Recent Comments

Prev  2616  2617  2618  2619  2620  2621  2622  2623  2624  2625  2626  2627  2628  2629  2630  2631  Next

Comments 131151 to 131200:

131151. chris at 10:08 AM on 3 October 2008
        What does CO2 lagging temperature mean?
        Re #27 Mizimi When presented with a ludicrous and blatantly incorrect paleotemperature "graph" of unknown provenance you consider it a "beautiful example to show there IS a limit to which CO2 can effect temperature changes.....(your post #16). However when presented with copious scientific data on the straightforward relationship between atmospheric paleo CO2 levels and paleotemperature (see my post #25) you suddenly lose your enthusiasm. Apparently you prefer nonsense that supports some sort of agenda position in preference to the science...try re-reading my post #26 on the nature of skepticism. Your "sub" point about paleo-warmth is unfortunately misplaced. In fact the evidence indicates that the warm periods in the past have been associated with lower biodiversity [***] and that it is the rapid increases in global warmth, largely associated in the past with tectonic events, that have been the drivers of major extinctions throughout Earth's history[*****]: [***]PJ Mayhew et al. (2007) A long-term association between global temperature and biodiversity, origination and extinction in the fossil record Proceedings of The Royal Society B 275, 47–53. Abstract: "The past relationship between global temperature and levels of biological diversity is of increasing concern due to anthropogenic climate warming. However, no consistent link between these variables has yet been demonstrated. We analysed the fossil record for the last 520Myr against estimates of low latitude sea surface temperature for the same period. We found that global biodiversity (the richness of families and genera) is related to temperature and has been relatively low during warm 'greenhouse' phases, while during the same phases extinction and origination rates of taxonomic lineages have been relatively high. These findings are consistent for terrestrial and marine environments and are robust to a number of alternative assumptions and potential biases. Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner. Our findings may have implications for extinction and biodiversity change under future climate warming." [*****]Major extinctions are associated with long lived perturbation of the climate system and the atmosphere. For example the early Jurassic extinction is associated with events (greenhouse gas induced warming) lasting 200,000 years: Svensen H et al (2007) Hydrothermal venting of greenhouse gases triggering Early Jurassic global warming Earth Planetary Sci Lett 256 554-566 Abstract: "The climate change in the Toarcian (Early Jurassic) was characterized by a major perturbation of the global carbon cycle. The event lasted for approximately 200,000 years and was manifested by a global warming of similar to 6 degrees C, anoxic conditions in the oceans, and extinction of marine species. The triggering mechanisms for the perturbation and environmental change are however strongly debated. Here, we present evidence for a rapid formation and transport of greenhouse gases from the deep sedimentary reservoirs in the Karoo Basin, South Africa......." likewise comprehensive analyses of the coincidence of major tectonic events, and resulting elevation of greenhouse gas levels, are associated with several of the major extinctions of the last 300 million years. Note that CO2 isn't the only player. Methane is implicated in several of these events (see especially the PETM below) and sulphurous oxides and their effects on ocean acidity and oxygen content are also implicated: Wignall P (2005) The link between large igneous province eruptions and mass extinctions Elements 1, 293-297 Abstract: "In the past 300 million years, there has been a near-perfect association between extinction events and the eruption of large igneous provinces, but proving the nature of the causal links is far from resolved. The associated environmental changes often include global warming and the development of widespread oxygen-poor conditions in the oceans. This implicates a role for volcanic CO2 emissions, but other perturbations of the global carbon cycle, such as release of methane from gas hydrate reservoirs or shut-down of photosynthesis in the oceans, are probably required to achieve severe green-house warming. The best links between extinction and eruption are seen in the interval from 300 to 150 Ma. With the exception of the Deccan Trap eruptions (65 Ma), the emplacement of younger volcanic provinces has been generally associated with significant environmental changes but little or no increase in extinction rates above background levels." R. J. Twitchett (2006) The palaeoclimatology, palaeoecology and palaeoenvironmental analysis of mass extinction events Palaeogeog., Palaeoclimatol., Palaeoecol. 232, 190-213 concluding paragraph: "Mass extinction studies have enjoyed a surge in scientific interest of the past 30 years that shows no sign of abating. Recent areas of particular interest include the palaeoecological study of biotic crises, and analyses of patterns of post-extinction recovery. There is good evidence of rapid climate change affecting all of the major extinction events, while the ability of extraterrestrial impact to cause extinction remains debatable. There is growing evidence that food shortage and suppression of primary productivity, lasting several hundred thousand years, may be a proximate cause of many past extinction events. Selective extinction of suspension feeders and the prevalence of dwarfed organisms in the aftermath are palaeoecological consequences of these changes. The association with rapid global warming shows that study of mass extinction events is not just an esoteric intellectual exercise, but may have implications for the present day." Notice that greenhouse environments are associated with the very delayed (millions of years) recovery of biota following these extinctions; Fraiser ML et al. (2007) Elevated atmospheric CO2 and the delayed biotic recovery from the end-Permian mass extinction Palaeogeog. Palaeoclim. Paleoecol. 252, 164-175 Abstract: Excessive CO2 in the Earth ocean-atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the end-Permian mass extinction by facilitating global warming, widespread ocean stratification, and development of anoxic, euxinic and CO2-rich deep waters. A broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction. Although previous studies of the role of excessive CO2 have focused on these "bottom-up" effects emanating from the deep ocean, "top-down" effects of increasing atmosphere CO2 concentrations on ocean-surface waters and biota have not previously been explored. Passive diffusion of atmospheric CO2 into ocean-surface waters decreases the pH and CaCO3 saturation state of seawater, causing a physiological and biocalcification crisis for many marine invertebrates. While both "bottom-up" and "top-down" mechanisms may have contributed to the relatively short-term biotic devastation of the end-Permian mass extinction, such a "top-down" physiological and biocalcification crisis would have had long-term effects and might have contributed to the protracted 5- to 6-million-year-long delay in biotic recovery following this mass extinction. Earth's Modern marine biota may experience similar "top-down" CO2 stresses if anthropogenic input of atmosphere/ocean CO2 continues to rise. The lesser extinction associated with the Paleo-Eocene-Thermal Maximum (PETM)55 MYA is probably the best characterised (not surprisingly since it's the most recent!) example of massive tectonic processes (the opening up of the N. Atlantic as the plates seperated) associated with enhanced atmospheric greenhouse gases, ocean acidification etc.: M. Storey et al. (2007)Paleocene-Eocene Thermal Maximum and the Opening of the Northeast Atlantic Science 316, 587 - 589 abstract: "The Paleocene-Eocene thermal maximum (PETM) has been attributed to a sudden release of carbon dioxide and/or methane. 40Ar/39Ar age determinations show that the Danish Ash-17 deposit, which overlies the PETM by about 450,000 years in the Atlantic, and the Skraenterne Formation Tuff, representing the end of 1 ± 0.5 million years of massive volcanism in East Greenland, are coeval. The relative age of Danish Ash-17 thus places the PETM onset after the beginning of massive flood basalt volcanism at 56.1 ± 0.4 million years ago but within error of the estimated continental breakup time of 55.5 ± 0.3 million years ago, marked by the eruption of mid-ocean ridge basalt–like flows. These correlations support the view that the PETM was triggered by greenhouse gas release during magma interaction with basin-filling carbon-rich sedimentary rocks proximal to the embryonic plate boundary between Greenland and Europe." And even the end-Cretaceous extinction (that did for the dinosaurs) seems to have had at least a significant component from massive flood basalt events (that resulted in the Deccan Traps in what is now India). In fact there is increasing evidence that the impact that resulted in the Chicxulub crater in the Yucatan post-dates the onset of the extinction by several 100,000's of years, and the extinction is associated with global warming (including a sudden contribution from the impact into limestone-rich deposits that vapourized massive amounts of carbonate (limestone) back into CO2): Keller G (2005) Impacts, volcanism and mass extinction: random coincidence or cause and effect? Austral. J. Earth Sci 52 725-757. Abstract: "Large impacts are credited with the most devastating mass extinctions in Earth's history and the Cretaceous - Tertiary (K/T) boundary impact is the strongest and sole direct support for this view. A review of the five largest Phanerozoic mass extinctions provides no support that impacts with craters up to 180 km in diameter caused significant species extinctions. This includes the 170 km-diameter Chicxulub impact crater regarded as 0.3 million years older than the K/T mass extinction. A second, larger impact event may have been the ultimate cause of this mass extinction, as suggested by a global iridium anomaly at the K/T boundary, but no crater has been found to date. The current crater database suggests that multiple impacts, for example comet showers, were the norm, rather than the exception, during the Late Eocene, K/T transition, latest Triassic and the Devonian-Carboniferous transition, but did not cause significant species extinctions. Whether multiple impacts substantially contributed to greenhouse worming and associated environmental stresses is yet to be demonstrated. From the current database, it must be concluded that no known Phanerozoic impacts, including the Chicxulub impact (but excluding the K/T impact) caused mass extinctions or even significant. species extinctions. The K/T mass extinction may have been caused by the coincidence of a very large impact ( > 250 km) upon a highly stressed biotic environment as a result of volcanism. The consistent association of large magmatic provinces (large igneous provinces and continental flood-basalt provinces) with all but one (end-Ordovician) of the five major Phanerozoic mass extinctions suggests that volcanism played a major role. Faunal and geochemical evidence from the end-Permian, end-Devonian, end-Cretaceous and Triassic/Jurassic transition suggests that the biotic stress was due to a lethal combination of tectonically induced hydrothermal and volcanic processes, leading to eutrophication in the oceans, global warming, sea-level transgression and ocean anoxia. It must be concluded that major magmatic events and their long-term environmental consequences are major contributors, though not the sole causes of mass extinctions. Sudden mass extinctions, such as at the K/T boundary, may require the coincidence of major volcanism and a very large Impact." Beerling DJ et al. (2002) An atmospheric pCO(2) reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils Proc. Natl. Acad. Sci. USA 99 (12): 7836-7840 Abstract: "The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO2 injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO2 and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO2 concentration (pCO(2)) levels with special emphasis on providing a pCO(2) estimate directly above the KTB. Our record shows stable Late Cretaceous/ Early Tertiary background pCO(2) levels of 350-500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO2 outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO(2) increase. Instead, we calculate that the postboundary pCO(2) rise is most consistent with the instantaneous transfer of approximate to 4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W(.)m(-2) would have been sufficient to warm the Earth's surface by approximate to7.5degreesC, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB."
131152. Philippe Chantreau at 19:52 PM on 2 October 2008
        The link between hurricanes and global warming
        If you have other pointers, HS, by all means post the links, I've already invited you to do so earlier on this thread.
131153. HealthySkeptic at 12:38 PM on 2 October 2008
        Can animals and plants adapt to global warming?
        Chris, It's interesting that you mention the review by Royer (D. L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675") Based on historical evidence, there is a real danger of a future return to a new ice age. So it makes sense to ask what concentration of carbon dioxide would be adequate to stabilize climate so as to extend the current inter-glacial indefinitely. Royer's work gives some idea of the range of concentrations needed. In the paper you cited above, he found that over the Phanerozoic, consistent levels of carbon dioxide below 500 ppmv are associated with the two glaciations of greatest duration... those that occurred during the Permo-Carboniferous some 300 Myr ago and the Cenozoic, within which we are now living. Cool climates were found to be associated with carbon dioxide concentrations below 1000 ppmv, while no cool periods were associated with concentrations above 1000 ppmv. Some support for the idea that moderately increased carbon dioxide concentrations could extend the current interglacial period also comes from the work of Berger and Lautre [A. Berger and M. F. Loutre, “An Exceptionally Long Interglacial Ahead?”, Science 297, 1287-1288 (2002). Working with projections of June insolation at 65 deg. N as affected by Milankovitch variations over the coming 130,000 yrs, they used a 2-dimensional climate model to show that moderately increased carbon dioxide concentrations, coupled with the small amplitude of future variations in insolation, could extend the current interglacial by some 50,000 years. The insolation variations expected over the next 50,000 yrs are exceptionally small and occur only infrequently, the last time being some 400,000 years ago. They also found that a carbon dioxide concentration of 750 ppmv would not extend the interglacial beyond the next 50,000 years. In addition, concentrations of less than 220 ppmv would terminate the current interglacial. Perhaps one day we will wish we never attempted to limit CO2 levels.
131154. HealthySkeptic at 11:50 AM on 2 October 2008
        The link between hurricanes and global warming
        Yes indeed, nothing like someone with "more awareness" to give us "pointers"... as long as those pointers are pointed in the right direction, right? :)
131155. chris at 08:46 AM on 2 October 2008
        Does Urban Heat Island effect add to the global warming trend?
        Re #1 Greg's post is incorrect, and highlights the problems associated with careless interpretations of pretty straightforward studies. The url that Greg cites relates to a study of temperatures in Los Angeles. This shows a rise of 2.8 Celcius over the past century. That's a massive rise in temperature. And of course much of it is due to an urban effect in the city. However the analysis of temperature rise associated with global warming (by NASA or the NOAA or the Hadley Centre in the UK, and so on) takes the urban heat effect into account, by either (i) ignoring all urban temperature data sets, or (ii) correcting urban data sets by comparison with surrounding rural data. The SPECIFIC error that Greg makes is in stating that "NASA which ascribes most of the warming this century in California to urbanisation". In fact NASA do nothing of the sort. If one looks at the surface temperature data compiled by NASA for California as a whole, the temperature increase is around 1 - 1.5 oC: http://data.giss.nasa.gov/gistemp In the NASA GISS data, the surface temperature has been corrected for urban effects, either by eliminating the latter or correcting this by referencing with respect to the rural data. The mistake that Greg has made is in taking the massive temperature rise of 2.8 oC for LA reported in the study that he links to, and then assuming/pretending that because NASA ascribe most of this temperature rise IN LOS ANGELES to urbanisation, that this applies to CA across the board. That's simply incorrect, as perusal of the NASA GISS temperature anomaly data indicates (see my link - you can create your own temperature anomaly data there). That's the SPECIFIC error in Greg's post. The more GENERAL error relates to the attribution of global warming to urban heat effects. It's rather obvious that massive attenuation of mountain glaciers and polar ice caps and sea ice, particularly in the Arctic, has ZERO relation to urban heat effects, since these regions are far from urban centres. Likewise the large warming of the ocean surface cannot have any relation to any urban heat effects. We could go back to California and look at this more closely. For example, in Northwestern USA, global warming has seen an extension of the wildfire season since the 1970's, resulting from an earlier onset of Spring (and Spring snowmelt), higher summer temperatures and an extension of the wildfire season into late summer. The greatest increase in wildfires is in the regions with elevations around 2000 metres, where progressively earlier Springs, and earlier Spring snowmelt reduces snow and meltwater protection of timber with respect to wildfire hazard. Once the snowmelt is completed, the forsts are rather quickly prone to combustion. Westerling, et al. (see abstract below) have shown that since the 1970's, global warming has extended the wildfire season by well over two months, with rather large increases in costs and damages. Obvoulsy the earlier Spring, greater summer temperatures, and greatly extended wildfire season in NW CA has nothing whatsoever to do with urban heat effects in LA! Westerling AL et al (2006) "Warming and earlier spring increase western US forest wildfire activity" SCIENCE 313, 940-943. Abstract: "Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt."
131156. Patrick 027 at 04:11 AM on 30 September 2008
        Volcanoes emit more CO2 than humans
        Because I mentioned the motion of charged particles in the Earth's magnetosphere ealier: (PS all the following (except stated formula) is just from visualization; so some uncertainty in some places) About motion (velocity v) of charged particles in magnetic field B, without other forces considered (if I'm not mistaken), where component of v parallel to B is vB, the component perpendicular to B is vp, all acceleration is is in direction of vector cross-product q(v x B) = q(vp x B), which is perpendicular to v, so that |v| is constant (q is electric charge (more generally, force F = q(E + v x B), where E is electric field (as a vector), and so acceleration is proportional to q/m, m being the mass); with E set to zero, let r be the radis of curvature of the trajectory projected onto the plane normal to B; so that |vp|^2/r = centrifugal acceleration = q/m * |vp x B| = q/m * |vp||B| r = (m/q) * |vp|^2 / (|vp||B|) r = (m/q) * |vp|/|B| 1. Constant field B: helix on a cylindrical surface (field lines parallel to surface), would would appear as a straight line on the surface if unrolled. |vB| and |vp| are constant. Radius of cylinder proportional to |vp|. 2. Change in magnitude of B in direction perpendicular to B (aside from 1., the easiest to visualize): The trajectory, or it's projection onto a plane normal to B, has tighter curvature in regions of higher B. This leads to a net displacement over the course of one revolution (to where v has the same direction). Their is thus a net drift in the direction that v has in the weaker B side of the field. Looking with B vectors directed toward you, positive charges revolve clockwise (turn to the right), and the net drift is directed with the stronger B field to the right. Negative charges: opposite. Smaller q/m ratio (as with proton compared to electron): larger radius of curvature, which itself means greater net displacement over each revolution, but also means greater variation in |B| over the range of each revolution, which means even greater net displacement over each revolution. 3. Variation in field strength along B - convergence or divergence of field lines (also means, over distance perpendicular to B, change in direction of B in the same dimension): helix on a conical surface (or something like that) - vB shrinks to zero and then reverses as larger B is approached, so the trajectory is 'repelled' by larger B values. This means |vp| must rise approaching larger B. In the other direction, as B shrinks, vp also approaches shrinks as v becomes more parallel to B. 4. Over distance perpendicular to B, change in direction of B, but in direction perpendicular to both B and to the direction along which the variation is detected: Suppose there is one field line, aligned with the z-axis, where x and y = 0, about which the particle is revolving in the same dimension. Case A: variation only in the x direction, all field lines parallel to y-z planes, where in the positive x axis, field lines have increasing slope dy/dz. In this case, when v is in the positive x direction, B is changing so that ... well, to make a long story short, I think the result is a helix on a cylinder, but the cylinder (whose axis is the z axis) is flattened in the x direction (?). Case B: braided (twisted) field lines. In this case, if one starts with vB in the positive z direction, then if the field lines curve around each other going in the postive z direction in the same direction as vp, then vp is less than otherwise, vB is more than otherwise, and the result is a helix on a cylinder (??) with a larger radius than otherwise for the same velocity in the x-y plane. If B is twisted in the opposite direction, the cylinder would have a smaller radius for the same velocity in the x-y plane. 5. Change in direction of B along B (curved field lines) This one is trickier to visualize... Locally one may consider approximately constant field strength and field line curvature; but when the radius of curvature is small enough or the range of positions large enough, constant curvature of field lines requires change in field strength along field lines, while constant field strenght requires increasing field line curvature toward a center of curvature, unless field direction is also changing as in case 4. above. --- There are someone conically shaped regions above each polar region; With B directed from the south pole to the north pole, if one visualizes the Earth with north pole pointing up, then within the ~ conic regions, B is downward, while outside the ~ conic regions, B is upward; B should increase in field strength toward the Earth. Thus, protons should have a net westward and electrons a net eastward drift especially outside of polar regions due to effect 2., many are 'repelled' from the poles due to effect 3. Effect 5 will also come into play (not sure of effect); 4, or at least 4B, is not a feature of a basic dipole field but I suppose it might occur due to disturbances or to the motions of charged particles themselves (and also within the core?).
131157. Patrick 027 at 02:47 AM on 30 September 2008
        Volcanoes emit more CO2 than humans
        ... I was thinking of the heat content of the material at a given temperature, and the the difference in heat capacity of two phases must be related to the latent heat of phase transformation - and it's dependence on temperature, by the requirement that whatever path is taken, taking one phase at T1,p1 and ending up at another phase at T2,p2, the same net change in heat content of the material must have occured. But that's an assigned temperature change. A cycle of out-of-equlibrium (time-delayed) phase transitions might concievably require a net mechanical energy input and so would produce heat... But see the last part of comment 53 (PS I had meant to identify that it was comment 46 which contained the paragraph I was correcting in comment 53).
131158. Patrick 027 at 02:41 AM on 30 September 2008
        Volcanoes emit more CO2 than humans
        "However, the specific heat of the material will also vary, and I suspect the end result of all this is no net temperature change over time." Well, now I'm not sure about that...
131159. Patrick 027 at 02:35 AM on 30 September 2008
        Volcanoes emit more CO2 than humans
        CORRECTION: PARAGRAPH IN "Patrick 027 at 14:27 PM on 24 September, 2008": "Dissipation: heat - atoms have to move around in a phase transition; conceivably, even in a short period, some portion of the atoms near phase transitions in the mantle might be cycled through different arrangements (statistically - I wouldn't imagine the phase transition is knife-edge, or that on that timescale it could get near equilibrium (?), and there are the gradual phase transitions from or to garnet, so I wouldn't expect it's the same atoms each time around) - that might be a location where there is some relative concentration of tidal dissipation into heat energy. Not that it would be a significant source of heat. I would try comparing it to the radioactive heat generation in the mantle per unit volume if I had the time. " Some of the logic I used above should be correct, BUT not the part about phase transitions dissipating the forcing that drives them into heat - that was totally wrong. Atoms move around due to thermal energy - those that have enough energy (statistically some fraction will, depending on temperature) can reach some threshold and leave the energy well of their former position in the crystal lattice (or in other situations: overcome the kinetic barrier to chemical reaction or nuclear fusion, etc.) and then fall into another position - in this case, kinetic energy is converted into potential energy, and then back into kinetic energy. Lack of thermal energy simply reduces the number of atoms that are able to move around like that, and so reduces the speed at which a phase transition can occur. Of course, if the final energy well is shallower or deeper than the initial, then there will have been a net exchange between kinetic and potential energy, which tranlates to taking up or giving off latent heat. Since material properties are temperature and pressure dependent (which is of course why the thermodynamic stability of a phase is dependent on these things), there could be a net latent heating or cooling over a cycle if the phase transition in one direction and in the reverse are not occuring at the same T,p - which of course will happen if there is a time lag due to the kinetic barrier. However, the specific heat of the material will also vary, and I suspect the end result of all this is no net temperature change over time. Except in the case that there is a net change in the microstructure over the course of many cycles - crystal grains have to form and reform, and if the grain sizes over time shrink, then there will be an increasing number of atoms whose energy is not as it would be within the crystal lattice... (PS this might build up to a point of dynamic equilibrium, beyond which factors that tend to increase grain size over time (annealing?) would balance those tending to reduce grain size over time. But anyway, as interesting as it is to consider tidal cycling of phase transitions in the mantle, I expect this is a very, very, very minor effect in the scheme of things.
131160. DB2 at 10:59 AM on 28 September 2008
        Does Urban Heat Island effect add to the global warming trend?
        Steve McIntyre looks at urban and rural temperature data since 1885 from Peterson www.climateaudit.org/?p=1859 and has a couple of graphs where the two subsets are separated. He has a couple of possibilities for the trend difference.
131161. Dan Pangburn at 09:18 AM on 28 September 2008
        Models are unreliable
        We seem to have drifted off point (as presented at 41 and 45). The Middlebury website is offered as a source for graphs of government and other credible data. Your disagreement with that data is with the government and the other sources, not me. The issue confronting humanity today is whether human produced carbon dioxide is causing global warming. The only indicator that it is comes from GCMs and then only when their users impose significant net positive feedback. Without significant net positive feedback, the GCMs do not predict significant Global Warming from increased atmospheric carbon dioxide. The proof that significant net positive feedback and therefore AGW does not exist DOES NOT USE anything from A/S. The proof that significant net positive feedback and therefore AGW does not exist DOES NOT USE anything from the Holocene. (For those interested, http://www.ncasi.org/publications/Detail.aspx?id=3025 , which uses data from many different proxies but excludes tree ring proxy data, is an assessment of the average global temperature for the last 2000 years.) This may be the source that Chris alludes to. It shows that the Medieval Warm Period, which was before the industrial revolution, probably reached higher average global temperatures than now and the steepest recent (around 1990) rate-of-change trend is about the same as it was at 4 other times in the last 800 years. A temperature trend direction change proves that there is no significant net positive feedback. Temperature data have been extracted from ice cores and are reported by NOAA and ORNL. All that is needed to determine if there is net positive feedback is a temperature trace for a long enough time to average out cyclic variation from random noise and other factors. The temperature trace does not even need to be correct in absolute terms just reasonably accurate in relative terms time-wise. This is obvious, even trivial, to me. Apparently the importance of the change in direction of temperature trend is not recognized by those who do not understand how feedback works. The trends used in the example in 51 are each about 5000 yr long and other trends have various lengths. The shortest Milankovich cycle is about 23000 yr. Milankovich can have no significant influence on the direction changes of the trends. Besides, the direction changes go both ways. You state “primary effects (raised CO2 levels) supplemented with feedbacks can be overpowered by other effects (reduced insolation during waning Milankovitch cycles)”. If feedbacks can be overpowered by other effects then ‘other effects’ determine which direction future temperature trends will go and predictions of GCMs are meaningless. Either way, the GCMs are invalidated as temperature predictors. That is pretty much the point.
131162. Mizimi at 22:50 PM on 27 September 2008
        What does CO2 lagging temperature mean?
        Quite so. Paleoproxy data are at best an indication of what conditions MAY have been like at some distant time in the past; equally they are mostly not relevant to current climate conditions because 'modern' land mass distribution is radically different from those times. What (little) can be deduced is that CO2 levels were considerably higher than todays and both plant and animal life flourished during the warmer periods (however high the actual temperature might have been).
131163. chris at 06:42 AM on 27 September 2008
        Models are unreliable
        Don't be silly Dan, It's you that is "worrying about a specific data point" or actually two specific data points. NUMBER ONE: I am basing my understanding of the strong relationship between paleoCO2 measures and paleotemperature measures right back through the last 500 million years, BASED ON HUNDREDS OF CONTEMPORANEOUS CO2 and TEMP MEASURES (see data in my references cited in the posts above) You are taking one specific part of the paleodat where there is evidence for glaciation (i.e a coolish/cold Earth) and assuming that there is no relationship with atmospheric CO2. However THERE IS NO CONTEMPORANEOUS PALEO-CO2 MEASURE THAT OVERLAPS THIS PERIOD...and therefore your focus on a specific data point is spurious. NUMBER 2: I am basing my understanding of the paleotemperature data of the last 2000 years which indicates that late 20th century and contemporary warming is well above anything experienced during this time period. THIS DATA IS BAED ON NUMEROUS DATA SETS USING NUMEROUS METHODS OBTAINED FROM MANY DIFERENT PLACES ON EARTH. You are making a blatant misrepresentation of the data by basing your interpretation on ONE data point, from, ONE location, using ONE method. For some reason you're trying to construct a whole edifice of misrepresentation based on single data points. And for some reason, despite your assertions of scientific credentials you can't seem to grasp that primary effects (raised CO2 levels) supplemented with feedbacks can be overpowered by other effects (reduced insolation during waning Milankovitch cycles)... ..your blatant fallacious misinterpretations of paleodata don't actually give us very much confidence in your misassertions aboutfeedbacks...
131164. Mizimi at 04:47 AM on 27 September 2008
        Arctic sea ice melt - natural or man-made?
        Phillipe: #253 I echo QM's comment; thanks also. I wonder what limitations there are to this effect..if any? On Krill: An article suggesting GW is the cause thro' loss of sea ice is countered by another pointing to the decline in blue whale numbers ( the whales provide iron through their excrement which is essential for the plankton) and another that challenges the data supporting the hypothesis. Another study shows krill at ocean depths well below that expected which suggests krill numbers may be higher than supposed. http://www.worldclimatereport.com/index.php/2004/11/11/krill-the-messenger/ http://www.asoc.org/Portals/0/decline%20of%20whales%20decline%20krill.pdf http://www.physorg.com/news123165274.html http://www.ccamlr.org/pu/e/sc/fish-monit/hs-krill.htm krill limits http://uplink.space.com/showflat.php?Cat=&Board=sciastro&Number=45459&page=1&view=collapsed&sb=3&o=0&fpart=
131165. Steve L at 04:32 AM on 27 September 2008
        Does Urban Heat Island effect add to the global warming trend?
        From the url in Greg's comment: "They tracked the number of extreme heat days and heat waves from 1906 to 2006. The team found that the average annual maximum daytime temperature in Los Angeles has risen by 5 degrees Fahrenheit (2.8 degrees Celsius) over the past century, and the minimum nighttime temperature has increased nearly as much." The first lines in John Cook's post: "It's well established that urban areas are warmer than surrounding rural areas. However, does Urban Heat Island (UHI) contribute to the global warming trend? Short answer, no." I think for Greg's comment to be relevant, we'd have to see Los Angeles versus rural So Cal or surrounding areas over the last 30 years, rather than an attribution since 1906 when Los Angeles was less urban.
131166. Dan Pangburn at 01:53 AM on 27 September 2008
        Models are unreliable
        Oh dear is right . . . Graphs of source referenced NOAA data are presented and you see “blatant misrepresentation”. The proof that significant net positive feedback and therefore AGW does not exist does not use Holocene data but you persist in worrying about a specific data point. You point out that other scientist’s have different interpretations of the Andean-Saharan ice age and you have decided which ones you agree with. Perhaps you do not realize that A/S is also not a necessary consideration to prove that significant net positive feedback does not exist in climate. The Scotese-Berner assessment of A/S defrays concern for planet-wide runaway temperature rise but the logarithmic decline in infrared radiation intensity with distance from the radiating surface with what is called the ‘saturation’ effect of atmospheric carbon dioxide refutes the ‘tipping point’ nonsense without any other consideration. Apparently you still don’t understand how feedback works. Perhaps we are not communicating. Let’s try a specific example. Look at the temperature trend from 55,000 ybp to 50,000 ybp. (This is from NOAA Vostok data as graphed in the second graph on the Middlebury website but the EPICA core shows about the same only shifted slightly in time.) See that this uptrend changes to a down trend at 50,000 ybp. This downtrend continues until about 45,000 ybp. This direction change from an up trend to a down trend could not take place if there were significant net positive feedback. Now look at the rest of the graph and see that there are many similar examples. Only the few who still believe that the rising atmospheric carbon dioxide level will have a significant effect on average global temperature are incorrect. Learn about feedback and then read 45 again.
131167. Greg Smith at 17:16 PM on 26 September 2008
        Does Urban Heat Island effect add to the global warming trend?
        It's not as simple as that. The link below is aprecis of new work from NASA which ascribes most of the warming this century in California to urbanisation http://www.nasa.gov/topics/earth/features/heat_wave_los_angeles.html
131168. chris at 16:36 PM on 26 September 2008
        Models are unreliable
        Oh dear... You don't seem to get it: (1) There is unfortuantely no paleoCO2 proxy that coincides in time with the late Ordovician paleoevidence for glaciation. Therefore we don't know the relationship between paleoCO2 and paleotemperature for that particular event. There's no point in pretending otherwise. (ii) Pretty much every case where we do have contemporaneous paleoCO2 and paleotemperature temperature proxies, the relationship between atmospheric CO2 and temperature is rather clear. See the list of scientific papers in my post #48. (iii) If one want's to assess scientific issues, one goes to the published science, not to dodgy outdated, and unattributed pictures on websites. (iv) Christopher Scotese seems a perfectly excellent chap. However his website was last updated around 2002, and his site is principally to illustrate tectonic effects on continental movement. Sadly his site happens to contain a completely incorrect graph of paleotemperature data. It's more of a child-like crude sketch. I've no idea where it comes from...(can you enlighten us?) (v) I've shown you a long list of papers, including a recent review that compiles all of the data up to around 2005/6. Unfortunately, rather than taking the effort to explore the science on this subject, you prefer to argue over a crude unattributed graph that is clearly incorrect....go figure! (vi) You have an advanced degree on Mechanical Engineering and so on...and yet you have spent an apparently significant eforrt in putting together a web page full of the most blatant misrepresentations. While real scientists assess multipile paleotemperature data sets obtained with many different methods from as many places on the earth as possible to obtain truly global (or at least hemispheric) paleotemperature estimates, you choose ONE data point, in ONE data set, from ONE place on Earth and presume to aseet that 400 years ago the globally averaged temperature was higher than now... (vii) Even though that's a dismal piece of misrepresentation, and Scotese's temperature data is clearly incorrect, and your arguments about feedbacks have no basis in science...... ..you are still asserting that you are right on these matters whereas all the climate, meterological, ocean, paleoenvironmental scientisits and so on are all incorrect.... I don't think so Dan.....why not make an effort to access the science on these issues. I've given you a wealth of sources that bear exactly on the subjuect of issue that containis the most up to date data.
131169. Dan Pangburn at 09:25 AM on 26 September 2008
        Models are unreliable
        The Andean-Saharan issue is simple. The ice age happened and the carbon dioxide level was much higher than now when it started. The chart uses data compiled by Christopher R. Scotese, Ph.D., University of Chicago, 1985, currently an Associate Professor geologist at the University of Texas at Arlington. Research interests include plate tectonics, paleogeography, and paleoclimatology and R. A. Berner, Department of Geology and Geophysics, Yale University. Contrary to your implication, they are university scientists. My understanding of feedback in a complex system comes from having an advanced degree in Mechanical Engineering and many years of engineering practice including rocketry, nuclear power, and meteorological satellites. Many engineers understand and successfully apply feedback in complex systems and have for many decades. Although climatologists use a somewhat different formulation, the end result is the same. Your discussion of feedback verifies that you don’t understand feedback very well. That explains why you don’t recognize that the temperature trend reversals during the previous glaciation (not talking about 100,000 year ice age cycles here) prove that significant net positive feedback does not exist in climate. If you use the same argument regarding the temperature trend reversals as you use for changes from glacial to interglacial then all temperature trends would be reversed by unpredictable solar changes which would make GCMs useless as climate predictors. I am puzzled as to why you call some of my comments “very odd” and then proceed to agree with them. The data that you disparagingly refer to as ludicrous is well referenced and came from NOAA as you could have easily discovered. I say that there is no significant net positive feedback and you claim that I said “there isn't a relationship between atmospheric CO2 lelvels and the earth's global temperature”. Some scientists express their interpretations and you say “science says”. More scientists and engineers are on record declaring that atmospheric carbon dioxide level has no significant influence on climate than there are saying that it does (Not that it matters).
131170. Patrick 027 at 14:18 PM on 25 September 2008
        Volcanoes emit more CO2 than humans
        "But the greatest heat transfer occurs in regular cycles at subduction zones and that is the interesting part. What besides tidal forces can cause these cyclic events?" But I've never seen anywhere any evidence or theorty to back up the first sentence there. The closest I've come to it was a website which seemed to be stating ENSO was caused by submarine geothermal activity, but it seemed to be (ill-informed) speculation - just guessing, really (and so I didn't bother to mention it until just now).
131171. Patrick 027 at 14:11 PM on 25 September 2008
        Volcanoes emit more CO2 than humans
        Another way of putting 'it': That the 155 W/m2 LW 'forcing accounts for 33 K temperature difference is itself theoretical (not so much uncertain, but it is theoretical), and couldn't be observation evidence against a 0.3 K/(W/m2) no-feedback (or feedback included in 'forcing') sensitivity.
131172. Patrick 027 at 14:07 PM on 25 September 2008
        Volcanoes emit more CO2 than humans
        That last part between ------ ------ is taken out of my comment from the earlier discussion; the second part of it is not a quote from the website.
131173. Patrick 027 at 14:04 PM on 25 September 2008
        Volcanoes emit more CO2 than humans
        -- " "PS - It's NASA that claims CO2 induced AGW is only 2% of GHG warming. I don't know how they arrived at that number. " Maybe they're comparing the anthropogenic forcing from the increase in CO2 to the total greenhouse forcing that exists (I think something like 155 W/m2, although that includes feedbacks (water vapor and clouds) that maintain the climate as is in the absence of change)? " -- 2 % of 155 W/m2 would of course be ~ 3 W/m2. Anthropogenic CO2 forcing is somewhere around 1.6 W/m2, which is about 1 % of 155 W/m2, of course. But the total anthropogenic greenhouse gas forcing is over 2 W/m2; anthropogenic aerosol cooling may bring total anthropogenic forcing down to ... 1.7 (?) W/m2. If the climate sensitivity without feedbacks is 0.3 K/(W/m2), then the ~ 155 W/m2 preindustrial greenouse 'forcing' would produce a warming of ~ 47 K. But the Earth's temperature would 'only' be ~ 30 (33 may be more accurate) K cooler without any greenhouse effect. Does this mean climate sensitivity without feedbacks is only 0.2 K/(W/m2) ? Probably not; climate sensitivity doesn't have to be independent of temperature, etc. There are other complexities one could point out - that removing all greenhouse effects would cause the Earth to ice over, so the actual temperature difference would be significantly larger than 33 K, that clouds also have an albedo effect and removing cloud greenhouse effect would also cause warming from the reduced albedo (before freezing over), etc, but that doesn't apply to the comparison above because the 155 W/m2 figure is only greenhouse 'forcing' and the 30 or 33 K figure only includes the greenhouse 'forcing' effect with albedo held constant. With feedbacks, a likely value of climate sensitivity is somewhere near 0.7 K/(W/m2). Remember from: http://blogs.abcnews.com/scienceandsociety/2008/07/tropical-storm.html my comment at "Jul 16, 2008 12:34:05 AM" From: http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdf -------- "Keeling_20051206" "Is There Still Time to Avoid ‘Dangerous Anthropogenic Interference’ with Global Climate?*# A Tribute to Charles David Keeling James E. Hansen NASA Goddard Institute for Space Studies, and Columbia University Earth Institute New York, NY 10025 December 6, 2005" Particularly interesting is the Climate sensitivity section, and in that, the ice age radiative forcings (which include ice albedo as well as greenhouse gas changes and other things), from which a climate sensitivity of 3/4 +/- 1/4 deg C per W/m2 forcing - (in this case the ice albedo, greenhouse gases, etc, are all put in as forcings for the sake of the calculation - Hansen is not implying that they were not feedbacks to other changes on a long time scale; the remaining feedbacks would include water vapor, clouds, etc.) - this is about what is suggested by computer climate models, though the later have some greater uncertainty. ------------- ... Specifically, from above source: ice sheets and vegetation albedo: -3.5 +/- 1 W/m2 greenhouse gases: -2.6 +/- 0.5 W/m2 aerosols: -0.5 +/- 1 W/m2 Total -6.6 +/- 1.5 W/m2 Change in temperature: -5 +/- 1 K Implied climate sensitivity: 3/4 +/- 1/4 K/(W/m2) For more on total radiative budgets (including the 155 W/m2 LW forcing): "Earth's Annual Global Mean Energy Budget" J. T. Kiehl and Kevin E. Trenberth
131174. Patrick 027 at 10:03 AM on 25 September 2008
        Volcanoes emit more CO2 than humans
        (PS descending lithospheric slabs - slower slabs warm up too much before reaching 660 km; they deform and may be deflected from the boundary; faster slabs stay cooler for longer and are more rigid - BUT even faster slabs experience out of equilibrium phase transitions in such a way as to reduce their rigidity by changing microstructures - so it is slabs descending at intermediate speeds that would be most likely to break through the 660 km barrier - see Karato for that and more. Also, along with the desceding lithospheric mantle is the (generally) oceanic crust, which is different compositionally - so ... etc...) ---- "Tidal Motion Influences Antarctic Ice Sheet ScienceDaily (Dec. 24, 2006) — New research into the way the Antarctic ice sheet adds ice to the ocean reveals that tidal motion influences the flow of the one of the biggest ice streams draining the West Antarctic Ice Sheet." http://www.sciencedaily.com/releases/2006/12/061221075130.htm "This unexpected result shows that the Rutford Ice stream (larger than Holland) varies its speed by as much as 20% every two weeks. Ice streams -- and the speed at which they flow -- influence global sea level." "So far, Rutford Ice Stream is the only ice stream where this type of temporal variation has been observed, but it is likely that the phenomenon is widespread, and so important to incorporate in computer models predicting the future contribution of the ice sheets to sea level rise." --- Okay, so the tides did have an extra trick up their sleeves. But here's the other aspect of the tides: how much variance is there beyond ~ 20 years? The biggest change beyond the tides themselves: spring-neap. Granted their is nonlinear behavior, particularly near coasts, etc. But I'd still expect most of the variation to be in the semimonthly spring-neap cycle. --- " "well, almost, there's a correction to be made from the eccentricities of the orbits, " - applies to both solar and lunar tides. " And there could be significant interaction beyond linear superposition of tidal bulges when one gets into coastal areas, shallow areas connected to deeper water... etc. (for example, when the beach slopes into the water (typical), one tide raises the water and brings it inland a little; another tide raises it more and brings it in farther - the combination of higher water and water farther inland might make the local volume of water involved proportional to the square of the sums of the tides... etc. - and obviously there is threshold behavior - if you are higher up you'd only get the highest high tides... etc.) -------- Sloshing Inside Earth Changes Protective Magnetic Field By Jeremy Hsu Staff Writer posted: 18 August 2008 http://www.space.com/scienceastronomy/080818-mm-earth-core.html "The Earth's overall magnetic field has weakened at least 10 percent over the past 150 years, which could also point to an upcoming field reversal." - or not. I saw a graph showing this gradual decline as part of a cycle, based on some archeological data, although I don't know how that idea has held up (I think it was in "The Cambridge Encyclopedia of Earth Science(s?)", from 1980, so it's been awhile... Otherwise, nothing in the article really indicates that what is happening is unusual in the past century or two or five or ten or twenty...
131175. chris at 05:04 AM on 25 September 2008
        Models are unreliable
        Re #47 No Scotese's temperatures are horribly incorrect (that's obvious surely). It's not clear where they came from (can you enlighten us?), and they clearly bear little relation to reality or to the paleotemperature data that is compiled extensively in the recent scientific literature (see citations at bottom of post for example). Try using Google Scholar or visit .edu sites (or your local University library - there are a number of relevant papers at the bottom of this post). In addressing scientific issues, one should address the science. ["The graph of CO2 and average global temperature during the Phanerozoic (all of the time that there have been complex life forms, the last 550 million or so years) at http://mysite.verizon.net/mhieb/WVFossils/Carboniferous_climate.html is as good as any."] No it isn't. Sadly it's a laughable parody of the data that has been complied in a large number of studies, and it's surprising that someone with an apparent interest in this subject would consider it to be so in the light of the abundant scientific data on this subject (see citations at bottom of this post). Obviously if one puts together a completely false representation of the scientific data on paleoCO2 and paleotemperature one shouldn't be surprised if one is led to fallacious interpretations. And suggesting that pointing out gross misrepresentation of the science based on ludicrously inadequate graphs using unspecified data on dubious websites with contrived misinterpretation, is "Lawyerlike advocacy and nit-picking", is a delightful lu-lu! As for feedbacks, I suspect you've managed to be misinformed through poor analysis or the perusal of dodgy sources (Christopher Monckton? isn't this supposed to be about science?). There's no question that raising atmospheric CO2 levels results in a re-equilbration of the Earth's temperature such that internal variations fluctuate around a higher equilibrium temperature (assuming volcanic/solar contributions are flattish), and that this involves feedbacks (e.g. a warmer atmosphere caused by enhanced atmospheric CO2 results in a higher concentration of water vapour.....enhanced warming results in enhanced ice melt and reduced albedo and so on)... The science indicates that the Earth responds to raised CO2 with a raised equilibrium surface temperature near 3 oC (+/- a bit). I'm not sure why you have a problem with this and feedbacks in general. Clearly during ice age cycles the dominant driver is cyclic variations in insolation due to slow variations in the Earth's orbital properties. It only requires that the insolation cycles dominate over the effects of CO2 (feedbacks included) to observe the relationships between temperature and CO2 levels in the Vostock core that you are so exercised over. If CO2 levels rise from 180-280 ppm over thousands of years(due to very slow solar induced warming) resulting in enhanced direct CO2 (greenhouse) warming with fast positive water vapour feedbacks and slower albedo feedbacks, and then the solar contribution diminishes, much of the atmospheric CO2 will still be there (for hundreds of years) as the temperature cools in the early stages of the next Milankovitch cooling cycle. And as the temperature cools due to decreased insolation, so the water vapour levels drop, even as CO2 levels remain high. That's not difficult to understand at all.. You make some other very odd comments. Yes, high levels of atmospheric CO2 will eventually be drawn out of the atmosphere. This is a very slow process (your own Vostock data show this). And of course "the rate of increase of carbon dioxide in the atmosphere is about half of what is calculated based on the amount added by humanity." Half of the CO2 we've released into the atmosphere has been absorbed by the oceans with a very measurable drop in pH (increased acidity).....already the absorption of our emissions by the oceans is decreasing due to the saturation of the upper oceanic waters. Each of these is problematic. All in all, you've chosen to use ludicrous data from some website to pursue the unsupported notion that there isn't a relationship between atmospheric CO2 lelvels and the earth's global temperature. And yet the science clearly shows otherwise (e.g. papers cited below). No one disputes the fact that CO2 is a greenhouse gas, and greenhouse gases cause the Earth to warm above its black body temperature (by around 30 oC worth of warming on Earth). Or do you consider that CO2 stops being a greenhouse gas above some concentration or other? Anyway, here's some of the science that one would hope you might access in place of dodgy websites: D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675. (this is a review compiles much of the published data) Even more recent studies supplement the information in Royers compilation and cover additional periods with new data sets right through the past several hundreds of millions of years: R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202 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. D. L. Royer (2008) “Linkages between CO2, climate, and evolution in deep time” Proc. Natl Acad. Sci. USA 105, 407-408 Zachos JC (2008) “An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics” Nature 451, 279-283. Doney SC et al (2007) “Carbon and climate system coupling on timescales from the Precambrian to the Anthropocene” Ann. Rev. Environ. Resources 32, 31-66. Horton DE et al (2007) “Orbital and CO2 forcing of late Paleozoic continental ice sheets” Geophys. Res. Lett. L19708 (Oct. 11 2007). B. J. Fletcher et al. (2008) “Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change” Nature Geoscience 1, 43-48.
131176. Patrick 027 at 03:20 AM on 25 September 2008
        Volcanoes emit more CO2 than humans
        Just to be clear: "well, almost, there's a correction to be made from the eccentricities of the orbits, " - applies to both solar and lunar tides. On reaching equilibrium solid + outer core Earth tides: My understanding is the natural frequencies of whole Earth oscillation is fairly high, enough that tidal deformations might be expected to approach equilibrium over the course of the tidal cycles - HOWEVER that is not the equilibrium tidal bulge shape; it is a balance between the tidal stress pulling the Earth toward that shape and the Earth's rigidity (outer core is constrained by mantle, and also by magnetic field although the later is probably weak in comparison, I'd think) which resists that. During the cycle there would be some correction for plastic deformation, which takes time. Where kinetic energy is not a big factor, plastic deformation doesn't have much of a natural frequency. Hence even if the tidal cycles are too slow to resonate with the solid or inner Earth's natural frequencies, the tidal deformation of the solid and inner Earth may be quite limited relative to the equilibrium tidal bulge in absence of rigidity - that is my impression, anyway. Of course, the tidal forcing on the solid and inner Earth includes both the direct forcing by the moon+sun (other astronomical contributions are very very small) as well as the forces on the solid and inner Earth produced by the responses of other parts of the Earth - the ocean and atmosphere - where the ocean is much more important in that matter. An important note - the term solar tide is also used to describe a diurnal cycle in the upper atmosphere (ionosphere in this case) that is driven by the diurnal heating cycle - this has nothing to do with the solar gravitational tidal forces - it is only a tide in the sense that is cyclical over a day. ---- A final (?) note on mantle convection: Besides rigidy or viscosity, another way to break through the 660 km boundary would be to build up kinetic energy before reaching it. But for the mantle, even relatively fast motion is just way too slow for momentum and kinetic energy to be significant factors. Where they are important is the atmosphere, ocean, magnetosphere, and outer core. An example in the atmosphere is the overshooting top of a thunderstorm, where kinetic energy built up in an updraft is converted back to convective available potential energy (CAPE) as it overshoots a static equilibrium level - it then falls back down. But in the mantle, overshooting far enough could overcome the barrier to convection - this could never happen in an overshooting top unless a superadiabatic lapse rate were found somewhere above the tropopause or if some other condensible vapor in the atmosphere were abundant enough to kick in at some higher level with sufficient latent heating - and either will essentially never happen (the later might conceivably happen on another planet). A case where a barrier could be broken through in the atmosphere involves conditional instability, where the air is stable to dry convection but unstable to moist convection; in that case, supplying enough energy to a moist air parcel near the surface to push it up, reach the lifting condensation level (LCL) where latent heating kicks in, and then a bit further to the level of free convection (? I think that's what the term is), then it can take off. A rising column of warm air may entrain moist air from below to continue feeding the process (especially if the updraft is rotating, but that's a whole other ...) (it can also entrain cooler dryer air from the sides and top, which weakens the process). Now it occurs to me that the latent heating at the 660 km boundary would actually increase the phase transition density variation from the phase transition that would impede convection, but perhaps the thermal expansion (from that portion of heat) effect is larger then the density variation that comes from the portion of the phase transition level shift caused by that same portion of heat - based on Karato, I take this as implied. Okay, enough of that, - that the tides are not a big factor doesn't itself demonstrate a lack of solar, volcanic, or geomagnetic changes, so ...
131177. Dan Pangburn at 03:20 AM on 25 September 2008
        Models are unreliable
        Chris: Your assertion “…talk a lot of nonsense…” may reveal that you simply do not understand how feedback works. The graphs in the Middlebury link are plots of data from NOAA and other credible sources. They speak for themselves and are as correct as the data sources. Apparently you accept Scotese’s temperatures. The carbon dioxide level at that time is from GEOCARB III as published in the American Journal of Science. The graph at http://www.globalwarmingart.com/wiki/Image:Phanerozoic_Carbon_Dioxide_png shows a lot of illogical scatter in Royer’s compilation but fair agreement between 30Myr filtered Royer, Copse and GEOCARB III. I have found no rational argument as to why the atmospheric carbon dioxide level should dramatically change prior to the temperature dropping into that ice age. The assertion remains that the temperature dropped while the carbon dioxide level was several times higher than now. The graph of CO2 and average global temperature during the Phanerozoic (all of the time that there have been complex life forms, the last 550 million or so years) at http://mysite.verizon.net/mhieb/WVFossils/Carboniferous_climate.html is as good as any. A lot of imagination is needed to see any correlation there between atmospheric carbon dioxide and average global temperature. You say “the warming oceans release CO2 into the atmosphere resulting in further warming”. That would be a ramp up in temperature. But then the ramp up changed direction and became a ramp down. And this direction change in temperature trend happened repeatedly during the last and previous glaciations. That could not happen if there was significant net positive feedback. For those who understand how feedback works, this temperature trend direction change proves that there is no significant net positive feedback. All that is needed to determine if there is net positive feedback is a temperature trace for a long enough time to average out cyclic variation from random noise and other factors. The temperature trace does not even need to be correct in absolute terms just reasonably accurate in relative terms time-wise. Without significant net positive feedback added atmospheric carbon dioxide does not produce significant increase in average global temperature. Even the flawed GCMs give that result. Those who think they “…know about greenhouse gases and their effects…” apparently do not recognize the significance of this observation. While determination of the magnitude and even the sign of net feedback in climate may be difficult using climatology (Spencer at a link in 41 above and also Monckton at http://www.aps.org/units/fps/newsletters/200807/monckton.cfm have done it), it is trivial, as described above, for someone who understands feedback, to deduce from the temperature record that net positive feedback does not exist. Many climatologists apparently don't know how feedback works so they don't realize this. Unaware of their ignorance, they impose significant net positive feedback in their GCMs which causes them to predict substantial warming from carbon dioxide increase. Without significant net positive feedback, the GCMs do not predict significant Global Warming. From Monckton’s paper “The IPCC overstates temperature feedbacks to such an extent that the sum of the high-end values that it has now, for the first time, quantified would cross the instability threshold in the Bode feedback equation and induce a runaway greenhouse effect that has not occurred even in geological times despite CO2 concentrations almost 20 times today’s, and temperatures up to 7 ºC higher than today’s.” Do you realize how many times you said in 46 that the sun started it? These were extracted from your text: “…insolation changes…”, “…primary inducer of the warming is increased solar radiation…”, “…decreased [s]olar insolation resulted in cooling…”, “…one “lowers the heater” that the Earth cools…” Solar variation is certainly a major part of it. Of the list of other possible contributors to climate change, some ignored, some subjectively parameterized; solar wind, clouds, vertical convection, cosmic rays, Milankovitch cycles, etc. and factors not yet discovered, only significant net positive feedback is readily ruled out. Influencing any of the others doesn’t look promising. Humanity needs to adapt to climate change. Warming is not a problem. If it gets too hot or wet or dry where you are at, move. There are currently places that lack permanent occupancy because they are too hot, too cold, too wet or too dry. Half of humanity may starve in the coming glaciation, however, because rice does not grow on ice. The high rate of change of the level of atmospheric carbon dioxide today is not relevant to climate change since the level of atmospheric carbon dioxide has no significant influence on climate. Eventually, excess atmospheric carbon dioxide will dissolve in the ocean which already holds over 50 times as much as the atmosphere. Interestingly, I have read that the rate of increase of carbon dioxide in the atmosphere is about half of what is calculated based on the amount added by humanity. In your lawyer-like advocacy and nitpicking of the scarcity of paleo data you appear to have completely missed the point of temperature trend reversals ruling out net positive feedback. I suggest that you break out of the box that you are in, adopt engineer/scientist-like objectivity and learn about feedback. There are legitimate reasons to constrain the use of fossil fuels. As the level of atmospheric carbon dioxide continues to increase, and it will, humans may find enclosed places becoming ‘stuffy’ sooner than previously. The consumer price rise of liquid fuels as a result of ‘peak oil’ will curtail their use and stimulate alternate fuels such as algae produced biodiesel. I have been antagonistic to coal for decades and am suspicious of claims that mercury, soot and acid can be effectively removed from the exhaust. When humanity gets past their unjustified paranoia regarding nuclear power and start building breeder reactors they will have all of the energy needed for millions of years. Enough to recharge their hybrids and even synthesize liquid fuel to go beyond battery range.
131178. Mizimi at 02:20 AM on 25 September 2008
        Arctic sea ice melt - natural or man-made?
        Phillipe: "Mizimi, your equation melting ice=colder ocean does not quite work out. Melting ice means no albedo and increased absorbtion of solar energy by the Arctic ocean, leading to higher ocean temp. Arctic biomass does not like it." I disagree; albedo is a function of colour and area: ice melt runoff and edge melt both have a cooling effect without substantially affecting area. The report at: http://www.imr.no/arctic/cruise_diary/phytoplankton_bloom_on_spitzbergen_bank places the low sea temperature and high level of bloom down to the effects of ice melt. "Later that day we moved closer to the ice edge and took an additional two Large Stations in waters with temperatures below zero. The first was in the area of highest fluorescence (i.e. largest phytoplankton bloom) based on the CTD transect taken earlier. It also corresponded to the area of lowest salinity, no doubt produced by ice melt and provided the necessary stratification to initiate the phytoplankton bloom.In contrast to the first two Large Stations there were many more copepods, mostly Calanus glacialis but also some C. hyperboreus which are indicative of Arctic Water. These copepods were feeding on the phytoplankton bloom. " With respect to the downturn in krill I have (at present)no definitive information: Googling 'krill' mostly lists a large number of sites claiming that overfishing of krill for commercial products is a major cause. Regarding biomass response to increasing CO2 levels - I make no assertions that biomass will respond radically in a short period of time. Sequestration by trees is a lengthy process, less so for woody shrubs etc. I repeat: commercial growers have proven there is a large response for CO2 concentrations up to 1000ppm (all other requirements being adequate).
131179. Mizimi at 01:38 AM on 25 September 2008
        Can animals and plants adapt to global warming?
        Chris: We are all driven by immediate self interest, firstly at the individual level, then at the social/tribal/national levels. We may at times put aside self-interest for the perceived good of the group we are in; that is survival..the first biological imperative. That is why some nations did not (and probably will not)sign up to protocols intended to stabilise/reduce CO2 emissions...because it was not in their national interests to do so. Regardless of the rationality involved at an academic level. China 'wants' a western(ised) lifestyle and is achieving that through economic expansion which itself relies on increasing energy usage. China will probably outstrip the US as the prime consumer of fossil fuels within a few years. I do not see China ( or any other developing nation) agreeing to limit fossil fuel usage because others are concerned that the climate may be altered to the detriment of certain life forms ( including man). They will put their (self-perceived)interests first. This is how mankind generally has always acted and probably will continue to do so. Much as I desire it to be otherwise (emotion again)in this respect I believe I am being pragmatic not stoic. I agree we can be, and should be, pro-active regarding many problems, (climate included) but inevitably someone is going to get hurt: Who decides that, and what if it turns out to be you that is going to suffer in some way? And regarding the sort of world we want to pass on to our descendants...who gets to decide that and what ctiteria do they use? Who gets to write the specification that the other 6 billion people on this planet have to comply with, even if it detrimental to their interests? Who decides what species should be preserved and what should not...and on what basis? The effects you ascribe to AGW are unproven in scale: the models that are used to predict both these events and their scale are incomplete and their predictions should therefore be treated with great caution.
131180. chris at 22:33 PM on 24 September 2008
        What does CO2 lagging temperature mean?
        There's a bit of a dichotomy in a small subset of posters between expressions ("desire for "precision", apparent concern for "valid criticism" and such like) and actions (contrived or inadvertent misrepresentation of the science; uncritical acceptance of nonsense from dodgy websites). What's the point of expressing a "desire for precision", when the rather precise data sets are ignored or overlooked in place of obviously fallacious presentations? This bears on the very meaning of "skepticism". Skepticism is surely valid criticism or doubt about interpretations, on the basis of an honest and reasonably informed relationship with the evidence. Skepticism is not piling on false arguments and trawling dodgy websites for stuff that suits a particular political/conspiracy/agenda position. If we're going to be skeptical (I hope we all are!), then we should be skeptical. The temperature data on the Scotese site that is repeatedly referred to in preference to the science is surely something that a skeptic should be skeptical about. Here it is again: http://www.geocraft.com/WVFossils/Carboniferous_climate.html Doesn't it looks very odd? One might expect a skeptic to question 10's and even a 100 million year block of rock-steady temperatures, and to observe that the Earth's temperature apparently dropped smoothly from 22oC 30-ish million years ago to 12oC now. And yet surely we know that the last couple of millions of years the Earth's temperature has fluctuated back and forth over a temperature range of 5 - 6oC. Now one might say that Scotese's graph is too compact to show the recent ice age cycles. However the late Ordovician glacial period is represented in the scientific paleotemperature/glacial record by a period of around 2 million years. If that can be shown, why not the large temperature variations during the recent ice age cycles? And if we have observed these large swings in the Earth's temperature during recent ice age cycles, doesn't that make you think that perhaps the Earth's temperature in the deep past might not be well-represented by many 10's and even 100 million year blocks of rock-steady temperature? ...skepticism anyone?
131181. gordon at 22:03 PM on 24 September 2008
        Mt. Kilimanjaro's ice loss is due to land use
        I think it's worth pointing out that Kilimanjaro has never held much water in it's glaciers and that summer melting has never been a source of water for the people below unlike in other areas. Interestingly enough, there seems to be some suggestions, within the scientific community, that increased precipitation, caused by global warning, may actually increase the amount of ice on Kilimanjaro and save the glacier.
131182. chris at 21:36 PM on 24 September 2008
        What does CO2 lagging temperature mean?
        Re #7, #15,#16 Wondering Aloud, HealthySkeptic, Mizimi You've been misled by a fundamental fallacy in some dodgy presentations of paleotemperature and paleoCO2 data that still appear on websites, unfortunately (Scotese's site is O.K., but he clearly needs to update/address his plaeodata that you and Dan Pangbourn on another thread have been confused by). One cannot take the very sparse paleotemperature and paleoCO2 data points, draw lines betwen these, and then concluded that the temperatures (or CO2 levels) in the intervening periods (10's or even 100's of millions of years!) are thus defined! It's unlikely (and we know it to be untrue) that temperatures were a rock steady 22 oC for vast periods of the past, in much the same way that we know that the Earth's temperature was a rock steady 15 oC during the last million years, which is what a misguided individual in the future might conclude from two temperature proxies (say 1000 years before our present and 430,000 years before) with a straight line drawn between them! It can be stated very succinctly: "THE RELATIONSHIP BETWEEN ATMOSPHERIC CO2 LEVELS AND PALEOTEMPERATURE CAN ONLY BE ASSESSED AT THOSE SPECIFIC TIME POINTS WHERE PALEOTEMPERATURE AND PALEOCO2 DATA ARE CONTEMPORANEOUS" Where we have data points for paleotemperatures and paleoCO2 levels that match in time, the evidence is rather strong for a CO2/temperature coupling. Where paleo temperatures are high paleoCO2 levels are high and cold/glacial periods are associated with low CO2 levels. There's now extremely abundant information on this dating back many hundreds of millions of years. A recent review compiles much of the data: D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675. Even more recent studies supplement the information in Royers review/compilation and cover additional periods with new data sets right through the past several hundreds of millions of years: R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202 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. D. L. Royer (2008) “Linkages between CO2, climate, and evolution in deep time” Proc. Natl Acad. Sci. USA 105, 407-408 Zachos JC (2008) “An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics” Nature 451, 279-283. Doney SC et al (2007) “Carbon and climate system coupling on timescales from the Precambrian to the Anthropocene” Ann. Rev. Environ. Resources 32, 31-66. Horton DE et al (2007) “Orbital and CO2 forcing of late Paleozoic continental ice sheets” Geophys. Res. Lett. L19708 (Oct. 11 2007). B. J. Fletcher et al. (2008) “Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change” Nature Geoscience 1, 43-48. And so on…..
131183. chris at 20:04 PM on 24 September 2008
        It's Urban Heat Island effect
        Re #3/#4 Mizimi: re #3: In any analysis/description of temperature variations in any field of science and technology, colours are associated with spectral features associated with temperatures. Therefor the red end of the spectrum is hot and the blue end of the spectrum is cold. One would observe the same in thermal colour imaging of body heat sources from infrared imaging: e.g: http://www.digitalinfrared.com.au/images/sample_back.bmp ...and so on. So why on Earth would they use "blue, green, indigo...", unless they were trying to deliberately confuse the observer! Re #4: with respect to your odd statement "isn't the comparison a bit off"? No the comparison isn't "a bit off". Perhaps you need to think about what is being represented in the two images before making an inappropriate interpretation!
131184. Patrick 027 at 14:27 PM on 24 September 2008
        Volcanoes emit more CO2 than humans
        Actually, the shear stress would be about the same, or at least the same order of magnitude, ~ 26 kPa =~ 1/4 atm =~ 4 psi. Unless the asthenosphere and below didn't hold themselves against it but pushed up or pulled down on the crust above. with constant mass per unit area and constant tidal acceleration with depth, it would increase by a factor of ~ 60 within the crust and lithosphere. BUT tidal acceleration drops to zero at the center, so it would only be a factor of ~ 30 - AND mass is concentrated at depth but area declines... per unit area at the surface, underlying mass is somewhat concentrated higher rather than lower, ... Well, you get the idea. 30 * 4 psi = 120 psi. But plastic deformation takes time; the core wouldn't hold itself against shear but the mantle would somewhat... well I did a visual estimate from a graph and came up with a factor of 2.35/6.37 *63.7 = 23.5; 23.5 * 4 psi = 94 psi =~ 6 atm = ~ 0.6 MPa - that's if the mantle acts like liquid, which I wouldn't expect, so it's likely a bit less than that, and perhaps closer to the original 4 psi. --- Dissipation: cracks: well, 100 psi = ~ 6 atm = ~ 0.6 MPa is the pressure found at 60,000/3000 m = 20 m below the surface - well, between 20 m and 30 m depending on the type of rock - the point is, any tensile stress due to tides is still, except in a very thin layer on top of the crust, just a reduction in the compressive stress due to the pressure. So brittle failure by pulling apart would be odd. I would expect heat and compression to, over time, weld cracks shut, which would limit the ability of many millions of tidal cycles to build up weaknesses in the material. (PS I've really gotten away from things I really know about here, but I suspect both heat and pressure combine to make the lower crust less brittle than the upper crust. This has an interesting effect on the deformation and fracturing patterns one may see in a cross section of mountain ranges (fractures tend to curve to near horizontal at depth - at least in the drawings I'm remembering - is that because of the reduced tendency to brittle failure at depth and/or is it something else?). Also, I think higher pressure increases viscosity, and from what I recall, below the asthenosphere, viscosity increases downward (until the core, of course).) There are, of course, 'pre-existing' cracks - joints and faults - I doubt the tides could ever pull these apart completely anywhere, but it could very slightly reduce compression, which might then reduce the threshold of shear stress necessary to cause sideways slips (which is the motion that would occur along any fault's plane) - so statistically one might look for earthquake (and volcanism) frequencies relative to variations in tides. But I wouldn't expect anything big. The presence of these faults and joints would also reduce the amount of tension that could be realized in the intervening rock. A little bit. Slightly. I'm downplaying it because it's not like the crust is just sitting there in space - it's stuck to the mantle. Even if there were a clean break all the way through the crust and lithosphere (and not just in the sense that the mantle is poking up through it), the mantle underneath would still transfer tensile stress to the crust above by pulling on it sideways (the horizontal shear stress)... Dissipation: heat - atoms have to move around in a phase transition; conceivably, even in a short period, some portion of the atoms near phase transitions in the mantle might be cycled through different arrangements (statistically - I wouldn't imagine the phase transition is knife-edge, or that on that timescale it could get near equilibrium (?), and there are the gradual phase transitions from or to garnet, so I wouldn't expect it's the same atoms each time around) - that might be a location where there is some relative concentration of tidal dissipation into heat energy. Not that it would be a significant source of heat. I would try comparing it to the radioactive heat generation in the mantle per unit volume if I had the time. Back to tidal accelerations of charged particles - in the Earth's magnetosphere, at 10 Earth radii from the center of the Earth, for example, tidal acceleration is on the order of 11 um/s2. How fast do charged particles travel in the magnetosphere of the Earth? I really don't know, so this is just a sample calculation, to be multiplied by whatever corrective factor is necessary later: How about 4 km/s ? At 10 Earth radii, it would then take on the order of 70,000 km path to cross a region of tidal acceleration in one direction. 70,000 km / (4 km/s) = 17,500 s (several hours). 11 um/s2 * 17,500 s =~ 190 mm/s. So the lunar tides could be expected to alter particle velocites in the magnetic field of the Earth at 10 radii out by on the order of 0.2 m/s, 1/20,000 of their velocity - if they are moving at 4 km/s. Of course, that doesn't account for the paths they take, typically a helical path rebounding from polar region to polar region along magnetic field lines, with either an overall eastward or westward drift (it may just be one or the other, or depend on charge, I forgot which). This means their east-west motion is quite a bit slower than their north south motion (overall, averaging over each turn of the helix), so they would pass through the same tidal acceleration field multiple times. However, if they are rotating with the Earth (I'm not clear on that part), that eliminates that concern (unless they are drifting west at high speed)... otherwise, they may come out of high tide drifting outward, drift east/west and then drift back down after passing low tide ... If it took ~ 20 hours (70,000 seconds) to exit a high tide or low tide, they might accumulate an extra velocity of ~ 0.8 m/s, which over 70,000 seconds would mean a displacement of ~ 56 km, which isn't much out of 70,000 km. ____________ Bottom line on tides: Yes they have effects, but outside of oceanic processes, they're really small. Oh, and (you probably realized this but it bears mentioning) tidal dissipation is not fixed by tidal forcing - if the Earth's properties (spin rate, ocean basin shapes and locations, natural frequencies, material properties) were different, tidal dissipation might be much higher or lower. If the tidal deformation were perfectly elastic, their would be no tidal dissipation - the Earth wouldn't be slowed down by the tides - which means there wouldn't be a net torque on the tidal bulges - for simple equilibrium bulge shape, that would imply the tidal bulge is either completely in phase (high tide occurs with moon overhead) or completely out of phase (high tide occurs with moon setting or rising, as seen from equator). On that note: A couple of interesting papers on the topic of tidal changes over geologic time (and one also discusses Milankovitch cycles): http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU2004_IAUC197%2FS174392130400897Xa.pdf... http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=pjab1977&cdvol=69&noissue=9&startpage=233... Which reminds me - if you went back in time far enough, you might reach a point where the tides (on Earth) were quite a bit more influential in things. Also, with solar tides included, that's almost a 50 % increase or decrease in tidal acceleration and tidal displacements from the lunar tides alone. That implies the tidal torque, a product of the two (integrated over the tidal density perturbation, multiplied by ... etc.), ranges from just under 1/4 of lunar tide alone at neap to around 2 times lunar tide alone at spring tides (with a reduced range when the moon is farther from the ecliptic). This is nonlinear. However, the average effects (on the torques) should add up linearly - this is because, over time, the lunar tidal bulge rotates relative to solar tidal forcing, so that the average solar tidal torque on the lunar tidal bulge is zero - and it works the other way around, too - well, almost, there's a correction to be made from the eccentricities of the orbits, although the tides will be smaller during the time of the month when the moon is moving slower, so...
131185. Patrick 027 at 11:40 AM on 24 September 2008
        Volcanoes emit more CO2 than humans
        Tidal stress from tidal acceleration acting on that same mantle column: 4000 kg/m3 * 500,000 m = 2 billion kg/m2 1.1 um/s^2 * 2 billion kg/m2 = ~ 2200 Pa. Tidal stress from horizontal tidal acceleration acting over 6000 km (this is just to get a sense of the order of magnitude - PS that 10 K warmer bit- just to see what's possible; I don't know what the typical temperature variation is outside of those descending lithospheric slabs.): 60/5 * 2200 Pa = 26400 Pa = ~ 1/4 atmosphere = ~ 4 psi - that would be the kind of stress you'd see in the crust directly from the tidal forcing of the moon. But the oceanic response would exert other stresses in the crust. 0.54 m * 1000 kg/m3 * 10 m/s2 = ~ 5000 Pa ~ 1/20 atmosphere = ~ less than 1 psi. What about shear stresses...
131186. Patrick 027 at 10:20 AM on 24 September 2008
        Volcanoes emit more CO2 than humans
        A few more comments about tides on Earth: fluid oscillations: another fluid oscillation is the inertial oscillation - the cyclical movement of fluid parcels in the absence of any other force but the coriolis force; if the movement is small enough that the coriolis force does not vary much of the course of the cycle, then inertial oscillation takes the form of anticyclonic circular trajectories. The frequency is proportional to the coriolis effect, which is proportional to the sine of the latitude; the period is 1/2 day at either pole and 1 day at 30 deg latitude N or S. Diurnal cycles might then resonate somewhat with inertial oscillations near 30 deg latitude (give or take - one has to adjust a bit for the solar day be slightly longer than a siderial day, and for the lunar diurnal tide period being a little longer still); one example is land-sea breeze cycles; another would be the diurnal tides (?). But there are other factors... PS there is no diurnal tide forcing at the equator but there could still be diurnal tides at the equator because the tides propogate as waves and so can travel around. This might open up the possibility of some resonant behavior near a pole from semidiurnal tides (?). --- when there is a crack, dent, or weak spot that doesn't support a load, the stress 'field lines' (I haven't heard that term used with stress but it works visually), when in steady state, must bend around and get concentrated around the edges of such 'imperfections' - this is what tends to make cracks grow. (Although with a compressive load, the crack might be squeezed shut in the process.) (When not in steady state - well, short-wavelength sound waves can penetrate through the space in front of a crack or gap, and then reflect off of the boundary, this is space which would be bypassed by more slowly varying forces. Which brings up what happens with longer-wavelength sound waves - there is diffraction around the gap, and some scattering off of it; as the wavelength gets longer relative to the size of the gap, the wave 'pays' less attention to the gap, etc...) So one could imagine that tidal stresses are concentrated slightly under valleys and trenches, and the edges of fault lines. But the same would be true for the more constant stresses from geologic forces. Consider mantle rocks with a density around 4500 kg/m3 (Mantle density ranges from a bit over 3000 kg/m3 to over 5000 kg/m3 with increasing depth (Karato p.13 diagram). ----- PS Karato p.123 - the issue with phase transformations with negative Clapeyron is a bit more complicated: first, the total phase transformation ringwoodite to perovskite + magnesiowustite has a negative Clapeyron slope. It is (not independently of the Clapeyron slope) endothermic, which means their is latent heat release upon ascent and latent heat uptake upon descent. That offsets the effect of density in opposing cross-660 km level convection. The density variation becomes bigger with bigger lateral temperature variation, however, while the latent heating effect does not. Thus, two layer convection is more favorable when there are bigger temperature variations driving updrafts and downdrafts - this also corresponds to higher velocity updrafts and downdrafts as the forces within each layer will be greater. I haven't actually read much of this chapter in Karato but one thing that has occured to me is that higher viscosity and rigidity could make whole mantle convection more likely (actually this was discussed with relevance to descending cold lithospheric slabs). What I'm thinking: If you have a stiff slab and you drive it into a wall with enough force (the buoyant force acting on a piece of warm mantle with a deep root below 660 km but protuding above that level, or the reverse for a piece of cold mantle), you might break through. If the slab deforms too easily, you could use the same amount of force and the slab will just bend against the wall. ... This might not be significant in most of the mantle because it may be warm enough and the deformation slow enough that rigidity or viscosity would not do much against the density variations at 660 km... But it would matter to cold descending lithospheric slabs. p.123 Karato: The Raleigh Number (one of those nondimensional numbers used to characterize fluid motion or lack thereof - others: Rossby number, Froude number, ...) ----- Anyway, Karato p.126 mentions a coefficient of thermal expansion of 20 ppm / K (in the context I think it's a volumetric expansion, which is what 'we' want here). Going with that number: A column of mantle 500 km vertically, 10 K warmer than surrounding mantle, with g ~ 10 m/s2, would be 200 ppm = 0.2 ppt less dense - 0.2 ppt * 4000 kg/m3 = 0.8 kg/m3; over the depth of the column, a difference of 0.8*1000*500 kg/m2 = 400,000 kg/m2. Times gravity: a pressure difference of ~ 4 MPa (about 40 atmospheres, ~ 600 psi). Subducting slabs on average are cooler than the surrounding mantle by several hundred degrees (Karato p. 129); although they don't descend straight down so having a 500 km column would be unlikely, I think. ...
131187. Quietman at 05:03 AM on 24 September 2008
        Arctic sea ice melt - natural or man-made?
        Philippe Re: 253: Interesting. Thanks.
131188. Philippe Chantreau at 03:51 AM on 24 September 2008
        Arctic sea ice melt - natural or man-made?
        Since some are also wondering where the "increase" (0.2% in extent) of Antarctic sea ice comes from, this is interesting: Author(s): Zhang JL Source: JOURNAL OF CLIMATE Volume: 20 Issue: 11 Pages: 2515-2529 Published: JUN 1 2007 Times Cited: 1 References: 34 Abstract: Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by the NCEP-NCAR reanalysis data, the model simulates an increase of 0.20 x 10(12) m(3) yr(-1) (1.0% yr(-1)) in total Antarctic sea ice volume and 0.084 x 10(12) m(2) yr(-1) (0.6% yr(-1)) in sea ice extent from 1979 to 2004 when the satellite observations show an increase of 0.027 x 10(12) m(2) yr(-1) (0.2% yr(-1)) in sea ice extent during the same period. The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979-2004 and the extended period 1948-2004.
131189. chris at 01:54 AM on 24 September 2008
        Can animals and plants adapt to global warming?
        Not really Mizimi, "as well as being able to address what we consider to be in the best interests of ourselves and our near, and not so near, descendants.".... is not (according to you ("evolution at work"). It should be obvious that mankind has put him/herself outside of the natural evolutionary process to the extent that we are very well able to decide ourselves how things progress in relation to our interaction with the rest of the natural world. We're not passive participants anymore. We don't have to sit back and wash our hands of the whole business, compelled only by individual immediate self-interest. In fact we'd be horribly irresponsible to take that attitude, and happily the scientists and policymakes are being rather more mature and responsible in adressing these issues. And of course "The question is what sort of a world we wish to live in and leave to those that follow us."...is not "Emotion at work". What an odd concept. If we decide that we prefer not to have to deal with rising sea levels, increased adverse weather conditions, widespread drought, ocean acidification, destruction of natural habitats and so on, we surely do this based on the most clear-headed and rational grounds. These aren't issues that are well served by "clever" soundbites!
131190. Mizimi at 00:57 AM on 24 September 2008
        Can animals and plants adapt to global warming?
        Chris: "as well as being able to address what we consider to be in the best interests of ourselves and our near, and not so near, descendants." Evolution at work. "The question is what sort of a world we wish to live in and leave to those that follow us." Emotion at work.
131191. chris at 00:25 AM on 24 September 2008
        Models are unreliable
        Re #41 & etc. Dan Pangburn Dan, you certainly do talk a lot of nonsense, and you seem to have gone to extraordinary lengths on your webpage to put together a deliciously incorrect view of the science! Let's look at just a couple of things: (1) ["The planet plunged in to the Andean-Saharan ice age 440 million years ago10 when the carbon dioxide level was over ten times higher than now."] No.....there certainly does seem to have been significant glaciation dated to around 445.6 mya - 443.7 mya, but the atmospheric CO2 levels for this period are simply not known. You seem to have fallen for the trick of some dubious character who has drawn straight lines across vast ranges (10’s to 100's of millions of years) of geological time based on some unspecified temperature estimates (your posts on this thread are displaying that odd habit of denigrating pukka science by misrepresentation while at the same time embracing stuff that is very obviously ludicrous rubbish!). I would expect everyone can understand the problem that if there are one or two paleo proxies (temp or CO2, for example) known for some periods in the past, that one can only say that that's what the temperatures/CO2 levels were AT THOSE PARTICULAR TIMES. One can't draw a line between the points and consider that the temperature/CO2 levels over vast intervening periods is thus established. Imagine an equally dumb geologist from the far future dating atmospheric CO2 level estimates from 430,000 years ago and 1000 years ago. "Goodness", he might say, extrapolating massively between limited data points in gay Scotese style, "highish CO2 levels right through this period. And yet there is evidence for multiple ice cap incursions right down to the South of England and deep into North America. Clearly there can't be any relationship between atmospheric CO2 and temperature" Doh! You need to go back and look at the relevant science, rather than trawling for dodgy “information” on websites[***]! The science has been compiled, for example, in a recent review by Royer: D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675. Or see: R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202 Or: 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…. Sadly there isn't a proxy CO2 measure for the late Ordovician glacial period. So we don't know if there is a mismatch between atmospheric CO2 levels and evidence for a cold spell then. It's rather clear (see Royer review, for example, and the masses of cited data therein, or the other articles cited just above) that where paleoproxies for atmospheric greenhouse gas levels and cold/warm spells are dated contemporaneously, that there is a rather good match (high CO2 associated with warm periods/low atmospheric CO2 with cold periods). (ii) Surely by now everyone can understand the rather simple contributions to ice age cycles and the fundamental differences between solar driven effects (with CO2/water vapour/albedo feedbacks) and greenhouse gas driven effects of the sort that we are now seeing. I find it hard to believe that you consider that you’ve found something worth making such a fuss over, as if there’s something about the lag between temperature and CO2 levels in the Vostock core that is not obvious, rather well-understood and pretty consistent with what we know about greenhouse gases and their effects. Let’s look at what happens during the ice age cycles driven by the small, painfully slow variations in the Earth’s orbital properties (Milankovitch cycles). As the pattern of insolation changes through these cycles the Earth warms (in a glacial to interglacial transition), ice sheets recede, albedo effects amplify the warming, the warming oceans release CO2 into the atmosphere resulting in further warming, atmospheric water vapour levels rise, and so on. Obviously, since the primary inducer of the warming is increased solar radiation, and the atmospheric CO2 rise is a result largely of the release of CO2 from the oceans, the temperature rises in advance of the atmospheric CO2 levels. That’s pretty obvious and uncontroversial (part of the lag is apparently also due to interhemispherical effects). Going the other way (your example of events 112,000 years ago), it’s not surprising that decreased polar insolation resulted in cooling in advance of the lowering of atmospheric CO2 levels. It takes rather a long time for atmospheric CO2 to be absorbed from the atmosphere, and there’s nothing surprising about the fact that as one “lowers the heater” that the Earth cools while CO2 levels remain relatively high, as CO2 is very slowly reabsorbed by the oceans and terrestrial environment.. And of course the CO2 level changes are small and the rates of change are tiny compared to present day, where the warming we are seeing is the result of enhanced greenhouse effects with a relatively constant solar insolation. So whereas during the last glacial to interglacial period, for example, atmospheric CO2 rose by around 80 ppm over 5000 years (1.6 ppm per 100 years averaged over the transition), now atmospheric CO2 levels are rising at well over 100 times faster (2-2.5 ppm per year). Everyone that takes the smallest effort to inform themselves is aware of the essential differences between ice age transitions (Milankovitch cycles drive extremely slow variations in atmospheric CO2 with very slow feedbacks) and present day warming (extremely rapid increases in atmospheric greenhouse gas concentrations resulting in rapid temperature increases). During ice age transitions the processes were sufficiently slow that the Earth’s temperature likely was near-equilibrium with the forcings (varying insolation, greenhouse gas levels and associated feedbacks). Now atmospheric greenhouse gas levels are rising far more quickly than the Earth’s temperature is able to keep pace with (the inertia from the massive ocean) and so we still have rather a lot of warming “in the pipeline” from current levels of atmospheric CO2, not to mention the amount of warming yet to be unmasked, as a result of man-made aerosolic countering of enhanced greenhouse-induced warming: e.g. V. Ramanathan and Y. Feng (2008) “On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead.” Proc. Natl. Acad. Sci. USA in press. http://www.pnas.org/content/early/2008/09/16/0803838105.abstract (iii) Your data on temperature/CO2 relationships are laughable. Just to choose one jaw-dropping example, there is one single data point in the Vostock core (1999 data set) that shows an anomalous temperature, and from this you conclude that “the average global temperature 400 years ago was significantly higher than now”! One data point from one location does not an “average global temperature” give. The pukka science carefully collects a range of proxy data from multiple sources using many different methodologies, taken from as many places on Earth as possible to assess careful paleoproxy temperature data that is truly globally (or at least hemispherically) averaged. You (having other fish to fry one suspects than assessing the best possible understanding from the available data) base your entire analysis on one data point, from one data set from one location on Earth. Oh dear! And so on. Happily the individuals and organizations that address these issues maturely and seriously don't fall for that sort of nonsense.... [***] In fairness to Christopher Scotese, his site is quite good. He does need to update his paleotemperature graph though!
131192. Patrick 027 at 15:09 PM on 23 September 2008
        Volcanoes emit more CO2 than humans
        "When the amplitude of the wave becomes significant compared to fluid depth, there are nonlinearities" And also when the displacements become significant compared to the wavelenth... --- "PS - It's NASA that claims CO2 induced AGW is only 2% of GHG warming. I don't know how they arrived at that number. " Maybe they're comparing the anthropogenic forcing from the increase in CO2 to the total greenhouse forcing that exists (I think something like 155 W/m2, although that includes feedbacks (water vapor and clouds) that maintain the climate as is in the absence of change)? I'll get back to sudden core motion changes tomorrow.
131193. Patrick 027 at 14:56 PM on 23 September 2008
        Volcanoes emit more CO2 than humans
        To be specific, 1.1 um/s (u used in leiu of 'mu'; um = micron) is the vertical tidal acceleration at the Earth's surface at points in line with the center of the Earth and the Moon, and is locally upward. The vertical tidal acceleration halfway in between those two points, in a ring on the surface, is downward and half the magnitude. Let 2*T be the vertical tidal acceleration on the surface of a sphere at the near and far point from a tide generating mass. Then, where N is the angle from near point (so N = pi radians (or 180 degrees) at the far point), The local vertical tidal acceleration is: dv = T * [ 1/2 + 3/2 cos(2N) ] And the local horizontal tidal acceleration (positive toward lower N): dh = T * 3/2 sin(2N) So the total range of each is 3T. T is linearly proportional to the distance to the center of the sphere experiencing the tides, and does not depend on the mass of the body experiencing the tides**. The shape and magnitude of the equilibrium tidal distortion can be determined by finding the surface for which the vector sum of the tide experiencing body's gravity and the tidal acceleration are normal (perpendicular) to that surface - the slope of that surface is thus dh/(g-dv) (or the negative of that, depending on perspective), which is almost equal to dh/g since |dv| << |g| **. **-thus far I have ignored the effect of the gravity of the mass anomaly of the tidal bulge itself. This would tend to make the tides a bit larger. When I tried to calculate the equatorial bulge in the same way I got half the actual value, so maybe the actual tidal bulge is twice what I have said so far - at equilibrium, that is (??). However, actually figuring out how a body is deformed is tricky (without knowing more than I do, anyway). The vertical tidal acceleration is related to increased spacing of (geo)potential surfaces - surfaces of constant potential energy - caused by the shape of the bulge. At equilibrium, density variations are only perpendicular to these surfaces. One could imagine a combination of vertical and lateral movement to shift the body around into this shape. As the potential surfaces are spaced differently, the pressure increase with depth increases at a different rate, so that density changes due to pressure changes should fit. However, one could also imagine a response involving initial decompression at high tide and compression at low tide (in response to the vertical tidal acceleration) - a sharp density discontinuity could shift up and down to match the equilibrium shape, but then the mass distribution below that point would not be at equilibrium The pressure variations at depth would then drive lateral movements toward equilibrium. The equatorial bulge is essentially at equilibrium because it's not be cycled or varied rapidly. Tidal deformation is cycled as objects spin through the tidal acceleration and tidal potential energy fields. The tidal bulge must then travel as a gravity wave (or some other wave) around/through the object. A freely propogating gravity wave travels due to the pressure gradients in the fluid caused by a vertical surface displacement through a fluid at a speed c = square root of (gH), where g is the gravitational acceleration and H is the fluid depth. It is a gravity wave because gravity supplies the restoring force. This formula is only true for a shallow fluid (compared to wavelength) which is below a vacuum or very low density material compared to itself, as is the situation for water waves under air. More generally, I think the speed is also proportional to the difference in densities across the surface divided by the density of the underlying fluid (this is an internal gravity wave). When the wavelength is not much longer, or is shorter, than the fluid depth, the full motion of the wave does not extend all the way down because (*I think - haven't done the math yet for myself*) vertical accelerations cummulatively cancel out the pressure variation due to the surface height displacements, so the wave only 'feels' some fraction of the fluid. When the amplitude of the wave becomes significant compared to fluid depth, there are nonlinearities... I don't think the compressibility of water has much effect on gravity waves, but more generally, gravity and elastic forces may both supply a restoring force. In solids, the elastic forces may include a resistance to shearing motion (as in a seismic S-wave, and also I think a 'Love' wave (kind of surface seismic wave) - (of course gravity is insignificant in S, P (compressional, like sound waves), Love, and Raleigh seismic waves). If and when the coriolis effect comes into play, there are also Kelvin waves, which are waves that move along lateral boundaries (like coastlines) with amplitudes that, in the case of constant fluid depth found immediately off the coast and a straight coastline (compared with the wavelength of the wave, I suppose), decay exponentially away from the coast. Such Kelvin waves travel at the same speed as gravity waves (at least in the case of wavlength >> fluid depth). There can also be inertio-gravity waves. Internal gravity waves also occur in a fluid with continuously varying density (the atmosphere), as opposed to a sharp interface - the math gets more complicated in that case. ... To make a long story short, there are certain natural frequencies of various modes of oscillation for the whole Earth, for ocean basins, etc, which depend on the size and shape and the speed and behavior of different kinds of waves. If a system is forced near it's natural frequency, it can resonate. If it is forced much faster than a natural frequency, there may not be much response. If the forcing is much slower, the system may just follow the forcing in near equilibrium (I think). My impression is that not much per unit volume deformation is required to distort the whole Earth by the tides because the horizontal movement is distributed over large vertical distances; the horizontal displacements would be of the same order of magnitude as the vertical displacements. Rather than coming back to it later, notice that implies a tidal strain (at equilibrium) (compressional, tensile, or shear) on the order of 50 cm / 6000 km, or ~ 0.1 ppm. I don't know what stress that would require within the crust offhand. If the whole Earth responded in the same way, the same would be true for the oceans - the vertical depth changes would be small because most of the surface changes would be supplied by changes in the sea floor (and there would be no noticeable changes at the coasts). But the ocean doesn't respond the same way, so the horizontal displacement in the open ocean may be on the order of a kilometer (which the coriolis force may act on so that water parcels move in loops). The changing water depth would also affect changes in the underlying crust and mantle, so it's complicated. Of the energy that is going into the tidal displacments, some comes back out - the 'elastic' fluid motion of the ocean (and outer core in as far as that's concerned), and the elastic deformation of the solid Earth (includes the mantle - it responds more rigidly to high-frequency cycling; plastic deformation takes time). Energy is lost to viscosity in fluid motions and in plastic deformation, electrical resistance in the core, and to any brittle failure that would occur, as well as microscopic fractures. (PS atomic spacing may vibrate about equilibrium spacing, where equilibrium is at the bottom of an 'energy well'. Over small vibrations the energy well is approximately parabolic, so there is a linear proportion of force to deformation (strain). But when atoms are pulled apart, the energy approaches a modest limit, whereas pushed in close enough and the energy shoots way up. Thus, extreme compression can store so much energy that when released, the atoms could fly apart (vaporization).) Anyway, not much tidal energy is lost outside the oceans on Earth. More energy may go into the solid Earth tides then is dissipated there because the energy can come back out to the extent that the Earth 'springs' back. -------------- At the surface of the sun, with all planets aligned, tidal acceleration is 0.981 ppt of the lunar tide on Earth's surface. That's on the order of 1 nm/s2. At 10 solar radii out from the center, it would be on the order of 10 nm/s2. I'm not sure how the solar wind's velocity varies as it moves away from the sun - it would be decelerated by gravity but it is also affected by the magnetic field (and vice versa). For the sake of having some ballpark figure: at 100 km/s, it takes ~ 7,000 seconds to cross a solar radius. In 70,000 seconds, the time taken to cross 10 solar radii, the tidal acceleration would make a difference in velocity on the order of 0.7 mm/s. Even out 100 solar radii, tidal acceleration might cause a variation on the order of 7 mm/s. It seems rather insignificant compared to a speed of even just 10 km/s, let alone 100 km/s or 500 km/s. Of course, while I've been mentioning tidal accelerations out to 10 Earth radii and 10 solar radii, I should mention that the formulas for tides I've been using are nice linearizations - approximations that will fail when the distance out becomes significant compared to the distance to the tide-generating mass. However, for a tide generating object a distance R from the center of the body experiencing tides, the approximation is not off by more than a factor of 10 within ~ 75 % of R toward the tide-generating mass, or ~5 times R in the opposite direction; it's not off by more than a factor of 2 within 1/3 R toward the tide-generator or just over half of R in the opposite direction.
131194. Patrick 027 at 11:47 AM on 23 September 2008
        Volcanoes emit more CO2 than humans
        Tidal motion: If a local tide h = A*sin(wt), where A is half of the range, the maximum rate of change of h would be A*w; w=2*pi*frequency; for the maximum possible semidiurnal lunar tide on Earth (where the moon is in the equatorial plane), the frequency (not adjusting for the moon's orbital motion, which would reduce the following numbers just a little) is roughly 2/(86400 s), so w = 2pi/(43200 s) = 0.000145 / s. Thus at the surface of the Earth, the maximum vertical velocity of an equilibrium tide is 0.039 mm/s; at the core/mantle boundary it would be about 0.012 mm/s (just over a tenth the typical fluid velocity in the outer core, and of even less importance to the geodynamo for other reasons). The corresponding velocity at 10 Earth radii from the Earth's center: 39 cm/s. The corresponding velocity on the surface of the Sun for all planets aligned, not adjusting for planetary motions, using a solar rotation period of 26 days (it's in that neighborhood, although it varies with latitude on the Sun): 5.8 microns per second. For what it's worth, the corresponding velocity at 10 solar radii from the Sun's center: 58 mm/s. But how would that pertain to the solar wind? What are tidal accelerations? Earth's surface g = ~ 9.81 m/s2 = G*massEarth/(radiusEarth^2) -- Moon's mass is about Earth's mass / 81 Moon's (average) distance from Earth is about 60.3 Earth radii. 1/81 * [(1/59.3^2)-(1/60.3^2)] = 0.12 ppm -- So the difference in lunar g from Earth's center to the sublunar point at Earth's surface, as a fraction of Earth surface g: 0.12 ppm. That's 1.1 microns per second squared. to be continued...
131195. Patrick 027 at 10:27 AM on 23 September 2008
        Volcanoes emit more CO2 than humans
        Specifically, about 89 % of the mass of the sun is within half it's radius from the center. This means that the size of the equilibrium tidal bulge above that point is nearly proportional to the fourth power of the distance from the center; and would only be close to 1/16 of it's surface value - more precisely, 1/(16*0.89) = 1/14.24 = 7.02 % of the surface value. At just 20% of the way to the center, only ~ 1 % of the mass of the sun lies above, so the equilibrium tidal bulge is rather close to 0.8^4 = 0.1^4 * 2^12 = ~ 41 % of the surface value. Keep in mind that the equilibrium lunar tide at the Earth's surface has a range of ~ 54 cm at the surface, or close to 16 cm at the core/mantle boundary (I say close to because while g is nearly constant in the mantle, it is not precisely constant); for what it's worth, at 10 Earth radii from the center of the Earth, it would be 5.4 km. If all the planets were aligned with the sun, the equilibrium tidal range at the sun's surface would be about 2.1 mm (close to how much your hair would grow in 5 in 6 days - and points on the sun would go through this range in a bit over 10 days, I think (half solar rotation period)) - at 20% below the surface, 0.86 mm; for what it's worth, at 10 times the solar radius from the sun's center, it would be 21 m (69 feet). to be continued...
131196. Philippe Chantreau at 06:19 AM on 23 September 2008
        The link between hurricanes and global warming
        Thanks Chris, nice to have someone with more awareness of the current litterature to give us pointers.
131197. Philippe Chantreau at 06:16 AM on 23 September 2008
        What does CO2 lagging temperature mean?
        The caveat in your argument is this adjective: valid. There is not that much criticism from skeptics that deserves it. Whatever is actually valid is being considered and is part of the scientific litterature. No offense, but you going for Beck's pathetic nonsense and plain lies does not indicate that your sense of what is valid is better than mine.
131198. Patrick 027 at 04:24 AM on 23 September 2008
        Volcanoes emit more CO2 than humans
        First two clarifications of what I wrote earlier: "So of the heat that goes into driving the convection, perhaps between 70 % and 85 % (halving the efficiency to approximate the effect of internal heat sources only) would then go on to the mantle." With just under 30 % conversion of heat to mechanical energy for the heat coming from the base of the outer core, with nearly linear temperature trend with depth and the temperature range being somewhat small compared to absolute temperature, a first approximation for a distributed source of heat within the outer core would be half that efficiency of conversion - just under 15 %. That heat would come from the overall temperature decline of the outer core. However, the volume per unit depth is not invariant but is proportional to the square of the radius. The mass distribution is a bit different because of increasing density toward the center (Karato p.13), and specific heat is not constant, but the distributed heat source from cooling would still likely be skewed toward the cooler parts of the outer core, so the overall efficiency for the conversion of heat from cooling would be less than half of the that of the latent heat from the base of the outer core from inner core growth. For my own curiosity I might sometime try to estimate the proportion of the two heat sources by comparing the "100 K every billion years would release 5.7 TW of heat" to a figure derived from specific heat - unfortunately a figure not easy to find for molten high pressure iron alloy. The other clarification: "Of course, some of the mechanical energy goes back into heat anyway, and some goes into electromagnetic energy, but some of that may go back into heat within the core (but I'm thinking it would go back into heat always at lower temperature (higher up within the core) than where it went into mechanical energy, so that entropy increases), ... etc." That's on average - that the mechanical and electromagnetic energy produced from heat at one temperature will on average go back into heat at a lower temperature - individual packets of energy may go back into heat at higher temperature, destroying entropy, provided other parts of the system are supplying the work (free energy) to drive such a process, and gaining entropy. In the absence of fluid motions, the magnetic field would decay - about exponentially - due to diffusion of the magnetic field. If the core were superconducting, this could not happen - any change in the magnetic field would produce a voltage that would drive an electric current that would restore the magnetic field. The finite conductivity of the material allows some of the electrical energy to go into heat, so that the magnetic field can diffuse and decay. According to Karato (pp.197-198 in particular), the magnetic field would essentially vanish in ten thousand years without a geodynamo to power it up. I would imagine the decay rate is used to estimate the power that must go into maintaining the field - this is rate of magnetic energy conversion to heat energy in the core itself. Because of uncertain toroidal field components in the core that are hard or impossible to detect directly from the surface (though they can be inferred by comparing the seismographic implications of different geodynamo computer models to seismographic observations, taking into account some inner core properties), the actual magnetic field energy density is uncertain, so that would be a source of uncertainty in the power necessary to maintain it. The magnetic field energy will be concentrated within the core - inferred from Karato p.199, the magnetic flux B in the core may be between ~ 3 and ~ 300 times the surface value (30 microTeslas) (B of a typical refrigerator magnetic is about 100 times the natural B at the surface). I think field energy density is proportional to the square of B, in which case the energy density is between 9 and 90,000 times the surface value, the volume of the core is ~ 16 % the volume of the Earth (more than 1/9) (for future reference, surface area of core ~ 30 % that of the whole Earth (which implies the mass of the core is about ~ 30 % the mass of the Earth, since gravitational acceleration is nearly constant within the mantle (that's somewhat of an accident of the specifics of the Earth's mass distribution, not a general principle)), radius of core ~ 54 % that of the whole Earth); the magnetic field changes wouldn't induce much of a current in the mantle and the mass of the magnetosphere and E-region dynamo are very small, so it makes sense to think that most of the geodynamo energy goes back into the heat energy of the core. Any mechanical and electromagnetic energy going back into heat within the core also includes that coming from composition-generated buoyancy. (But I think some small portion of electromagnetic energy must radiate away into space as the Earth moves and the field changes.) As long as I'm on this, notice that 'stretching' the field lines, contorting them by uneven fluid motions, increases the magnetic energy density by putting a greater length of field lines into a unit volume. An interesting analogy could be made between that and the conversion of potential to kinetic energy in the atmosphere to sustain nearly-geostrophic wind shear as isotherms are elongated (without changing the average temperature gradient), such as by a growing wave pattern. There are big differences but there's a cool geometric similiarity. --- "And then you need to add the extra gravitational forces from jupiter and full alignments. If they can affect the sun they can certainly effect the Earth." The vast majority of tidal forces on Earth is from the moon and sun (solar tides being about half the magnitude of lunar tides, I think (roughly from memory ratio of masses divided by cube of ratio of distances: ~330,000*80 * (0.384/150)^3 =~ 0.44 - just under half). Remember planetary tides on the sun from: http://blogs.abcnews.com/scienceandsociety/2008/07/global-warming.html#comments A more complete comparison: height of equilibrium tidal bulge raised on sun by planet, as fraction of that raised on earth by moon, [ignoring out-of-equilibrium complexities of crust,ocean reaction (no Bay of Fundy on sun?)] expressed as ppt (parts per thousand): Jupiter: 1.33 Venus:.. 1.27 Earth:.. 0.590 Mercury: 0.563 Saturn:. 0.0647 Mars:... 0.0179 Uranus:. 0.00122 Neptune: 0.000375 Pluto:.. 0.0000000191 SUM:.... 3.84 Tidal acclerations at solar surface generated by planets, as ppt of lunar tide on earth, : Jupiter: 0.340 Venus:.. 0.325 Earth:.. 0.151 Mercury: 0.144 Saturn:. 0.0165 Mars:... 0.00458 Uranus:. 0.000311 Neptune: 0.0000957 Pluto:.. 0.00000000488 SUM:.... 0.981 The sums would be approached when Venus and Jupiter and a few others are aligned or close to aligned with the sun. When Jupiter-Sun-Venus forms a right angle, the tides on the sun will be more limited. (PS notice Saturn plays a much larger role in the 'solar jerk' (where the importance of a planet is proportional to it's mass times it's distance) than it does in tides on the sun (mass divided by distance cubed). This would have some implications for Fairbridge's concepts. It would also be instructive to consider the product of the above numbers, which gives the tidal acceleration that acts on the tidal bulge: In ppm of equilbrium lunar tides on Earth: Sum of products:.. 1.04 Product of sums:.. 3.77 Jupiter by itself: 0.454 The distinction between the first two is a nonlinearity. This is the tidal force per unit area of the sun per unit density variation with depth at the sun's surface, relative to a theoretical equilibrium lunar tide on Earth. The density variation within the Earth is distributed with some significant concentration near the surface and near the core/mantle boundary. The mass of an equatorial bulge is produced by the vertical displacment of a density contrast. The density variation within the sun is quite small near the surface; one has to get almost halfway to the center before the density is comparable to the ocean, ~ 60 % of the way to the center to find densities similar to that of the Earth's mantle; the great majority of the Sun's mass is contained within half it's radius from the center. to be continued...
131199. chris at 21:39 PM on 22 September 2008
        Svensmark and Friis-Christensen rebut Lockwood's solar paper
        Re #4 Mizimi, Perhaps you need to look again and think a bit more carefully. John Cook explains it very straightforwardly in his article and the two graphs of Svensmark and Friis-Christensen rather speak for themselves. i.e. according to Svensmark and Friis-Christensen's analysis presented in the graphs above, changes in the CRF mediated by solar activity have made zero contribution to the warming of the last 30-odd years. If anything the CRF contribution is a slight cooling one.
131200. chris at 21:21 PM on 22 September 2008
        The link between hurricanes and global warming
        Re #10 and #14 (Mizimi and HealthySkeptic) Why should we take account of the appeals to authority of a 78 year old retired scientist just because he happened to be an authority on hurricanes during his working career? Gray is demonstrably wrong in many of his assertions, and as with all science, his comments should be judged according to the evidence, and not because he's given platforms for bombastic assertions, and you might happen to like what he says. If you look at the numbers that Gray asserts about hurricane numbers, for example (Mizimi reproduced these in post #10), you can see the first problem. As Gray presumably knows full well (after all he's published on the very subject - see Goldenberg et al, 2001 below), the issue is not about total numbers/frequencies of hurricanes and tropical storms, but the increased numbers of high category (Cat 4 and 5) storms in a warming world. That's pretty obvious from reading John Cook's top article. Gray's other major assertion that is in complete contradiction with the evidence is his insistence that global warming is the result of internal variation in the ocean circulations. One may as well point out the other rather unfortunate habit of Gray which is to use ludicrous strawmen and other fallacious "arguments" with which to attack the straightforward science. So he is wont to state, for example, that hoary chestnut of contrived ignorance that climate models are no good because they can't predict the weather two weeks ahead [***]! Gray is either being incredibly ignorant of the science or mendacious...take your pick. [***]http://www.washingtonpost.com/wp-dyn/content/article/2006/05/23/AR2006052301305_pf.html Putting aside Gray, the issue is reasonably clear, even if this is an area of climate science, and the consequences of man-made global warming, that are not very well-defined as yet. The following seems pretty straightforward: (i) everyone seems to agree (Gray, included) that recent years (last couple/few decades) has seen enhanced activity of hurricanes and tropical storms in terms of intensities (Goldenberg et al, 2001; Emanual, 2005; Hoyos et al, 2006; Curry et al, 2006; Elsner et al, 2008). (ii) everyone seems to agree that the enhanced intensity of tropical storms and hurricanes is related to the enhanced sea surface temperatures (SST) that have been directly measured. In fact it was William Gray that first established a causal link between hurrican intensity and SST way back in 1968. (iii) it seems pretty well established that enhanced SST during the period of enhanced high category hurricanes is largely the result of the global warming measured during this period (Barnett, 2005; Trenberth and Shea, 2006; Elsner, 2006). If the Earth warms, the SST warms, and it is the thermal energy in the surface waters of the sea that provide the destructive power of tropical storms. Barnett, T. P. et al (2005) Penetration of human-induced warming into the world's oceans Science, 309, 284–287. Elsner JB (2006) Evidence in support of the climate change - Atlantic hurricane hypothesis Geophysical Research Letters 33 L16705 Elsner, JB et al (2008) The increasing intensity of the strongest tropical cyclones. Nature 455, 92-95 (see link in John Cook's top article). Emanual K (2005) Increasing destructiveness of tropical cyclones over the last 30 years Nature 436, 696-688 (link in John Cook's top article). S. B. Goldenberg, C. W. Landsea, A. M. Mestas-Nuñez, W. M. Gray (2001) The Recent Increase in Atlantic Hurricane Activity: Causes and Implications Science 293, 474 - 479 C. D. Hoyos et al. (2006) Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity Science 312 94 - 97. K. E. Trenberth and D. J. Shea (2006) Atlantic hurricanes and natural variability in 2005 Geophysical Research Letters, VOL. 33, L12704 etc. etc. --------------------------------------------------- here's some of the abstracts of papers cited above: C. D. Hoyos et al. (2006)Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity Science 312 94 - 97. Abstract: "To better understand the change in global hurricane intensity since 1970, we examined the joint distribution of hurricane intensity with variables identified in the literature as contributing to the intensification of hurricanes. We used a methodology based on information theory, isolating the trend from the shorter-term natural modes of variability. The results show that the trend of increasing numbers of category 4 and 5 hurricanes for the period 1970–2004 is directly linked to the trend in sea-surface temperature; other aspects of the tropical environment, although they influence shorter-term variations in hurricane intensity, do not contribute substantially to the observed global trend." 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." **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." 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."

Prev  2616  2617  2618  2619  2620  2621  2622  2623  2624  2625  2626  2627  2628  2629  2630  2631  Next