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Comments 130901 to 130950:

130901. Quietman at 16:44 PM on 30 October 2008
        It's the sun
        Mizimi That is interesting. I am planning to build a greenhouse to counteract the cooling conditions here. Is the increased albedo because of the plastic? I was planning on using tempered glass and translucent fibreglass.
130902. Patrick 027 at 15:04 PM on 30 October 2008
        Arctic sea ice melt - natural or man-made?
        Rossby waves: First, notes on vorticity. Vorticity = dv/dx - du/dy ; that is, the variation in the meridional wind component (v = Dy/Dt) going from west to east, MINUS the variation in the zonal wind component (u = Dx/Dt) going from south to north. Or in any coordinates (s,n) where facing in the direction of positive n, s points to the left, then the vorticity is the rate of change in the n direction of the s-component of velocity over n MINUS the rate of change in the s direction of the n-component of velocity; voriticity = d(Dn/Dt)/ds - d(Ds/Dt)/dn. (where Dq/Dt for any q is the velocity in the q direction; D/Dt is the langrangian or material derivative, which means it is the time derivative following the motion of the air; hence Dq/Dt is the rate of change of location along q following the air's motion.) Vorticity is the sum of two components: shear vorticity, and orbital or curvature vorticity. If there were only orbital/curvature vorticity, then the motion is simply rotation about a point. At each point at which this is the case, du/dx = - dv/dy, and d(Dn/Dt)/ds = - d(Ds/Dt)/dn, for any orientation of (s,n) axes. Over the space in which the vorticity is constant, the air would be rotating as if parts of the same rigid object, and there would be no deformation (if the air were tagged with shapes, the shapes would be rotated but remain the same size and shape). If only shear vorticity is present, then for a given location it will be possible to find some orientation of (s,n) such that one of d(Dn/Dt)/ds or d(Ds/Dt)/dn is zero. Suppose it is the first which is zero; in that case vorticity = shear vorticity = d(Ds/Dt)/dn. Where there is only shear vorticity, the wind is not changing direction. It is possible to have shear vorticity and orbital/curvature vorticity of opposite signs, in which case, if of equal magnitude, the total vorticity would be zero. One such case would be a wind field in which the streamlines form concentric circles, but outside of the central point or a central circle, the wind speed is inversely proportional to the distance from the center. Within the central circle, there would have to be some vorticity, or if there is only vorticity at the central point, that would have to be infinite vorticity (but just at one point, so that the vorticity integrated over area (for now, call that C) would be finite). To be continued...
130903. Patrick 027 at 11:22 AM on 30 October 2008
        Arctic sea ice melt - natural or man-made?
        ... well, now I'm not quite sure about the lack of form drag (the phase of pressure relative to displacement) with non-vertically propagating gravity waves, but anyway, moving on: If the forcing is at lower frequency than the buoyancy frequency, then: Vertical propagation occurs. surfaces of constant phase (crests and troughs) tilt with height. An interesting thing about these kinds of waves is that the group velocity is at right angles to the wave vector (which is perpendicular to the crests and troughs). The wave vector is in the direction of phase propagation. The group velocity is parallel to the crests and troughs. Relative to the air, for gravity waves emanating from the surface (such as from wind blowing over ridges), the crests and troughs move downward at an angle but build upward (along themselves) at an angle (at the group velocity), so that in steady state conditions, the wind blows through a stationary tilted crest and wave pattern. The pressure perturbation and vertical displacements are positioned so that there is form drag - there is higher pressure on the windward sides of the ridges and lower pressure on the lee sides. Thus there is a net force on the ridges, which means the air is losing momentum to the ridges. However, as each layer of air loses momentum to the layer below by the same process, it gains momentum from the layer above. If the gravity wave propagates upward without dissipation, there is no net loss of momentum. Ultimately the momentum transfered to the solid Earth from the air by the form drag is then taken from the air at levels where the gravity wave is dissipating (or otherwise ceasing to propagate as just described?). When the winds vary in time, the formation of gravity waves will change and I expect those changes to propagate at the group velocity. The winds and static stability can and will change with height, which will affect gravity wave propagation. Where the wind is slower, the frequency of the waves is reduced relative to the air following its motion - my understanding is that this (perhaps just because of the period of motion, or perhaps also because the tilts change so the group velocity goes farther away from the vertical?) allows for enhanced thermal and mechanical damping of the wave at such levels (per unit volume ?). Mecahnical damping would be by viscosity - including eddy-viscosity (the eddies in this case would be on smaller scales); concievably it might include something else**??. Thermal damping can occur because there are pressure perturbations in a gravity wave, which cause small adiabatic temperature variations, which then cause small variations in radiative (photons) cooling rates, which is not an adiabatic process and will reduce the gravity wave amplitude. In such gravity waves, the perturbation velocity and motion is parallel to the constant phase surfaces (crests and troughs, etc.) and oriented so that the horizontal projection is parallel to the mean wind. Inertio-gravity waves are gravity waves in which the fluid parcel oscillations are slow enough (slow wind, very very very broad ridges, low static stability) for the coriolis effect to become significant - so that the perturbation trajectories form ellipses rather than a line segment (following the air with the mean wind). As this happens, the coriolis effect becomes part of the restoring force. I haven't gone thoroughly through the math but from what I've read ("Introduction to Dynamic Meteorology - Third Edition" by James R. Holton - see chapters 7 and 9 in particular for gravity waves) vertically propagating inertio-gravity waves must have frequencies (following the motion of air parcels) between the buoyancy frequency (generally much much more rapid, and in that limit, crests and troughs approaching vertical) and the inertial oscillation frequency (proportional to the coriolis effect, and in that limit, crests and troughs approaching horizontal). I'm not sure what happens when the frequency is less than the inertial oscillation frequency - I suppose in that case the wave can't propagate. That might be why, in the context of inertial oscillations in the ocean excited by the wind, I've read that these can not propagate toward higher latitudes (but I was skimming that material, so don't take my word for it). Typically ridges don't have the profile of an endless sinusoidal wave with constant wavelength. Wind blowing over irregular topograph, or a single ridge, may excite a spectrum of gravity waves; depending on conditions, some may propagate vertically and some others may decay with height exponentially. (Of course, at high amplitudes, nonlinear effects, such as wave-wave interaction, may become a bigger factor). Sometimes conditions may allow vertical propagation but only up to some level, at which point the waves don't propagate further. I expect there'd be evanescent waves above that level (because the amplitude can't discontinuosly jump to zero - the same condition that requires evanescent electromagnetic waves beneath a reflecting surface). The gravity waves may reflect from that level. Repeated reflection between the surface and the upper level can generate trapped lee waves (Holton, p.284). Reflection may play some role in downslope windstorms but nonlinear processes are important in that phenomenon (Holton, p.284-285; also try looking up 'Froude number', 'hydraulic jump'). Without going into all details, Holton p.284: "Amplitude enhancement leading to wave breaking and turbulent mixing can occur if there is a 'critical level' where the mean flow goes to zero," - 'critical level' in the original is italicized instead of in single quotes (see also 'Scorer parameter'). Gravity waves with downward group velocity may occur presumably upon reflection from above - perhaps they could also occur from wind blowing underneath and relative to a disturbance in the air, though I haven't read of anything like that. Gravity waves can be excited by wind blowing over cumulus convection, and also may be produced by that convection itself (in that case, gravity waves may radiate away from the disturbances). 2. Rossby waves (to be continued)...
130904. Patrick 027 at 05:35 AM on 30 October 2008
        Arctic sea ice melt - natural or man-made?
        "Try to remember my background is engineering not climatology or theoretical physics. " I have a little bit of engineering and basic physics background but I'm not sure exactly what you mean about eddy currents in electricity. However, I really haven't begun to explain how these mechanical waves propagate. So to correct that, here are two important examples: 1. Gravity waves exited by wind blowing over sinusoidal ridges. Take the (arbitrarily-defined) layer of air closest to the surface. Without wave-breaking, the air moves up and down over ridges. It thus has to accelerate. So there will be pressure variations. Take the next layer of air - because the first layer is displaced, the next layer must be displaced, etc. As a function of the wavelength of the ridges and the wind speed, there must be some frequency of oscillation for the air as it blows through this set-up. If the air is stable (potential temperature increasing with height), air displaced vertically will tend to fall back to where it was, and oscillate about an equilibrium level - in the absence of forcing, this continues except for thermal (radiative - photons) and mechanical dissipation of the potential and kinetic energy involved. This natural frequency is called the buoyancy frequency or Brunt-Vaisalla (sp?) frequency. If the forcing of gravity waves is at a higher frequency, (unless I have this backwards), then the gravity waves produced by wind blowing over ridges decrease exponentially with height; there is no vertical propagation of the energy. There is no form drag - that is, the pressure perturbations associated with the gravity waves are aligned with vertical displacement maxima and minima so that there is no sideways forcing. The dissipation that would occur is by viscosity, which would occur in the absence of gravity waves (wind blowing across the surface tends to lose momentum to the surface (and hence the Earth), and wind at different levels at different speeds can exchange momentum via viscosity, though that is not generally a dominant factor in atmospheric motions away from the surface). On the other hand, if the forcing frequency (determined by the wind and the wavelength of the ridges) is less, than ... to be continued...
130905. Quietman at 16:16 PM on 29 October 2008
        Arctic sea ice melt - natural or man-made?
        Patrick So you are saying that eddy waves are similar to eddy currents in electricity rather than in aerodynamics? Try to remember my background is engineering not climatology or theoretical physics.
130906. Patrick 027 at 14:57 PM on 29 October 2008
        Arctic sea ice melt - natural or man-made?
        ... I think that - either when there is zero EP-flux or when the EP-flux divergence is zero?, then the wave is not dissipating (or amplifying or breaking) and so is not altering the mean state (it must be the first, because even without EP flux divergence, there is some alteration - but maybe it has to be reversed in time?). In such a case a wave can propagate by making only temporary changes (as electromagnetic waves may nudge the matter in a transparent material along the way (which affects how the wave propagates).
130907. Patrick 027 at 12:43 PM on 29 October 2008
        Arctic sea ice melt - natural or man-made?
        "Re: 276 I am just guessing but doesn't direct nonstop sunlight on the poles during a 6 month long day have a little to do with this?" YES! (And that will bear on any changes in solar forcing, but in and of itself is just part of the regular seasonal cycle which changes on timescales of several thousand years and longer...) "Re: 277 I have no clue as to what that means. Are you talking about wind or radiation? Eddys are circular currents caused by turbulence (in water or air) so I do not follow. " Not about electromagnetic radiation as in photons. These are mechanical waves. Waves are often thought of as sinusoidal in some way, but one can have a single wave pulse. There's phase velocity and group velocity - for dispersive waves, not the same thing. (Energy propagates witht the group velocity.) In order for waves to occur there must be a restoring force - gravity, pressure, elasticity, etc... In the context of geophysical fluid dynamics, I'm not sure exactly if there is a distinction between eddies and waves. Eddies can propogate. Rossby waves involve rotation. Cyclones that develope in midlatitudes are an aspect of baroclinic waves, which I think may be considered a kind of Rossby wave... It is true that in order for baroclinic instability to occur, there must be some vertical level, called a critical level (or steering level in this case, for obvious reasons) where the wind averaged across the baroclinic wave (a basic state wind) is equal to the velocity of the motion of the baroclinic wave (at least in the case where the average wind is not changing direction with height); however, above and below, the wave is propagating through the air. Even if we ignore vertical motion, the air at the center of a cyclone is not necessarily going to be at the center of the same cyclone in the near future; Even if a cyclonic circulation is strictly two-dimensional and axisymmetric, so that at any instant the streamlines (parallel to the wind vector at each location) are circles, propagation of this streamline pattern can be such that individual trajectories spiral into and out of the cyclone and in some cases may curve anticyclonically. ... Often an analysis of the atmosphere is made using zonal averages - these are averages over all longitudes - so that they might be graphed in two dimensions (if averaged over some specific time period or at some particular moment in time, etc.). Then there are zonal means, mean temperature, zonal (westerly) wind, and the mean meridional circulation (north-south and up-down). Motions that average to zero are attributed to eddies. Correlations of some parts of eddies with other parts of eddies can yield nonzero eddy fluxes - for example, in this perspective, the average eddy temperature deviation is zero, the average eddy meridional wind velocity is zero, but the average of the product of the two can be nonzero - thus there is a nonzero northward temperature flux by eddies. The average zonal velocity of eddies can also be zero, but a correlation between eddy zonal wind velocity and eddy meridional wind velocity can yield a nonzero northward eddy flux of zonal (westerly) momentum. The average of the square of the eddy wind speed will be nonzero, and hence so will the eddy kinetic energy. One way of analyzing how eddies affect the mean is by looking at the EP flux, which is a mathematical expression derived from distributions of eddy temperature and momentum fluxes, and is related to the eddy potential vorticity flux. In this perspective, everything 'eddy' would include some of such things as (internal) gravity waves, (internal) intertia-gravity waves, Rossby waves (baroclinic waves, planetary waves, etc.), equatorial Rossby waves, Rossby-gravity waves, and Kelvin waves; thus these can all have eddy fluxes. I'm a bit vague on much of this, but the gist of what I've gotten is: These waves can propagate through the atmosphere in some ways; depending on the type and at least sometimes the wavelength of the wave, there can be a index of refraction assigned to parts of the atmosphere which is a function of the wind field, the coriolis effect (varies with latitude), stability, and/or quantities derived from those things - vorticity, potential vorticity, etc. Waves may propagate horizontally only or they may also propagate vertically. Relevant to either direction, there can be critical levels. There may be regions where the wave can not propogate in an oscillatory manner - upon reaching a boundary it may be felt on the other side as an evanescent wave, one which decays exponentially away from that boundary - if another boundary is reached where it can again propagate, perhaps some of it will have tunneled through the barier (perhaps analogous to electron tunneling, considering the quantum-mechanical wave nature of electrons; also perhaps analogous to the evanescent portion of an electromagnetic wave which exists on the opposite side of a reflecting surface). Some gravity waves are actually evanescent waves - for example, a gravity wave produced by wind blowing over a ridge may decay with height and have vertical phase planes vertical with - zero group velocity? - whereas otherwise a gravity wave produced by wind blowing over a ridge will propagate vertically (the energy will propagate with the group velocity, and this carries momentum). Waves may be concentrated by variations in the index of refraction. They may reflect. They may over-reflect - I'm not sure but maybe that's analogous to the stimulated emission of radiation. Generally, disturbances may radiate waves. Waves may grow, and thus must be taking something from the background state they inhabit. They may dissipate, and in doing so they may deposit momentum back into a background state. Waves can also break (like waves crashing on a beach). I started going into this because wave-mean interactions are important in the global circulation; wave propagation also is important in stratospheric and mesospheric motions; etc...
130908. Mizimi at 05:49 AM on 29 October 2008
        Temp record is unreliable
        Thanks Chris; somehow I missed the link. This thread is about temperature records and how reliable /accurate/representative are they. CO2 levels are assumed to vary only slightly due to effective atmospheric mixing, but this is very different from temperature which has much greater variation. Given the paucity of temperature recording stations I cannot accept that the data used for models is sufficiently representative of the global condition, and thus the resultant of the model is questionable. Even satellite records are questionable as recently demonstrated by the modification needed to the attitude correction algorithm.
130909. chris at 05:46 AM on 29 October 2008
        Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????
        Re #24: That's incorrect. The overall trend of the last 5 million years has been a mildly cooling one. Re #21 There's no such thing as "normal" temperature in relation to the Earth. The Earth is on a journey through time, and it's properties (atmosphere, temperature, biosphere, geology and so on) evolve according to a whole range of intrinsic and extrinsic factors. For human kind and the current biosphere, "normal" only really has a meaning in relation to evolutionary adaptedness. The biosphere in its current state is adapted (i) to the relatively cool period of the last several million years, and (ii) to a world with rather more continuous and connected environments that has, until the recent past, allowed migration as a fundamental means of adapting to climate change.
130910. chris at 05:31 AM on 29 October 2008
        Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????
        Re #23 The notion that one can change reality or somehow diminish real world implications with semantics is a dismal notion...it's politics, not science. The world is warming..the evidence indicates that the massive enhancement of greenhouse gases is a dominant causal factor....our understanding of the climate system and its response to enhanced greenhouse effect indicates that we're very likely to get a considerable amount of additional warming. That's "global warming"...and it's already causing "climate change"... As for the "shift in emphasis" from "Global Warming" to "Climate Change", much of that "shift" has come from the sectors of the political spectrum, especially in the US, that has had such a degrading effect on the entire US sociopolitic during the last several decades: So, for example, it was Frank Luntz, the Republican party strategist, that urged Republican candidates in a memo some years ago, to use the phrase "climate change" rather than "global warming", because (in his words): "Climate change is a lot less frightening than global warming". At that time, Luntz's aim was to misrepresent the science and to play the "uncertainty" game ("there's no proof that cigarette smoke causes cancer"..."there's no proof that aspirin enhances the liklihood of Reyes syndrome in children".."there's no proof that CFC's denude high altitude ozone concentrations" etc. etc. ad nauseum). Happily, like an awful lot of people that combine politics with at least a semblance of honesty, Luntz has shifted his viewpoint, such that he said in an interview a couple of years ago: "It's now 2006...I think that most people would conclude that there is global warming taking place and the behaviour of humans is affecting the climate..." The take home messages are, first, that the natural world sadly doesn't bow to ones' political pursuasions (see King Canute's political advisors!), second, that on the supposed use of semantics to politicise/downplay real world consequences, one should be a little more careful in assessing where the politicizations are coming from.... ....and third, if one considers that it is appropriate to misrepresent and deliberately misunderstand the science in pursuit of political agendas, one might consider who is actually benefitting from one's contrived misrepresentation...one might discover at some future time that one was being treated as a chump to service someone else's agenda!
130911. Mizimi at 05:31 AM on 29 October 2008
        It's the sun
        FYI: University of Almeria (Spain): A study by Pablo Campra (published in the Journal of Geophysical Research)on the effect of greenhouses in western Almeria province reports an 0.3C/decade drop in temp over the last 25 yrs....roughly the same as the rise in temp for the rest of the world during that time. Western Almeria has over 30,000 hectares of plastic covered greenhouses supplying produce to European supermarkets. The plastic sheeting increases the local albedo, reflecting sunlight back into space. The plants grown also act as a carbon 'sink' absorbing around 10 tonnes of carbon/hectare...an annual equivalent of 300,000 tonnes of carbon.
130912. Mizimi at 05:18 AM on 29 October 2008
        What does CO2 lagging temperature mean?
        Chris: You have listed catastrophic events which cannot be predicted and occur infrequently; yes, they had an enormous effect ( from which life recovered) but in the scheme of things were relatively transient. As such they should be factored out of any attempt to model climate.
130913. chris at 21:05 PM on 28 October 2008
        CO2 measurements are suspect
        Re #9 The ocean isn't really "covered by a few ships". The oceans have a scattering of data stations in isolated islands (see map in the World Data Centre For Greenhouse Gases in John Cook's top article). It's pretty hard to see what your difficulty is. If we can measure CO2 in the atmosphere from a whole slew of data stations in isolated positions around the world situated away from urban centres, and these give rather similar atmospheric CO2 measures (yearly averaged), then we can be pretty confident that we are obtaining accurate and valid measures of the atmospheric CO2 concentration, particularly if we have extended time series that allows us to determine year on year variations in the level from individual sites. That's rather consistent with what we understand about the nature of atmospheric gases that are highly diffusive, and so are pretty well mixed on the annual basis. Of course it's important to monitor yearly averages if we wish to determine the year on year variation in atmospheric CO2 levels, since there are significant intraannual (cyclic) variations, especially in relation to the yearly cycle of plant growth and decay that is dominated by the N. hemisphere seasonal growing/decay cycle. And we do know what the CO2 levels west of the Brazilian rainforest are. We have data from Huancayo in Peru from various periods in the 1980's. These are within a few ppm of the global average from the ocean surface stations (or the Mauna Loa observatory). We have data from Easter Island that lies to the west of the Brazilian rainforest. Likewise these data are within a few ppm of the rest of the globally averaged data. I expect you can find more data from sites west of the Brazilian rainforest if you try (it really depends how interested you are in finding out this stuff). We do know what the atmospheric CO2 levels are in the Sahara. We have extensive data from Assekrem in Algeria in the N. Sahara, for example. The data are rather close to the atmospheric CO2 levels measured from the globally averaged data (or the Mauna Loa data). In other words wherever we look, we find a rather consistent set of atmospheric CO2 concentrations throughout the world, so long as these are measured in isolated sites unperturbed by major sources of atmospheric CO2.
130914. Quietman at 14:54 PM on 28 October 2008
        Volcanoes emit more CO2 than humans
        Patrick Re: 108 Maybe not global, I was thinking on a much more localized scale (as in the cause of El Nino) that has wide effects (as in El Nino).
130915. Quietman at 14:51 PM on 28 October 2008
        Arctic sea ice melt - natural or man-made?
        Patrick Re: 276 I am just guessing but doesn't direct nonstop sunlight on the poles during a 6 month long day have a little to do with this? Re: 277 I have no clue as to what that means. Are you talking about wind or radiation? Eddys are circular currents caused by turbulence (in water or air) so I do not follow.
130916. chris at 08:50 AM on 28 October 2008
        Temp record is unreliable
        Re #34 No, not paleoproxies. That's clear from the data I linked to: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf (see page 3) The atmospheric CO2 record is the directly measured atmospheric CO2 either in the atmosphere (from the many sites around the world and the continuous record from Manua Loa since 1959), and trapped in bubbles in ice cores extending back many 100's of thousands of years, but at a high resolution extending back 1000 years: e.g. D. M. Etheridge et al (1996) "Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" J. Geophys Res. 101, 4115 -4128. and later extended to 2000 years: CM Meure et al (2006) "Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP" Geophys Res. Lett. 33 Art. # L14810
130917. Dan Pangburn at 07:07 AM on 28 October 2008
        CO2 lags temperature
        At post 43 above “for the last glaciation” appears to have been mistakenly interpreted as the transition from interglacial to glacial. The words were intended to be understood as ‘during the glacial period’ which excludes the interglacials and transitions to avoid these murkier periods and also to avoid significant influence of Milankovitch cycles. It may have been less ambiguous to have said “during the last glacial period” because what is meant is the period from about 115,000 ybp to about 20,000 ybp (and previous glacial periods). Similarly in post 45, ‘glaciations’ is intended to mean ‘during the glacial period’. Of course the planet is warmer because of ‘greenhouse gases’ than it would be without the effect. Most people that are knowledgeable on climate understand that positive feedbacks occur with carbon dioxide and water vapor and should understand that the climate responds to NET feedback which is the combined effect of all feedbacks, both positive and negative whether known or not. Much less well understood is that there has to be substantial negative feedback because the trends in the temperature record prove that the NET feedback can not be significantly positive. Without significant net positive feedback, the GCMs do not predict significant global warming. The lag of atmospheric carbon dioxide level to changes in global average temperature in paleo data is readily explained by the change with temperature in solubility of carbon dioxide in water.
130918. chris at 23:39 PM on 27 October 2008
        Water vapor is the most powerful greenhouse gas
        Re #9 Yes water vapour amplifies the warming. One needs to be a bit more explicit in relation to the question of whether it amplifies the source of the warming (it does under some circumstances). So in general it's more explicit to state that water vapour amplifies the effect of the source of warming to which raised water vapour concentrations is a response. So yes, raised water vapour amplifies the warming. It "makes it larger" (it "exaggerates" or "increases" the warming). As your definitions indicate "amplification" is an appropriate word; there's nothing emotive about it! It doesn't have a cooling effect. And as you also indicate the GMT is somewhat higher than it would be otherwise be...
130919. Mizimi at 07:01 AM on 27 October 2008
        CO2 measurements are suspect
        Most of the stations are located in the N hemisphere, very few in the southern, and the ocean is covered by a few ships. I would be a lot more comfortable with the idea that CO2 is rapidly homogenised if we had some hard data from the areas not currently monitored, especially since most of them are not industrialised. For example: we might well find that the CO2 levels west of the Brazilian rainforest are higher than 'average' or that Saharan levels are markedly below. The point is we don't know and we should.
130920. Mizimi at 06:41 AM on 27 October 2008
        Water vapor is the most powerful greenhouse gas
        Amplify: lit. to increase or make bigger. 1. To make larger or more powerful; increase. 2. To add to, as by illustrations; make complete. 3. To exaggerate. So by what means does any GG ( water vapour inc.) amplify the source of warming? It doesn't. It moderates the rate at which heat is lost which means the GMT is somewhat higher than it would otherwise be.
130921. Mizimi at 06:00 AM on 27 October 2008
        It hasn't warmed since 1998
        Dan: I just did a simple linear calc 0.18/decade for 10 decades = + 1.8c rise. Totally wrong I know but it was to illustrate a point that even if the 30 year trend continues in a linear fashion ( which it can't as the real effect is logarithmic) we would only see GMT rise to 15/16C by 2008.
130922. Mizimi at 05:51 AM on 27 October 2008
        Temp record is unreliable
        Chris: "If one examines the high resolution atmospheric CO2 record over the last 1000 years,"...... What highres records are we talking about please? Paleoproxies?
130923. Patrick 027 at 14:09 PM on 26 October 2008
        Arctic sea ice melt - natural or man-made?
        Characteristics of the atmosphere can be divided into a mean state (as in zonal mean - averaged over all longitudes) and eddies. Eddy winds blow north and south, east and west; average of eddy wind velocity would be zero (unless...?). Eddy thermal anomalies are warm and cold; average is zero. But correlation can exist so that the average eddy heat and momentum fluxes are nonzero. These eddies are waves. They can propagate. They can be 'emitted' (generated, grow), can be reflected, can be absorbed, depending on the type of wave and conditions of the atmosphere.
130924. bit_pattern at 14:02 PM on 26 October 2008
        Is Pacific Decadal Oscillation the Smoking Gun?
        Thank you!
130925. Patrick 027 at 13:58 PM on 26 October 2008
        Arctic sea ice melt - natural or man-made?
        Basic info on global circulation patterns: Troposphere: latitudinal variations in solar heating drive thermally direct Hadley cells - altered and enhanced by the role of water vapor: Widespread sinking over subtropics; adiabatic warming, radiative cooling. Rising in cumulus convection (hot towers) in the ITCZ - latent heating, adiabatic cooling. Seasonal Variation in forcing: ITCZ migrates north and south; the most intense Hadley cell is from the ITCZ to the winter subtropics. Seasonal land-sea contrasts: monsoons, enhanced by water vapor (latent heating). Also, Walker Circulation. Hurricanes, cumulus convection, land-sea breezes and mountain-valley breezes. -- Baroclinic instability in midlatitudes: Eddies carry heat polewards, concentrate zonal (westerly) momentum from north and south, transfer zonal momentum downwards to surface. Drives a thermally-indirect Ferrel Cell. -- Stratosphere and Mesosphere: Radiative equilibrium would be a temperature maximum around stratopause, Latitinal variation is - in lower stratosphere, warmest on the summer-side of the equator, but still cooler at summer pole; going up, latitude of greatest temperatures shifts all the way to summer polar region (happens while still in stratosphere). Winter polar region very cold. Circulations driven by propagation of mechanical energy upward from troposphere drive stratospheric and mesospheric motions that alter the temperature distribution: Quasi-stationary planetary waves produced in the troposphere can (under certain conditions) propagate upward - this can only happen with westerly winds with certain ranges of speeds - this happens in winter; not in summer. In winter, planetary waves propagate upward and dissipate in the stratosphere, which drives poleward motion; BREWER-DOBSON circulation in the stratosphere is upward over tropics, poleward into the winter hemisphere, and downward at higher latitudes. This warms the mid and high-latitude lower stratosphere and cools the tropical tropopause. Sometimes this happens in bursts called 'sudden stratospheric warmings'. But on average the winter polar stratosphere is still colder than the winter midlatitude stratosphere. Some gravity waves produced in the troposphere can propagate up to the mesosphere where they are dissipated, driving motion that is from the summer hemisphere to the winter hemisphere, with upward motion over the summer high latitudes and downward motion over the winter high latitudes. This cools the summer upper mesosphere and warms the winter mesosphere. Thus on average: At tropopause, coldest over tropics (the tropopause is highest over the tropics). In the lower stratosphere, summer polar region is warmer, tropics are colder, midlatitude winter is a bit warmer again, but the polar winter is colder. Higher in the stratosphere, there is a general decline in temperature from summer pole to winter pole. This continues somewhat into the mesosphere, except starting in the lower mesosphere winter high latitudes, the temperature gradient reverses; going up this condition spreads across the tropics and all the way to the summer pole, so that in the upper mesosphere and mesopause region, the summer pole is cold and the winter pole is warmer.
130926. Patrick 027 at 13:23 PM on 26 October 2008
        Volcanoes emit more CO2 than humans
        That last comment was about "'Dead' planets might be livable after all". hope to get back to AO discussion within a few days...
130927. Patrick 027 at 13:20 PM on 26 October 2008
        Volcanoes emit more CO2 than humans
        That was interesting. One important point is that the heat would take time to build up from such a process. In spite of all the Earth's internal heat, it counts little for regional or global scale climate (directly), because the heat flux is very small. For internal heat to make a difference to surface temperatures on a large scale, the heat flux has to be significant compared to the heating by radiation from the planet's star. Assuming a rocky crust as on Earth, the thermal gradient must then be that much greater, which means perhaps a thin crust on a molten mantle.
130928. Quietman at 11:40 AM on 26 October 2008
        It's the sun
        It is becoming more apparent that we picked either a very bad time or a very good time to screw with mother nature because the earth itself is very active as well as the sun. This is not a coincidence.
130929. Quietman at 11:34 AM on 26 October 2008
        Volcanoes emit more CO2 than humans
        Patrick I found a little more background data: Evidence Mounts For Arctic Oscillation's Impact On Northern Climate: ScienceDaily (Dec. 20, 1999)- A growing body of evidence indicates that a climate phenomenon called the Arctic Oscillation has wide-ranging effects in the Northern Hemisphere and operates differently from other known climate cycles. Arctic Oscillation Has Moderated Northern Winters Of 1980s And '90s: ScienceDaily (July 10, 2001) - The Arctic Oscillation has been linked to wide-ranging climate effects in the Northern Hemisphere, but new evidence shows that in recent decades it has been the key in preventing freezing temperatures from extending as far south as they had previously. Synchronized Chaos: Mechanisms For Major Climate Shifts: ScienceDaily (Aug. 2, 2007) — In the mid-1970s, a climate shift cooled sea surface temperatures in the central Pacific Ocean and warmed the coast of western North America, bringing long-range changes to the northern hemisphere. It seems that someone has been ignoring this data for quite a few years now. I wonder why.
130930. chris at 09:57 AM on 26 October 2008
        CO2 measurements are suspect
        Re #7, Well yes, that's rather the point. If one wants to obtain reliable global estimates of atmospheric CO2 concentrations, it makes sense to sample the atmosphere in isolated locations far from major sources of CO2 production. So one expects to see a bit of variability of atmospheric CO2 in measurements made in industrialised countries especially in the Northern hemisphere, and of course there is the yearly plant growth/decay cycle dominated again by the N. hemisphere. However if one examines the yearly average of atmospheric CO2 in isolated locations (there are dozens of these), the variability is low. These locations give a good measure of the global CO2 in the well-mixed atmosphere averaged on a yearly basis. Obviously local measures of CO2 concentrations can be somewhat higher, especially in or near cities (where they can be locally very much higher). There's masses of data that indicate that rather obvious consequence of measuring near human sources of CO2 (industrial/transport/heating etc.). Clearly if one wishes to assess the extent to which global atmospheric CO2 concentrations are changing in time, one asesses the global average on the time scale of good atmospheric mixing (e.g. annually) at the wealth of sites in isolated locations far from CO2 sources... ..it ain't rocket science!
130931. chris at 09:35 AM on 26 October 2008
        Is Pacific Decadal Oscillation the Smoking Gun?
        Re #42: The infrared electromagnetic (EM) radiation reaching the earth's surface is transformed to thermal energy which is re-irradiated eventually as longwave infrared (IR), having a lower energy than the incident IR. This longwave IR has energies that overlap with those of the vibrational transitions of certain atmospheric gases. These are molecules with asymmetric bond vibrations; i.e. CO2, H2O, CH4 and others (symmetric diatomic molecules that dominate the atmospheric composition - O2 and N2, don't absorb this longwave IR). So electronic transitions aren't excited, nor are bonds broken. However the absorbed longwave IR is either re-emitted by the greenhouse gas molecules, or else the gases transfer their thermal energy to other molecules directly by collision (thermal energy is essentially the same as heat). This has the effect of suppressing the escape of IR into space, and thus warming the atmosphere. In other words, the longwave IR emitted by the earth's surface radiates essentially "upwards" into towards space; however the "trapped" IR is re-emitted in all directions, and so the return of thermal energy to space is suppressed. I suspect that's what the sentence is summarising...
130932. Mizimi at 08:45 AM on 26 October 2008
        CO2 measurements are suspect
        Well, the World Data Centre for GG's shows more than 1% differences...eg... Syowa Station * Japan NOAA/GMD 13CO2 2007 379ppm Hegyhatsal * Hungary HMS CO2 2007 405ppm Minamitorishima * Japan JMA 2008 380ppm Puszcza Borecka/Diabla Gora * Poland 2008 398ppm A small sample, there are others. 7% differential....5% differential; a bit difficult to accept the idea that there are no significant global variations in CO2 levels. Especially when no-one has bothered to measure the rather large areas mentioned in #1
130933. Mizimi at 08:15 AM on 26 October 2008
        Human CO2 is a tiny % of CO2 emissions
        Depends what you define as 'short', 'medium' or 'long'. Yes, atmospheric CO2 levels have risen in the last 50 years or so....is this short or medium? Climate-wise I suggest it is very short. Paleoproxy data shows atmospheric CO2 rising and falling by very much greater levels over longer periods of time. The system is clearly never in equilibrium. 'More or less in balance' is a cop out. How much out of balance does it have to be before you consider it not in equilibrium? How does all that CO2 locked up as carbonate sediment compare to the oil/gas/coal deposits? And that form of sequestration is still going on. Human population is expected to grow from 6 to 9 billion by 2100...which equals (roughly) 540 million tons of carbon locked up in people for say, 60 years? And yes, people die, but the release of carbon back to the environment is not immediate. No dynamic system can be in equilibrium...
130934. bit_pattern at 08:08 AM on 26 October 2008
        Is Pacific Decadal Oscillation the Smoking Gun?
        I have a question - my grasp on physics is pretty basic and I was using this article to make a point on an internet forum and this was the response I got. Can you possibly give a brief explanation? "Greenhouse gases absorb outgoing longwave radiation" I am not sure what this is trying to say. The absorption of energy must culminate in some sort of effect. Either the energy excites e-, causing it to jump from a lower energy level then falling back again; emitting light during the drop. Or the energy absorbed breaks bonds. Or the energy is reflected. Do you know what this is trying to say?
130935. Dan Pangburn at 02:39 AM on 26 October 2008
        It hasn't warmed since 1998
        

        It is unclear how the calculation at 15 was made. NOAA data is available at LINK and Hadley data at http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt . These both show a trend of about +0.1 degree per decade. Although short term trends can be misleading, like the 22 year run up from 1976 to 1998, the dramatic drop of global average temperature in 2008 may be indicative of a change in character of the climate. The current UAH satellite numerical data (these data consist of the differences of lower atmospheric temperature from the 1979 thru 1998 average) is at http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt . According to these data, the AVERAGE GLOBAL TEMPERATURE for the first 9 months of 2008 is LOWER than the average from 2000 thru 2007 by an amount equal to 43.1% of the total linearized increase (NOAA data) during the 20th century. Since 2000, the CARBON DIOXIDE LEVEL HAS INCREASED by 14.4% of the total increase since the start of the Industrial Revolution.

130936. Quietman at 15:03 PM on 25 October 2008
        It's the sun
        pps Sorry, I put it in the "CO2 measurements are suspect" thread since I could not find a more pertinant thread for it.
130937. Quietman at 05:05 AM on 25 October 2008
        It's the sun
        chris Re: Otherwise it's not obvious - Greenhouse gases yes, to some large extent. But there is still more to it in my view. PS I put a link to yet another GHG in the volcano thread that might interest you.
130938. chris at 03:40 AM on 25 October 2008
        CO2 measurements are suspect
        Nice pudding Quietman, but it doesn't really go with the main course. This thread (and my posts) is about the accuracy of global CO2 readings and the mixing of the atmosphere on the annual timescale. The fact that efforts are being made to measure the concentrations of atmospheric NF3 is a seperate issue and not related at all to the accuracy of atmospheric CO2 measurements. Note that NF3 concentrations are extraordinarily low (I calculate around 42,500,000 times lower that those of atmospheric CO2 based on the info in your link)...no doubt it hasn't been easy to measure these...or perhaps no one has bothered up to now...
130939. Quietman at 11:45 AM on 24 October 2008
        CO2 measurements are suspect
        chris May I offer you a little pudding perhaps.
130940. chris at 08:43 AM on 24 October 2008
        There's no empirical evidence
        Re #11 A skeptic would easily recognise that Beck's analysis is nonsense! see, for example, post #172 here: http://www.skepticalscience.com/solar-activity-sunspots-global-warming.htm remember that this is a "skepticalscience" site...we should make at least a little effort to be skeptical!
130941. chris at 08:38 AM on 24 October 2008
        It's the sun
        Re #179 Well yes, the large scale global warming of the last 30-odd years hasn't had a significant solar component. If anything the solar contribution has been a slight cooling one during the last several decades. Even those that push for solar contributions such as the cosmic ray flux concede that the solar contribution has been negligible at best. So solar contributions to warming in recent decades just isn't a viable proposition. The evidence is flat against it. Otherwise it's not obvious what else can have contributed significantly to warming other than the very well characterized massive enhancement of the Earth's greenhouse effect.
130942. chris at 08:28 AM on 24 October 2008
        It warmed before 1940 when CO2 was low
        Re: #2 (and #1) ..and yet there is a massive amount of evidence that the warming of the last 30 years is not "natural". The warming has followed the truely massive increases in CO2 emissions especially since the 1960's. Atmospheric CO2 concentrations rose rather slowly throughout the early 20th century. They were approaching 300 ppm in 1900 and reached 320 ppm in 1962. Since then we've raced up to 386 ppm. That's the likely source of the large scale global warming of the last 30-odd years. So to suggest that "our contribution, of various sources, not just CO2 is negligible" (whatever that might mean!) just doesn't accord with the real world evidence. I'd like to know what these "arguments presented against CO2" that "have some merit" actually are...can we have a list please?
130943. chris at 07:14 AM on 24 October 2008
        Is Antarctic ice melting or growing?
        Re #15 Monaghan and Bromwich seems to me to be essentially confirmatory in relation to our understanding of the Antarctic and the implications of a warming world. They point out that while the Southern oceans have warmed significantly in the last few decades, that this hasn't resulted (as far as we can tell) in enhanced snow deposition. They suggest that a predicted 2-3.5 oC of Antarctic warming in the current century might yield a 10-20% increase in snowfall, with a potential mitigating effect on sea level rise. However it's not clear (to me anyway!) whether this relates to NET Antarctic mass. After all, a 2-3.5 oC temp rise in the Antarctic (there hasn't been much overall warming there so far, much as models predicted) might be expected to yield significant melt at the continental margins (as we're seeing in Greenland), which might or might not balance or overpower excess snow deposition... There's a certain extent to which this is somewhat academic. Other than the expected mass loss in the Antarctic peninsula and to a lesser extent in the West Antarctic ice sheet, significant Antarctic ice mass loss hasn't been much factored into the consequences of global warming. As predicted by models from 20 years or so ago (see post #66 in the "Arctic sea ice - natural or man-made" thread: http://www.skepticalscience.com/Arctic-sea-ice-melt-natural-or-man-made.html ..Antarctica is partly insulated from the effects of global warming largely due to the peculiar ocean currents in the deep Southern latitudes, and the very efficient transfer of thermal energy to the high Northern latitudes. So the concerns (in relation to sea level rise) in a warming world relate largely to Greenland. No one expects Antarctica to melt significantly. Monaghan and Bromwich is consistent with that expectation. I'd still like to know whether they consider that their modelling of enhanced snow fall through the latter parts of the 21st century, due to enhanced Antarctic temperatures in a world warming under the influence of enhanced greenhouse gases, is a NET contribution to sea levels, or is independent of any warming-induced contribution to sea level rise from enhanced melt at the low altitude continental margins. I get the impression from their paper that they haven't considered the latter....that's not what their paper is about....
130944. Quietman at 04:55 AM on 24 October 2008
        Volcanoes emit more CO2 than humans
        Patrick In a new article at MSNBC titled ‘Dead’ planets might be livable after all they explain planetary tidal forces in the manner that I see them (inferring from the Solar Jerk) but carried to more of an extreme than we experience. The hypothesis is the same however, it's only a matter of degree.
130945. Dan Pangburn at 18:58 PM on 23 October 2008
        Models are unreliable
        It was somewhat surprising to discover that the study of climate science does not require any exposure to the ‘theory’ (it is widely and successfully applied practice in some engineering disciplines, especially electrical, mechanical and aeronautical) of dynamic systems with feedback control. Their ignorance has resulted in climatologists coming up with their own expression for feedback and the perception that feedback in climate is somehow different from feedback in other systems. In effect it isn’t (for more, see 49 above). Earth’s climate is a dynamic system that is controlled by NET feedback. A lack of understanding of dynamic systems with feedback and how they work has resulted in many articles being published that a reviewer who was knowledgeable in dynamic systems with feedback would quickly recognize as patently false. Climate publications are staffed by climate scientists. Articles for publication in climate publications are peer reviewed by climate scientists. None of them appear to be knowledgeable in dynamic systems with feedback and thus they are unable to recognize information that is readily shown to be false and should never have been published. Feedback means that the output (results, response) influences the input. Feedback can be positive or negative. Positive feedback means that the output is greater than it would be without feedback. Negative feedback means that the output is reduced from what it would be without feedback. Net feedback is the effective feedback when there are both positive and negative feedbacks. If net feedback is positive the trend must continue up at a progressive rate. The effect on a savings account balance with compound interest is a familiar example of net positive feedback. Complexity does not alter how net feedback works. Now look at any credible historic temperature data. To be credible, a temperature trace must be for a long enough time to average out cyclic variation from random noise and other factors such as ENSO. The temperature trace does not even need to be correct in absolute terms just reasonably valid in relative terms time-wise. It should also be substantially longer than any smoothing period that was employed in generating the data set. A temperature trend can not change direction from up to down if net positive feedback exists. If there is at least one change of average global temperature trend from up to down (a down trend of average global temperature can not exist with net positive feedback) without an overpowering external influence, it proves that net positive feedback does not exist. There are many and there are downtrends. Therefore net positive feedback does not exist. Without net positive feedback the climate computer models (GCMs) do not predict significant global warming from increased atmospheric carbon dioxide. There are other issues with GCMs and their use as described at 32 above. Climate scientists and climate scientist wannabes who claim that ‘the science says’ are simply ignorant of an important part of science that is relevant to the issue. Climate scientists, in their ignorance, impose net positive feedback on their GCMs which causes them to falsely predict that added atmospheric carbon dioxide causes significant global warming.
130946. DB2 at 06:50 AM on 23 October 2008
        Is Antarctic ice melting or growing?
        A 2008 paper by Monaghan and Bromwich takes a different approach to the Antarctica question. http://polarmet.mps.ohio-state.edu/monaghan/papers/monaghan_bams_7747.pdf They look at 50 years of temperature and snowfall records for the continent. With temperatures they note that "In contrast to widespread temperature increases globally, instrumental records indicate statistically insignificant (p>0.05*) seasonal and annual near-surface temperature changes over continental Antarctica from the late 1950s through 2000." Snowfall data has larger uncertainties and cyclical changes, but they write "there has been little overall change in Antarctic snowfall during the past 5 decades" When looked at on decadal time scales, atmospheric models indicate that snowfall over Antarctica could possibly rise by as much as 5% for each 1°C increase in temperature. The researchers write that "if global climate model projections of 2-3.5°C temperature increases over Antarctica by the end of this century are accurate a ~10%-20% increase in snowfall might be expected if the 1960-2004 sensitivity relationship holds." And in this regard, they note that "a 15% increase of Antarctic snowfall would mitigate an additional ~1 mm per year of global sea level in 2100 compared to today."
130947. chris at 06:37 AM on 23 October 2008
        CO2 lags temperature
        Really Quietman? What specific ("more recent..") evidence informs your opinion that the greenhouse effect doesn't supplement the Earth's global temperature such that we are around 30 oC warmer than we would otherwise be without the greenhouse effect (taking into account the variations I pointed out in 14 and positions of the continents and that sort of thing)? Which specific concepts that were "assumed it to be correct" are now "also incorrect"? In what manner specifically does the determinations "more recently" "point in the wrong direction"? Please be specific.
130948. chris at 05:26 AM on 23 October 2008
        Ice age predicted in the 70s
        Re #3: It's easy to be misled by the titles of papers. The examples you've asserted as supporting a 1970's perspective of global cooling don't actually do so. Your second article sounds like it does: Convection in the Antarctic Ice Sheet Leading to a Surge of the Ice Sheet and Possibly to a New Ice Age T. Hughes, Science Vol. 170. no. 3958, pp. 630 - 633 (1970) But it's just a potentially misleadingly worded title. If you read the paper it's got zero relevance to a possibility of a "new ice age" in the near (i.e. "near" from a 1970 perspective). It's about the GENERAL nature of ice Antarctic ice sheet advance that might (within a particular "surge" theory) be linked to the glacial cycles within the Pleistocene. So it's about how glacial periods might in general occur. That's very clear from reading the paper. It's also evident just from reading the abstract: abstract: "The Antarctic surge theory of Pleistocene glaciation is reexamined in the context of thermal convection theory applied to the Antarctic ice sheet. The ice sheet surges when a water layer at the base of the ice sheet reaches the edge of the ice sheet over broad fronts and has a thickness sufficient to drown the projections from the bed that most strongly hinder basal ice flow. Frictional heat from convection flow promotes basal melting, and, as the ice sheet grows to the continental shelf of Antarctica, a surge of the ice sheet appears likely." So it's a theoretical study of a mechanism for ice sheet advance during glacial cycles. It doesn't address the possibility of any such event during the current Holocene, and has nothing to do with 1970's scientific perception of global warming or cooling or any such thing. Likewise it's understandable why Peterson et al. didn't include your other paper as a "cooling"/Ice Age" one: Return of the ice age and drought in peninsular Florida? Joseph M. Moran, Geology 3 (12): 695-696 (1975) Although the title (and the rather odd abstract) might suggest that the paper is about the "return of the ice age", the question mark highlights the fact that the author is rather equivocal over such a conclusion. Here's how he ends his (very brief) note: "While there is an interesting parallel between recent and late-glacial events in the tropics, no clear cause-effect relation has been established between the current hemispheric cooling trend and precipitation trend in peninsular Florida. Also, even if a linkage were established, there is no certainty that the hemispheric cooling trend will not reverse itself in a few years. Rather than portraying a bleak future for Florida’s water supply, therefore, the observations presented here should serve as stimuli for further monitoring and research to promote understanding of the controlling atmospheric phenomena." In other words, the paper relates to precipitation trends with potential implications for water supply in Florida, and the author indicates that there isn't any necessary relation between cooling and precipitation trends and indicates anyway that the cooling trend might reverse itself. So neither of your suggestions - absolutely not the first one which is totally irrelevant to 1970's perspective on cooling/warming or otherwise, - nor the second one can be taken to support the notion of any 1970's scientific perception of global cooling (by the criterion that Paterson et al. set of a paper with a clear projection of climate change or discussing an aspect of climate forcing relevant to time scales of decades or centuries). Morgan's short note doesn't come to any conclusion - the "cooling" "...might reverse itself in a few years".
130949. Quietman at 03:10 AM on 23 October 2008
        Arctic sea ice melt - natural or man-made?
        Patrick Re: Ozone - Agreed Somewhere here there are links to papers on ozone that agree with what you said (I don't remember where).
130950. Patrick 027 at 15:47 PM on 22 October 2008
        Arctic sea ice melt - natural or man-made?
        ... But also: ozone chemical reactions will be affected by temperature. Temperature affects circulation. Ozone affects temperature. Circulation affects temperature and ozone. The enhanced warming at low levels in high latitudes, is strongest in the colder months, and might actually be reversed (reduced warming relative to some other latitudes, at least over water (?)) in some portion of the summer or near that time.

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