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Comments 129201 to 129250:

129201. Mizimi at 08:10 AM on 19 December 2008
        Determining the long term solar trend
        The amount of CO2 we put into the atmosphere is large when considered on its own. What remains there is about 50%, the rest ends up in the oceans. So of the 2.7 x10e13 kg we emit, roughly 1.3 x 10e13 stays to increase the 3 x 10e15 kg of CO2 already there. In that context the amount we add is small....very small.
129202. Quietman at 08:01 AM on 19 December 2008
        It's the sun
        WA When I say it's the sun, I am generalizing. I see it as an engineering "root cause". Our orbit about the sun is a combination of the results of the sun in it's formation of the solar system. The combined gravitational effects of the system as a whole and the tectonic tides resultant. The effect of tectonics on the planets climate via changes to ocean circulation which in turn effect air circulation and control climate, added to the 8 minute charge cycle and irregularities in the solar wind and plasma forcing from sunspots. ie. a domino effect.
129203. chris at 06:07 AM on 19 December 2008
        What does CO2 lagging temperature mean?
        Re #34 Yes it's interesting. It does quite a good job of pursuing a false argument and an excellent job of being fixed in time nearly 10 years out of date. Most of the article is about the lag of CO2 changes relative to temperature changes during ice age transitions. That's fine except the authors pursue the fallacious argument that because CO2 was a feedback response to solar insolation changes during ice ages, that CO2 variations can't drive temperature variations. They present this quite slyly as a "cause/effect" dichotomy....paraphrasing: "since CO2 changes were an effect during the ice age cycles and in pre-industrial times, they cannot be a cause now"! In fact some of the data they present merely reinforces the rather limited variation in atmospheric CO2 levels that occur under natural circumstances without catastrophic increases in CO2 (from massive tectonic events or terrestrial impacts, or massive burning of fossil fuels now), or very very slow drawdown of CO2 levels by weathering. E.g. they make a big play over the fact that the earth cooled a bit during the 2000 years from 7000-5000 years ago while atmospheric CO2 rose by 10 ppm. But 10 ppm over 2000 years (0.005 ppm per year) is 4 years worth at present rates of greenhouse gas emissions. That's around 4-500 times slower than the current increase in atmospheric CO2. A 10 ppm change over 2000 years is hardly going to affect climate, and clearly in a world with little variation in atmospheric CO2 levels, any climate variations must be dominated by other things (a small residual Milankovitch cycle affecting N. hemispheric insolation in this case I believe). It's unfortunate that the presentation is frozen in time around 2000. For example they present data by Pagani et al (1999) and Pearson and Palmer (1999) that appears to be "in conflict with greenhouse theories of climate change". But here's Pagani in 2005 showing that contrary to the assertions by the authors of your "article" that atmospheric CO2 was only 385 ppm in the middle Eocene, that the evidence indicates levels were actually 1000-1500 ppm, and in fact the slow, slow decline of CO2 levels through the Paleogene was likely the cause of ice sheet development and expansion in Antarctica. Pagani M (2005) "Marked decline in atmospheric carbon dioxide concentrations during the Paleogene" Science 309, 600-603 Abstract: The relation between the partial pressure of atmospheric carbon dioxide (pCO(2)) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO(2) from the middle Eocene to the late Oligocene (similar to 45 to 25 million years ago). Our results demonstrate that pCO(2) ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during the Oligocene, and reached modern levels by the latest Oligocene. The fall in pCO(2) likely allowed for a critical expansion of ice sheets on Antarctica and promoted conditions that forced the onset of terrestrial C-4 photosynthesis. Likewise Pagani has recently presented evidence that the ability of the Arctic and Antarctic to maintain ice sheets is effectively controlled by CO2 thresholds (< ~750 ppm for the Antarctic; <~ 280 ppm for the Arctic). DeConto RM et al (2008) Thresholds for Cenozoic bipolar glaciation Nature 455 652-655. and the role of CO2 levels in setting thresholds for glaciations is more widely suppoorted by the science: e.g.: Lunt DJ et al (2008) Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels. Nature 454, 1102-1104 likewise recent data indicate that the relationship between climate and atmospheric CO2 levels in the Miocene are not so "chaotic" as the authors of your article would like us to believe: W. M. Kurschner et al (2008) “The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of the terrestrial ecosystem” Proc. Natl. Acad. Sci. USA 105, 499-453. ...and so on…. It seems the site you linked to is a nice little family business (Dad chairman, two sons are President and vice President and Mum is the "Operations Manager"!). Every page has a "Donate" button and no doubt they have such a nice time with everyone's donations they just don't have time investigate the literature properly or to keep their "info" up to date. I hope you left a donation Mizimi!
129204. Wondering Aloud at 02:24 AM on 19 December 2008
        It's the sun
        Actually Quietman I'm not saying it is the sun, it might be, but it doesn't seem that's explaining things very well either. I think the sun is acting very weird compared to what I expected. I think uncertainty absolutely dwarfs the signal we are looking at, and every time I try to look at any indvidual piece of the puzzle it seems uncertainty grows.
129205. chris at 22:57 PM on 18 December 2008
        Water vapor is the most powerful greenhouse gas
        re #45 It's all due to CO2-induced warming Mizimi.....at least none of it is due to "addition" by man (or ladies for that matter). Man can't "add" water vapour to the atmosphere. The atmospheric water vapour levels are essentially "defined" by the atmospheric temperature and pressure. We've already determined (see post #20) that the amount of water vapour released into the atmosphere by burning stuff, cooling towers and so on is a tiny proportion of the water vapour released into the atmosphere by the natural evaporative cycle (we calculated mankinds contribution is around 0.005% of that released by natural evaporation). What happens to all of that water (e.g the vast amount from natural evaporation)?. It all comes straight out as precipitation. What stays in the atmosphere is what the atmosphere can support in relation to the atmospheric temperature and pressure. In fact the research indicates that the atmosphere tends to maintain a relatively constant relative humidity (i.e. raised absolute humidity with increasing temperature and vice versa). In the paper[***] that Tom Dayton refers to (Tom links to an info summary), the water vapour levels increase right throughout the troposphere to the high altitude/low pressure regions. The authors note that as the atmospheric temperature fluctuates (e.g. the strongish La Nina cooling), so the atmospheric water vapour levels follows (such that a constant relative humidity is roughly maintained). Each of these observations is consistent with our understanding of the response of the atmospheric water vapour concentration to temperature, and its rather short term response to temperature changes (after Pinatubo the atmospheric water vapour levels dropped even ‘though we were still releasing water vapour into the atmosphere from cooling towers!), and is incompatible with the notion that mankind's emissions (a miniscule proportion of the natural evaporative contribution), can somehow affect the atmospheric water vapour levels. [***] A. E. Dessler et al (2008) Water-vapor climate feedback inferred from climate fluctuations, 2003–2008. Geophys. Res. Lett. 35, L20704, abstract: Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q increased with increasing global-average surface temperature, although some regions showed the opposite response. RH increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of λq = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere. I'm not totally convinced by the clouds snippet you linked to. Again reading the full paper[*****] a couple of things stand out: (i) the large proportion of those 124 stations are in S. Calif, along the Gulf coast and along the Eastern seaboard. So vast regions of the US aren't covered, and it's possible that a small rise in cloudiness in these built up regions may relate to their location in built up areas of the US (??). The authors acknowledge this: "Quantitative estimates of the uncertainties of the U.S. cloud trend during 1976–2004 shown in Fig. 8b are difficult to derive because of the poor coverage by the 124 military stations and the subjective nature of the human observations." and: "Although the 124 U.S. military stations provide useful data for total cloud amount up to the present, they have limited spatial coverage and are inadequate for monitoring regional trends in the western and other parts of the country." (ii) satellite data show a decreasing cloud trend during this period worldwide. So either the military station trend is a localized one..or isn't correct...or the satellite trend is incorrect...or the two series are measuring different things (e.g. low level clouds from ground observations vs high level clouds from satellites). I think one can quite reasonably be skeptical about drawing too many inferences from empirical cloud data so far. The main point of Dai and Trenberth's paper is that replacement of human cloud monitoring (as done in the military bases) by automatic monitoring systems, is a backwards step.. Note that although mankinds water vapour emissions don't have a significnat effect on greenhouse levels of atmospheric water vapour, we can probably influence the hydrological cycle by land use effects. and of course we are indirectly influencing the atmospheric water vapour levels by our CO2, methane, nitrous oxide emissions! [*****]Dai, A., T. R. Karl, B. Sun, and K. E. Trenberth, (2006) Recent trends in cloudiness over the United States: A tale of monitoring inadequacies. Bull. Amer. Meteor. Soc., 87, 597-606
129206. chris at 22:26 PM on 18 December 2008
        Models are unreliable
        You're not paying attention Dan. This was all explained to you in posts #78 and #80 above. Remember that the earth's orbital parameters are characterized by three major cycles having periods near 100,000 years, 41,000 years and 23,000 years. Since these cycles are out of phase a rather complex insolation pattern accrues from the "summation" of the cycles which matches the ice core data quite well. You'd benefit from reading this paper which describes some of the data in a manner that you could probably understand. Figure 2 is interesting; it illustrates the extraction of the earth's orbital cycles by Fourier transformation of ice core data on proxy temperature and 18O variations. The power spectrum shows clear strong peaks at 111,000, 41,000 and 23,000 years, which matches the orbital cycle frequencies rather well: Kawamura et al (2007) "Northern hemisphere forcing of climate cycles in Antarctica over the past 360,000 years" Nature 448, 912-919. You would also benefit from reading some of the papers John Cook discusses in his article on top of this thread. You shouldn't be frightened of the science Dan. Averting your eyes from scientific papers with schoolboy insults will only leave you woefully misinformed.
129207. chris at 09:52 AM on 18 December 2008
        Human CO2 is a tiny % of CO2 emissions
        come on Mizimi, pay attention... My post #19 was very short and easily readable. Surely you can't have missed the phrase: "....apart from the glacial periods of the past few million years when atmospheric CO2 dropped towards 180 ppm." btw I made a tiny typo in post #19. "(around 20 million years)" should have read "(around 10 million years)" consistent with my post #13.....
129208. Quietman at 09:35 AM on 18 December 2008
        It's the sun
        WA I agree it's the sun, just not TSI. Check out the recent articles about the magnetosphere and plasma discharges. Between gravitational stresses causing increased tectonic activity, plasma discharges and changes in heat and intensity of the plasma from sunspots are looking more and more like the culprit. Too bad the IPCC never looked into this part of the science.
129209. chris at 05:12 AM on 18 December 2008
        CO2 lags temperature
        Goodness Dan, you are a master at contrived misunderstanding! This was all explained to you in posts #78 and #80 here: http://www.skepticalscience.com/climate-models.htm I have a horrible feeling that you're just ignoring the explanations and cited papers which essentially resolve your confusions. Let’s try again: ONE: The Milankovitch cycles do not only account for the major glacial <-> interglacial transitions. Remember that the earth’s orbital properties are characterized by three major cycles. Remember also that the three cycles [~100,000 year (eccentricity), 41,000 year (obliquity) and the 23,000 year (precession)], are out of phase. It’s not so difficult to understand that the interplay of these cycles gives multiple cyclical insolation changes that impact not only the major transitions, but the patterns of temperature variation within glacial and interglacial periods. That’s easy to see if one takes the parameters of delta-temperature or delta 18O from cores and Fourier transforms these with respect to time. Out pops as clear as day, strong peaks at frequencies at 111 kyr, 41 kyr and 23 kyr. Have a look at the paper I’ve recommended to you a couple of times now (Figure 2 shows the power spectra of delta 18O and delta T): Kawamura et al (2007) "Northern hemisphere forcing of climate cycles in Antarctica over the past 360,000 years" Nature 448, 912-919. You would also benefit from reading some of the papers John Cook discusses in his article on top of this thread: (Petit et al, 1999 and Shackleton, 2000 are useful) TWO: It’s been explained to you rather often now that our understanding of climate sensitivity (the earth’s temperature response to doubled atmospheric CO2) comes from a number of analysis of real world measurements. It doesn’t come from “computer use” whatever that might mean. Obviously GCM models are parameterized according to our knowledge of real world phenomena, so it wouldn’t be surprising if computer models were compatible with the climate sensitivity independently determined from analysis of the real world. You can read about the wealth of real world measurements that bear on this data here, for example: http://www.skepticalscience.com/climate-sensitivity.htm THREE: Poor Dan…reduced to telling porkies in para 4…how sad! Of course your logical fallacy that I highlighted in post #56 was the deceit that because ice age cycles weren’t driven by CO2 (CO2 amplified the response), that “added atmospheric CO2 today does not drive temperature”; that’s a grating example of the fallacy of the single cause. BTW, it’s good to see that you’ve dropped the fallacious “argument” that temperature downtrends with still highish CO2 levels doesn’t “prove that net positive feedback does not exist”. So you’ve learned one thing, which is admirable, and that’s really the value of boards like this. and you've had your “rational explanation” many times now (e.g. “ONE” just above in this post). FOUR: Your last paragraph is a delicious restatement of your fallacy of the single cause. it really isn’t difficult to understand Dan (I suspect you're just not trying!): (A) CO2 is a greenhouse gas. Raised atmospheric levels cause the earth to warm all else being equal. A large number of empirical (and theoretical) analyses indicate that the earth responds to raised CO2 with a warming near 3 oC per doubling of atmospheric CO2. (B) During ice age cycles the primary driver of temperature variations are Milankovitch cycles (see “ONE” just above). The warming is amplified by raised water vapour and raised atmospheric CO2 (see Mizimi’s post #57). The raised CO2 levels were small and extraordinarily slow – more than 100 times slower than the rate at which CO2 levels are rising now. The raised CO2 amplifies the Milankovitch warming and incidentally produces its own water vapour and albedo positive feedback. (C) Now the primary driver of temperature change is direct pumping of massive amounts of fossil fuel-derived CO2 into the atmosphere at a phenomenal rate. (D) Do you understand Dan? CO2 is a greenhouse gas. However it gets into the atmosphere it results in warming (all else being equal) equivalent to something around 3 oC per doubling of atmospheric CO2.
129210. Mizimi at 04:34 AM on 18 December 2008
        Human CO2 is a tiny % of CO2 emissions
        The paleo temp record at http://www.climateaudit.org/?p=835 indicates SST's ranging over 5C for the past 1.3 million years during which time the CO2 level has been 'more or less' around 300ppm. Air temps would have ranged even further. How do we reconcile this?
129211. Mizimi at 04:20 AM on 18 December 2008
        Water vapor is the most powerful greenhouse gas
        "a network of 124 U.S. military weather stations with continuous human observations provides useful information of total cloud cover averaged over the contiguous United States, and suggests an increasing trend (~1.4% of the sky covered per decade) in U.S. total cloud cover from 1976 to 2004, with increases over most of the country except the Northwest." http://www.tiimes.ucar.edu/highlights/fy06/dai.html Clear indication of increasing WV over the time period global warming has 'accelerated'. The question is, how much is due to man's additions and how much to CO2 induced warming?
129212. Dan Pangburn at 02:24 AM on 18 December 2008
        Models are unreliable
        Here again you use a time period that includes the murky transitions from interglacial to glacial and glacial to interglacial instead of sticking to a period that excludes the transitions and the interglacials. Stick to the time period from about 110,000 ybp to about 20,000 ybp. Then the Milankovitch effect is very small but along with other factors still drives the temperature. The effect of the atmospheric carbon dioxide at that time must have been even smaller since it does not drive the temperature. We know that because the record shows that temperature trended down when the carbon dioxide level was higher than when the temperature was trending up. If you have a rational explanation that proves otherwise than give it. Your endlessly quoting fellow victims of group-think proves nothing. Oh, and in the world that I am in, there is 6% more arctic ice than last year, average global temperature in 2008 is the lowest this century and the atmospheric carbon dioxide level has increased since 2000 by about 14% of the total rise since the start of the industrial revolution. What world are you in?
129213. Dan Pangburn at 23:51 PM on 17 December 2008
        CO2 lags temperature
        Chris claims to grasp that solar variation was the main cause of temperature variation during the last glacial period. That is, from about 110,000 ybp until about 20,000 ybp. That does not include periods of transition from glacial to interglacial or interglacial to glacial. He/she claims that CO2 is a greenhouse gas. Good. That has been well known for years. But then Chris loses it. The 3 C warming that he/she has stated repeatedly is a prediction of faulty computer use and Chris fallaciously states it as if it were fact. Apparently Chris is unable to come up with any rational explanation for how a temperature down trend could take place while the atmospheric carbon dioxide level was higher than it had been during a temperature uptrend as it did repeatedly during the last and previous glacial periods. Therefore he/she simply dismisses as a ‘logical fallacy’ that this proves that temperature was not driven by atmospheric carbon dioxide level at that time. That doesn’t cut it. Let’s hear the rational explanation. Elsewhere Chris has claimed to grasp that added increments of carbon dioxide have less influence on temperature when the atmospheric carbon dioxide level is higher than the same size increments do when the level is lower. Good. That also has been well known for years. But then Chris apparently fails to grasp that increased increments of atmospheric carbon dioxide level now have even less influence on climate than the same size increments did during the last glacial period when they did not drive temperature.
129214. chris at 23:17 PM on 17 December 2008
        CO2 lags temperature
        Re #57 Pretty much. The lag may not be as much as that and there are clear hemispheric diferences in the onset of warming during glacial cycles. But yes, the Milankovitch warming is amplified by a rapid (essentially instantaneous) water vapour feedback. The CO2 comes from the deep oceans largely I believe. Note that increased plant growth reduces atmospheric CO2, so this should act against warming-induced recruitment of CO2 from terrestrial sinks. I think that the rising sea-levels innundate very larger areas of shallow continental margin and so that reduces plant biomass somewhat returning some CO2 to the atmosphere. But ocean sinks are the main source of enhanced CO2 during the warming phases of the glacial cycles I think...
129215. chris at 23:05 PM on 17 December 2008
        Models are unreliable
        You keep repeating the same fallacious non-sequiters Dan without addressing straightforward critique. 1. Real world observations strongly support positive feedbacks to CO2-induced warming. We can measure the major feedback (enhanced water vapour) in the real world (see papers cited in my post #84), and recent work has reinforced the identification of the water vapour feedback and its quantitation: e.g. Dessler et al (2008), Water-vapor climate feedback inferred from climate fluctuations, 2003–2008, Geophys. Res. Lett., 35, L20704 for a layman's description see: http://www.nasa.gov/topics/earth/features/vapor_warming.html the identification and effects of the albedo feedback can be seen very clearly in the Arctic, and so on..So there’s no value in pretending that what exists doesn’t exist. 2. It’s rather well understood that the ice age cycles are driven by slow sinusoidal cycles in the earth’s orbital properties that alter the pattern of insolation. Sinc atmospheric CO2 levels respond very slowly to drops in global temperature (driven by Milankovitch cycles, for example), it’s not surprising that there is a significant lag between Milankovitch cooling and reduced CO2. Note that these CO2 changes in response to temperature during glacial cycles are rather small and extremely slow. They occur more than 100 times more slowly than the present rate of change in atmospheric CO2 resulting from massive burning of fossil fuels. It’s a logical fallacy to attempt the deceit that because CO2 variations weren’t the primary driver of temperature changes during ice age cycles (it amplified the changes of course), that massively increased atmospheric CO2 levels won’t increase the earth’s temperature under conditions of relatively stable insolation. 3. …and yes, we all know that the earth’s temperature varies as the logarithm of the atmospheric greenhouse gas concentrations. Welcome to the 19th century! This really has been known for more than 100 years. As we also all know, the earth’s temperature responds to enhanced atmospheric CO2 with somewhere near 3 oC of warming per doubling of atmospheric CO2. So yes, if we ramp up the atmospheric CO2 concentrations we expext that the world will warm. That’s also pretty consistent with real world observations. It's the greenhouse effect Dan!
129216. Dan Pangburn at 22:02 PM on 17 December 2008
        Models are unreliable
        Actually a valid assessment of GCM predictions is fairly simple. But clear thinking might be prevented by the preconceived notion that increased atmospheric carbon dioxide is a significant cause of global warming. It might help to realize that the climate scientists who promote this notion did not need to learn about Dynamic System Analysis yet they impose substantial net positive feedback (feedback is a factor in Dynamic System Analysis) in their Global Climate Models which causes the models to predict significant global warming. Without the imposition of substantial net positive feedback the GCMs do not predict significant global warming. You can avoid being hoodwinked by the group-think bias of others by looking at the ‘raw’ data. First observe closely the temperature trends and carbon dioxide levels during the last glacial period (e.g. from 110,000 ybp to 20,000 ybp) as available on the web from NOAA. The data was extracted from proxies archived in the Vostok Antarctica ice cores. This is the same data that, in an unfocused view, was used in An Inconvenient Truth the substantially fictional movie that misled so many. A close look at this data exposes the mistake. The digital temperature data is available at http://cdiac.ornl.gov/ftp/trends/temp/vostok/vostok.1999.temp.dat and digital data for the Carbon dioxide levels from http://cdiac.ornl.gov/trends/co2/vostok.html . To facilitate the examination, this data is graphed as the second graph at the Middlebury web site given in post #41. If atmospheric carbon dioxide was a significant driver of average global temperature the temperature could not be in a declining trend when the atmospheric carbon dioxide level was higher that it had been when the temperature was in a rising trend. It is astounding that some supposedly cognitively competent people cannot seem to grasp this. Lacking any other knowledge one might think that if the atmospheric carbon dioxide level increases enough it may then significantly drive temperature. But when the carbon dioxide level is higher, increased increments of carbon dioxide have less influence than the same size increments had when the atmospheric carbon dioxide level was lower. Thus average global temperature was not significantly driven by atmospheric carbon dioxide level during the previous glacial period and atmospheric carbon dioxide level has even less influence on climate now.
129217. chris at 10:41 AM on 17 December 2008
        Models are unreliable
        re #83 Remember that water vapour is a feedback. Its atmospheric concentration is a consequence of the atmospheric temperature (and pressure), and so the levels of water vapour respond largely to variations in the atmospheric temperature. These respond rather quickly (days-months), and so the atmospheric water vapour levels are near equilibrium with respect to the atmospheric temperature. So you can't add water vapour to the atmosphere in the manner that you suggest. Thus volcanic eruptions don't add water vapour (nor does evapo/transpiration)....in general they reduce water vapour. For example, after the 1991 Pinatubo eruption the atmospheric water vapour levels fell in response to reduced atmospheric temperature as a result of the cooling effect from the blasting of particulates high into the atmosphere and the reduction of solar irradiance at the surface [***]. So water vapour can never be a “primary forcing”. It’s quite well understood that the primary driver of the ice age cycles is the slow, slow sinusoidal variations in the earth’s orbital parameters (Milankovitch cycles). As the Milankovitch insolation takes the earth through a glacial to interglacial transition, the awesomely slow primary atmospheric warming is amplified essentially immediately by the water vapour positive feedback that occurs as a spontaneous response to atmospheric warming. This is further amplified by a slower responding CO2 feedback (which recruits its own enhanced water vapour as a positive feedback). The reverse happens during the waning phases of the Milankovitch cycles. Of course water vapour responds essentially passively to ANY forcing that results in a change in atmospheric temperature. Following volcanic eruptions the atmosphere cools and water vapour levels drop as observed [***]. And as the atmosphere warms under the forcing of massively enhanced greenhouse gas concentrations, so the atmospheric water vapour concentration response passively as a positive feedback. We can observe this in the real world too [*****]. [***] e.g. B. J. Soden et al. (2002) Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor. Science 296, 727-730. Abstract: The sensitivity of Earth's climate to an external radiative forcing depends critically on the response of water vapor. We use the global cooling and drying of the atmosphere that was observed after the eruption of Mount Pinatubo to test model predictions of the climate feedback from water vapor. Here, we first highlight the success of the model in reproducing the observed drying after the volcanic eruption. Then, by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling. These results provide quantitative evidence of the reliability of water vapor feedback in current climate models, which is crucial to their use for global warming projections. [*****] e.g. Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253 Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening Science 310, 841-844. Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback . J. Climate 21, 3282-3289 Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data. J. Geophys. Res. 113, art #D14110 Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912
129218. Wondering Aloud at 06:01 AM on 17 December 2008
        It's the sun
        Keep telling yourself... "it's warming rapidly... it's not the sun..." Meanwhile back on planet Earth. http://sohowww.nascom.nasa.gov/data/realtime/mdi_igr/512/ Worst part about all of this is there should be a big lag before any noticeable cooling. In other words this winter should be warm based both on AGW and "it's the sun" theories. Anyone who thinks it is warm this winter is either very lucky or needs professional help. We need about +30C the rest of the year to get back up to average. At present we are about 55 C low on that. Please don't tell me it's warm in Europe (record snow falls) or Siberia (-60) that makes up for it. Spring was 3 weeks late of average and hard freeze was one month early. A couple more years of warming like 2007 and 2008 and you are going to see famine in the United States. Our local Ag reporter told us harvests were off 15% from predicted in the US this year because of low temperatures.
129219. Wondering Aloud at 05:51 AM on 17 December 2008
        What does CO2 lagging temperature mean?
        When all is said and done, the Temperature goes up first than the CO2 in all of the ice core records and the cave records as well. That means CO2 cannot be the driver of the climate in the pastrecord. LeChatlier's principal can then explain the swings in CO2 levels. In other words warming clearly causes CO2 to increase. The fact that a hypothetical mechanism can be proposed that the CO2 increases the warming doesn't alter the underlying fact that the past record does not tell us that CO2 causes warming. It may or may not cause warming, I had thought it certainly would, but the more I learn the less certain I am. In the past it was not a significant driver of climate despite much wilder concentration swings than we are likely to see. I also can't see how one can look at the record and suggest warming if it happens and CO2 increase when it happens would not be a net benefit to the biosphere.
129220. Mizimi at 05:49 AM on 17 December 2008
        It's cosmic rays
        A thought: cosmic rays are essentially protons, alpha and beta particles (90%,9%,1%) and since it is well known that both alpha and beta particles cause condensation trails in cloud chambers thro' ionisation, does it not follow that in appropriate atmospheric conditions they would cause condensation nuclei to form? And that the extent of such formation would depend on the quantity and energy levels of these particles? Also, is the ratio of particles always the same or is there variation which would allow for increased/decreased cloud formation regardless of the overall level of CR's?
129221. Wondering Aloud at 05:36 AM on 17 December 2008
        Latest satellite data on Greenland mass change
        While it isn't a big deal this statement "The rate is also increasing over time, suggesting an acceleration of mass loss." does not appear to be correct. (See below link) In addition I have wonderful video of our NASA friends telling us that the Maldives etc. would vanish by the year 2000. None of these claims made over the last 20 years appear one bit closer to coming true. Indeed in every specific instance they used sea level is down or land area is up. (Bangladesh) Maybe we should lay off this kind of claim. http://wattsupwiththat.com/2008/12/05/satellite-derived-sea-level-updated-trend-has-been-shrinking-since-2005/ I recently saw a paper using the original data as opposed to the "corrected" data on sea ice extent that claimed it had been increasing over the last 30 years. I didn't buy that as significant either but it was far more convincing than the minipulated pseudo data we see too often.
129222. Mizimi at 05:29 AM on 17 December 2008
        CO2 lags temperature
        CO2 lags warming by 800 -1000 years, therefore warming is initiated by increased TSI ( whether M cycles or sun activity is moot). That would increase WV which re-inforces the initial warming and temps begin to rise, releasing CO2 from open water and from increased plant growth. No?
129223. Mizimi at 05:17 AM on 17 December 2008
        We're heading into an ice age
        QM: Yes, and it makes rather a nonsense of trying to assign mean sea level deviations to global warming. The Isles of Scilly is a group of around 50 islands some 45km south west of Cornwall, England. They have been inhabited since (at least) the bronze age, some 4000ya. At low tide, stone houses, roads and field perimeters are revealed, dating from that time, so either msl has risen a few metres in 4000yrs or the islands have sunk.....how to tell the difference?
129224. Mizimi at 05:06 AM on 17 December 2008
        Models are unreliable
        Not forgetting that WV is also a GG, and has considerably greater warming effect than CO2. And that during glacial cycles the amount of WV would decrease thus adding to a more rapid/longer cooling cycle. In order to reverse WV driven cooling you need to get more WV into the atmosphere...through volcanic action or increased evapo/transpiration. If you don't increase the WV content significantly CO2 levels would have to rise dramatically to get you out of the glacial cycle. But we don't see such patterns in the CO2 record, so the primary forcing has to be increasing WV.
129225. chris at 03:02 AM on 17 December 2008
        Misinterpreting a retraction of rising sea level predictions
        No, I addressed your point in my response in post #14, Healthy Skeptic. To be specific: The linear warming trend in the Fawcett/Jones data is exactly that. A linear warming trend (or, to be precise, three linear warming trends, two strongish, one weak), is simply a mathematical fact. You consider that the linear trend is "skewed" "by the effect of the two lowest points in 1999 and 2000. But those two points are representative of the global temperature anomaly around that time. The point that "skews" the progression of the global temperature is 1998 which was lifted around 0.2 oC above the long term trend by the strongest El Nino of the 20th century. So there is a very clear warming trend in the data. It's mathematically precise in relation to linear regression of an 11 year running average of the raw data, and is more apparent in the analysis presented in which the effects of internal variations (due to ENSO) are removed. The point that Jones and Fawcett are making is that there is no scientific basis for proposing that there hasn't been any greenhouse-induced warming since 1998. Of course one can argue endlessly over temperature variations during very short periods, and the fact that the temperature anomaly has been steadyish for the last couple of years is cat-nip for those who want to progress spurious "arguments". Fawcett and Jones are just pointing out (yet again!) that those arguments don't have much basis in fact. Of course we'd like to wait a few years to see how things progress. In the meantime the most reliable means of adressing the temperature anomaly trend is to consider substantial running averages in which internal variations are roughly averaged out....
129226. Patrick 027 at 16:43 PM on 16 December 2008
        Arctic sea ice melt - natural or man-made?
        Just to be clear, everything in comments 352 up to here has been focused on (two-dimensional) barotropic Rossby waves. -- For waves that can be described by cos(k*x + l*y - w*t): -- 1. WAVE GEOMETRY (2 dimensions, (x,y)): A WAVE WITH WAVE VECTOR (k,l): phase lines are parallel to: y = -k/l * x because along a phase line: constant = y*l + k*x y*l = - k*x + constant (For y north, x east orientation of x,y: if k and l are both positive or both negative, the phase lines are aligned from northwest to southeast. If they are of opposite sign, the phase lines are aligned from southwest to northeast. If l = 0, the phase lines run from north to south; if k = 0, the phase lines run from west to east.) _______________ wave vector = (k,l) magnitude of wave vector = M = (k^2+l^2)^(1/2) unit vector in that direction = (k,l)/[(k^2+l^2)^(1/2)] = (k,l)/M Direction of wave vector: Angle counterclockwise from positive x direction: A_n cos(A_n) = k/M sin(A_n) = l/M (note: this is the n direction) _______________ unit vector perpendicular to wave vector (to the right) = (l,-k)/[(k^2+l^2)^(1/2)] = (l,-k)/M Direction of (l,-k)/M : Angle counterclockwise from positive x direction: A_s = A_n - pi/2 (radians) cos(A_s) = l/M sin(A_s) = -k/M (note: this is the s direction) ________________ 2. THE DISPERSION RELATION (w as function of spectrum (wave vector)): FOR BAROTROPIC ROSSBY WAVES, with the PV gradient in the positive y direction, and only due to beta, where beta = del(f)/del(y) (Hence, y is north, x is east) (FOR such waves, k is never positive (on a planet with prograde rotation such as most planets, where del(f)/del(y) is never negative) - the wave vector's x component is never positive - the wave vector can be westward, southwestward, northwestward, and in the limit of k=0, it can approach northward or southward - thus, A_n can be between 90 and 270 deg (pi/2 and 3pi/2 radians); A_s can be between 0 and 180 deg (0 and pi radians)). From p.85 Cushman Roisin: w = -beta * R^2 * k / [1 + R^2*(k^2+l^2)] = -beta * k / [1/R^2 + (k^2+l^2)] = -beta * k / [1/R^2 + M^2] = -beta * cos(A_n) * M / [1/R^2 + M^2] where R is the external Rossby radius of deformation, R = (g*H)^(1/2) / f ** NOTICE THAT if 1/R^2 goes to zero (or in the limit of the product (M*R)^2 going to infinity), the dispersion relation above reduces to the proportionality that would occur if the ratio of PV anomaly to RV anomaly were constant: w proportional to -beta * k / M^2, which is equal to -beta * cos(A_n) / M ** w is positive because beta is positive and k is negative. ______________________ PHASE SPEEDS: in the x direction: cx = w/k = -beta / [1/R^2 + (k^2+l^2)] = -beta / [1/R^2 + M^2] (cx is always negative; phase propagation is never eastward.) --- in the y direction: cy = w/l = -beta * (k/l) / [1/R^2 + (k^2+l^2)] = -beta * (k/l) / [1/R^2 + M^2] = -beta / ( tan(A_n) * [1/R^2 + M^2] ) = +beta * tan(A_s) / [1/R^2 + M^2] = (k/l)*cx (cy is positive if l is positive, negative if l is negative; phase propagation is northward for positive l, southward for negative l.) --- in the direction of the wave vector (k,l) (in the n direction): c = w/M = w/[(k^2+l^2)^(1/2)] = -beta * k / ( [1/R^2 + (k^2+l^2)] * (k^2+l^2)^(1/2) ) = -beta * k / [ (k^2+l^2)^(1/2) / R^2 + (k^2+l^2)^(3/2) ] = -beta * k / [ (k^2+l^2)^(1/2) / R^2 + (k^2+l^2)^(3/2) ] = -beta * k / [ M / R^2 + M^3 ] = -beta * k/M / [1/R^2 + M^2] = -beta * cos(A_n) / [1/R^2 + M^2] --- cos(A_n)/c = 1/cx = k/M / (w/M) = k/w cx*cos(A_n) = c sin(A_n)/c = 1/cy = l/M / (w/l) = l/w cy*sin(A_n) = c cy = k/l * cx = cos(A_n)/sin(A_n) * cx ________________________ GROUP VELOCITY x and y components: cgx = del(w)/del(k) = -beta / [1/R^2 + (k^2+l^2)] - -beta * k * 2k / [1/R^2 + (k^2+l^2)]^2 = -beta / [1/R^2 + (k^2+l^2)] + beta * 2k^2 / [1/R^2 + (k^2+l^2)]^2 = -beta / [1/R^2 + (k^2+l^2)] + beta / [1/R^2 + (k^2+l^2)] * 2k^2 / [1/R^2 + (k^2+l^2)] =(-beta / [1/R^2 + (k^2+l^2)] ) * (1 - 2k^2 / [1/R^2 + (k^2+l^2)] ) = w/k * (1 - 2k^2 / [1/R^2 + (k^2+l^2)] ) = w/k - 2*w*k / [1/R^2 + (k^2+l^2)] ) = -beta / [1/R^2 + M^2] + beta * 2k^2 / [1/R^2 + M^2]^2 = +beta / [1/R^2 + M^2] * (2*k^2/[1/R^2 + M^2] - 1) --- cgy = del(w)/del(l) = +beta * k * 2l / [1/R^2 + (k^2+l^2)]^2 = +beta * 2*k*l / [1/R^2 + (k^2+l^2)]^2 = +beta * 2*k*l / [1/R^2 + M^2]^2 _______________ Group velocity vector = [del(w)/del(k), del(w)/del(l)] = [cgx,cgy] Magnitude of group velocity = cg cg = (cgx^2 + cgy^2)^(1/2) = beta * ( 1/[1/R^2 + M^2]^2 * (2*k^2/[1/R^2 + M^2] - 1)^2 + 4*k^2*l^2 / [1/R^2 + M^2]^4 )^(1/2) = beta / [1/R^2 + M^2] * ( 4*k^4/[1/R^2 + M^2]^2 - 4*k^2/[1/R^2 + M^2] + 1 + 4*k^2*l^2 / [1/R^2 + M^2]^2 )^(1/2) = beta *2*k / [1/R^2 + M^2]^2 * ( k^2 - [1/R^2 + M^2] + [1/R^2 + M^2]^2/(4*k^2) + l^2 )^(1/2) = beta *2*k / [1/R^2 + M^2]^2 * ( M^2 - [1/R^2 + M^2] + [1/R^2 + M^2]^2/(4*k^2) )^(1/2) -- IN THE LIMIT of 1/(M*R)^2 = 0, cg = beta *2*k / [1/R^2 + M^2]^2 * [1/R^2 + M^2]/(2*k) = beta / [1/R^2 + M^2] ~= beta / M^2 -- (PS A VECTOR IS EQUAL TO A VECTOR SUM OF all orthogonal components. Any set of orthogonal components can be used.) Component of group velocity parallel to any other vector [a,b]: cg component = cg*cos(angle) = dot product of two vectors = cgx*a + cgy*b cg*cos(angle) = (cgx^2 + cgy^2)^(1/2) * cos(angle) = cgx*a + cgy*b cos(angle) = (cgx*a + cgy*b) / cg ____________ RECAP OF cgx and cgy: cgx = del(w)/del(k) = -beta / [1/R^2 + M^2] + beta * 2*k^2 / [1/R^2 + M^2]^2 cgy = del(w)/del(l) = +beta * 2*k*l / [1/R^2 + M^2]^2 -- Group velocity vector = [ -beta / [1/R^2 + M^2] + beta * 2k^2 / [1/R^2 + M^2]^2 , beta * 2k*l / [1/R^2 + (k^2+l^2)]^2 ] = beta * [ -1 / [1/R^2 + M^2] + 2k^2 / [1/R^2 + M^2]^2 , 2k*l / [1/R^2 + M^2]^2 ] = beta / [1/R^2 + M^2]^2 * [ - [1/R^2 + M^2] + 2*k^2 , 2*k*l ] ________________ Component of Group velocity parallel to wave vector: cgn = (k,l)/M "dot" [cgx,cgy] = beta/M * [ -k / [1/R^2 + M^2] + 2k^3 / [1/R^2 + M^2]^2 + 2k*l^2 / [1/R^2 + M^2]^2 ] = k/M * beta * [ -1 / [1/R^2 + M^2] + 2k^2 / [1/R^2 + M^2]^2 + 2*l^2 / [1/R^2 + M^2]^2 ] = k/M * beta / [1/R^2 + M^2] * [ -1 + 2*k^2 / [1/R^2 + M^2] + 2*l^2 / [1/R^2 + M^2] ] = k/M * beta / [1/R^2 + M^2] * (2*M^2 / [1/R^2 + M^2] - 1) ________________ Component of Group velocity parallel to phase line (to the right of wave vector): cgs = (l,-k)/M "dot" [cgx,cgy] = beta/M * [ -l / [1/R^2 + M^2] + 2*l*k^2 / [1/R^2 + M^2]^2 - 2*l*k^2 / [1/R^2 + M^2]^2 ] = -l/M * beta / [1/R^2 + M^2] *** NOTE: The component of group velocity in the direction of (l,-k) of the wave with wave vector (k,l) is equal to the c of a wave with wave vector (l,-k) (not too surprisingly!). _______________ IN THE LIMIT OF k going to 0, |l| = M, cgs*(|l|/l) = cgx = cx __________________ cgn = 0 when k = 0 or when: 2*M^2 / [1/R^2 + M^2] = 1 2*M^2 = 1/R^2 + M^2 M^2 = 1/R^2 (M*R)^2 = 1 For negative k, cgn is (positive/0/negative) when (M*R)^2 is (greater than/equal to/less than) 1. __________________ group velocity in direction of wave vector relative to phase speed in direction of wave vector cgn - c = = k/M * beta / [1/R^2 + M^2] * (2*M^2 / [1/R^2 + M^2] - 1) + beta * k/M / [1/R^2 + M^2] = k/M * beta / [1/R^2 + M^2] * 2*M^2 / [1/R^2 + M^2] = k/M * 2*M^2 * beta / [1/R^2 + M^2]^2 For waves with negative k, cgn is always less than c. ___________________ IN THE LIMIT OF 1/(M^2*R^2) = 0, cgn ~= k/M * beta / [1/R^2 + M^2] ~= k/M * beta / M^2 cgs ~= -l/k * cgn ~= -l/M * beta / M^2
129227. Mizimi at 09:18 AM on 16 December 2008
        What does CO2 lagging temperature mean?
        An interesting read... http://www.co2science.org/subject/c/summaries/co2climatehistory.php
129228. Mizimi at 08:51 AM on 16 December 2008
        Water vapor is the most powerful greenhouse gas
        Had a quick look at the summary page which talks about measuring total WV content of the atmosphere....but no mention of assigning values to WV from global warming as distinct from WV evaporating from human activities. It;s all lumped together as 'WV'.
129229. chris at 06:32 AM on 16 December 2008
        What 1970s science said about global cooling
        When you start "to critically question scientific evidence" please let us know! Denialist don't deny facts....denialists deny the evidence. And one shouldn't "deny an unproven hypothesis". The mature approach to hypotheses is to assess them with respect to the evidence. We know you're not an evidence sort of chap, but global warming is essentially undeniable, and the role of massive man made enhancement of greenhouse gas concentrations is sufficiently supported by the evidence that it requires some pretty specious argumentation to deny this (and I haven't seen you present any sort of evidence-based argument for anything here, but I haven't read all your posts (!), and perhaps you can point out one or two examples). Of course if you source your information from dismal newspaper "articles" and dodgy graphs from web sites and such like, then you're very likely to be horribly ill-informed on the subject. AGW is strongly supported by the evidence. It's sufficiently strongly supported that mature[*] and well-informed policymakers consider it appropriate to address the problems. [*]by mature I mean those that make an effort to be well-informed on the science, are dismissive of specious arguments and misinformation, and are able to engange in considered discussion on policy implementation.
129230. chris at 00:21 AM on 16 December 2008
        CO2 lags temperature
        Sadly you're wallowing in logical fallacy Dan. Two things we know: (i) the ice age cycles were drived by the slow cyclical variations in the orbital properties of the earth, and the associated variation in the pattern of insolation (solar irradiation at the surface) drove temperature variations. (ii) atmospheric CO2 is a greehouse gas. The Earth has a temperature response to raised CO2 somewhere near 3 oC of warming per doubling of atmospheric CO2. It's fallacious to attempt to insinuate that those two rather well-characterized phenomena are sumehow mutually exclusive! I don't think too many people here are buying logical fallacies Dan!
129231. chris at 00:11 AM on 16 December 2008
        Models are unreliable
        Do you really expect that logical fallacies are going to fool anyone on a skeptics board Dan? The ice age cycles were/are dominated by Milankovitch cycles (insolation pattern variations resulting from achingly slow cyclical variations in the Earth's orbital properties). Carbon dioxide is a greenhouse gas. The Earth has a warming response to raised atmospheric CO2 of the order of 3 oC per doubling of atmospheric CO2. Each of those phenomena apply to the Earth's temperature response and both of the statements are true. They're not mutually exclusive as you attempt to insinuate. It's logically fallacious to attempt to pursue the deceit that only one thing can influence a particular parameter (like the earth's temperature).. the fallacy of the single cause. Here's what the evidence idicates rather clearly: (i) there is a clear relationship between atmopheric CO2 levels and earth's temperature throughout the last 500 million years (see citations in my post #48). (ii) this is entirely consistent with the well-established fact that CO2 is a greenhouse gas, enhanced levels of which contribute to a warming response (amplified by feedbacks like raised water vapour and albedo response that we can observe and measure in the real world). (iii) During the slow, slow ice age cycles insolation effects result in a second-order cyclical temperature variation... it ain't rocket science Dan!
129232. Patrick 027 at 16:13 PM on 14 December 2008
        Arctic sea ice melt - natural or man-made?
        ..."the negative of the cosine of the angle between y and s directions." It implies that the angle between y and s directions is an 180 deg more or less than the angle between x and n directions, which can be confirmed geometrically. The angle between x and s directions is the same as the angle between y and n directions, but the angle between x and n directions is the angle between the y direction and the negative s direction.
129233. Patrick 027 at 16:00 PM on 14 December 2008
        Arctic sea ice melt - natural or man-made?
        CORRECTION of a paragraph above, with changes noted ***: "Say that s*** is the distance perpendicular to n****, that is, perpendicular to the 'wave envelope vector' (dk,dl); such a vector would be in the direction (dl,-dk) (90 deg to the right) or opposite that, (-dl,dk) (90 deg to the left). Let's have it be the FIRST*** one, so that coordinates s,n are a rotation of x,y. "
129234. Patrick 027 at 15:38 PM on 14 December 2008
        Arctic sea ice melt - natural or man-made?
        I figured out the error I made in sections 2c and 2d in comment 352 (PS and I may have made this error earlier as well when discussing group velocity). Recap: The linear superposition of two waves of equal amplitude, with average wave vector (k,l) and average angular frequency w, with wave vector difference between them 2*(dk,dl) and difference of angular frequency = 2dw: cos[(k+dk)*x + (l+dl)*y - (w+dw)*t] + cos[(k-dx)*x + (l-dl)*y - (w-dw)*t] = 2 * cos(k*x + l*y - w*t) * cos(dk*x + dl*y - dw*t) which can be seen as a wave with wave vector (k,l) and angular frequency w (with phase lines with slope dy/dx = -k/l) modulated by a sinusoidal wave envelope with 'amplitude wave vector' (dk,dl) and frequency dw (with 'amplitude phase lines' with slope dy/dx = -dk/dl). The magnitude of the wave vector (k,l) is M = (k^2+l^2)^(1/2), and the wavelength of the wave with that wave vector, measured in the direction of the wave vector (perpendicular to phase lines) is 2*pi/M (and so on for 'amplitude wave vector' (dk,dl) ). Now, here's the error: "dw/dk and dw/dl can be treated as partial derivatives of w as a function of k and l, in other words as the components of the gradient of w in k,l space" To borrow a phrase from Ted Stevens, NO! As with w/k, w/l, and w/M (phase speeds in x direction, y direction, and direction of wave vector ("THE" phase speed))for the wave with wave vector (k,l), wave vector magnitude M, dw/dk, dw/dl, and dw/dn are the phase speeds of the wave envelope in the x direction, y direction, and direction of 'amplitude wave vector' (dk,dl), respectively, where dn = (dk^2+dl^2)^(1/2) is the magnitude of half the vector difference between the wave vectors of the two linearly superimposed waves. As with the wave with wave vector (k,l), the phase speeds dw/dk and dw/dl do NOT add as vector components to give a vector in the direction (dk,dl) with magnitude dw/dn - it won't generally have that magnitude nor will it have that direction. The inverses, however, do have the relationship of vector components; (dk/dw,dl/dw) = dn/dw *(dk,dl)/dn, where (dk,dl)/dn is the unit vector in the direction of (dk,dl). So what is the group velocity, and what are it's vector components? This is where it would have helped me avoid a mistake if I had been using the 'del' symbol for partial derivatives; it is important to differentiate (pun intended) among the different kinds of derivatives. The group velocity for a wave with wave vector (k,l) is the gradient of w over wave vector space at the value (k,l), with the component in the k direction being the component of group velocity in the x direction, and so on for l and y, or for any other set of orthogonal components that could be used (the component in the direction of a vector (a,b) in k,l space would be the component of group velocity in that direction in x,y space. The gradient is a vector with components equal to partial derivatives; group velocity = (cgx,cgy) = [del(w)/del(k) , del(w)/del(l)], where del(a)/del(q) is the partial derivative of a with respect to q. The key is that del(w)/del(k) is NOT generally equal to dw/dk, even in the limit of infinitesimal dw and dk such that dw/dk is equal to a derivative. This is because dw is the total difference in w over a specific distance in k,l space in a specific direction. Only if that direction were only in k - that is, if dl = 0, would then del(w)/del(k) be equal to dw/dk (in the limit of infinitesimal dk). More generally, in the limit of infinitesimal differences, dw = del(w)/del(k) * dk + del(w)/del(l) * dl; dw/dn = del(w)/del(k) * dk/dn + del(w)/del(l) * dl/dn That is - only part of dw is due to dk, etc (and so on if we were discussing three-dimensional waves). dk and dl are components of the vector with magnitude dn in the direction of (dk,dl)/dn, which is of course that vector, (dk,dl). dw/dn IS the component of group velocity in that direction, because it is equal to the partial derivative of w in that direction, given how dn was defined. This is the phase speed of the wave envelope in the direction of its wave vector. It has vector components in x and in y, which are equal to dw/dn * dk/dn and dw/dn * dl/dn, respectively. These are not components of the total group velocity, however, because they are components of a component vector. One would have to add to each component the component of the other component of the group velocity to find the total group velocity components in x and y. Say that n is the distance perpendicular to s, that is, perpendicular to the 'wave envelope vector' (dk,dl); such a vector would be in the direction (dl,-dk) (90 deg to the right) or opposite that, (-dl,dk) (90 deg to the left). Let's have it be the second one, so that coordinates s,n are a rotation of x,y. In that case, del(w)/del(s) is the component of group velocity in the s direction, which adds with the vector in the n direction with magnitude dw/dn to give the total group velocity. Of course one won't observe such a group velocity for a wave envelope that does not vary in s. More generally, if a wave envelope has a rectangular checkerboard pattern that is described with two sets of 'phase lines' intersecting at right angles (as the nodal lines would do), then the two 'phase speeds', each of one set of wave envelope 'phase lines' in the direction perpendendicular to those 'phase lines', form a complete set of components of the group velocity. The group velocity will be the velocity of the checkerboard pattern, which can be defined by the motions of points (such as node intersections), as opposed to lines. ... Suppose we instead take s and n as coordinates locally defined in k,l space as being perpendicular and parallel to the wave vector (k,l) (with magnitude M) of a wave, respectively (or parallel and perpendiclar to phase lines of that wave, respectively), with n 90 deg to the left of s, so that n is in the direction of (k,l) and s is in the direction of (l,-k). Then group velocity can be described with components: cgn = del(w)/del(n) in the direction of phase propagation, which is in the direction of the wave vector and cgs = del(w)/del(s) in the direction along phase lines, to the right of phase propagation. The vectors (cgs,cgn) and (cgx,cgy) are the same vector, the group velocity, described in different coordinates - s,n and x,y, respectively. Using dot products with unit vectors that define s and n directions ( (l,-k)/M and (k,l)/M, respectively), cgs = (cgx,cgy) "dot" (l,-k)/M = 1/M * (l*cgx - k*cgy) cgn = (cgx,cgy) "dot" (k,l)/M = 1/M * (k*cgx + l*cgy) which implies that l/M is the cosine of the angle between y and n directions and the cosine of the angle between x and s directions, while k/M is the cosine of the angle between x and n directions and the negative of the cosine of the angle between y and s directions. (which can be confirmed geometrically).
129235. AlecRawls at 15:09 PM on 14 December 2008
        Svensmark and Friis-Christensen rebut Lockwood's solar paper
        There does not need to be a secular trend in solar activity for solar activity to create warming. It simply has to be high. A constant high level of solar activity (averaged over the 11 yr. cycles) will warm the earth, says 500 million years of the geologic record. This idea that there must be an upward trend in solar activity over a period (like 1975-2004) in order for warming to be explained by solar activity is like saying that you can’t heat a pot of water unless you keep turning the flame up. Having the flame set on high is supposedly not enough. This is a bizarre mistake for people to be making. Have we forgotten that the oceans form a vast heat sink? In terms of climate science, the earth is in effect a big pot of water. For as long as there is reduced cloud cover, if that is the mechanism by which solar-magnetic activity warms the earth, this reduced cloud cover will keep feeding energy into the oceans (both directly, and from air warmed up over the relatively sunny land masses). There does not need to be an ever decreasing level of cloud cover for this to occur. But John is right about one thing. Go look at these papers by supposedly competent scientists and they do indeed look at the wrong derivative. Instead of looking at the zero derivative (level of solar activity) are looking at the first derivative (trend). Here is the last line of Usoskin et. al., 2004:

        Note that the most recent warming trend, since around 1975, has not been considered in the above correlations. During these last 30 years, the solar total irradiance, solar UV irradiance, and cosmic ray flux, has not shown any significant secular trend, so that at least this most recent warming episode must have another source.

        Stupidest thing I ever heard! Well, maybe not given the competition, but it is still up there. The only thing I can figure (other than trying to avoid stepping on AGW toes) is that these eminent scientists somehow forgot that they were talking about a pot of water. Of course a continued high level of GCR/ low-level of cloudiness would continue to feed energy into the oceans. What were they thinking? Well, we know what they were LOOKING AT: the simple correlations, and lagged correlations, between solar activity and temperature. Somehow they let themselves substitute these simple correlations for the physical process itself. Lagged correlation is a little better, but it is still does not model the physical process. It would not be hard to estimate, for each level of global temperature, the level of solar activity that tends to create warming rather than cooling. Then estimate, for each increment of solar activity above this level, how much the rate of warming tends to increase. This could easily be combined with a physical model of the heat storage capacity of the oceans. Fitting such a model to the data would yield a picture over time of the heat store (ocean temperature) and the solar driven additions and subtractions from it. Logically, we would expect to find some periods where solar activity was increasing but the earth was still cooling, because the increase still hadn’t brought the level of solar activity back to the level necessary to create warming. These instances would be misinterpreted as counter-evidence to the sun-temperature link if we were looking at trend instead of level. It’s just obvious that looking at trend is wrong. It doesn’t fit how the world works. We have all the data. It’s just a matter of decomposing it more intelligently. Once we realize that we should be looking at level, not trend, the implications of Svensmark’s graph come into focus. You can see from the close fit between the plot of Galactic Cosmic Radiation and the de-trended temperature curve that there is very little trend in GCR over the second half of the 20th century. The average over the 11 yr cycles was consistently high, what Solanki calls “grand maximum,” or as high as anything seen in the geologic record. That’s why we had warming. The flame was turned up under the pot for sixty years. Why wasn’t warming uniform? The Pacific Decadal Oscillation. Take out the PDO and, as Svensmark’s graph shows, the ups and downs of the 11 yr. solar cycle match the ups and downs in the temperature anomaly. If you want, you can look at Svensmark as graphing de-trended temperature against de-trended GCR (where the GCR trend is essentially zero). What the graph shows is that changes in GCR do a very good job of explaining (statistically) the changes in temperature. From here you can see how John’s interpretation of Svensmark’s graphic is wrong. He thinks that because the ups and downs of GCR perfectly explain de-trended temperature, the trend in temperature must be explained by something else. But the “something else” is the LEVEL of GCR. It’s STILL the cosmic ray flux that is at work. 60 years of relatively cloudless skies kept pumping heat into the oceans (or so the evidence seems to indicate). John has a lot of company in getting this wrong. Usoskin and Solanski got it wrong in their 2004 paper and they are AGW skeptics. Thus apparently this is not a motivated error, but just collective incomprehension of something that ought to be pretty easy to sort out. Dang. Who hasn’t used a stove? My posts here and here, My posts here and here, but they don’t go as far into this particular issue as this comment does.
129236. chris at 11:16 AM on 14 December 2008
        Did global warming cause Hurricane Katrina?
        That's incorrect Healthy Skeptic. Perhaps you are unfamiliar with the science on this issue. I've had a look at the newspaper interview (!) you are sourcing your info from and it's pretty poor stuff. Much of the "article" is assertions about the absence of an increase in the number of hurricanes...Gray concludes a section with "The hypothesis that increasing carbon dioxide in the atmosphere increases the number of hurricanes fails by an even wider margin when we compare two other multi-decade periods..." However it's clear from John Cook's top article that the issue isn't about the number of hurricanes but the number of high intensity (cat 4/5 hurricanes), and these have increased in line with raised sea surface temperatures (SST), as Gray acknowledges. So most of the "article" is uncontroversial. Unfortunately Gray's asertions about the source of raised SST doesn't accord with the scientific evidence, since: ONE: The evidence indicates that the global rise of SST has a major component of man-made warming due to greeenhouse gas emissions: e.g. Barnett, T. P. et al (2005) Penetration of human-induced warming into the world's oceans Science, 309, 284–287. Abstract:"A warming signal has penetrated into the world's oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change." [TWO] The AMO (Atlantic Meridonal Overturning) that Gray speaks of is likely to have made only a small contribution to increased SST: e.g.: K. E. Trenberth and D. J. Shea (2006) Atlantic hurricanes and natural variability in 2005 Geophysical Research Letters, VOL. 33, L12704 Abstract:"The 2005 North Atlantic hurricane season (1 June to 30 November) was the most active on record by several measures, surpassing the very active season of 2004 and causing an unprecedented level of damage. Sea surface temperatures (SSTs) in the tropical North Atlantic (TNA) region critical for hurricanes (10° to 20°N) were at record high levels in the extended summer (June to October) of 2005 at 0.9°C above the 1901–70 normal and were a major reason for the record hurricane season. Changes in TNA SSTs are associated with a pattern of natural variation known as the Atlantic Multi-decadal Oscillation (AMO). However, previous AMO indices are conflated with linear trends and a revised AMO index accounts for between 0 and 0.1°C of the 2005 SST anomaly. About 0.45°C of the SST anomaly is common to global SST and is thus linked to global warming and, based on regression, about 0.2°C stemmed from after-effects of the 2004–05 El Niño." [THREE] Analysis of the dominant causative influence on high SST supports the conclusion that GW results in raised SST results in increased tropical storm intensity, rather than the alternative (AMO---> raised SST): e.g. Elsner JB (2006)Evidence in support of the climate change - Atlantic hurricane hypothesis Geophysical Research Letters 33 L16705 Abstract: "The power of Atlantic tropical cyclones is rising rather dramatically and the increase is correlated with an increase in the late summer/early fall sea surface temperature over the North Atlantic. A debate concerns the nature of these increases with some studies attributing them to a natural climate fluctuation, known as the Atlantic Multidecadal Oscillation (AMO), and others suggesting climate change related to anthropogenic increases in radiative forcing from greenhouse-gases. Here tests for causality using the global mean near-surface air temperature (GT) and Atlantic sea surface temperature (SST) records during the Atlantic hurricane season are applied. Results show that GT is useful in predicting Atlantic SST, but not the other way around. Thus GT "causes" SST providing additional evidence in support of the climate change hypothesis. Results have serious implications for life and property throughout the Caribbean, Mexico, and portions of the United States." ...and so on. If we're really intested in understanding these issues, we really should be addressing the evidence from the science, and not unsubstantiated assertions from newspaper articles!
129237. chris at 10:43 AM on 14 December 2008
        The Mystery of the Vanishing Ocean Heat
        You seem to have a problem with the truth Healthy Skeptic. Unfortunately Dr. Nils-Axel Morner is stating something that is not true. He's perfectly within his rights to diseeminate falsehoods in interviews... ..but why listen to rubbish that people say in interviews? We know how sea level measurements are made, and we know how the IPCC report on this extensive research (see papers in my post #27). So what's to be gained from pretending that things are not as they are? I don't really understand your approach to this. On the one hand you want to portray yourself as a "skeptic". However your approach to the science is decidedly unhealthy. You don't seem to care to address the science but prefer unsubstantiated stuff from interviews and dodgy websites. I'm not denigrating Dr. Nils-Morner. I'm pointing out that he is asserting things that aren't true. I accept that you seem to prefer untruths on the subject of climate science (the rubbish on previous CO2 measurements from a German scholl teacher...the nonsense on paleotemperature/paleoCO2 relationships from a wildly inaccurate sketch of "data" and so on...) In science Healthy Skeptic, it's all about the evidence. You choose not to address this. That's fine..it's your choice. But don't pretend that propagating falsehoods has anything to do with "skepticism"!
129238. chris at 04:28 AM on 14 December 2008
        Evaporating the water vapor argument
        Your comment doesn't make much sense Healthy Skeptic. What humor are you referring to with respect to "the vast majority of AGW alarmists"? Can you give us an example please? After all Douglas and I are referring to something rather specific. You seem to be making a generalized assertion about something and it's not obvious what you're referring to. Example please...
129239. chris at 02:35 AM on 14 December 2008
        Determining the long term solar trend
        #16 Some plants grow better with raised CO2 and some don't. Since plants also require water and nutrients, the idea that plants will continue to show enhanced growth in a world with higher CO2 levels, and that this will result in "locking up" of significant CO2, is fallacious. In any case, the limits on plant growth and CO2 sequestration are dominated by land use/deforestation, and not be CO2 levels. The notion that "reaction mass increases roughly 100% for every 10C rise" is an empirical finding from physical chemistry and doesn't apply to biological systems. Your other points about cycles don't really accord with real world considerations either. The rate of drawing excess CO2 out of the atmosphere is very slow, and so there isn't really any significant "draw down" of the vast amounts of CO2 we're pumping into the atmosphere apart from that amount that is partitioning into the oceans. It's plain to see that atmopsheric CO2 levels are rising at a phenomenal rate (over 100 times faster than during the last glacial to interglacial transition which is the most recent example of a natural change in atmospheric CO2 levels)...so your "cycle" clearly isn't acting.. The "small amount of extra CO2 we release" is certainly not "small"! It's enormous. It's an amount that could only be sustained for a truly tiny period (several hundred years), and it's occuring at a rate that were we to carry doing so for several hundred years we would effectively return to the atmosphere all of the CO2 in fossil fuels that took several hundreds of millions of years to form... You are correct 'though, that the massive amounts of extra CO2 that we release "will not substantially affect the cycle". The cycle responds very slowly to enhanced CO2, and so any feedback elements are going to be rather insignificant in their abilities to mitigate our truly massive increases in atmospheric CO2...
129240. chris at 02:08 AM on 14 December 2008
        Determining the long term solar trend
        #15 That's just incorrect Healthy Skeptic. Raised greenhouse gases cause the atmosphere to warm and to increase the concentration of water vapour. That's a straightforward prediction from our understanding of atmospheric physics....... and we can measure this in the real world. There is no evidence that increased water vapour has a "cooling" effect that you speculate on. Since warmer air has a higher capacity for water vapour there is no necessary increase in clouds with enhanced water vapour. In any case clouds don't just reflect solar radiation. They also also efficiently trap outgoing thermal radiation (even an unhealthy "skeptic" must have direct experience of that fact!) and retain heat in the surface and lower atmosphere. Since we have a wealth of paleodata on the relationship between Earth's temperature and atmospheric CO2 levels, and the data indicate a clear correlation between temperature and CO2 (highish temperatures when CO2 is high and lowish temperatures when CO2 is low), a skeptic would have every reason to be skeptical about your proposed cooling efect of water. It's pretty clear that increased water vapour enhances CO2-induced warming. try this, for example: http://www.nasa.gov/topics/earth/features/vapor_warming.html
129241. Dan Pangburn at 01:18 AM on 14 December 2008
        CO2 lags temperature
        During the last and previous glacial periods there were temperature and carbon dioxide up-trends and downtrends. Credible data from Vostok and EPICA showing these trends are readily available (e.g. the first graph above). Close examination of these data shows unequivocally that on many occasions temperature trended down for centuries while carbon dioxide level was higher than it had been during a prior temperature uptrend. This shows that, at least at that time, temperature was not driven by carbon dioxide level. It is well known that added increments of carbon dioxide have less influence than previous increments. This has been elucidated using the added-blankets metaphor. Since there is more carbon dioxide in the atmosphere today than during the glacial periods, added increments of carbon dioxide today have even less influence than they did during the glacial periods when they did not drive temperature. Thus added atmospheric carbon dioxide today does not drive temperature and AGW that is based on increased atmospheric carbon dioxide is a mistake.
129242. Quietman at 16:59 PM on 13 December 2008
        We're heading into an ice age
        Mizimi Plates literally float. They can shift, rise or fall. There are no true continents, what we see is a result of large pieces of lighter material breaking and mergeing or subducting. There is no real difference between sea floor and land other than elevation. So while Australia is relatively free from volcanism it is still subject to plate tectonics which are constantly active but change intensity and speed is cycles.
129243. Tom Dayton at 14:31 PM on 13 December 2008
        Water vapor is the most powerful greenhouse gas
        There's a new satellite-based study of the relationship of water vapor to CO2 by Dessler and colleagues on NASA.gov (the Earth section). It nails down the specific feedback effect's size.
129244. chris at 06:27 AM on 13 December 2008
        Human CO2 is a tiny % of CO2 emissions
        It hasn't been far-off 300 ppm (generally a bit lower)for millions of years (around 20 million years), apart from the glacial periods of the past few million years when atmospheric CO2 dropped towards 180 ppm. That's what the evidence indicates. see papers cited in post #13 above...
129245. Patrick 027 at 16:17 PM on 12 December 2008
        Arctic sea ice melt - natural or man-made?
        CORRECTION " (**The component of Group velocity parallel to phase lines - amplitude propagation along phase lines - is fastest at intermediate tilts between phase lines being aligned with the PV gradient and being perpendicular to it**). " Actually, that's for the group velocity y-component with basic state PV gradient parallel to y. The fastest group velocity component parallel to phase lines occurs when the phase lines become parallel to basic state PV contours. Of course, for finite-width wave envelopes, this should be equal to phase propagation of the same wave described instead as having phase lines aligned with the PV gradient, with amplitude varying sinusoidally along phase lines... etc. ------------ A wave envelope can be limited in multiple dimensions. In **C0** in was limited in the x direction. One could consider the case of a wave envelope limited in both x and y, in which case aspects of **C0** and **C1** would be combined; there could/would be group velocity in both x and y; new phase lines would grow on the outskirts in the x direction (in the direction of group velocity minus phase motion - if the wave envelope is not spreading out too quickly, then old phase lines will decay on the other side of the wave envelope). ---------- Group velocity: THE group velocity of a wave is determined by the frequency as a function of the spectrum - specifically, it is in (x,y) space equal to the gradient of w in wavenumber space (k,l) (and so on for three dimensional waves, etc.) - thus it has components that are partial derivatives dw/dk and dw/dl. ----- (I'm using d for partial derivatives here but partial derivatives are written with a "del" symbol (not the same as the gradient operator symbol, which I believe is called "Del", which is an upside down capital greek letter Delta; the del symbol looks a little like the lowercase greek letter delta, but is smoother - it looks like a backwards '6'. I also used 'd', as in 'dw','dk','dl' above, as values (representing a difference in w, k, or l) that may or may not be infinitisimal in size. The propper symbol to use in that case is the lowercase delta, or particularly for sizable differences, capital Delta. I'm going to continue to just use dw, dk, and dl here, though.) ----- But in order to actually see amplitude propagation (wave envelope propagation) at the group velocity, there must be variation in amplitude. This can be produced by linear superposition of additional waves that or only infinitesimally different parts of the spectrum. In that case, amplitude variations are very spread out in space and the group velocity of the interference pattern is about the same as (dw/dk,dw/dl). However, as the amplitude variations become more concentrated in space, the ratios of the differences of w to the differences of k and l between wave pairs won't be exactly the same as the derivatives dw/dk and dw/dl for each linearly-superimposed component - and each component may have different dw/dk and dw/dl for it's own k and l. While a wave envelope will propagate with some average or effective group velocity, it will also tend to spread and weaken (or contract and intensify up to a point and then spread and weaken - one or the other might happen in one direction while the opposite happens in another direction) and the phase lines may take on different tilts in different parts of the wave envelope, which might then be described by multiple overlapping wave envelopes, etc..., as there are a range of group velocities present. While wave envelope propagation perpendicular to phase lines can always be seen as being at a group velocity component in that direction, the group velocity along phase lines may lose any meaningful distinction with phase propagation, as in the checkerboard pattern example; this suggests (at least for Rossby waves) that the group velocity component parallel to phase lines will get smaller when the wave envelope wavelength in that direction get's smaller, just as phase speed is smaller for smaller wavelengths, and as described for the checkerboard pattern, both propagation of phases or along phases each vary qualitatively the same way with wavelengths in both directions.
129246. Patrick 027 at 16:13 PM on 11 December 2008
        Arctic sea ice melt - natural or man-made?
        ... In **CASE C2**, the checkerboard pattern - the nodes of the vorticity wave, u' wave, and v' wave, form a set of rectangles for each wave. Contours of wave values thus are nearly rectangular near the nodes but become more rounded toward the centers of the rectangles. In this checkerboard pattern, parallel to either set of parallel nodes, wave values vary sinusoidally. In the x direction, the u' and vorticity waves are in phase and 180 deg out of phase (depending on y), while they are 90 deg or 270 deg out of phase in the y direction. In the y direction, the v' and voriticity waves are in phase and 180 deg out of phase (depending on x), while they are 90 deg or 270 deg out of phase in the x direction. Because of the constant proportionality in the x direction of u' with vorticity and in the y direction of v' with vorticity, the propagation in the y direction does not vary with x and the propagation in the x direction does not vary with y. (The propagation of the wave of course occurs as u' and v' act across the PV gradient to increase PV where the PV anomaly gradient is in one direction and decrease the PV where a component of the PV anomaly gradient is in the other direction; a maximum moves toward where values increase and away from where values decrease, a minimum moves toward decreasing values and away from increasing values; the derivative in space of a sinusoidal waveform is another sinusoidal waveform either 90 or 270 deg (depending on view point) out of phase; a moving sinusoidal waveform produces variations at fixed locations that are sinusoidal in time, etc, so propagation of a otherwise unchanging wave pattern will have rate of change of PV, RV, u', v', etc, 90 or 270 deg out of phase (in the direction(s) of propagation) from the wave pattern of the instantaneous values of PV, RV, u', v', etc, respectively, and with the amplitude of the time derivative wave in proportion to the amplitude of the instantaneous value wave - a proportion that can vary in the direction of propagation but does not vary in the perpendicular direction). -- But what about **CASE C1**, or more generally, when a wave does not form an infinite pattern but has only nonzero amplitude (or amplitude above OR below some threshold) in a single limited region that is not part of a repeating sinusoidal variation (or some linear combination of those) of amplitude? (PS this does not describe any propagation of the checkerboard pattern; the modulation of amplitude of one wave by another sinusoidal function has a group velocity but this is not the group velocity of the whole pattern; to illustrate such a group velocity, one must multiply the whole wave form by yet some other amplitude-modulating function, etc...) Take **CASE C1** for example. The vorticity wave is a wave train along the x-axis, symmetric about y, that is nonzero only over some finite range of y. If the basic state PV gradient is not parallel to either axis, as in **CASE C1b**, then the wave is tilted and the 'amplitude wave' (better term - the wave envelope) will move with some group velocity in y that is a function of the wavelength in x (and therefore a function of wavenumber k), where the group velocity y component is precisely the derivative dw/dl for the k value - w is a function of (k,l) for Rossby waves and waves in general; this is how group velocity can be defined for a wave that is not part of a specific interference pattern of specific waves). In **CASE C1a**, the y component of group velocity is 0; the wave envelope doesn't propagate in y. The physical explanation is qualitatively the same as in **CASE C2(b and a, respectively)**. A narrow wave envelope should slow propagation in the x direction for the same reason that k affects propagation in y and l affects propagation in x for the checkerboard pattern. But that is only part of the story. In both **C1a** and **C1b**, as in **C2**, there are closed wave streamlines around the wave vorticity maxima and minima, as there are u' and v' waves. But in **C2**, both u' and v' reach maxima and minima along the nodes of the vorticity wave, and there values go toward zero approaching the next vorticity maxima or minima. In **C1**, in the y direction, there is not other vorticity maxima or minima. Instead, u' and v' values must decay toward zero going away from the center of the wave envelope - Refering back to how the wind field can be determined from the vorticity field, the length scale of this decay to zero will increase with increasing wavelength in the x-direction (note consequences for group velocity, this is somewhat** qualitatively similar to how k affects propagation in y and l affects propagation in x for the checkboard pattern, though perhaps for additional reasons). Outside the vorticity wave envelope, this wind field must also be irrotational; this works because while -du'/dy must reverse sign (in the y direction) in order for u' to decay to zero, dv'/dx can keep the same sign out to large |y| (though it approaches 0 as v' approaches 0). One can get a qualitative handle on this (and some of the other issues discussed above, including group velocity of tilted waves) by considering each phase line as a string of circular vorticies (remember that the wind speed of each is inversely proportional to distance from the center of each). Each contributes to the wind field v' in between vorticity maxima and minima phase lines, and not just at points on the same y value as the vortex; hence, v' is larger at any one y value due to voriticity at other y values (though the vorticity at the same y will have the greatest effect). Meanwhile, the u' fields of any pair of vortices also adds to increase total u' outside the pair but the values partly cancel in between the pair (with the total u' from that pair being of the sign of the u' from the stronger of the two vorticities). And so on... vorticity phase lines of constant amplitude over y has constant v' over y as well, zero u', and if only one line of vorticies, v' would be constant over x on either side of the line. But variation of vorticity amplitude along a phase line allows nonzero u' (as described above for both cases **C1** and **C2**, thus allowing some propagation in the y direction if there is a PV gradient in x ----- [PS another way to look at that: suppose instead of holding x and y oriented to the wave structure, hold x and y so that the PV gradient is just in y, but the wave is tilted. The wind field of each vortex will, by displacing PV contours, increase PV on one side and decrease PV on the other, with zero PV change along a line in the y direction centered on the vortex. In a tilted wave, the vortices along a phase line (along a vorticity wave crest or trough) lie in each other's PV changing regions. Where their is constant amplitude along the phase line or where there is an amplitude minimum or maximum (constant amplitude at that point), provided symmetry about that maximum or minimum, then the effects cancel and there is zero PV change at that point, but where vorticity is not symmetric along the phase line about a point, or generally where vorticity changes along the phase line or changes sign, the effects at the location of one vortex by the other vortices can be or will be unbalanced, so that PV is changing at that point along the vorticity crest or trough, hence there can be or will be amplitude propagation in the direction parallel to phase lines]. -----), and variation of v', but unlike **C2**, where the v' is kept proportional to vorticity over y, for **C1**, the parts of the wave near y=0 may generally have less v' per vorticity as there is on the edges of the vorticity wave envelope - the stronger vorticies have proportionately weaker v' at the same y due to the weaker vortices at other y values, while the weaker vortices have stronger v'. Furthermore, outside of the vorticity wave itself, there is still v' (and u') from the vortices within the wave envelope (that their magnitudes decrease faster with distance from the vorticity wave envelope for shorter wavelengths in the x direction (higher k) can be seen as a consequence of the wind field at any one point depending less on the finer details at some distance). This means that, initially, phase propagation speeds (in the x direction) are slower in the center of the wave envelope as they are on the outskirts. This means the waves bend into V or U shapes (and the wave envelope expands due to the extent of v' (and u' for **C1b**)). The wave is tilted relative to (x,y), above and below y=0, in opposite directions. This bending then allows for amplitude propagation away from the center (where the amplitude falls) and toward the wave envelope edges; for **C1a**, this is symmetrical about y=0, for **C1b**, the variation of basic state PV in the x direction can introduce some asymmetry - the tilts relative to the PV gradient direction won't be equal and opposite; conceivably they might be the same sign; they can't have the same magnitude, though; ----- (**The component of Group velocity parallel to phase lines - amplitude propagation along phase lines - is fastest at intermediate tilts between phase lines being aligned with the PV gradient and being perpendicular to it**). This could be seen as two wavetrains of equal and opposite phase tilts relative to x,y directions, but with wave envelope aligned in the same direction, that were initially linearly superimposed, but then seperated as each had it's own group velocity (and possibly different phase phase speeds, if the PV gradient is not parallel to y). However, each of these wavetrains can be expected to undergo the same process (modified by different phase tilts, etc.) as occured with the original wavetrain. Alternatively, depending on wave envelope form, there might never be complete seperation (thought the amplitude at the center will continually decrease) - the wave might continue to spread with a range of group velocities (corresponding to those group velocities of all linearly superimposed component waves) with the phase lines curving into U shapes. Another way of veiwing this is to consider a string of vorticies of alternating sign (representing the wave train, aligned with the wave envelope); rather than consider the motion of the vorticities, one can think of it as vorticities that are not moving but with each generation of vorticity phase lines continually producing a new generation of new vorticity crests and troughs that are 90 or 270 deg out of phase from the parent generation. The total wave propagates because the third generation is 180 degrees out of phase from the first, as is the forth from the second, etc, so that they cancel each other. But with amplitude confined to a wave envelope centered at y=0, any generation will produce a next generation that is more spread out in y and has lower amplitude at y=0. Thus the third generation does not completely cancel the first at y = 0, but that allows a portion of the first generation to continue to act to produce an additional second generation (generation 2B ?), and so on... so that the first generation might eventually be canceled out, but by that point ... etc...
129247. Dan Pangburn at 12:18 PM on 11 December 2008
        Models are unreliable
        Contrary to the statement in post #80 “No one says that "all temperature trend direction changes are brought about by Milankovitch cycles", so let's not make stuff up”, the statement “So it's quite straightforward to understand how the net insolation effect can produce a pattern of cyclical temperature variation as observed in the record” and several similar statements in post # 80 indicate that Chris seems to realize that temperature up trends and downtrends were not driven by atmospheric carbon dioxide level in the past. In post #73 with the statement “We all know that the Earth's equilibrium temperature response has a logarithmic relationship to the atmospheric CO2 concentration” Chris appears to also understand that added increments of carbon dioxide have diminishing influence on temperature. But then Chris and apparently the rest of the alarmists fail to put the two observations together which would prove to them that temperature trends now are also not driven by atmospheric carbon dioxide level.
129248. Quietman at 11:20 AM on 11 December 2008
        A Great Science Fiction Writer Passes - Goodbye Dr. Crichton
        This is what "State of Fear" is about and like all of Michaels works is based on his investigations and conclusions drawn from same and then voiced in the form of a novel. It was one of, if not his best, works. The following is a paragraph from environmentalism as a religion in a speech at the Commonwealth Club, San Francisco, CA, September 15, 2003 How will we manage to get environmentalism out of the clutches of religion, and back to a scientific discipline? There's a simple answer: we must institute far more stringent requirements for what constitutes knowledge in the environmental realm. I am thoroughly sick of politicized so-called facts that simply aren't true. It isn't that these "facts" are exaggerations of an underlying truth. Nor is it that certain organizations are spinning their case to present it in the strongest way. Not at all---what more and more groups are doing is putting out is lies, pure and simple. Falsehoods that they know to be false. Thank you Michael. R.I.P.
129249. Patrick 027 at 05:28 AM on 11 December 2008
        Arctic sea ice melt - natural or man-made?
        Correction sec.2e.: **CASE C2a**: Now, in this case, if the basic state PV gradient is in the y-direction (the 'default setting' for this overall discussion), then for Rossby waves, dw/dl should be zero at l=0. There is *** N O T *** 'amplitude wave' propagation in the y direction; the phases propagate in the negative x direction.
129250. Tom Moore at 00:24 AM on 11 December 2008
        Latest satellite data on Greenland mass change
        At face value, the graph suggests that there was a mass gain going on until quite recently, perhaps 2005. If so, this past couple of years doesn't seem like much to worry about.

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