Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

Climate change: Water vapor makes for a wet argument

Posted on 2 September 2010 by James Frank

When skeptics use the argument 'Water vapor is the most powerful greenhouse gas', they are trying to imply that an increase in CO2 isn't a major problem. If CO2 isn't as powerful as water vapor, which there's already a lot of, adding a little more CO2 couldn't be that bad, right? What this argument misses is the fact that water vapor creates what scientists call a 'positive feedback loop' in the atmosphere — making any temperature changes larger than they would be otherwise.

How does this work? The amount of water vapor in the atmosphere exists in direct relation to the temperature. If you increase the temperature, more water evaporates and becomes vapor, and vice versa. So when something else causes a temperature increase (such as extra CO2 from fossil fuels), more water evaporates. Then, since water vapor is a greenhouse gas, this additional water vapor causes the temperature to go up even further—a positive feedback.

How much does water vapor amplify CO2 warming? Studies show that water vapor feedback roughly doubles the amount of warming caused by CO2. So if there is a 1°C change caused by CO2, the water vapor will cause the temperature to go up another 1°C. When other feedback loops are included, the total warming from a potential 1°C change caused by CO2 is, in reality, as much as 3°C.

The other factor to consider is that water is evaporated from the land and sea and falls as rain or snow all the time. Thus the amount held in the atmosphere as water vapour varies greatly in just hours and days as result of the prevailing weather in any location. So even though water vapour is the greatest greenhouse gas, it is relatively short-lived. On the other hand, CO2 is removed from the air by natural geological-scale processes and these take a long time to work. Consequently CO2 stays in our atmosphere for years and even centuries. A small additional amount has a much more long-term effect.

So skeptics are right in saying that water vapor is the dominant greenhouse gas. What they don't mention is that the water vapor feedback loop actually makes temperature changes caused by CO2 even bigger.

This post is the Basic version (written by James Frank with a contribution from John Russell) of the skeptic argument "Water vapor is the most powerful greenhouse gas".

0 0

Printable Version  |  Link to this page

Comments

Prev  1  2  3  

Comments 101 to 144 out of 144:

  1. KR at 14:18 PM, I trying very hard not to break into uncontrollable laughter, you are making it very hard not to. I have made it abundantly clear that the terrestrial temperature is measured at ground level, as does the BOM notes. I also pointed out that it is always lower than the air temperature which is measured 1.2m above ground level, and always higher than the soil temperature, which obviously is the temperature IN the soil, so I cannot understand what you are confused about as I have well made the distinction. Go back and read the relevant posts again, carefully. With regards to the minimum temperatures, whilst the readings are taken at 0900hrs, all this does is mark the end and beginning of each day. The minimum temperatures whether air or terrestrial will have occurred at some point within the preceding 24 hours, most likely during the night, not long before sunrise, in both cases each will be at the coldest point of the night. I repeat, the ground temperature is not the soil temperature, it is the AIR temperature taken AT ground level, not in the ground. In the ground measurements are identified as soil temperatures. What we call surface temperature as recorded by weather stations is the temperature at a standard height 1.2m above ground level, and if you don't know there generally is considerable variation in air temperatures in the first few metres above ground level.
    0 0
  2. Correction, you are getting me confused now. It is the SOIL temperatures which are ALWAYS HIGHER than the MINIMUM air or terrestrial temperatures, anyway this is clear from the BOM tables irrespective of what I might have written. The terrestrial minimum temperature is always lower than the minimum air temperature, which I believe is what I asked you originally to explain as to why this is so if back radiation warms the surface.
    0 0
  3. KR, I see I did make a mistake in one post by mixing up higher and lower when referring to the relative temperatures, terrestrial and soil. My apologies. However it would have been obvious it was a simple mistake by reading the table referred to where the differences are obvious, and my other posts where I had referred to the differences correctly.
    0 0
  4. johnd - I perhaps have been reading to quickly with regards to that chart, myself. That said, it's an agricultural data product, and not specifically intended as a measure of back radiation; hence the lack of back radiation data on it is rather unsurprising. However: My basic confusion (still unresolved) on your question is as to what, exactly, you feel this particular data set shows as issues with back radiation amounts? Back radiation measured, repeatedly, with different instrument sets, since the 1950's? It's definitely there, and in the amounts predicted by theory.
    0 0
  5. scaddenp at 07:52 AM and KR at 23:09 PM. With regards to the question "how fast would temperatures have dropped if there was NOT back radiation", that really is not what we are seeking to understand. What I would like to understand is why with soil temperatures radiating warmth from below, and air temperatures measured at about 1.2m above ground level supposedly providing back radiation, why then do the minimum temperatures AT ground level fall so low. We know that normally temperatures quickly fall as distance from the surface increases, but as these terrestrial minimum temperatures indicate, whatever warmth contained in the air just 1.2 m above the ground is not enough to stop even more warmth being lost at ground level. Whilst focusing on this difference of minimum temperatures over a short 1.2m distance, we should also consider what differences we would find between the maximum temperatures recorded by a thermometer in the shaded enclosure and an exposed thermometer at ground level, especially when considering just what factor direct solar radiation has on evaporation as against back radiation. Whilst stations such as Alice Springs may measure back radiation, the network of stations that BOM use from across all of Australia to collect data for agricultural use are exactly the appropriate ones to use in a thread regarding water vapour, in that determining the conditions that drive evaporation is perhaps the most important part of understanding why the water vapour in the atmosphere varies as it does. What is there to tell us that conditions in the atmosphere drive the evaporation instead of evaporation driving conditions in the atmosphere? It is of little use to measure back radiation unless this can then be measured in how it manifests itself as heat arriving and being absorbed at the surface, and whilst the BOM data only gives the nett result without breaking it down as to individual inputs that determine the nett result, those nett results expose an situation that is inconsistent with what input back radiation is supposed to have. With regards to clouds, firstly I don't think the climate has ever been stable, a quick look at any cycle over any time frame indicates short term cycles within longer term cycles within even longer cycles. However I have seen some information from NASA that concludes that overall, clouds have a nett cooling effect, rather than a warming effect on the earth.
    0 0
  6. johnd - Cold air right at ground level, warmer up 1.2 meters; sounds like the classic conditions for radiation fog. The ground cools via radiation after the sun goes down, radiation that will only be absorbed (80%+?) after ~100 meters or so), air right at the ground (~1 meter) cools with the ground by conduction. 1 meter of air isn't going to stop much of that ground source IR! Keep in mind that the back radiation numbers are for a deep mass of air, not 1 meter layers. Exactly what I would expect, quite frankly. No inconsistency whatsoever. Measuring back radiation is of considerable use if you're calculating the Earth energy budget. If you disagree, I suggest you run that disagreement past Trenberth :)
    0 0
  7. Colder temperatures closer to the ground is a temperature inversion and it needs specific conditions to occur. Maybe your BOM stations have the data to check it. Firstly, it needs still night air so that cold dense air can accumulate close to the ground. Next you need clear skies and dry air. Why? because under these conditions backradiation is reduced allowing the ground cool efficiently by radiation to space. Got a BOM station in northern Queensland to compare with? This is text book stuff. Say "Essentials of meteorology: an invitation to the atmosphere". And yet again, in discussion of water vapour and evaporation effects on climate, your BOM stations are largely irrelevant because the processes that matter happen at sea. As far as I can see, you dont study either the text book or basic physics because you believe both wrong. However, I dont think you can make a cogent argument for them being wrong until you first understand what our best model is.
    0 0
  8. scaddenp at 07:13 AM, if you have been looking at the BOM site, checking the terrestrial minimum temperatures that we have been discussing, you would have seen that as a rule it is always the same, every day, at every station, including those in Queensland and Northern Territory, the terrestrial minimum is nearly always lower than the station minimum temperature, and only on the odd occasion is it otherwise. Apart from those odd occasions the only difference is by how what magnitude lower is the terrestrial minimum. I assume by your post that you haven't been checking the data as it is updated daily and so are merely speculating. Unless you understand what is actually occurring in the real world then how can you be so sure that you are applying the correct physics principles. The data from these BOM stations is most relevant because this particular theory of back radiation applies over both land and the oceans, the only difference being that the data being collected from these stations is happening under more easily controlled conditions on an ongoing basis and from a well distributed network covering a wide variety of conditions allowing greater analysis. With your understanding of basic physics and studying of the text books, I was hoping that you might be able to correlate what is being measured on a daily basis with the physics theory that applies, so perhaps dispense with the speculation and put forward some credible explanation.
    0 0
  9. Johnd has not bothered to read Spencers' home experiment showing backradiation so he does not understand the basics. He feels it is better to keep an open mind. The temperature of the backradiation is less than the temperature of the surface. That is why you get the temperatures you see in your chart. It is exactly what is expected. The total backradiation is higher than the sun because it is emitted from the entire atmosphere and the sun is a point source. Spencer describes it as 30-75 degrees colder. Yes Johnd, it is confusing that a colder atmosphere can warm the surface with backradiation. Read the links to Spencer where he explains the effect. The backradiation keeps the surface warmer than it would have been, but does not provide heating in the way you seem to be expecting. I see you are over 100 posts on this now and still have not been able to get the basics. Another 100 or so and it will be a contest with the waste heat thread.
    0 0
  10. Michael sweet - well you did warn me not to bother. I see what you mean. Sigh. Johnd - guilty as charged - I only gave BOM site cursory look. And while I find the idea the that BOM network is better for climate than the global radiation network laughable, I do agree that physics should work at the BOM sites. And it does. The ground is much more efficient radiator than air, so even when no inversion takes place, the boundary layer will have overnight minimum lower than air above. If you insist on using the BOM network, then to see the effect of backradiation, you need to compare data where backradiation is different. Use humidity as proxy for backradiation. Compare rate of overnight cooling from approximately same temperature between time of high humidity and low humidity. You really need hourly data to do this properly but temperature min/max range between say Alice Springs and Northern Queensland should you give a crude idea.
    0 0
  11. michael sweet at 07:18 AM, I'm not sure whether you were claiming expertise as a psychic or as a comedian, but your claim regarding the Spencer's articles left me ROTFLMAO. On the contrary I have read about Spencer's experiment and it should have been obvious that this discussion was leading towards it being introduced, and I thank you for doing so. I was reluctant to introduce it myself as invariably, as often witnessed on this site, whenever Spencer is referenced to support an argument, Spencer's credibility is questioned and thus by association, used to question the credibility of the argument being put. With the Spencer experiment having now been introduced, it allows what he measured to be compared to what BOM measure and record as the terrestrial minimum temperature. The obvious difference is that BOM only record the minimum whilst Spencer tracked it continuously. However Spencer claims that his insulated box is a crude IR thermometer and that he is measuring infrared radiation of heat energy resident in the sky, whilst BOM are measuring ambient temperatures at ground level with a simple thermometer totally exposed on all sides. The first question is really whether or not Spencer is measuring anything different then what a simple thermometer lying on the ground measures? The second question relates to the principle of back radiation which has it that the heat contained within any body also radiates outgoing energy even though it is receiving incoming energy. If the temperature on the ground falls below the temperature of the air just 1.2m above it, why then is not the outgoing, or back radiation of that body of air received by the air just immediately below it? The theory of the transfer of thermal energy by radiation does not explain it, however the principle of convection does. The other point that Spencer's experiment is relevant to relates to earlier points made about how the high temperatures that the direct solar radiation produces at the surface are a greater force driving evaporation than back radiation. In his experiment he found that during the day the solar radiation caused temperatures that flat-lined for about an hour at the limit of the instrument, that being 158F. He expressed surprise at seeing temperatures so high, which in turn really surprised me. I would have thought that EVERYBODY knew just how hot anything receiving direct solar radiation can get. This is really school-kid stuff with most people learning early by burning their hand picking something up off the ground. This perhaps relates to another of my concerns, that being that despite all the claimed knowledge of the physics and theories, a large number of people have little or no knowledge of how it all manifests itself in the real world on a daily basis.
    0 0
  12. The point of looking at Spenser article was to show that even skeptics accept the backradiation is a reality and can be demostrated with back yard equipment. However, the real stations that actually measure all the radiation elements do so with sophisticated instruments, quantify it and then use it for calculating the global radiation balance.
    0 0
  13. scaddenp at 07:35 AM, the point I was making is that what Spencer is tracking with his crude IR thermometer supposedly reading back radiation from the sky, is the same as that what a simple thermometer lying on the ground would track. The problem perhaps is the term back-radiation itself. I think everybody accepts that any body or matter that contains heat will exhibit such energy and allow the transfer of such heat through all mediums. Obviously any medium that has a higher heat content than those adjacent will transfer such energy at a rate relative to the heat differential that exists between them until such time equilibrium is reached. What is the situation then? No nett transfer of heat energy as outgoing and incoming are equal. In the physical world it is the nett results that are relevant, and back-radiation only affects the rate of the nett transfer of heat, not the direction. In the environment that Spencer conducted his experiment, and BOM record their terrestrial minimum, convection is the major form of heat transfer as it is in all the atmosphere, and it too responds accordingly to the magnitude of the heat differential. So it comes back to the original question, what was Spencer's experiment tracking that a thermometer lying on the ground wasn't?
    0 0
  14. John - you are again making wrong assumptions. I really wish you would read the science of doom article I pointed to long ago. What you are describing is the laws of CONDUCTION. back radiation is not conduction. What you say makes no sense because of this fundamental difference. If you had no greenhouse gases, the warm ground would warm the atmosphere by conduction - just not very much. Spenser's experiment was aimed at reducing conduction effects and concentrating on the radiative energy transfers.
    0 0
  15. Just read your post more carefully... In ground thermometer, the measuring device equilibrates to surroundings by conduction and so is measurement the temperature of the immediate surroundings. With thermopile. BOTH ends of the thermopile equilibrate to surrounding by conduction, but only one end of the thermopile is heated by IR. This makes the device directional. If you turned it face the ground rather than the sky, then you measure the outgoing LR. Point it at the sky and you measure DLR (backradiation). If you measure both (and the short wave as well), then you can see the individual heat balance like the Trenberth diagram but on an hour by hour basis. And by the way, while I think Spencer is wrong on many things, he does science the right way - publishing his ideas in reputable journals.
    0 0
  16. scaddenp at 11:08 AM, Phil, the thermometer used by BOM to measure terrestrial minimum temperature is not IN the ground, but "placed close to the horizontal and just above the surface of the ground" as described on the BOM site. This is a picture of such a thermometer in place. As can be seen the bulb is not in contact with anything, only the capillary tube being in contact with the wooden base. The reason I introduced the matter of the terrestrial minimum temperature is because it measures conditions that are closer to those that prevail at the point where evaporation takes place. As Spencer's experiment shows, whether it is day or night, the ambient air temperature is not an indicator at all of what heat energy is made available at the surface to drive the evaporation process. Whilst there may be sophisticated instruments to measure back radiation, it basically only measures what a simple thermometer on the ground measures, or what a bare-footed kid chasing the cows in on a frosty morning, and again at high noon, and that is that what his face feels 1.2m above the ground is not what the soles of his feet feel, if he lets them touch the ground long enough to register any sensation that is. That is exactly where the energy that drives evaporation is inputted into the process. If back radiation is any factor at all in driving the evaporation process, then consider this. The lowest overnight temperature at the surface is the baseline that determines what heat energy is left in the atmosphere once all that accumulated from the input of solar energy has been dissipated. Following the energy budget diagram posted earlier, it is clear that all the flows of heat energy are depending either directly or indirectly on the input of solar energy. After the terrestrial minimum temperatures have been reached any increase in energy that will manifest itself as radiation between the surface and the atmosphere can only have come from the solar energy absorbed either directly into the atmosphere, or after having first been absorbed by the land and oceans and then transferred by convection, evaporation or radiation into the atmosphere. Apart from the energy being transferred by radiation and back radiation which indicates a nett transfer of 66 from the surface to the atmosphere, the single biggest form of nett heat transfer from the surface to the atmosphere is evaporation at 78. As mentioned by someone earlier, the diagram is not a very good one at representing the true energy budget and flow of heat, but if anyone persists with using it simply because there is none better, then it has to be considered as a whole, and defended by correlating what it appears to illustrate with what actually occurs in the physical world. So far I haven't seen that being the case. I also think that Spencer gets some things wrong, though I do believe he is right regarding negative feedback. I also agree he is doing things the right way, though from a different perspective. Instead of looking to add further confirmation to what many accept as a foregone conclusion, an easy thing to do, he applies some lateral thinking, an approach sadly lacking in a world ruled by the confines of logic, and challenges that perhaps of the two faces of a coin, the heads side is not the necessarily the defining side.
    0 0
  17. johnd - I take it you have not read my post on the conditions relevant to radiation fog? The ground radiates to the sky, with said IR being intercepted over the first 100+ meters or so. The first 1 meter of air intercepts very little of this energy. The ground then cools the air via conduction. That's why (when it progresses to the condensation point) this effect of cold low level air is called "radiation fog". It occurs via IR radiation heat transfer. There's really no puzzle here.
    0 0
  18. John - I am perfectly aware of where the thermometer is and always have been. And the temperature of the seawater actually IS what matters for evaporation. Spenser's experiment does not show any different at all. And no, your ground thermometer or barefoot kid most certainly does NOT measure what radiation instruments do and while you persist in this belief, we get nowhere. And actually that IS a good diagram for true energy budget. So evaporation is next biggist compared radiation? So what? It is tiny compared to radiation its also second smallest. Furthermore, to keep hammering a point, evaporation is phyusically limited and cannot be a forcing. As to science - what a complete mischaracterization! That is actually insulting. Science creates models, uses them to make predictions and checks prediction against measurement LOOKING for discrepancy not confirmation. Science is founded on combination of logic and observation. Use both. I see KR has answered your question well since you seem to have ignored my answer in 109.
    0 0
  19. KR at 05:35 AM, so is that the reason monitoring stations are 1.2m above ground level, the first metre of air intercepts very little energy. ;-) Perhaps you can explain why it intercepts very little of this energy, taking into account these relevant points. The carbon cycle requires that all CO2 will either return to the surface to be sequestered or is released from the surface, an equivalent to the entire atmospheric content of CO2 every 3 or 4 years and it cannot do that without having an increased presence in the first metre, and isn't it considered a major factor in intercepting energy. All evaporation occurs also at the very surface so it also is unable to move to the upper atmosphere without maintaining an ongoing presence in that first metre of air. Apart from the situation at night when temperatures at ground level fall below those 1.2m above, any solar energy that is absorbed by the atmosphere as shown on the budget diagram, if it is not directly absorbed from incoming solar radiation, then it comes via the surface either as convection, evaporation or surface radiation, and during that transfer, the temperature is higher at the surface and decreases with altitude, so obviously more energy is held in that first metre than in any metre above it.
    0 0
  20. scaddenp at 07:20 AM, Phil if you could quantify the radiation measured against what a thermometer measures as heat at the surface over the same time frame then that would help make the distinction.
    0 0
  21. johnd - The first meter intercepts fairly little energy because it's only the first meter. The IR from the ground is absorbed in the first couple hundred meters (80+% in the first 100, if I recall correctly) due to the optical depth of air to IR. If that's not understandable, I don't know what I can say to explain it to you. (I thought of saying "if that's not clear", but I didn't want to add to the issue...) As to CO2 "...having an increased presence in the first metre" - absolutely not. CO2 is very well and evenly distributed in the atmosphere. If anything, in areas where sequestration was taking place, you would expect CO2 levels to decrease slightly based upon sequestration rates and the (very high) diffusion rates. Please look at some of the information on radiation fog (fog produced by the nocturnal cooling of the surface boundary layer to a temperature at which its content of water vapor condenses) here, here, and here. It's really pretty simple. The ground radiates IR (cooling), which is intercepted over 100+ meters (distributing that energy away from the ground), and by conduction cools the first meter or so.
    0 0
  22. KR at 12:34 PM, regarding how well CO2 is mixed in the atmosphere, you will find this study of CO2 levels measured by surface stations interesting. http://www.atmos-chem-phys.net/8/7239/2008/acp-8-7239-2008.pdf In particular note what variations can occur over a few days, as well as the huge variations that occur over the course of the year due to seasonal conditions, up to or in excess of 50ppm, certainly very much more than a slight decrease, as well as how much the CO2 varies between locations. Given the processes that transport the CO2, the distribution of it has a lot in common with how heat is distributed as well as moisture, so would you say that they too are well and evenly distributed in the atmosphere. We know and accept that water must return to the surface to complete the hydrological cycle and so too does CO2. The amount of CO2 that is in the carbon cycle moving between the sources and sinks, all of them at the earths surface, is about 30 times that which is released by the combustion of fossil fuels.
    0 0
  23. scaddenp at 07:20 AM, Phil, on the contrary, I think we are getting somewhere. So, a thermometer lying on the ground, or a barefoot kid does not measure what radiation instruments measures. What they both measure is the result of solar radiation being absorbed by matter or objects on surface, sufficient radiation to heat the surface to the point a bare foot kid would be unable to stand still for fear of burning his feet, or as I mentioned earlier, enough to fry an egg in some cases. That leads us back to the question as to where does the energy come from that drives evaporation, is it that heat absorbed from the solar energy that can burn the soles of the kids foot, or is it the back radiation that he is unable to sense as it can only be measured by radiation instruments?
    0 0
  24. John, this is getting a bit repetitive but I will try... At the surface, radiation is being received as short wave from sun, and long wave from the atmosphere. The radiation is absorbed by atoms/molecules in that surface (at top for ground, in first few metres for water). This radiation energy converts to added kinetic energy for these atoms. Collectively this is heat, and what the thermometer measures. Conduction comes into play. The energy is transferred, atom to atom, both downward below the surface and to molecules of the atmosphere at the boundary, which collide with others to transfer energy up. In liquids, some of that energy also goes into evaporation. So the surface loses energy and thus is cooled by those processes. The amount of energy the can be moved away by conduction and evaporation is strictly limited by physical laws. As energy is absorbed, more and more radiation energy is converted to kinetic energy in the atoms. However, moving atoms (or more to point, the charged particles of the atoms) lose energy by radiation. The temperature of surface (the amount of kinetic energy in the atoms) stops rising when the losses by radiation match the energy coming in. Surface radiation goes up. For the temperatures at the earth surface, this radiation is long wave as opposed to the short wave coming in. The atmosphere is transparent (it doesnt absorb) to short wave, but GHG do absorb the longwave, convert to kinetic energy and so heat the atmosphere. Moving particles again, so atmosphere emits radiation, some of which goes down to the surface again. Its not an efficient emitters because atmosphere re-absorbs radiation, then emits again and so on. This is the backradiation. What happens to your thermometers? Well in day time, shortwave from sun and backradiation both heat. Surface heats faster than atmosphere because it absorbs the radiation whereas atmosphere is only heated by conduction and the limited absorption of surface radiation by GHG. Conduction is more important closer to the ground. At night, the surface continues to radiate effectively for its temperature but now only warmed by backradiation. As it is efficient radiator is cools faster than atmosphere and again conduction works in reverse, cooling air closer to the ground. As temperature of ground drops, surface radiation reduces and so back radiation also is reduced but not hugely as whole thickness of the atmosphere is involved in radiation, absorption and re-radiation. You can see the relative night time drops if you go to site that actually measures the radiation as well as the temperature. And in case I need to say it... A thermometer does not measure radiation - it may measure the energy converted to atomic motion by an absorber however.
    0 0
  25. John, it comes from BOTH sun and backradiation as has been explained. Why is it so hard to understand this? You can sense the backradiation if you go into your backyard at night - note the lack of instant freezing to death. However, your sensors are more likely to notice the conduction from your warm body to the cooler night air. Have you bothered to compare ground cooling rate between clear and cloudy night yet?
    0 0
  26. johnd - I am sadly beginning to feel that you are being deliberately obtuse on this thread. You can certainly feel back-radiation and it's effects. Go outside on a warm night, turn your face to the sky. Then, for comparison, go inside to your kitchen, open the freezer, and face that from a foot away (outside the downdraft). You will feel the difference! I tend to use the back of my hand for this - for some reason I find that's pretty sensitive to thermal radiation, and I can even to some extent navigate in the dark - picking out doorways and cooler windows directionally, even though the air temperature doesn't change based on orientation of my hand. The temperature at any location is the sum of all the inputs - conduction from the ground, back-radiation from the sky, etc. As to CO2 distribution - there are certainly +/- 1 to 2% regional variations, as shown here: But given the rates of diffusion of gases, that's not going to have a distribution effect over a few meters - it takes kilometers of distance to induce a diffusion time delay. The first meter of air will not have a different concentration of CO2 than the next 2-3 meters unless you're playing with a CO2 fire extinguisher. Water vapor, due to it's state changes and extreme temperature sensitivity (and the fact that it adjusts to local conditions over hours or days, not centuries like CO2) is much more varied in distribution. Think 'clouds'. Enough said here. Johnd - the effect you had issues with (cold ground air) is what's behind radiation fog; there is no mystery there whatsoever. Look it up. Your issues on this thread have become more and more murky, to the extent that I (and perhaps others) can no longer tell what you are concerned about. The core of this thread is that water vapor is a powerful greenhouse gas with a short time constant - evaporating or condensing very quickly due to local temperature changes. This makes water vapor primarily a feedback, not a forcing, as other factors such as CO2 are much more long-term; water vapor adapts to and amplifies those relatively fixed factors. End of discussion for me, johnd.
    0 0
  27. KR at 02:53 AM, I can't let you go without asking what is the relevance of the CO2 map. It does not represent measured CO2 distribution, but rather CO2 emissions attributed to human activity, so instead is basically a population density map.
    0 0
  28. Re: johnd (126) Then try this one: The Yooper
    0 0
  29. scaddenp at 14:54 PM, I think it is quite clear that the various processes that occur at the very surface and the few centimetres immediately above are not only very complex, but as yet not adequately understood or quantified. I would rate the status of such processes somewhat similar to those driving clouds, both in terms of complexity, and of current understanding, both of which are probably the most important processes of all when it comes to understanding climate change. As we have seen, what happens at the surface and immediately adjacent to it, is somewhat different to what happens just above it in the zone occupied by weather stations which have, and still do provide the basic data that allows both weather and climate to be quantified and analysed. The significance of this difference has not been lost on those who research agriculture, or indeed those who practice it. For them, it is the micro-climate, right at the earths surface that is important, that zone where solar radiation transfers it's energy to the soil and water, where evaporation takes place, NOT so much what happens 1.2m above where the weather stations are located which is above the zone in which most crops grow. If there is any nett transfer of knowledge between those involved in agricultural research, and those in climate research, I would not be surprised if it was from the agricultural scientists who research this micro-climate, to the climate scientists. The bare foot boy I mentioned earlier, was a proxy for the knowledge that those who are physically involved in the environment accumulate both by casual observation, and from a vested interest in what is really happening within that micro-climate, knowledge that many whose understanding of the climate comes from theories and formulas, and have not had the opportunity to relate what has been learned, to what is perhaps not so readily apparent without such a vested interest. With regards to the lack of freezing to death in ones backyard at night, that I imagine would be conditional on firstly the location of the backyard, and secondly that of the nights being shorter than 24 hours.
    0 0
  30. Daniel Bailey at 13:16 PM, that map is CO2 8km up. The reference earlier was to CO2 levels as measured at surface stations, and how it is transported by the weather systems. The mention in my post above of the micro-climate is also relevant to CO2 , given CO2 sources and sinks are generally at the immediate surface, so CO2 levels in the first couple of centimetres are likely to differ from those at higher elevations and be subject transportation by conditions in effect at those lower levels.
    0 0
  31. johnd, are you arguing that small variations in CO2 level within a few centimeters of the surface play a significant part in global temperatures? That SEEMS to be what you are getting at... it just doesn't make sense. The whole reason CO2 is such a significant greenhouse gas (aside from its longevity) is that it spreads high up through the atmosphere. A thin layer has very little impact on temperatures... it is the huge altitude range that CO2 occupies which allows it to produce significant additional warming. Your 'few centimeters' of CO2 at the surface would produce an insignificant amount of greenhouse warming... almost all of which would also be produced by water vapor even if the CO2 weren't there. It's like arguing about the impact of a falling pebble while ignoring the rockslide behind it. That said, it should be understood that when readings show 390 ppm at various surface stations around the world and in satellite measurements at higher altitudes that is effectively the baseline CO2... the amount after it has been well mixed through the atmosphere. Regions downwind of major emissions areas will have that baseline PLUS some additional amount of CO2 which hasn't dispersed yet. So yes, there are localized variations in CO2, but only in that in some regions it is higher than the commonly cited values because it hasn't had time to mix through the atmosphere yet.
    0 0
  32. CBDunkerson at 19:58 PM, for CO2 the carbon cycle starts and finishes at the earths surface. That requires that every 3 to 4 years the equivalent amount of the entire CO2 content of the atmosphere rotates through the various sources and sinks at the surface, passing through those few centimetres both in and out, which is probably where it also either absorbs or releases most of the thermal energy it carries as it circulates. The seasonal variations also show that CO2 levels vary around 20 to 40ppm or even more over the course of the year, remembering that the CO2 released through the burning of fossil fuels is only about 1/30 of that released by natural processes. In addition to the offset in the timing of release and increased sequestration, the location of the sources and sinks may be far apart. If sea surface temperatures are a factor in whether CO2 is being released or sunk, then the circulation and concentration levels may be quite convoluted and as variable, but more difficult to track then say local temperatures, wind speeds and precipitation. Further, given the direct warming effect of CO2 is quite small, and it is the amplifying effect of water vapour that produces most of the greenhouse effect, with the quite large variations in CO2 concentrations throughout the annual cycle, then if water vapour is as sensitive as it is thought, then one would expect the variations in water vapour to respond with even larger amplified responses that then flows through to increased variations in clouds in both volume and distribution.
    0 0
  33. My apologies - the map I posted here is indeed an emissions map (as johnd pointed out), not a concentration map. The appropriate map is the one Danial Bailey posted here. This also more clearly demonstrates the point I was trying (rather badly) to make: that when johnd thought that CO2 concentrations varied significantly with a range of a few meters, he was quite wrong. My apologies if my original post was misleading/incorrect.
    0 0
  34. johnd - CBDunkerson is quite right; small variations at ground level (to the extent there are any) will have insignificant effects on global warming. AGW is driven by radiative imbalances, which occur in the upper troposphere - the more GHG's present, the higher the emission mean for IR in the atmosphere, and the warmer the planet has to be to reach radiative balance. The cooling air at ground level is part and parcel of the "radiation fog" effect - a completely understood phenomena. That's a red herring in regards to climate change, quite frankly, and is no longer worth discussing. Water vapor has its primary effect in the upper troposphere as well - I can't find the link right now, but the fact that the primary IR emissions to space from water vapor come from above the cloud layers is why fairly simple average values are of use in global climate models. Clouds (lower in the atmosphere) do have an effect, but at a level where the consensus isn't certain whether it's net positive or net negative feedback - that's where most of the +/-1.5C in feedback for CO2 doubling comes from.
    0 0
  35. Re: KR (132) I was a little lazy in my previous linked graphic (it was a little dated, being from 2003). The AIRS site has more up-to-date graphics, like this one from 2009: I note in passing that Bermuda is still a world-leader in emissions. :) The Yooper
    0 0
  36. I think the point being missed with regards to both water vapour, the subject of this thread, and CO2 is whilst the effects may be felt in the upper atmosphere, the causes of water vapour, evaporation, and of the natural releases of CO2, human emissions are tiny by comparison, 1/30th, all are due to conditions that prevail in the micro-climate that exists at the earths very surface, both over land and the oceans. As I pointed out earlier, those whose interest lies in what happens within that micro-climate find conditions somewhat different to those whose interest begins with data collected 1.2m above ground level, and it will be such that as understanding of the processes that occur within that micro-climate improve, the causes, that will feed into providing greater understanding of the macro-climate, and the effects. I think the way in which the BOM data I referred to was generally dismissed because it was deemed to be for agricultural purposes is indicative of the lack of appreciation of just how important understanding the processes of the micro-climate is to the overall understanding of the climate generally, and the weather systems which ultimately define what the climate is at any given point of time.
    0 0
  37. KR at 02:47 AM, you wrote "the fact that the primary IR emissions to space from water vapor come from above the cloud layers" Can you clarify that as I'm not sure what you mean, given that as water vapour rises it progressively gives up it's heat, condensing into clouds, the last of the heat being given up by whatever is remaining of the water vapour, obviously, at the level of which the highest clouds form.
    0 0
  38. human [CO2] emissions are tiny by comparison, 1/30th
    Johnd, that is a sophistic partial truth which is arrived at by focusing on one side of a natural cycle rather than considering the net amount. It has already been addressed on this site. How do human CO2 emissions compare to natural CO2 emissions? (argument #28)
    The natural cycle adds and removes CO2 to keep a balance; humans add extra CO2 without removing any.
    0 0
  39. Bibliovermis at 06:10 AM, the point being made is that until complete understanding is reached about what drives the natural sources, and sinks that are able to accommodate seasonal variations many times the total amount of human emissions, then there are many assumptions having to be made. One could be that the natural cycles adjusts to seek a balance. If that is the case what are the limits that any imbalance reaches either side of balanced before the natural balances adjust to overcome imbalances over or under? Are the responses linear or do they progressively ramp up, or down responding to the degree of imbalance? Is it absolutely certain that natural CO2 emissions are not rising faster than offsetting natural sinks in response to increased temperature?
    0 0
  40. johnd at 06:37 AM, correction, that should read "If that is the case what are the limits that any imbalance reaches either side of balanced before the natural PROCESSES adjust to overcome imbalances over or under?"
    0 0
  41. Johnd - "not understood" - simply not true. We MEASURE all this stuff. You are looking for microscopic local changes and inferring this can drive large scale global trends while at the same time arguing that the MEASURED increase in backradiation from greenhouse gas - a much larger forcing - is insignificant. I am sorry but you seem to engaged in wishful thinking only. I have wasted enough time trying to explain. I'm out of here.
    0 0
  42. Also, the "dismissing" of BOM data because was because it measured what was important to agriculture, every seen it is perfectly well understood and explicable from known physics but it did not measure the variables necessary for investigating water vapour/radiation relationships. Also your continuing insistence on understanding carbon cycle is interesting. AR4 models do not on the whole include carbon cycle at all - because it assumed to be a slow feedback. The understanding of what part of our emissions remains in atmosphere is from measurement again. This is looking for excuses not looking for truth.
    0 0
  43. johnd #138: "Is it absolutely certain that natural CO2 emissions are not rising faster than offsetting natural sinks in response to increased temperature?" Yes. Yes it is. We know that the steady increase of atmospheric CO2 (and ocean carbonic acid) over the past century has been due to human emissions. See 'empirical evidence that humans are causing Global warming'. Besides, how can you really think that warming is causing the CO2 rise when the CO2 has been increasing steadily while warming has undergone numerous significant fluctuations... no correlation.
    0 0
  44. johnd - IR is more dominant as an energy pathway than latent heat (evaporation/condensation). Latent heat moves 80 W/m^2 into the atmosphere, while IR moves 356 W/m^2 into the atmosphere (Trenberth 2009). Atmospheric emissions of IR to space are 169 W/m^2, with an estimated 30 W/m^2 from clouds. Evaporation is not the dominant energy pathway, not by a factor of 4. Your statements contradict the actual measurements.
    0 0

Prev  1  2  3  

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.



The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2020 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us