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From: Bill Ward on 22 Dec 2008 14:17 On Mon, 22 Dec 2008 14:45:55 +0000, Don Klipstein wrote: > In article <pan.2008.12.17.16.01.14.695665(a)REMOVETHISix.netcom.com>, Bill > Ward wrote in part: > >>And Kr is used to increase the temperature of incandescent filaments. >>Why don't you explain that one too? It involves convection and thermal >>conductivity, not radiation. > > Krypton increases filament temperature for given filament dimensions and > power input only in comparison to more thermally conductive gases, such as > argon and the usual argon-nitrogen mixture. The same filament with same > power input would be hotter still in a vacuum. Exactly. But W sublimes in a vacuum, shortening the life of a high T lamp. By using Kr and a halogen, the W can be chemically scavenged from the bulb and redeposited on the hot filament, extending the useful life. As you say, Kr is used because it has a higher MW and lower thermal conductivity, keeping the heat from conducting/convecting away as fast as the other inert gases. A little thermal conductivity can replace a lot of radiative transfer.
From: Whata Fool on 22 Dec 2008 22:48 don(a)manx.misty.com (Don Klipstein) wrote: >In <hj8kk4le5784bdo5pf3r64g5rda9h6mv7r(a)4ax.com>, Whata Fool said in part: > >>> I think that has been modelled already somewhere, and it may not take me >>>long to find such a model. Expect much cooler, with a much lower >>>tropopause. Expect the 350 mb level to have temperature close to what it >>>has now, but to be in the stratosphere. >> >> What? How is the stratosphere defined? By lack water and water >>vapor? >> >> Wouldn't the whole atmosphere be stratosphere if there was no water >>or GHGs? > >>>water vapor is a greenhouse gas - currently having roughly double to a few >>>times as much GHG effect as CO2 has now. >>> >>> - Don Klipstein (don(a)misty.com) >> >> >> Does that infer that CO2 could ever have as much GHG effect as >>water vapor? It would take 50 times as much. > > CO2 has 9-26% of GHG effect at current (or maybe recent) atmospheric >concentrations. > >> But water cools the surface by at least 10 or 20 degrees, and >>the phase change is a big part of that cooling process. > > I would beg to differ about surface being 10-20 degrees cooler on >average when wet than dry. The Amazon rainforest and the nearby parts of >the Atlantic are not 10-20 degrees cooler on average than the Sahara. What "surface" do you mean, the soil or sand, or the air two meters above the ground? Sidewalks in NYC can get too hot to walk on barefoot, I suggest the ocean surface and the ground on the banks of the Amazon is always less than 100 F. >> Doesn't the fact that water evaporation provide a lot of >>cooling of the "surface" suggest that the surface would be warmer >>without water or GHGs? > > The heat goes somewhere - it does not get destroyed. It becomes part of >the burden of radiational cooling of the atmosphere by GHGs. You seem to be contradicting your (and the current thought) premise that the atmosphere would be cooler (or even below freezing), by saying that cooling the atmosphere is a burden. > Keep in mind that a blackbody in Earth's orbit, with a GHG-free >atmosphere or none at all, would be cooler than Earth is now. And since >Earth has thermal IR emissivity being a higher percentage than its >absorption of solar radiation, with GHGs removed and albedo unchanged it >would be colder than a blackbody. > > - Don Klipstein (don(a)misty.com) It isn't even rational to say "or none at all", when the sun is shining on the east facing slopes of mountains, there would be a lot of thermal transfer to nitrogen, with no way for the nitrogen to cool at that rate. Oxygen would not be much different than nitrogen. Frankly, I don't think you are able to focus on a hypothetical situation without drifting back to the learned atmospheric physics. I also disagree with the statements in; http://www.engr.colostate.edu/~ramirez/ce_old/classes/ce422_ramirez/CE422_Web/WaterVapor/water_vapor_CE322.htm about an atmosphere with no GHGs being below freezing. Eight hours or more of sun warming the surface to more than 120 F and the nitrogen warming and convecting upward would moderate the surface temperature almost as much as the present atmosphere, but would not be cooled by radiation. Please defer to those who are not to specialized to consider other possibilities.
From: Whata Fool on 22 Dec 2008 22:59 don(a)manx.misty.com (Don Klipstein) wrote: >In article <8arok4d5gteparmsehc91aqmkl75prve8o(a)4ax.com>, Whata Fool wrote: >>don(a)manx.misty.com (Don Klipstein) wrote: >> >>>In article <0ikpj41k4v8j7oikln12bjsk3dg44hrc0g(a)4ax.com>, Whata Fool wrote: >>>>don(a)manx.misty.com (Don Klipstein) wrote: >>>> >>>>>In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, Bill >>>>>Ward wrote in part: >>>>[snip] >>>>>>Just keep in mind you can't actually heat a hot source from a cold >>>>>>target. All you can do is slow the rate of cooling of the hot source. The >>>>>>sky is cold, the surface is hot. >>>>> >>>>> GHGs will slow the cooling by making outgoing radiation from the surface >>>>>absorbed at a lower, warmer level, which radiates half its radiation >>>>>downward. >>>>[snip] >>>>> - Don Klipstein (don(a)misty.com) >>>> >>>> >>>> Do you mean "cooling of the surface", meaning the solid or >>>>liquid surface rather than the lower atmosphere? >>>> >>>> >>>> If N2 doesn't radiate much in longwave, then any cooling is >>>>faster than almost no cooling at all. >>>> >>>> All the atmospheric radiation physics is interesting, but we >>>>have a few men claiming life on Earth could suffer displacement or >>>>death if the increased CO2 causes a slower cooling of the lower >>>>atmosphere. >>>> >>>> If there was no radiation cooling of the lower atmosphere >>>>without any GHGs at all, is there some mystical way that more GHGs >>>>can cause slower cooling than 100 years ago. >>> >>> The lowest part of the atmosphere does get cooled by the surface. >>>And GHGs in the lower atmosphere have their radiation going towards the >>>surface, in addition to all of the radiation that the surface would have >>>received without them. >>> >>> And GHGs in the lower atmosphere don't merely cool - they receive >>>radiation from the surface and can be warmed. >> >> There is the normal warming in daytime even from IR through clouds, >>but any major warming always comes with wind shift. >> >> There is a constant loss of energy to space from the atmosphere, >>the atmosphere is never a source of energy as some writings seem to >>suggest. >> >>>> I am well aware of the temperature records and averaging, >>>>but physics works the same way all the time, and with zero GHGs >>>>equaling zero cooling, doesn't GHGs mean cooling, and more GHGs >>>>mean more cooling, and less GHGs mean less cooling. >>> >>> Except for GHGs making the surface warmer than otherwise by adding >>>radiation to that already heading to the surface, and GHGs in the lower >>>atmosphere can experience radiational warming from the surface. >>> >>>> Statements that are not consistent are confusing. >>> >>> - Don Klipstein (don(a)misty.com) >> >> I don't think you are really making the comparison of the present >>Earth and an Earth with an N2 and O2 atmosphere no GHGs or water. >> >> It is even bizarre that anyone would claim the atmosphere could be >>cooled more than at present by interaction with the surface, and that is >>what you seem to be claiming. >> >> I agree that GHGs in the lower atmosphere can and do return part >>of the surface radiation back to the surface, but even with clouds, >>there is cooling at night if the wind is not bringing warmer air. >> >> I don't understand the obsession with GHG theory, it is partially >>right but saying that the Earth would be 33 degrees colder without GHGs >>is a fallacy that might lead to the spectre of additional CO2 cooling >>the Earth instead of warming it. >> >> The big fallacy is in the big change in the station locations >>used in the averaging, there should be no confidence at all in the >>results of the change of dozens or hundreds of locations used, even >>if anomalies are used because some locations have different ranges >>of diurnal temperatures, and that can have an effect on the minimum >>temperature anomaly. > > We do have lower troposphere temperature interpretations from satellite >data since 1979. Check out the "temperature lower troposphere" data from >RSS and the similar product from UAH. But the base line used goes back further than that, and from my everyday observation of airport construction the urban growth gained speed after 1950. >> I suggest that a study of only maximum daily temperatures of >>only the same locations might show something entirely different. > > Worldwide, I expect increase of GHGs to cause that to increase less. >Meanwhile, nighttime temperatures as well as daytime temperatures affect >snow and ice cover, and change of that affects how much sunlight Earth >absorbs. > > - Don Klipstein (don(a)misty.com) Total GHGs have only increased from an average of 2.03 percent to 2.04 percent in the last 200 years, and you believe this has had a big effect on temperatures? Please try to remember that water vapor is a GHG. It seems very evident that a nitrogen atmosphere would be much warmer without water, and the same without any GHGs.
From: Don Klipstein on 23 Dec 2008 21:45 In article <pan.2008.12.22.16.51.13.543198(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 22 Dec 2008 02:11:15 +0000, Don Klipstein wrote: > >> In article <pan.2008.12.15.07.25.04.110636(a)REMOVETHISix.netcom.com>, Bill >> Ward wrote in part: >> >>>On Mon, 15 Dec 2008 03:49:54 +0000, Don Klipstein wrote: >>> >>>> In article <pan.2008.12.02.09.04.49.526817(a)REMOVETHISix.netcom.com>, >>>> Bill Ward wrote: >>>>>On Tue, 02 Dec 2008 05:55:11 +0000, Don Klipstein wrote: >>>>> >>>>>> In <pan.2008.11.26.21.17.23.310423(a)REMOVETHISix.netcom.com>, Bill >>>>>> Ward wrote: >>>>> >>>>>Do you think that the "wet adiabatic" environmental lapse rate is >>>>>related to latent heat, or is it simply less than the dry adiabatic >>>>>lapse rate because it's not at equilibrium? >>>> >>>> It is less due to latent heat. >>>> >>>> The "1 size fits all figures" that I have heard are 3.5 degrees F per >>>> 1,000 feet for the wet one and 5.4 degrees F per 1,000 feet for the dry >>>> one. >>>> >>>>>>> Is it primarily by radiative transfer, or convection? It seems to >>>>>>> me >>>>>>>it must be convective, simply because warm, wet air is less dense >>>>>>>than cold, dry air, and quickly rises to maintain the lapse rate. >>>>>> >>>>>> Much of the time the answer is a significant factor other than >>>>>> radiation and vertical convection. Much of the "global convection" >>>>>> involves air movement within a degree of horizontal, and often >>>>>> forming clouds when moving upwards. Sometimes the lapse rate there >>>>>> is between the "dry adiabatic" and the "wet adiabatic" rates and the >>>>>> clouds have billowy cumuliform tops or are cumuliform throughout. >>>>>> Sometimes "warm advection" occurs more at cloud-top level than at >>>>>> cloud-base level (from the windspeed being greater higher up in the >>>>>> troposphere), causing the clouds to be stratiform. >>>>> >>>>>OK, that all sounds plausible, but I'm not sure how much effect the >>>>>horizontal component would have, other than the obvious mixing. >>>> >>>> The horizontal component involves atmospheric heat transfer from the >>>> tropics to the poles. It is very significant. It leads to frontal >>>> inversions, which cover significant area ahead of warm fronts >>>> (including areas where the warm fronts fail to reach at the surface). >>>> It leads to existence of stratosphere at middle and upper latitudes at >>>> pressure levels below that of the tropical tropopause. >>>> >>>>>>>IR radiated from the surface would be quickly absorbed by WV, clouds, >>>>>>>CO2, and other GHGs, and at 500W/m^2 would be overwhelmed by the 10's >>>>>>>of kW/m^2 available from convection of latent heat. >>>>>> >>>>>> Half the Earth's surface has no clouds overhead at any altitude. >>>>> >>>>>Surely you mean "at any given time". Or are there really regions >>>>>comprising half the Earth's surface that have never had a cloud in the >>>>>sky? >>>> >>>> I did mean "at any given time", and "those given times" in "those >>>> given locations" account for half the world lacking clouds at any >>>> altitude. >>> >>>OK, I'll buy that as an average. But I'll bet the tropics are far more >>>likely to be cloudy than the polar regions, and that's where most of the >>>cooling occurs. >>> >>>>>> The surface manages to radiate *somewhat* to outer space at night >>>>>> when the air overhead is clear - otherwise there would be no such >>>>>> thing as nighttime frost when air 2 meters above the surface is at +2 >>>>>> degrees C (a fairly common situation). Some of the outgoing >>>>>> radiation can easily be absorbed and reradiated a couple or a few >>>>>> times by GHGs, but net of that is upward (and upward net is reduced >>>>>> by increase of GHGs). >>>>> >>>>>OK, no argument with that. I look at it as the surface radiating to a >>>>>target warmer than 3K space, but it's the same math. >>>>>> >>>>>>>At night, convection stops, but cooling is not required at night. >>>>>>>Convection kicks in during the day, when cooling is needed. >>>>>> >>>>>> Cooling still occurs at night by radiation. 5 AM temperature has a >>>>>> great rate of being less than 10 PM temperature. Upper level of >>>>>> radiation by atmosphere at night has half of its radiation to outer >>>>>> space. That heat comes from radiation from surface - even if >>>>>> absorbed and reradiated a couple times along the way. >>>>> >>>>>Agreed. At night the flux is always outward. >>>>> >>>>>> The "upper radiation level" also varies greatly with wavelength. >>>>> >>>>>Do you mean the "effective radiating altitude", which is calculated, or >>>>>some sort of integrated spectrum involving all the photons reaching a >>>>>surface outside the atmosphere, like a satellite imager? Neither I, >>>>>nor apparently Google, is familiar withe the term "upper radiation >>>>>level". >>>> >>>> Looks like I did not choose wrds well - it should have been >>>> "effective >>>> radiating altitude". >>>> >>>> Keep in mind that the "effective radiating altitude" is very fuzzy, >>>> since some wavelengths radiated by the surface have good atmospheric >>>> transparency (and a fairly clear shot to space) as long as there are no >>>> clouds, others have low chance of reaching the 500 mb level without >>>> being absorbed, and some are in-between - with absorption and >>>> reradiation varying directly with concentration of GHGs. >>> >>>That's my point. It's not well enough known to claim 1.5W/m^2 is going >>>to make any difference at all. All it takes is a minor negative feedback >>>loop to correct for that small an effect. >> >> The Ice Ages having temperature swinging 10-plus K from slight periodic >> changes in insolation show that we have a lot of positive feedback. > >Has that actually been shown, or just inferred? If there were >significant positive feedback, it would have shown up in the ice core >signal as an exponential runaway to the rail. For long term stability, >you need negative feedback. You can have positive feedback without latchup. Example: Armstrong regenerative receiver. The ice core data do indicate CO2 atmospheric concentration lagging temperature by about 800 years. (But temperature lagged CO2 since Industrial Revolution.) >>>>>>>I don't see how radiative cooling is even necessary below the cloud >>>>>>>tops, since there's plenty of cooling capacity from convection. >>>>>> >>>>>> When frost or dew forms on the ground and on cars and trucks, the >>>>>> heat >>>>>> loss has a very impressive rate of by being by radiation. >>>>> >>>>>True, but radiation is peanuts compared to the available cooling >>>>>capacity of latent heat during the day. If the surface radiation were >>>>>blocked, convection could easily make it up. >>>> >>>> What about on days when there is no convection past the 750 mb or so >>>> level for even a minute? (I see plenty of those even with sky >>>> half-clear and cumulus clouds present.) What about in Arctic and >>>> upper-midlatitude areas where change in radiation balance during the >>>> 18 or whatever hours per day with little convection has a >>>> significicant effect on snow/ice cover, and that affects how much >>>> solar radiation the surface absorbs? >>> >>>It's the total transferred power that counts. It doesn't take much >>>latent heat convection to make up for a lot of radiation. The place to >>>look for changes is where the cooling is greatest, not places which are >>>already being warmed by the tropics. >> >> Cooling is significant in the polar areas. The global insolation map >> in >> the Wiki article on insolation shows the polar areas getting about 1/3 >> as much insolation as the tropics do. Cooling is even more than 1/3 >> that of the tropics, since global circulation transfers heat from the >> tropics to the polar regions. > >Doesn't that mean the tropics still provide the majority of the cooling? Yes, that is true, but that does not negate the significance of cooling in the polar and near-regions - nor the significance of ease of changing temperature of the surface and lower troposphere in the polar and near-polar regions. >> Where the surface can warm significantly before convection occurs is >> probably where the world can warm more if GHGs increase. I would also >> expect more warming in areas where warming reduces surface albedo. > >Aren't those areas already colder than average? I would say not - the world has upward anomaly in temperature of surface and surface-level atmosphere and lower troposphere overall, which is greatest in the Arctic. >>>>>>>Once the energy reaches the tropopause, as you imply, it's a pretty >>>>>>>straight shot to 3K deep space, since there's not much atmosphere >>>>>>>left to absorb IR. >>>>>>> >>>>>>>Perhaps it's easier to see if you look at the lapse rate as bounded >>>>>>>at the top by the effective radiating temperature, and consider the >>>>>>>surface temperatures as derived from that and the adiabatic lapse >>>>>>>rate. >>>>>> >>>>>> That gets complicated by half the troposphere having lack of >>>>>> clouds at >>>>>> any altitude, and there are separate adiabatic lapse rates for clear >>>>>> air and clouded air. The global atmospheric average is close to the >>>>>> "wet" one, leaving upward mobility of lapse rate in the clear half >>>>>> of the world and in clear layers of the atmosphere in the clouded >>>>>> half of the world. >>>>> >>>>>At any given point, the applicable lapse rate should be obvious, >>>>>depending on whether cloud is present. I'm not convinced the lower >>>>>"average" environmental lapse rate has much to do with latent heat. It >>>>>might just be off-equilibrium due to transport lags or the like. >>>> >>>> It just happens to be that the "average lapse rate below the >>>> tropopause" is close to the wet adiabatic one. Close to the equator, >>>> it is more than coincidental - global circulation (from atmosphere >>>> below_tropical_tropopause_pressure_level as-a-whole) being warmer >>>> towards the equator and cooler towards the poles has air in the >>>> intertropical convergence zone rising. That largely establishes the >>>> lapse rate in the ITCZ as being close to the wet adiabatic one from >>>> the levels of the bases of the deep tall tropical convective clouds >>>> to the tropical tropopauuse. Below that cloud base level where >>>> those clouds form, the lapse rate is close to the dry adiabatic one >>>> at hot times of the day, and less at other times. >>>> >>>> Although it sounds like global circulation merely forces upward air >>>> movement in the ITCZ and that should cause clouds other than the >>>> billowy cumulus of natural convection, those show up anyway (along >>>> with a lot of clear air). Surface temperature in the ITCZ is not >>>> uniform. For one thing, some parts of the ITCZ have daylight and >>>> others have night. Also, ocean currents cool the ITCZ unevenly. So, >>>> upward air movement in the ITCZ occurs in hotspots where natural >>>> convection is sufficient to account for the upward global atmospheric >>>> circulation in the ITCZ - and the clouds there are billowy >>>> thunderheads, with many having anvil tops. >>> >>>I've often seen precipitation falling out of the anvil, many times never >>>reaching the ground. The energy in a thunderstorm is staggering, and >>>seems far more than IR could ever provide. Most of that energy had to >>>have come from the surface, and there's really no way back down. It >>>seems to me it has to radiate to space. >> >> Little of the surface is covered by thunderheads. >> >> And the atmosphere at the level of tropical anviltops is so cold, that >> it actually experiences slight warming from radiation. The air >> eventually does cool by radiation where it descends. >> >>>Thermals are what got me started on this issue. I asked myself just how >>>much IR it would take to lift a sailplane at a thousand feet/minute. I >>>immediately had doubts that IR is significant. The energy is clearly >>>mechanical energy of convection, and the cloud (if any)sitting on top of >>>the thermal has to represent an order of magnitude more energy from >>>latent heat. >>> >>>Thermals may not be all that common on the average, but when they do >>>occur, they must carry orders of magnitude more energy than IR. >>> >>>When I look (longingly) at pictures of tropical islands, I see very >>>familiar looking clouds. I have to assume the dynamics are similar, and >>>that they are common in the tropics. So I need a lot of convincing >>>evidence before I'll believe their heat transfer ability is somehow >>>comparable to an already cold polar surface or similar situation. All >>>it would take is a slight modulation of humidity or lapse rate to have >>>large effects on the power transmitted, far greater than the 1.5W/m^2 >>>CO2 forcing assumed in the climate models. >> >> I agree that tropical thunderstorms lift warm air accounting for >> thermal power densities many times the solar constant. However, that >> heat is mostly not radiated at the tropical tropopause - the anviltops >> are at about the same temperature as the surrounding clear air at the >> same altitude, and it is actually colder at that altitude in the tropics >> than in the middle latitudes. > >I don't see why the actual region where it's radiated to space matters. >Once the heat is lifted, there's no way it can be pumped back down to the >warmer surface without radiating more energy to an even colder heat sink. > >Cooling is cooling, no matter where it happens. > >> Cooling of the tropics is ultimately mostly from radiation from >> altitudes lower than the tropical tropopause and from global >> circulation. > >That seems plausible. > >>>> Do keep in mind that there is global atmospheric circulation at >>>> altitudes and pressure levels that are troposphere in the tropics and >>>> stratosphere elsewhere. Air rising through the ITCZ to close to the >>>> 100 mb level does not all go down there but some descends elsewhere >>>> poleward. And a lot of that moves poleward at altitudes where the is >>>> little hope of convection to such level from the surface, due to >>>> surface being cooler than in the ITCZ. At some of these >>>> extratropical-stratospheric altitudes and pressure levels, atmosphere >>>> is even usually warmer than it is over the ITCZ because over the ITCZ >>>> it is so cold (from cooling by uplifting) that local radiation balance >>>> warms the air moving largely horizontally at/near the tropical >>>> tropopause level. It cools by radiation in order to descend >>>> elsewhere, with much of that done during the descent - especially in >>>> the polar regions. >>> >>>That seems reasonable, but I don't see how it really affects the >>>tropical convection cells. That's how the energy got up there in the >>>first place. >> >> I don't think radiation does much to tropical convection cells. >> >> But if the polar regions warm with increase in reception of solar >> radiation, then horizontal temperature gradient will decrease. That >> will slow global circulation, which means slightly less cooling of the >> tropics. > >Why? It seems to me it might provide even more effective global cooling >by restricting the radiation to warmer areas, rather than letting the warm >air escape to the cooler poles. Remember the 4th power term. For one thing, the tropics only radiate more to the extent they actually warm (or 4th power thereof). I expect the tropics to warm only slightly as a result of global circulation slowdown by increase of temperature of more extreme latitudes. Also, if we have an increase in GHGs, then radiation directly to space will be more restricted to coming from upper atmosphere. And if the surface albedo decreases from warming of the polar regions, then reception of sunlight increases. But if radiating ability of everywhere at all altitudes from surface to upper stratosphere is unchanged and surface albedo is unchanged, then changing evenness of surface temperature would not change "root-mean-4th_power" temperature, which is what determines radiation outgo. (Actually that is an oversimplification - for one thing, changing radiation distribution only leaves "root-mean-4th_power" temperature unchanged if radiation burden is not shifted towards areas where there is either more or less water vapor.) If "root-mean-4th_power" of temperature is unchanged and evenness of temperature changes, making the temperature more even will raise the average and making it less even will lower the average. >> The tropics will warm slightly as a result, and the thunderstorms >> would have to become a little more intense. > >Which would increase the latent heat component. Yes it would - limiting a few things: 1. Area covered by tropical thunderstorms - that could decrease in response to warming - since their ability to move heat appears to me likely to increase more than the amount of heat to be moved should the tropics warm. I have noticed that when there is little net vertical velocity in the air in my area (according to appropriate maps) and there are convective clouds, there is usually less cloud cover and more clear air when it is warmer - even though more precipitation falls from convective clouds when it is warmer. 2. Along with that - warming of the tropics would be limited - for one thing by making it easier to move the heat elsewhere. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 23 Dec 2008 22:19
In article <pan.2008.12.22.17.42.33.380297(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 22 Dec 2008 12:39:09 +0000, Don Klipstein wrote: > >> In article <pan.2008.12.09.17.36.37.607052(a)REMOVETHISix.netcom.com>, Bill >> Ward wrote: (With snip of at least stuff already quoted more than 3 times) >>>On Tue, 09 Dec 2008 07:09:08 +0000, Don Klipstein wrote: >>> >>>> In <pan.2008.12.04.08.02.57.92862(a)REMOVETHISix.netcom.com>, B. Ward >>>> wrote: >>>>>On Thu, 04 Dec 2008 03:45:45 +0000, Don Klipstein wrote: >> >>>>>> But CO2 is close to blackbody within some range of wavelengths >>>>>> where >>>>>> emission is close to peak of a 218 K blackbody. And the range does >>>>>> widen somewhat when there is more CO2 in the atmosphere. >>>>> >>>>>Look at this graph: >>>>> >>>>>http://upload.wikimedia.org/wikipedia/commons/7/7c/ >>>>>Atmospheric_Transmission.png >>>>> >>>>>Now please tell me if you think the CO2 absorption spectrum (3rd graph) >>>>>is similar to the 210K blackbody emission spectrum line in the top >>>>>graph. >>>> >>>> I did not claim that - I merely claimed (using maybe better words now >>>> than before) that CO2 in the atmosphere radiates close as well as a >>>> blackbody does within the 15um-peaking band. >>>> >>>> The 210K spectrum does indeed have its peak close to CO2's 15 um >>>> band, >>>> so CO2's 15 um band will absorb and radiate some very significant >>>> amount at 210K. >>> >>>My guess from looking at the spectra would be less than half as much, >>>assuming the area under the spectrum is proportional to power. >> >> Yes, that band looks to me eyeball-estimate worth 20-25% of blackbody >> radiation at 210 K and less at higher temperatures. > >That looks about right to me also. How can we carry on a decent argument >if you keep agreeing with me? ;-) > >>> And water shares the band. >> >> The atmosphere according to the above link has around 50% transparency >> of water vapor in that band, though I'm sure that varies widely since >> concentration of water vapor in the atmosphere is far from constant. > >So shouldn't any effect of changes in CO2 be reduced by roughly another >50% to account for the water vapor? >> In polar areas where surface temperature has more upward mobility, >> there is less water vapor and CO2 accounts for a higher percentage of >> GHG effect. >> >> Worldwide, CO2 accounts for 9-26% of GHG effect. > >Have you seen any derivation of that figure other than the RealClimate >blog? Wikipedia mentions that range, in their article on "greenhouse gases": "water vapor, which contributes 36-70% carbon dioxide, which contributes 9-26% methane, which contributes 4-9% ozone, which contributes 3-7%" And about 1-1/2 paragraphs later, it says: "The higher ends of the ranges quoted are for the gas alone; the lower ends, for the gas counting overlaps.[5][6]" Using accounting system making CO2 9%, then water vapor is 36%. Reference 5 is noted to be at RealClimate. Reference 6 is Kiehl, J. T.; Kevin E. Trenberth (February 1997). "Earth�s Annual Global Mean Energy Budget" (PDF). Bulletin of the American Meteorological Society 78 (2): 197-208. http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/ RadiationBudget.pdf I see 26% and 60% figures for CO2 and H2O respectively there, page 203, last column in Table 3. The "Combined with overlap effects" column says CO2 is 32 parts, H2O is 75 parts out of 125. The first column has CO2 other than overlap being 29 parts out of 125, and H2O other than overlap accounts for 71 parts out of 125, and where they overlap is 7 parts out of 125. That is for GHG effect in clear air. That same table also has parts each out of a total of 86 in the first 2 columns for GHG effect where it is cloudy. 36-66% for H2O and 9-26% for CO2 comes from Ref. 5, http://www.realclimate.org/index.php?p=142 Looks like RealClimate is making CO2 a little less important than the other reference. >> I suspect the wide >> range is in large part due to water vapor concentration being very far >> from constant. Another factor is probably diversity of temperature >> shifting relative radiation abilities of different wavelength bands of >> different GHGs. > >Those seem like important factors that should be measured, not estimated. <SNIP following material lacking further dispute so far> - Don Klipstein (don(a)misty.com) |