large (both effects make it harder for shorter wavelengths to be amplified). (Perhaps, since the effect of S on self-propagation has a proportionate effect on RV at all levels, the two effects nearly cancel (?) so that the effect on vertical spread of RV dominates (?)). However, this doesn't appear to take into account the relationship between the IPV gradients, S, and the vertical shear - although larger IPV gradients would enhance both self-propagation and wave growth, so perhaps the instability is not so sensitive to that. ---- ALTHOUGH, I wonder what happens if one IPV gradient is much weaker than the one across the reversal (for either baroclinic or barotropic instability) ---- **(PS note that propagation in the horizontal direction is actually, to be safe, along isentropic surfaces (for adiabatic motion), in the IPV perspective). But notice that in the above, the description seems to be of two single layers or surfaces with IPV gradients, rather than a horizontal IPV gradient that continuously changes over vertical distance. Indeed that is about the case. Although I'd guess analysis of the more widespread IPV gradient case would yield similar results. For the real troposphere, however, the case of two distinct surfaces with opposing IPV gradients actually works as an approximation. There are IPV gradients generally throughout the atmosphere, but the are generally weak in the bulk of the atmosphere; there is a relatively sharp increase in the IPV gradient along isentropes going across the tropopause and into the stratosphere; the gradient is generally increasingly cyclonic IPV toward the poles, which is dominant in the atmosphere as a whole. For reasons discussed in comment 313 above, the generally equatorward temperature gradient at the surface is such that the dynamics are as if there is an IPV gradient of increasingly cyclonic IPV toward the equator (this could be better understood with an approximation that isentropes' slopes decrease suddenly going toward the surface, and then continue equatorward just above the surface; the piling up of isentropes next the the surface results in a increasing S or increasingly thick layer of high S going toward the equator, and a sharp increase in IPV magnitude along isentropes upon entering the high S layer (that's the most important part of this, I think) - notice the similary of this situation to what happens crossing the tropopause along an isentrope (PS I think IPV surfaces can be used to define the tropopause at mid-to-high latitudes (while isentropic surfaces cross the tropopause), but at low latitudes, isentropic surfaces don't cross the tropopause so much while IPV surfaces do. Undulations of the tropopause are associated with IPV anomalies; a depression in the tropopause tends to be associated with a cyclonic IPV region). Thus, to a first approximation, the troposphere might be described in terms of generally opposite surface and tropopause IPV gradients - as if the three dimensional troposphere could be described by a two dimensional hologram! (But that is only an approximation). In fact, in the fully three dimensional description of baroclinic instability, describing what happens within the air, there is no IPV gradient necessary; baroclinic instability depends fundamentally on a temperature gradient and the coriolis effect (although beta and IPV gradients will modify behavior, they are not the fundamental reason for the existence of baroclinic instability). If there is no IPV gradient within the air, however, there will be an IPV gradient at the top and bottom boundaries because a temperature gradient implies sloping isentropes and these isentropes must hit the floor and cieling unless there is a layer of high static stability to collect them (which itself would tend to require an IPV gradient within the air). As I recall Holton's description (Ch. 8) suggests that a temperature gradient at the lower boundary (the surface) is necessary for baroclinic instability. But that seems a little odd - is there a way to have baroclinic instability away from the surface? (it can certainly be away from the top of the atmosphere). Well, it may not be likely because of the dominance of beta in IPV gradients within the air, and also that while there is westerly shear associated with the typical temperature gradients, it is generally westerly from the surface on up in the midlatitudes. ...
129045. Patrick 027 at 12:55 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        (388 clarification): The similarity between all three is that there is a switch, in going from flow slower than free wave phase speeds, to faster flow, in the positioning of Rossby wave rigdes and troughs, maxima and minima in water level (corresponding to the same in potential energy and the reverse in kinetic energy), and maxima and minima in pressure (corresponding again to potential energy and the reverse in kinetic energy). The extra similarity between the water flow and the gas flow is the potential for a hydraulic jump and the analogous potential for a shock wave (I think). --------- I think the 1/4 wavelength relationship for damped Rossby waves relative to topographic forcing might be specifically for the resonant wavelength; other wavelengths near the resonant wavelength might tend to be close to that phase relationship, etc... (?). -------- Nonlinearities II: breaking waves Waves of significant amplitude can become nonlinear and break. For example, for surface waves on water ... BACKGROUND there is a spectrum of gravity waves; waves with wavelengths much shorter than water depth are called deep water gravity waves; they are dispersive. They decay in strength over the depth of the water because the vertical accelerations of the up-down motion of any one layer partly cancel the effect of water level on pressure, thus reducing the forces that accelerate the water in deeper layers. Waves with wavelengths much longer than water depth are called shallow-water gravity waves. They are nondispersive - the phase speed c = w/k (thus w = c*k) is constant for all wavelengths, and thus the group velocity = del(w)/del(k) = c is the same as the phase speed (in the direction of phase propagation). They are approximately constant with strength through the depth of the water layer just because there is not enough depth for significant weakenning. Tsunamis travel through the open ocean as shallow water gravity waves because they have such long wavelengths. When any wave approaches shallower water, it slows down (for shallow water waves, c = sqrt(g*H); deep water waves are always slower because (I think) they don't 'feel' the full H). Thus waves refract toward shallower areas. The energy of the wave becomes concentrated into a smaller depth and also I think into a smaller wavelength (because the front of the wave reaches shallower water before the back and slows down first, I presume). Thus the amplitude increases.) (There is up-down motion of water as a wave passes (1/4 cycle out of phase with horizontal motion), as the surface moves up and down. This decreases with depth, because water at the bottom can only slide along it(except for the porosity and permeability of the bottom material, but let's set that aside for now) (although there is up-down motion associated with a bottom slope, but that's either in phase or 1/2 cycle out of phase with the horizontal motion). Thus the up down motion is associated with vertical stretching and shrinking, balanced and caused by convergence and divergence, which is forced by the spatially varying and cycling horizontal pressure gradient that is caused by gravity and the undulations of the water level at the surface (if the air had a larger density, the effect would be reduced; the pressure gradient per unit water level slope would be reduced and thus wave propagation would be slower, - the same as if the air were of insignificant density by comparison but if g were less - hence the use of a 'reduced gravity'. This is how internal gravity waves travel. The (internal) gravity waves in the atmosphere exist because of a more gradual stratification that can be quantified by N. Internal gravity waves can tilt, etc...)). Because of the back and forth motion, if the amplitude is large compared to wavelength, crests are sharpenned and troughs are broadened (I think). There's also something called Stokes' drift but I don't know much about it. Speed is faster in greater depth, but the crest of the wave has deeper water than the trough. This effect can be ignored for sufficiently small amplitudes (the anomaly water level is only used to compute the pressure gradient; otherwise only the basic state depth is used - an example of linearization). But for large amplitudes relative to water depth, the crest travels faster than the trough. Eventually the wave breaks. And there is surf. The atmosphere can also have surf (I've actually seen the term used in this context) from breaking Rossby waves. Unfortunately, no one has yet figured out how to hang 10 on a Rossby wave (a PhD thesis paper topic?). I have no idea what 'hang 10' actually means. (Eddies can be shed from meandering jets and currents - see Cushman Roisin p.250). -------------- Nonlinearities III: waves having waves, sharing energy Wave energy from one part of the spectrum can 'bleed' into other parts of the spectrum. There's something called nonlinear triad interaction/resonance??, but I don't know much about it (but it may have something to do with combinations of thee wave vectors which form triangles). This can happen with gravity waves and also I think Rossby waves. When a Rossby wave's amplitude is very large, conceivably the wave IPV gradient could become larger than the basic state IPV gradient. Because the wave IPV gradient reverses periodically across wavelengths, there is a potential for barotropic and/or baroclinic instability (see below), so maybe an intense wave can break down into smaller waves that way (?), but I'm not sure if this particular process is significant in the atmosphere. ---------------- Nonlinearities IV: geostrophic turbulence (see Cushman Roisin p.219-221, 257-261) Vortices of like sign tend to merge and under some conditions can survive for a long time (Great Red Spot - such a persisent state is prevented in the Earth's atmosphere and ocean by disruptive and dissipative forces of external origin relative to the fluid (Cushman-Roisin, p.261)). Vortices embedded in a basic state PV gradient that radiate Rossby-wave type disturbances tend to drift toward PV of the basic state of the same type (Cushman Roisin p.257-259 - PS on page 259, Cushman-Roisin mentions the "southeastward" drift of Hurricanes as being caused by this effect - I'm pretty sure that's a typo and it was supposed to be "southeastERLY" - as in "northwestward"). Perhaps this is also how and why vortices of like sign would tend to merge? Persistent strong nonlinear vortices may coexist with weak linear waves in between them (Cushman-Roisin, p.220-221). ___________________________ Barotropic and Baroclinic Instability: If there is a reversal of the IPV gradient somewhere, then there can be some combination of barotropic and/or baroclinic instability about the reversal. On one side of the reversal, the waves propagate one way, and the opposite on the other, if left to themselves; they thus propagate relative to each other. If there is a basic state wind shear, then the waves might be carried back - if one or both are propagating upstream, the wind shear might slow or reverse the propagation of one set relative to the other. The wind field from one wave can extend across the reversal; this wind field tends to produce a wave that is 1/4 wavelength out of phase, in the direction of free Rossby wave propagation on it's side of the reversal, from the waves on the other side. the wind field of the new wave will tend to produce a wave on the first side of the reversal that is out of phase in the same way, and that happens to be in phase with the first wave. Thus these two sets of waves can mutually amplify each other. If the two sets across the reveral are in phase or 1/2 wavelength out of phase, they do not amplify each other (or cause each other to decay) but they cause each other to propagate away from being 3/4 wavelength out of phase and toward being 1/4 wavelength out of phase. If the two sets are 3/4 wavelength out of phase, they cause the mutual decay of each other. So at anywhere except at 1/4 and 3/4 wavelength out of phase, but peaking at in phase and 1/2 wavelength out of phase, the waves act on each other's spaces to bring them away from mutual decay (strongest at 3/4 out of phase but occurs anywhere from 1/2 to 1 or 0 to -1/2, etc.) and toward a state of mutual amplification (strongest at 1/4 wavelength out of phase but occurs anywhere from 0 to 1/2 wavelength out of phase). The combination of different wave propagation directions and their speeds (which is largest for long wavelengths and large IPV gradients on either side with small S, etc., depending on whether it is more baroclinic or barotropic instability) and wind shear across the reversal, may continually tend to disrupt the phase alignment (unless they themselves cancel each other), but as the phase alignment shifts, the mechanism described above can change the phase propagation speeds - the amplification is not as rapid but the phase alignment can still persist - however, for some wavelengths and some conditions, it will be impossible; the necessary phase locking is prevented (See Bluestein p.207-211; Holton Ch.8; Cushman-Roisin p.250, Ch.16, Ch.7; Martin; Wallace and Hobbs, etc.). Of course, if the waves extend away from the reversal, the influence of the other waves is reduced and their own self-propagation dominates. This could result (before accounting for basic state wind shear) in a continuation of the tilt of the wave in the same sense as is found if connecting the phase lines (planes or surfaces in three dimensions) across the reversal. In that case, the group velocity is then directed away from the reversal in both directions, which makes sense since that's where the wave activity is being produced (but of course, carrying wave energy away will reduce the amplification at the source). Enhancing this tilting tendency is if the magnitude of the basic state IPV gradient continues to increase away from the reversal (where it was zero, unless there is some gradient along the reversal, but that gradient must be small in comparison to the perpendicular gradients on either side, I think). In order for the instability to occur, it must also be the case that somewhere (likely near or at the reversal), the air must be moving with the growing wave pattern and vice versa. Because the air (or water) in such a critical level is not moving through the wave pattern, the waves' wind fields continually deform material surfaces or lines in a one-way, non-cycling manner. In the case of a reversal in the horizontal (technically, horizontal along an isentropic surface for the IPV perspective), this requires an IPV maxima or minima at the reversal. This is barotropic instability. In this case, the deformation of IPV contours around the critical level is such that the band of maximum or minimum IPV (a sort of shear line), marking the reversal of the IPV gradient, breaks up into seperate vortices. I'm not sure but I think these might be called Kelvin's cat's eyes (??). Such a feature is also present in Kelvin-Helmholtz instability, which is a general phenomenon that can occur on various spatial scales with various orientations - vertical shear, which has to be sufficient to overcome vertical static stability where that occurs (sometimes absent in the boundary layer), has Kelvin Helmholtz instability that may be made apparent by billow(s?) clouds. In fact, this instability is at least partly responsible for the puffy texture of cumulus clouds (the air is rising (and may have different horizontal momentum) within the cloud, thus the edge of the cloud may have some maximum in wind shear). It is also interesting to note that, in so far as the basic state IPV gradient is from wind shear and not just variations in S and/or f, the tilting of a decaying barotropic Rossby wave (interpolating through the 3/4 out of phase relationship) is that which occurs when the basic state wind shear deforms a untilted barotropic Rossby wave - as I described somewhere above, the eddy momentum flux by waves tilted with the shear, the average across wavelengths of u'v', is such that the waves tend to concentrate momentum in the direction of the basic state shear - causing a jet to grow stronger. And the barotropic instability description suggests such a wave tilt may have some convergence of group velocity and thus wave energy toward the maximum in basic state shear, and the the waves decay. On the other hand, those waves which are tilted in the opposite direction will pull momentum out of a jet and across a basic state shear zone, tending to reduce the shear (averaged across wavelengths) - and these are the waves that could grow by barotropic instability if the propagation properties and conditions are right. (SEE also wave-mean interaction, coming up). This is actually analogous to the more familiar small scale turbulence in a shear zone - for example, the atmospheric boundary layer (the lowest part of the atmosphere, which exchanges momentum with the surface via friction and eddy fluxes). Shear causes eddies to grow; those eddies are tilted against the shear and on average transport momentum toward the surface. The basic state shear might concievable tend to tilt the eddies with the shear, so that they would decay and pull momentum back from nearer the surface (as if there were negative eddy-viscosity). However, on these scales, smaller eddies can produce yet smaller eddies, losing kinetic energy to eddy viscosity, and the smallest eddies easily lose kinetic energy to molecular visocity (Someone wrote a poem about this!). If the reversal occurs in the vertical, it is Baroclinic instability ...
129046. Philippe Chantreau at 12:32 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        You're still not getting it. This may be how it was done years and years ago. I don't think that anyone ever came up saying "let's require authors to publish cites too." It happened to become the norm because it is so useful to those doing research and computers are so well suited for that kind of stuff. How long as it been since you've done any kind of research, even a superficial cursory search online? OK, look: this is a normal thing, everybody in science does it. Look this up: http://www.pnas.org/content/100/18/10393.abstract Not only that article has a complete list of citing aricles, but even a link for every one of them. The PNAS page even gives you an option of being alerted if the article is cited. Elsevier does the same. All science journals online give you these kind of options. You just never noticed because you never paid attention. Get out there, do some searches and use the tools. Geez...
129047. Patrick 027 at 10:35 AM on 11 January 2009
        Volcanoes emit more CO2 than humans
        "They just figured out, after 30 years of AGW hype, that the NE part of the US (and eastern Canada) has not warmed and in fact has gotten colder while the west coast warmed." And the interior of the continent? And Europe? And Asia? And Africa? And South America? And Australia? And Antarctica? And the oceans? And the glaciers? The tropical mountain glaciers? And the forests, and the birds, and the plants?...
129048. Steve L at 10:28 AM on 11 January 2009
        Latest satellite data on Greenland mass change
        For 11 Mizimi, from Wikipedia: "Some scientists believe that global warming may be about to push the ice sheet over a threshold where the entire ice sheet will melt in less than a few hundred years. If the entire 2.85 million km³ of ice were to melt, it would lead to a global sea level rise of 7.2 m (23.6 ft).[2] This would inundate most coastal cities in the World and remove several small island countries from the face of Earth, since island nations such as Tuvalu and Maldives have a maximum altitude below or just above this number." You can't both be right.
129049. Steve L at 09:14 AM on 11 January 2009
        Latest satellite data on Greenland mass change
        D'oh! Thanks Quietman -- WA: please post your NASA video.
129050. chris at 09:13 AM on 11 January 2009
        La Nina watch: March update
        The answer to both your questions is yes... Here's the UK Hadcrut3 global temperature analysis, for example: http://www.cru.uea.ac.uk/cru/data/temperature/crutem3gl.txt

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