Open thread for various climate science-related discussions. Suggestions for potential future posts are welcome.
> .5% of the atmosphere being the absorbing gasses.
Leo G — think about plate glass, ordinary window glass.
Look through the flat side and it seems clear.
Look through it edge on — and it looks dark green.
What’s the difference? A tiny amount of material that absorbs some of the light, adds up over the distance.
Got one of those handy infrared thermometers?
Try this: http://mynasadata.larc.nasa.gov/P18.html
On the height, of course — remember that above the troposphere, the water has frozen out, so there’s very little water vapor to get in the way of a photon headed outward.
It’s not just the direction, it’s how many molecules can get in between between the photon and space. The higher you go the better chance the photon will depart the planet, not just because the horizon is “lower” than 50 percent but because the atmosphere is thinner going upward.
Credit for this image at the NASA link goes to Forrest Mims.
Try it at night on clear vs. cloudy nights too.
Ray @ 1097, another hmmm. On both pro and con sites i have visited, it appears that most info is that of re-emmitance. You are only about the third person who attributes collisions to release of a significant amount of the energy. This seems natural to me. But again, not a scientist, so have to unfortunately use my “spidey” senses all to often. :)
Jim 2 1098 – more homework? Thanx! LOL! If you lived here in Vancouver, you would probably pshaw that 4% stat in the middle of November. Sometimes it seems that it is 100%.
Hank @ 1100 – that was the second thing I did when i got my IR thermo (I specialize in radiant heating so it is a useful tool). Yes, I read somewhere that 90% of all our atmosphere is in the troposphere so that would make perfect sense about height allowing the photon to flee our world. :)
Again, thanx to all of you who are taking the time and sharing your knowledge.
# 1093 – “or a CERN experiment using real particles.”
gavin, I suspect that what Greg Goodknight was trying to say is that all the models in the world don’t prevent us from needing to build a particle accelerator to learn what will actually happen, not that CERN has anything to do with modeling the climate. Nonetheless, it is a poor example for making his point for two reasons.
First, there *is no* consensus model on what will happen when we switch it on because it is exploring a regime beyond our current theories. An exploration experiment cannot be meaningfully compared to a verification experiment where you are pretty sure what is going to happen but are just checking to make sure you are right. For an example of the latter, many experiments have been done to verify that our theoretical prediction for the fine structure constant is accurate, and so far they have validated the prediction to something like 10 significant figures.
Second, there *is* heavy modeling and simulations that will go on at the LHC in order to extract a very weak signal from a very large amount of noise, so if you don’t trust our ability to build models and simulations that can do this, then what you logically must believe is that the whole LHC experiment is destined to be a failure.
Comment by Greg Goodknight — 28 December 2009 @ 7:37 PM:
I am curious how you think the gotcha game is fairly played. You have come on here advocating that a small number of recent studies of a climate effect of, as yet, unknown strength and a poorly elaborated mechanism trumps sixty years of serious research on climate forcing, and then claim foul when called on your facts.
@Greg Goodknight — 28 December 2009 @ 7:28 PM
“…can we agree that a 100% increase in solar magnetic energy might also have a significant effect?”
It might have an effect, but if it does, it’s not obviously significant – see
Would you also like to comment on the correlations you see between O3 and GCR, magnetic field and GCR, and CO2 and Temperature in the graphs at
Leo, Ray is giving it to you straight: Until you get very high up in the troposphere, where there are far fewer gas molecules period, an excited greenhouse gas molecule is almost certain to relax through collision with another molecule (more likely a non-greenhouse molecule given that they are 99.5+% of the atmosphere), thus converting its quantum vibrational energy into ordinary kinetic energy, rather than through spontaneous emission of a new photon.
This is where those arguing that CO2 just doesn’t have enough heat capacity to account for much warming go terribly wrong: CO2 doesn’t have to have any heat capacity, it delegates that job to the other 99.5+% of the atmosphere.
And don’t confuse water vapour’s percentage of the atmosphere with relative humidity:
#1079 #1088 Greg Goodknight
Ah, the nobody will sufficiently fund poor Svensmark conspiracy. I saw that in his television show too. Was wondering if that would show up in thread.
Wasn’t the reason Columbus had such a hard time getting funding for his voyage because his calculations, distances and time scales were incorrect so the various science committees he visited said don’t fund this guy he is not very good at this… until of course he met a Spanish lady that … well, may have been enamored in some fashion…
I’m still waiting for you to show that current forcing is 7.2 W/m2. Remember, if GCR’s are causing our current forcing of 3.6 W/m2 and GHG also should be causing around 3.6 W/m2, to show that GCR’s are doing what you are saying they are doing, you need to show that current radiative forcing is 7.2 W/m2, or prove that the added GHG’s do not increase forcing (i.e. the added GHG’s are not GHG’s, only the pre-industrial GHG’s are GHG’s).
#1093 Greg Goodknight
Well, Gavin has a darn good point here.
Modeling data is a science not a game. You can’t just put a bunch of numbers in a bowl and someone holds it up in the air; then you pull numbers out one at a time and check them; and toss out the numbers you don’t like until you finally get the number(s) you like and voila, it’s GCR’s for the win causing current radiative forcing above thermal equilibrium to the tune of around 3.6 W/m2 with bounds.
PS I must apologize to you on one point. On my Svensmark page I did not have the link to the article Gavin pointed you too and that was the one I was thinking about. i have updated the page:
Re Leo G –
This is one of several misconceptions sometimes encoutered about gases and the greenhouse effect. Perhaps people get these ideas because people who otherwise know how it works try to simplify the explanation too much sometimes (ie the briefest explanation is that greenhouse gases trap heat, but that’s not very intellectually satisfying, is it?). Some schematic diagram might show the atmosphere as a single layer at some height that absorbs, emits, and reflects photons.
Composition – what is well mixed and what is not:
Many gases are actually quite well mixed in the troposphere and stratosphere and mesosphere and even up into the lower thermosphere – this layer of well-mixed gases can be called the ‘homosphere’, the layer above this is the ‘heterosphere’, and the boundary is the ‘turbopause’ (or ‘homopause’?).
The reason is that eddy-mixing generally dominates over molecular diffusion beneath the turbopause (until you get within a very short distance of the surface (or surfaces – leaves, etc.) – then molecular diffusion becomes important again, as does diffusion for heat transport).
Below the turbopause, the atmopshere decreases roughly exponentially with height because the downward pressure gradient produces an upward force that holds the weight of the air above, and the change in weight with height is proportional to the pressure itself (it would be exactly exponential if not for variable temperature, and of very minor importance in the atmosphere in general, composition, and of some importance very high up, the change in gravity with height).
Where molecular diffusion dominates, different components of the atmopshere decay in concentration upwards at a rate proportional to their own molecular masses, as if they were their own atmospheres (so that the average molecular mass drops with height, as atomic O, and then He, come to dominate, whereas N2 and O2 dominate most of the atmosphere’s mass) with variations from that driving upward or downward diffusion which balances chemical reactions and escape to space, etc. (photodissociation is more likely at high altidudes, synthesis reactions are more thermodynamically favored at higher densities, so larger molecules tend to diffuse upward while atoms tend to diffuse downward, … etc.).
(You might wonder, how could eddy-diffusion dominate over molecular diffusion in the stratosphere and lowermost thermosphere, which are so stably stratified? Well, molecular diffusion increases with decreasing density, and even though the stratosphere is stratified, there is still some mixing that occurs (I don’t know a lot of specifics thereof), and molecular diffusion is just so slow a process in most of the atmosphere that eddy diffusion still overpowers it.)
This all applying to neutral components – the magnetic field starts to dominate the motions of charged particles as collisions become less frequent going higher – this happens for electrons before more massive positive ions, so there is a region (The E region dynamo) where winds across the magnetic field can cause electric currents.
So gravitational sorting is a major mechanism for variations in composition above the turbopause (which technically could be defined at somewhat different positions for different constituents, because molecular diffusion occurs faster for some molecules or atoms within the same bulk gas).
What else causes compositional variations – answer, spatially-varying sinks and sources (chemical reactions in the air (ozone, CH4), physical reactions in the air (water vapor), fluxes to or from the surface of the Earth (water vapor, CO2, CH4, O2 …).
But in order to succeed in creating significant compositional variations, theses sources or sinks must be rapid relative to the rate of mixing. This is very much the case for water vapor, which is concentrated near the surface within the troposphere and has signficant horizontal variability. Ozone is also definitely not well-mixed.
I don’t know if CH4 stops being well-mixed at some height below the turbopause (UV radiation can break it down), but it is well mixed at least in the bulk of the troposphere. It oxydizes on the timescale of a decade or two, but mixing processes can overpower that (and the oxydation is not strongly concentrated to one small part of the atmopshere, although my guess is it’s slower in polar winters, since it is mediated by hydroxyl radicals produced by UV hitting water vapor, though the net reaction uses up not water vapor but oxygen, and produces water vapor and CO2, both in relatively small amounts compared to the water vapor and CO2 otherwise present, although the water vapor production above the troposphere has some significance (the branch of the water cycle above the tropopause is quite a bit slower than below, where the residence time of water in the troposphere is only a bit over a week)).
CO2 is essentially well-mixed. It is not perfectly constant – there are some variations associated with latitudinal and seasonal and regional variations in the sources and sinks – in the high northern latitudes (much land vegetation, significant seasonal variation) there is a significant seasonal cycle which is not as apparent elsewhere. Near the surface these variations may be larger – they may be especially large underneath forest canopies (with a CO2 diurnal cycle as well) – but these larger variations don’t have much of an effect on radiative forcing of the climate because they are limited to small volumes near the surface. (I think the seasonal cycle is also small enough to be neglected in determining radiative effects without much error – or at least, the error wouldn’t continually accumulate since it is a seasonal cycle). For radiative purposes, to a good first approximation, CO2 concentration (as a molar fraction of air) is constant.
Another distinction between the vast majority of the mass of the atmosphere and a the higher upper atmopshere – the lower freqency of molecular collisions has an effect on how air interacts with radiation.
In the absence of collisions, a molecule (or atom or ion, generally speaking) can absorb a photon and become excited. If it is excited it can emit a photon. They need not be of the same energy since there are generally multiple possible excited states. It might also be possible for a single molecule to transfer energy among states within itself ???.
(PS A group of molecules all moving at the same speed in the same direction will have a line spectrum, with some minor broadenning of the absorption/emission lines by quantum uncertainty effects. For a gas at nonzero temperature, the random motions of molecules introduces varying doppler effects that broaden the individual lines. — There is also pressure or collisional broadenning, caused by molecular/atomic collisions; this form of broadenning dominates at least in the lower atmosphere.)
But collisions change things. If collisions are frequent relative to the photon absorptions or emissions, an excited molecule likely will transfer it’s energy as heat to the whole of the air, and a molecule likewise can become excited by molecular collisions and then emit a photon. Thus, the essentially transparent gases (for LW radiation at least, O2 and N2) gain and lose heat energy by the absorption and emission of photons by the gases with significant absorption/emission cross sections**. If there is radiative heating, this will tend to heat the gases or other agents that are absorbing radiation, but molecular collisions transfer this heat to the whole air, and keep the different substances within the air at nearly the same temperature locally; etc. for cooling. Note this process of thermalization also tends to result in a distribution of thermal energy in thermodynamic equilibrium (with molecular velocities fitting a particular statistical distribution, and so on for excited states, etc, including distribution of energy among the different states within molecules) – this condition is called local thermodynamic equilibrium.
HENCE, it is generally innacurate to say photons are absorbed and then ‘re-emmitted’. The gases which have absorption spectra emit photons at a rate according to their temperature.
I think (but am not sure) that local thermodynamic equilibrium is a good approximation for conditions up to 70 km – this encompasses the vast majority of mass and opacity (properties that affect radiative fluxes) of the atmosphere.
It is important to note that most to almost all of the radiant energy emitted by the sun and by the Earth and atmosphere and other planets is emitted by processes occuring at local thermodynamic equilibrium and thus obey the statistics of blackbody radiation for the temperatures of the emitting masses. An example of emission from a process not at local thermodynamic equilibrium is fluorescence. A population of energized particles within a mass that don’t fit into the thermodynamic equilibrium distribution may be described as ‘hot’.
**(statistically, a molecule or absorbs and emits photons in a particular direction as if it were a perfect blackbody with a particular cross section facing that direction; typically, molecular orientations are random within a gas, so the same effective cross section should face all directions, as if the molecule were a spherical blackbody of that size. Note that if there were pure scattering, a particle has an effective scattering cross section, and for isotropic distributions of orientations, it would be as if the particle is a mirrored sphere (except, scattering is often not isotropic relative to incident photons). The extinction cross section is equal to the sum of absorption and scattering cross sections. A particle that has both scattering and absorption cross sections may act as a partially-mirrored ‘gray’ object, but it is mathematically equivalent to consider the effects on radiation as the effects of two seperate objects, one only scattering and one a blackbody. The density of (extinction, scattering, absorption, emission) cross section in a unit volume is equal to the contribution of (extinction, scattering, absorption, emission) to optical depth per unit length; along a path, for a given population of photons moving in one direction, the fraction transmitted over a given optical depth is equal to exp(-optical depth); in other words, it decays exponentially over optical depth. exp(-optical depth) = trasmissivity; 1- exp(-optical depth) = absorptivity if the optical depth is entirely due to absorption. At local thermodynamic equilibrium, *** emission cross section = absorption cross section, where the emission cross section is the effective cross sectional area that emits as if a perfect blackbody in the direction it faces, so absorptivity = emissivity, so at local thermodynamic equilibrium the fraction of incident photons from a direction that are absorbed over a given path is equal to the fraction of blackbody radiant intensity that is emitted from that path length in that direction. Over an isothermal expanse with pure absorption/emission, the intensity of the radiation emitted in a direction exponentially approaches that of a perfect blackbody of the same temperature with increasing optical depth in the same direction – it doesn’t keep increasing without bound because as the intensity approaches the blackbody intensity, absorption per unit distance approaches the same rate as emission per unit distance, so the intensity approaches an equilibrium with the material. If temperature is changing along optical depth, however, then the intensity of the radiation is always catching up to the blackbody radiation for the temperature at a location, and the difference is larger if the temperature variation is larger over a smaller optical depth; this causes a difference in radiant intensities in opposite directions, so that there is a net radiant intensity directed from higher temperatures to lower temperatures. Note, however, that if the temperature fluctuates up and down over sufficiently small optical depth, then the direction of net radiant intensity at a given location isn’t necessarily in the direction determined by the temperature gradient at that location, as it is affected by temperature variations at more distant locations. Generally, the net radiant intensity is affected by the temperature variations that are ‘visible’ from a given location. The shorter the distances that photons travel between absorption and emission relative to the length scales of temperature variation, the smaller the net fluxes. Scattering of radiation can further reduce the distances that photons travel between absorption and emission. It is possible to build a greenhouse effect based on pure scattering, but in that case, the only temperature that is relevant is the surface.
***Note that this works along one particular path for one specific wavelength (and where relevant, polarization (ice crystals can hang in the air with preferred orientations), and where relevant, phase (ie if optical properties fluctuate at a rate comparable to frequency of radiation, then … but that’s of little importance in this context). Because blackbody radiant intensity varies over wavelength (or frequency) and because optical properties can and do vary with wavelength (or frequency), the total effect can be complicated, and the absorptivity for all radiation is not generally equal to the emissivity for all radiation, for example, even at local thermodynamic equilibrium.
To find radiative fluxes across an area or in the direction normal (perpendicular) to that area, it is necessary to sum intensities over solid angle (a unit solid angle is like a bundle of directions; solid angle is measured in steradians; there are 2*pi steradians in a hemisphere). Intensity is the flux per unit area per unit solid angle in that direction. Because the flux per unit area is less if the same intensity of radiation is slantwise relative to the unit area, the intensities must be weighted by the cosine of the angle from normal before summing to find the total flux per unit area. Thus, for isotropic radiation (same intensity over all directions) the flux per unit area is not equal to 2*pi * the intensity – it is actually just half of that.
The result is that, of a given initial population of photons at a given frequency (or wavelength) and, where relevant, polarization, etc, that are emitted upward or downward across a horizontal surface, with an isotropic intensity distribution, or any distribution over multiple directions with different angles from vertical, the transmitted fraction over vertically-measured optical depth doesn’t decay exponentially, but decays as a sum of exponential decaying components, with those at the most slantwise directions decaying most rapidly per unit vertical distance.
But qualitatively, the effect is similar to considering radiation in one particular direction.
The temperature of the surface and the vast majority of the atmosphere is too low to emit much at wavelengths shorter than about 4 microns, whereas solar radiation is mainly at wavelengths shorter than 4 microns. Thus, it is convenient to divide the spectrum into two major parts, SW radiation (shorter than about 4 microns) and LW radiation (longer than about 4 microns).
The surface and atmosphere are heated by absorption of SW radiation; there is significant scattering of SW radiation, and some of the scattered radiation is not ever absorbed by the atmosphere or surface but is instead reflected back to space.
The greenhouse effect is based on opacity (effects of scattering and effects of absorption/emission) for LW radiation. For Earthly conditions, scattering is a minor issue for LW radiation. Opacity to LW radiation is contributed by water vapor, CO2, clouds, methane, ozone, and a few other gases. Each of the gases has it’s own absorption spectrum. Clouds tend to have more similar effects over a broad range of wavelengths.
Because of general decreasing temperature with height in the troposphere****,…
****(effective global temporal average effect, can vary over diurnal cycle, season, and region, some inversions are found within the troposphere, such as at poles, especially in winter, where the atmopshere is heated by horizontal transport of air from lower latitudes and the surface is not heated much or at all by SW radiation but continues to cool by emitting LW, some of which goes directly to space (air also emitting LW radiation upward and downward, but doesn’t cool to the same temperature of the surface by the time it reaches that location, and downward LW radiation to the surface is less than surface LW emission; there is also some sensible heat transfer to the surface under such conditions (mixing? (can be forced by winds even when the atmosphere is stable to vertical overturning), conduction at the surface),
…increasing LW opacity within the troposphere reduces the upward LW flux at the tropopause. Increasing LW opacity within the stratosphere also increases the downward LW flux at the tropopause except at the point where the stratosphere has hidden enough of the darkness of space, so that further increases in opacity actually reduce the downward LW flux because of the increase in height within the stratosphere – although it should be noted that at some latitudes and seasons, the increase in temperature with height does not occur in the lower stratosphere. As opacity increases, the upward and downward LW fluxes at the tropopause approach each other as the photons going in either direction are coming from regions with more similar temperatures. When the net LW flux (upward – downward) approaches zero, the effect is saturated. Externally-forced changes to either the net SW or net LW flux at the tropopause level is called tropopause-level radiative forcing.
CO2 tropopause level forcing is saturated near the center of it’s absorption band, but the shape of it’s spectrum is such that, after such saturation, as CO2 is doubled, the width of the portion of the band that exceeds some amount of opacity increases by some amount, so the effect over the LW spectrum is a radiative forcing logarithmically proportional to CO2 amount.
Tropopause level forcing is often given for an equilibrated stratosphere. Generally, increase LW opacity can increase stratospheric radiative cooling, and with the troposphere and surface conditions held fixed (not entirely unrealistic – the temperature response times tend to be longer than in the stratosphere because the troposphere is convectively coupled to the surface, which includes the ocean, which has a large heat capacity), the stratosphere reaches a temporary equilibrium by cooling. For solar brightenning, the stratosphere will instead warm to equilibrate temporarily. These temperature changes cause changes in the LW flux at the tropopause, so the effect on the troposphere and surface (*#*) see below) are more comparable to tropopause level forcing by different types of forcings (solar vs greenhouse vs other) after stratospheric equilibration is taken into account. The stratosphere will again change and have some feedback as the troposphere and surface respond, but those changes will be similar for similar tropospheric and surface responses (*#*).
(*#*) The temperatures at each level within the troposphere and at the surface are convectively coupled****(see above) (because radiative fluxes alone tend to make the lower atmosphere unstable to convection****(see above) ), so that changes in radiative heating and cooling at one vertical level tend to cause a convective heat flux response that spreads the heating or cooling change vertically; thus, the troposphere and surface tend to shift temperatures together in response to tropopause level forcing (but with regional, latitudinal, seasonal, diurnal, etc, variations from that general pattern, due in part to general circulation structur, the spatial concentration of surface albedo feedback, and also, the temperature dependence of the moist adiabatic lapse rate – **** see above). This isn’t to say that the climate isn’t affected by changes in radiative heating or cooling vertical (and horizontal, for that matter) distributions within the troposphere – it is, because the rates of convection matter, and circulation can affect cloud and humidity distributions and temperature distributions, etc, but in this regard, I think*****(not completely sure?) the radiative feedbacks (water vapor and surface albedo feedback in particular, and the general spatial-temporal temperature change pattern within the troposphere and on timescales longer than diurnal) to global average temperature change tend to produce similar results to the same global average tropopause forcing that overwhelm the differences in forcing by different gases (CO2, CH4) or by the sun, etc, so long as the forcing patterns are not too idiosyncratic.
The effect that a gas or cloud has is reduced by the presence of other gases or clouds – for such gas-gas interference, this depends on overlaps in the absorption spectra. Generally, most such overlap involves water vapor, although I think there may be some overlap between CH4 and N2O. Important point – in terms of potential to absorb radiation from the surface over the whole of the troposphere or atmosphere, the water vapor overlap may be larger than in terms of tropopause-level radiative fluxes. This is because water vapor is concentrated in the lower troposphere, and thus tends to be relatively warm. Of the parts of the spectrum at which water vapor is significantly opaque for the whole troposphere, there are portions that are relatively transparent in the upper troposphere. Other gases and higher level clouds can reduce upward LW radiation at the tropopause by hiding the warmer water vapor that is closer to the surface. Similar considerations are required for clouds.
See also some of the discussion here
Thank you so very much for this explanation of the conflict between libertarianism and AGW. It explains so much!
It often seems that there is a basic confusion (e.g. in the new model – data comparison post) with some posters about what a typical ‘climate’ model consists of.
Making the generous assumption that there is genuine confusion and not just trolling, maybe it would be useful to find some way to stress that the various climate models are physical models, built on inputs and physical interactions, not statistical models fitted to observation ( and describe the exceptions of sub grid scale features etc).
On the other hand, this kind of information is readily available here and elsewhere. It just seems that sometimes a whole series of posts saying things like ‘i could fit any random proxy to that data and match as well as the climate models’ or ‘the models don’t prove a link between CO2 and temperatures as any rising index would work the same’ could be prevented with a little bit of climate model fundamentals.
[Response: Check out the FAQ (and Part II). – gavin]
Leo G., look up equipartition. All the IR radiating from the warm surface causes an excess of energy in the CO2 vibrational mode. Energy tends to equilibrate among all the active modes of a system, so energy has to flow into the kinetic energy modes. Also, the CO2 vibrational state in question is long-lived, so there is plenty of opportunity for collisions to occur.
Greg Goodknight, I’m all for the CLOUD experiment, but doubt whether it will be “clean”. They’re trying to do something very difficult. It’s interesting, though that you seem to reject all the other experimental evidence that shows CO2 is a significant warming agent. For instance, you don’t even acknowledge the other phenomena I mention that a GCR mechanism could not explain. Now why would that be?
Present human power use averages about 13 terawatts, that is to say, 1.3 x 10^13 watts. The surface area of the Earth is about 5.1007 x 10^14 square meters. Therefore the power use, 100% converted to heat, corresponds to 0.025 watts per square meter. By way of contrast, the solar flux absorbed by the climate system is 237 watts per square meter.
Divide A by B. Discuss.
Greg Goodknight: I find the cosmic ray theories in light of an energetic sun (an 8000 year maximum in the latter 20th century, if you believe Solanki) to be more convincing than an unverified positive feedback warming teased from a 0.01% increase in the fraction of the atmosphere that is CO2, *some* of which is from fuel uses.
BPL: GCRs have been stable for 50 years. Global warming turned up sharply beginning about 35 years ago. Meanwhile, CO2 correlates with temperature anomalies to the tune of r = 0.874, which physicists and statisticians refer to as “pretty damn close.”
Here are six good reasons the sun is not causing global warming:
Here is the CO2-temperature statistical relation:
And here is the physical mechanism:
To my way of thinking it is looking like the “Myth of Sol” might be a future post. Ironically, the sun is used to “prove” the arguments of both warmers and skeptics.
A second good topic would be the water vapor response, forcing, feedback or both? Gavin’s blanket analogy was as bit simplistic. The climate’s response to increased water vapor is a touch unpredictable both in the next impact of increased cloud cover (blanket or reflection) and quite possible increases in convection.
The physics of co2 as a greenhouse gas is about played. Yes, co2 gets excited by LW and re-emits. Move along nothing to refute there. The temperature change due to a doubling of co2 alone is pretty clear as well, approximately 1 degree C. Arrhenius, BTW was attempting to prove co2 variation caused glacial interglacial periods. His estimated impact tended to follow his preconceived notions instead of science. A pitfall that all should avoid.
And Gavin thank you for this interesting unthreaded.
Greg Goodknight: The seven day delay between a strong Forbush event and the detected decrease in cloud cover is another SKY/CLOUD mechanism.
BPL: It’s especially interesting in light of the fact that the average cumulus cloud lasts only 20-30 minutes.
Gavin, something that might be interesting —
EOS V90 #50 15 Dec. 2009
“Earth Sciences Push Radiative Transfer Theory”
“2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics”
No– this is NOT another “nukees” topic. It’s about math, and about how the same equation describes both radiative transfer (RT) and particle transport, “so geophysicists and nuclear scientists are interested in the same mathematical and computational techniques…. there were two sessions of immediate interest to the geophysics community: “Radiation transport in the Earth sciences” and “Transport in stochastic media.” The former session was composed almost entirely of invited papers by RT experts in … especially the cloudy atmosphere. The speakers showcased progress, often at the fundamental level, capitalizing on the common mathematical language….”
That’s my nomination for a differently managed topic, one with axe-handle moderation, no crap, no nonsense, no nitwits, and an invitation to some very patient teacher who can use it to address the fascinating, wonderful thing about reality — that one equation turns out to have great power understanding two very different real-world situations.
I know this happens in science-and-math. I know it’s wonderful when it does, because it illuminates areas and brings scientists from what would be thought completely different areas together to do the math.
If you all can get at this as a teaching tool, it’s a basic lesson in how science works and how math is wonderful. Maybe AGU will do it anyhow — but it brings together climate and nuclear science and engineering, both topical now.
I don’t pretend I could follow the math. But I could follow _people_ who follow the math. Maybe set up a separate invitation-only discussion to go through it the first time, filtering for sincere effort to learn, then make a public teaching tool out of it.
Oh, I know, I’m asking for more of your copious spare time (wry grin).
“(ie the briefest explanation is that greenhouse gases trap heat, but that’s not very intellectually satisfying, is it?)”
Amen. I like your approach.
I sometimes wonder if a compilation in simple list form of the variables, constants, and parameters used in some representative models wouldn’t sow a little cognitive dissonance in those who tend to make dismissive characterizations of the computer modeling.
Hi, Paul (#1053), I’m pretty much in agreement with you. Scientists are false-positive conservative, and it could very well be we have passed variou tipping points (esp since the climate is so sensitive to very small perterbations — acc to Hansen’s STORMS OF MY GRANDCHILDREN). I think I typed too fast about this thermostat thing, and how we could bring us back to a very good climate state. I know that in the pipes are already terrible disasters, wars, conflicts, a vicious, killer musical chairs over ever-diminishing life supports (food, water, habitable areas).
At this point we could choose to end the party of proligacy and gluttony (which is making us sick in many many ways anyway, and killing our spirits), and cut our losses from AGW. Those people (our descendents) who might survive into the future would also need some of the energy/resource efficient/conservative & alt energy measures and technology we create and implement.
Of course, we may also need to start digging mass graves, then millions of years from now, assuming we don’t go into the Venus syndrome Hansen talks about and there are still people extant, they could be faced with our dilemma — use that coal/oil (us) & start another massive die out through global warming, or keep us in the ground. (I actually thought of a movie that could be made of such an era — COME HELL AND HIGH WATER.) Of course, they won’t have any ancestral respect for us/coal — they’ll probably even be spitting on us — so that won’t be the issue. The main issue would probably be the threat of global warming in conjunction with a brighter sun beating down and a more fragile state. Unless of course there just aren’t any scientists, bec it’s all hand-to-mouth existence, and they just don’t know any better. Well, that sounds a bit like today, considering how people ignore the scientists, except now its a matter of striving to protect our profligacy-to-gluttony existence.
Patrick, I have copied and pasted your answer into my homework file (and I thought reading through Hawkins “A Brief History of Time” was tough. Man you guys must be very strict teachers! LOL!). Thanx for your time and effort.
Ray @ 1112 – yes this seems more “real” to my way of understanding. Sorta like the old sight expirement from science 10, rolling ball bearings in a pietry dish. Difference is that the “energy” imparted to CO2 is not from my hand moving the dish. Thanx again.
#1069 Greg Goodknight
I read 2.3.2 (Laschamp event) in the Kirby paper and the conclusions, and am wondering how this supports the case for warming based on GCR’s? There’s no smoking gun here, and the ambiguities are pretty large. Pardon my cherry picking, but I did not want to post the whole section here.
“No evidence of climate change was observed in the GRIP (Greenland) ice core during the Laschamp event .”
Granted GRIP is not global but there are more models than grip for the past 100kyrs. Also, granted, there were several climatic effects coincident with the Laschamp event. But where is the global temperature rise? We know that the PDO and AMO, etc., affect specific regional weather/climate on specific related time scales so it would not be out of the realm of feasibility that the Laschamp event may have caused, or been part of a cause for climatic variation, but of course correlation is not causation.
The GRIP data showed that Laschamp coincided with a Dansgaard-Oeschger event. So maybe that caused, or was the major cuase of the regional climate change?
A brief, sharp reduction of North Atlantic deep water (NADW) production was recorded (i.e. towards colder conditions), coincident with the Laschamp event.
But this could be related to deep ocean heat content overturn related to the Dansgaard-Oeschger event, thus supporting the idea that the climatic variations were not GCR related.
The Laschamp event was 40kyrs ago. There have been a lot of temp models from various sources showing the past 100 kyrs. Where is the big temp rise??? Let us not forget that the geomagnetic field, according to the paper, fell to around 10% of its present strength. Where is the warming???
The line of reasoning is pretty darn far from a smoking gun for GCR’s. When combined with GCM’s and industrial GHG that are quantified in amount and relative forcing… you simply don’t have any other mechanism?
Yes, I might not know what I’m talking about but to me this is pretty simple reasoning when in the absence of another mechanism and while we have the smoking gun of quantitative GHG’s and CO2 (minus C-14), including their relative radiative forcing… this should falsify your conception on GCR’s or at least make you think about what is really more likely to be driving the positive forcing now.
I’m wondering if you had read this?
There was a post about water vapor and its feedback:
Greg Goodknight: RC has made it clear the opinion here is that the lack of gcr trend since the mid 50’s means that gcr as a significant cause of warming, but since that doubling was already underway by then it would seem to me the lack of a later trend does not falsify the gcr theories.
BPL: Then what would falsify it? Please be specific.
Oh, dear: “archeomagnetic jerks”
Energy & Environment, January 2009 –
Climate Change And The Earth’s Magnetic Poles, A Possible Connection. adriankweb.pwp.blueyonder.co.uk
Some requests for future topics:
1) Our knowledge of the distribution of vegetation during periods in the past that represent climates that may occur again due to global warming. Specifically the Pliocene (3 million years ago, for 3 degrees C), the Eocene (50 million years ago, 5 deg. C) and the Cretaceous hothouse. Can we answer questions such as were deserts larger or smaller than today, and with what certainty?
2) The possibility of a runaway greenhouse due to extreme anthropogenic CO2 emissions, compared to conditions during the Cretaceous hothouse and the recovery from the Snowball Earth episodes.
3) In section 18.104.22.168 of the 2007 AR4 report (WG1), the text seems to suggest we can constrain solar variability by observing the many other stars that are similar to our sun. If this is true, it would be nice to have a guest post from an astronomer commenting on how this is done, and to what resolution.
Re Blair Dowden – runaway greenhouse effects –
The term runaway (in the context of positive feedback) generally refers to a climate sensitivity that is either infinite or negative. It must be noted, however, that this can happen within certain ranges, so that a runaway feedback stops at some equilibrium where climate senstivity goes back to being finite and positive.
Examples – the runaway positive feedback that occurs when the 0 deg C isotherm (and/or neighboring isotherms, taking into account effect of salinity on freezing point…?) is at sufficiently low latitudes (note the point at which this occurs depends on meridional heat fluxes (and I have seen a diagram which showed that for some conditions the climate is unstable again when the ‘ice line’ is at sufficiently high latitudes), which, among other things, should tend to be smaller when the Earth spins faster (I think), as it did in the geologic past…) occurs because, along with whatever mix of feedbacks exist, a change in position of the 0 deg C isotherm leads to a net positive feedback that causes a change in temperature that causes a greater change in position of the 0 deg C isotherm, etc. But this condition does not occur when the isotherm is sufficiently far from the lower latitudes, and also, the feedback gets dramatically weaker when the lowest latitudes freeze over.
Water vapor feedback – when the temperature gets sufficiently high, the water vapor feedback is strong enough that increasing temperatures don’t increase the outgoing LW radiation anymore. Thus, if the radiative forcing is just somewhat smaller, the temperature will decline until the runaway condition is eliminated, and the outgoing LW radiation starts to decline; if the forcing is somewhat larger, warming continues until a new regime is reached where outgoing LW radiation again increases. (with caveats about Top-of-atmosphere vs tropopause level, etc…)
It must be noted that if the temperature ever did get so high as to reach such a runaway water vapor feedback, it wouldn’t be a permanent condition; a change in forcing could still result in cooling back to a stable climate, assuming the oceans haven’t boiled off (takes time) and the CO2-drawdown by weathering has shut down leaving geologic emissions to accumulate (takes time).
So a short-lived extreme forcing would still fail to lead us to Venusian conditions. I don’t think we could get there if we tried. That’s not to say that extreme damage couldn’t be done even falling far far far short of runaway feedback.
However, just as the runaway surface (snow/ice) albedo and water vapor feedbacks occur within limits, it’s possible to suppose smaller scale runaway feedbacks. In the limit of small, what if you looked at a graph of equilibrium temperature over forcing, and under a magnifying glass, found that it had a number of sharp steps in it. In a vague way this does happen (ie on a day sometime in the future, conditions will occur so that once a cumulus cloud has reached a certain point, it will continue to grow without additional forcing because of the latent heating) although the butterfly effect eliminates any meaningful relationship with such ‘micro-tipping points’ in the context of longer-term climate. On a larger scale more relevant to climate, … biogeochemical feedbacks involving CO2 and CH4 (? I’m not suggesting that I suspect that these lead to runaway feedbacks)- but even if these did form a runaway feedback within limits between stable equilibria, it might not seem that way if the response time is large compared to the the time that the external forcing is above the threshold…
From the WSJ – maybe a start to reduction?
Spaceman Spiff: Read what I wrote and what you quoted again. I said that there are variations in the 11 year cycle, and in a separate post I have noted the long term solar variations on top. However, we haven’t a working model for any of it except a crude version of a generic 11-yr/22-yr sunspot/magnetic cycle, and even in this case I don’t believe the results are ab initio (although this is not my field, and I’d have to go read the more recent literature).
1. “cycles” are different from “variation”; although not ab initio, the models have been fit to past oscillations (not quite periodic), and have made predictions about the future. If the predictions are proved to be accurate (this will take decades), then interest in the mechanisms will become more piqued.
898, BPL, thanks for the links. I do not find them as persuasive as you do. More later, perhaps. For now I just want to acknowledge reading them. About this: That it exists only in the minds of denialists, Prof Trenberth expressed concern, that he later tried to walk back, and Motl has also expressed the belief that warming has temporarily ended (possibly for decades.) It isn’t just denialists.
850, tamino: As for your claim that I “used a statistical technique with very low power to detect a change,” you just made that up to throw some dirt on my analysis.
Are you saying that you are unfamiliar with the concept of statistical power? True, the Chow test may have a high false positive rate if the error degrees of freedom are not adjusted for autocorrelation of the residuals, but the method you used has a low power to detect changes if they are there.
Once again, so many straw men.
Barton Paul Levinson, (1124) falsification is typically achieved when a theory predicts something that is not true. What do you think has risen to that level by the GCR theories? By Solanki, the sun’s magnetic output increased dramatically in the 40’s, and remained in that high magnetic energy state until very recently. It doesn’t take a “trend” in GCR flux to present a continued forcing during that time, approaching that attributed to CO2 with theorized positive feedbacks. We have a Forbush event measurement showing the equivalent of a 2 watt per sq. meter forcing. Larger than that needed from CO2 effects to account for the 20th century warming. We don’t know how much of the 20th century forcing was due to GCR, but it is non zero and it can conceivably be nearly all.
[Response: ‘Non-zero’ is a truism, but actually you don’t have any idea what sign it is likely to be. If this effect is more than negligible (still not determined), the impact it will have on the forcing depends very strongly on where and when and at what altitude any clouds might be affected. There has been no calculation of this from the CLOUD group or Svensmark. This has of course got be a simulation, since it is not observable, and when it has been done (such as by Pierce and Adams) (and they are not the only ones to have done this), it shows a very small impact. You can’t keep saying that this is a big effect (and still be credible) if you ignore the need for such calculations, and then ignore the results when they don’t go in your preferred direction. There is still uncertainty here and maybe newer calculations will show larger effects, but maybe they won’t. – gavin]
BPL, (1117) You’re confusing the creation of cloud condensation nuclei with the appearance of visible moisture condensing about the CCN when conditions are favorable.
Reisman (1122) Yes, I read Pierce and Adams. It would seem the paper by Svensmark et al. actually finding a large cloud response to GCR in the real world trumps the simulations of reality that suggested they couldn’t. Also, the 20th century forcing found (iirc) for CO2 by the IPCC was closer to 1.6 W/m2.
Gavin (response to 1093) — It isn’t a “sneer” to note that if a conflict between an observation of reality and a simulation exists, that reality should be declared the winner, and no sneer was intended. Just a reality check.
By the way, I do appreciate the Glasnost shown in this thread, I do hope it’s a permanent change to RC’s mode of operation.
Matthew: Motl has also expressed the belief that warming has temporarily ended
BPL: Motl is a good physicist, but a raving lunatic when it comes to climate science. I dissect his “it’s cooling!” example here:
GG: I do appreciate the Glasnost shown in this thread, I do hope it’s a permanent change to RC’s mode of operation.
BPL: Gee, you’re not a troll, are you, Greg? A troll would never accuse his opponents of being Communists. That would be provoking. “Glasnost” my aunt’s purple asterisk.
It’s dangerous to accuse an old anti-Communist like me, who lost family to the GULAG, of being a Communist. Just letting you know.
If reality/observation trumps simulation, care to explain why the Laschamp excursion saw loads of GCRs hitting the earth, and the climate responding by…not changing?
If you believe the Svensmark hypothesis, there should have been a massive response. There was none.
Barton Paul Levenson says:
All true. But how the climate responses is still a mystery. One thing not often discussed is the convection issue. More water vapor can and should lead to more storms that should increase the convective release of energy. Also increased water vapor should lead to more cloud cover that could be feedback or forcing. It is an interesting puzzle that is far from solved.
BTW I don’t know if you want to label me as a skeptic, denialist or butthole but climate is a touch chaotic. I often refer to Tosnis and his use of chaotic math to try to sort out natural versus anthropogenic sources of climate change.
The atmosphere is a huge reservoir that is capable of buffering short and long term impacts in a variety of ways. While we may be on a path to destruction, mother earth may be smarter than we think. It is time for us to attempt to expand our knowledge of our environment not to blindly accept studies with known high margins of error. The total impact of water vapor in a changing climate is the least understood of all the GHGs. Worthy in my opinion of further scrutiny.
For the data page: Climate Wizard (h/t Gareth)
Suggestions for threads:
State of the art of modelling the ice sheets (WAIS and GIS) and predicting their disintegration modes (eg through oceanic coupling).
State of the art of including ice sheet dynamics in GCMs.
Suggestion for threads:
Methodologies for assessing climate risk metrics for input into corporate risk assessments.
Now here’s something I don’t understand. On the one hand, (1)we have a mechanism that is part of the standard model of Earth’s climate. We know with 100% certainty that this mechanism is operational. We have a very good idea of how it works, the forcing it provides. The mechanism explains not just the warming in the late 20th century, but many other phenomena as well, and it has strong support from many independent lines of evidence and confirmed predictions, many of which would be difficult to explain any other way. On the other hand (2)we have a putative cause where we really don’t understand the mechanism; the evidence of whether it is even operational is weak and conflicting; we have no working model for it; to even posit this mechanism you have to posit some very strange post hoc delays in the climate system; and the sole reason why it is posited is to explain late-20th Century warming. Hell, really, it is no more than a gleam in the eyes of a few solar physicists.
Now, tell me: What possible scientific rationale would there be for choosing 2) over 1)? Doesn’t this strike you as an astounding example of special pleading? I mean just how big a curve do you want us to grade your proposed cause on?
Gary Goodnight, you wrote “It doesn’t take a ‘trend’ in GCR flux to present a continued forcing during that time, approaching that attributed to CO2 with theorized positive feedbacks.”
As I already responded (twice) to your previous such claims, any forcing that becomes constant must result in Earth’s energy imbalance shrinking as outgoing radiation rises in response to rising temperature. And that’s not happening. So the lag from change in GCR flux before the 1950s cannot be this long. Same reason the increase in the Sun’s radiance up to the 1950s cannot have its effect lagged. See the links in my previous responses.
An old question worth another look — evaporation, heat engine power for storms as oceans warm (less difference in temperature means a less powerful heat engine, if I recall correctly — which goes against the ‘stronger big storms’ idea, and also suggests less power behind the transport of humid warm air from the tropics up to higher elevations).
I tried to find the paper I remembered on this from a few years ago (I think the author commented on it in a thread at Tamino’s) and didn’t find that. But I found a more recent paper:
Dear RC, a lot of your readers put in a lot of time trying to understand climate. And some of them do very well creating their own blogs for the purpose of public education etc. But most of us learn a little bit and then go and argue with people on this or other blogs. It seems like maybe there’s a better way that all of this energy can be put to use. Can we help the science at all?
There’s climateprediction.net, which is pretty cool. And I actually think that the surface stations project was interesting — it wasn’t done with cooperation in mind (actually, I don’t know much about it), but perhaps it is an indication that something useful can be done with folks’ energy, given proper guidance. The only other examples I can think of (not climate-related, though) are Christmas bird count, and some shore clean-ups that document the kinds of garbage found.
#1130 Greg Goodknight
Based on the peer reviewed work and the peer response to that work your assumptions and beliefs are tantamount to wishful thinking on your part.
You apparently have not realized that the warming is already accounted for with GHG’s. Again, I reassert, if you are correct and current continued forcing is attributable to GCR’s the total current forcing must be around 7.2 W/m2, or GHG’s are not GHG’s (in other words, if you are right and GCR’s are causing the bulk of current radiative forcing changes, then adding GHG’s that are well known to trap heat in our atmosphere will have no effect and therefore are not GHG’s).
Your pointing out that forcing for CO2 by IPCC being around 1.6 W/m2 (1.49 to 1.83) is indicating that you are ignoring other forcing components such as:
– Tropospheric Ozone
– Black Carbon on Snow
Please state for all here that you actually believe current radiative forcing to be 7.2 W/m2 so that we can confirm your inferred assertion.
The convoluted manner of your assertions ignore mountains of well understood.
I think it is important for you to realize that wishful thinking is not scientific evidence.
So again, I ask are you saying GHG’s are not GHG’s?
Are you saying GHG’s are GHG’s and current radiative forcing would then be estimated on the mean to be around 7.2 W/m2?
These are pretty simple questions and you still have not answered them, though I have asked repeatedly for you to explain your contradictive assertions.
If it’s GCR’s, GHG’s are not GHG’s or have much lower heat trapping potential than is currently well know.
YOU ARE SAYING THE MAJORITY OF SCIENTISTS FOR THE PAST 150 YEARS ARE WRONG. PLEASE PROVIDE ‘EVIDENCE’ TO THIS ASSERTION OR STOP POSTING STATEMENTS CLAIMING THAT YOUR ‘WISHFUL THINKING’ (ARGUMENT FROM IGNORANCE AND/OR NAIVETE) IS SCIENTIFICALLY ACCEPTABLE.
Greg Goodknight says: 30 December 2009 at 5:17 AM
“By the way, I do appreciate the Glasnost shown in this thread, I do hope it’s a permanent change to RC’s mode of operation.”
Considering the truly abysmal quality of many posts appearing here, I have to believe that all these dark mutterings about deleted posts are just another gaming tactic. “Oh, that RC, all the -good- contrarian posts are censored, they try to make us look bad by only letting lunatic oppos post there”.
But maybe that’s true. You think?
a 2 watt per square meter solar forcing, more than equal to the best guesses for CO2 warming
Leaving CO2 aside for a moment, the expected effect of a 2 W/m^2 radiative forcing change can be estimated fairly accurately. The equilibrium temperature (in degrees Kelvin) of a planet is given by:
T = k S1/4
For all planets, except Venus, the value of k will be about 46 and no more than 48, even counting albedo and everything else. The value of S for Earth is roughly 1366 W/m^2.
You can do the math to estimate the effect of a 2 W/m^2 change in solar irradiance. It’s no more than 0.2C.
[Response: Earth is not a black body and even if it was 2 W/m2 in forcing is equivalent to 11 W/m2 in solar irradiance. -gavin]
BPL: BPL: Motl is a good physicist, but a raving lunatic when it comes to climate science. I dissect his “it’s cooling!” example here:
My point here is that the lack of continued warming has been commented on by many scientists, not just “denialists”. Several were quoted in the Der Spiegel article that made the rounds. Most (as far as I can tell) do believe that the warming will resume, but if that resumption waits a couple more decades (as it might), then the IPCC projections will all be wrong.
Re 1141 – about that…
1. more evaporation – specifically, for any heat transfer from the surface, there tends to be some ratio of latent heat flux to sensible heat flux that depends on the temperature and the wetness of the surface.
Increasing the surface temperature and assuming same relative humidity, if the rest of the temperature of the troposphere stayed the same, or even if it changed only as much as the surface, there would still be greater CAPE (convective available potential energy, which includes effect of latent heating; APE is available potential energy which is generally used in the context of dry adiabatic processes but extends to horizontally-extensive overturning with locally-stable stratification) per unit air that goes into an updraft.
However, with a general tendency to approach a moist-adiabatic lapse rate (*not everywhere at all times), the temperature at higher levels will tend to increase more, so that the CAPE of the next parcels will tend to fall back to what it was before the surface warming (*?) (alternatively, if the upper troposphere warmed first, convection would be reduced, warming the surface, etc.).
BUT the tropopause height is supposed to increase, and my understanding is that this increase may be great enough to result in a tropopause that is not only less warmed than the surface but may actually be colder than before, in spite of the reduced lapse rate. (I’d guess this would be more so for increased greenhouse forcing, which generally cools the stratosphere, than for increased solar forcing, which generally warms the stratosphere).
So if the convection extends upwards to higher levels in proportion to tropopause height changes, perhaps the Carnot-cycle efficiency will increase (???).
… the Carnot-cycle efficiency will increase (???). (This appears to make sense considering that for top-of-the atmosphere fluxes, the effective brightness temperature (global average whole-spectrum) at equilibrium will be unchanged in response to greenhouse forcing, except for albedo feedbacks … of course, the increase in tropopause height by itself would tend to increase the SW heating below tropopause level at the expense of the stratospheric heating; the temperature can be different than the effective brightness temperature and it is the tropospheric temperatures that matter most in this issue…)
The strong water vapor feedback in the tropics (at least the moist parts) would tend to decrease the net LW cooling of the surface significantly – it would also decrease SW heating of the surface, but up to a point I think the LW effect dominates, so the convective cooling of the surface would tend to increase. But conceivably much of that additional convective flux (especially that which is required to balance the closing of the atmospheric window between 8 and 12 microns) goes to balance increased LW cooling in the lower troposphere associated with water vapor (?)…
Many times I hear about the “dip” in temperatures between the 1940’s and 1975 and I have to wonder if the aerosol loading from setting off so many tons of explosives has been considered?
How one would get at the data I don’t know, but the coincidence of timing is persuasive.
First we’d have to get some samples of the types of explosives commonly used, set them off and take note of the amount and type of aerosol produced, and how long it hung around.
That would give us a basis for analysis.
I am curious about the SST anomaly pattern shown in recent weeks by Unisys here:
First, the deep water formation region north of Iceland has been quite warm for weeks. I would think that would inhibit deep water formation. On the other hand, if the warm surface water is more or less just sitting there, why isn’t it cooling, since that should also slow the arrival of warm water from the south? Any particular explanation/implications?
Why the very warm patch along the east coast of Greenland? Does that have any implications for glacier speed by weakening the ice shelves?
Note the very cool patch east of New Zealand. Is that related to the huge iceberg that was south of that area a few weeks ago. In other words, could such an iceberg cool the surface that much?
I realize all of this could just be noise, or due to particular cyclical currents, but would appreciate any clarifications.
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