Water Vapor Feedback

Guest Post by Willis Eschenbach

Well, another productive ramble through the CERES dataset, which never ceases to surprise me. This time my eye was caught by a press release about a new (paywalled) study by Gordon et al. regarding the effect of water vapor on the climate:

From 2002 to 2009, an infrared sounder aboard NASA’s Aqua satellite measured the atmospheric concentration of water vapor. Combined with a radiative transfer model, Gordon et al. used these observations to determine the strength of the water vapor feedback. According to their calculations, atmospheric water vapor amplifies warming by 2.2 plus or minus 0.4 watts per square meter per degree Celsius. (See Notes for sources)

Hmmm, sez I, plus or minus 0.4 W/m2? I didn’t know if that was big or small, so I figured I’d take a look at what the CERES data said about water vapor. As the inimitable Ramanathan pointed out, the distribution of water vapor in the atmosphere is shown by the variations in the clear-sky atmospheric absorption of upwelling longwave.

distribution of water vapor watts shown by clear sky absorptionFigure 1. Distribution of Atmospheric Water Vapor, as shown by absorption of upwelling surface longwave (LW) radiation, in watts per square metre (W/m2). In areas of increased water vapor, a larger amount of the upwelling radiation is absorbed in clear-sky conditions. Absorption is calculated as the upwelling surface longwave radiation minus the upwelling top-of-atmosphere (TOA) longwave radiation. The difference between the two is what is absorbed. Contours are at 10 W/m2 intervals.

As Ramanathan saw, there’s only one greenhouse gas (GHG) that shows that kind of spatial variability of absorption, and that’s water vapor. The rest of the GHGs are too well mixed and change too slowly to be responsible for the variation we see in atmospheric absorption of upwelling surface radiation.. OK, sez I, I can use that information to figure out the change in clear-sky absorption per degree of change in temperature. However, I wanted an answer in watts per square metre … and that brings up a curious problem. Figure 2 shows my first (unsuccessful) cut at an answer. I simply calculated the change in absorption (in W/m2) that results from a one-degree change in temperature.

change clear sky atmospheric absorptionper degree

Figure 2. Pattern of changes in clear-sky atmospheric absorption, per 1°C increase in temperature. This is the pattern after the removal of the monthly seasonal variations.

The problem with Figure 2 is that if there is a 1°C increase in temperature, we expect there to be an increase in watts absorbed even if there is absolutely no change in the absorption due to water vapor. In other words, at 1°C higher temperature we should get more absorption (in W/m2) even if water vapor is fixed, simply because at a higher temperature, more longwave is radiated upward by the surface. As a result, more upwelling longwave will be radiated will be absorbed. So I realized that Figure 2 was simply misleading me, because it includes both water vapor AND direct temperature effects.

But how much more radiation should we get from a surface temperature change of 1°C? I first considered using theoretical blackbody calculations. After some reflection, I realized that I didn’t have to use a theoretical answer, I could use the data. To do that, instead of average W/m2 of absorption, I calculated the average percentage of absorption for each gridcell, as shown in Figure 3.

distribution of water vapor shown by clear sky absorptionFigure 3. As in Figure 1, showing the distribution of water vapor, but this time shown as the percentage of upwelling surface longwave radiation which is absorbed in clear-sky conditions. Contours are at intervals of 2%, highest contour is 40%. Contours omitted over the land for clarity.

This is an interesting plot in and of itself, because it shows the variations in the efficiency of the clear-sky atmospheric greenhouse effect in percent. It is similar to Figure 1, but not identical. Note that the clear-sky greenhouse effect in the tropics is 30-40%, while at the poles it is much smaller. Note also how Antarctica is very dry. You can also see the Gobi desert in China and the Atacama desert in Peru. Finally, remember this does not include the manifold effects of clouds, as it is measuring only the clear-sky greenhouse effect.

Back to the question of water vapor feedback, using percentages removes the direct radiative effect of the increase in temperature. So with that out of the way, I looked at the relationship between the percentage of absorption of upwelling LW, and the temperature. Figure 4 shows the average temperature and the average absorption of upwelling LW (%):

atmospheric upwelling lw absorption vs temperatureFigure 4. Scatterplot of 1°x1° gridcell average atmospheric absorption and average temperature. The green data points are land gridcells, and the blue points show ocean gridcells. N (number of observations) = 64,800.

As you can see, the relationship between surface temperature and percentage of absorption is surprisingly linear. It is also the same over the land and the ocean, which is not true of all variables. The slope of the trend line (gold dashed line in Figure 4) is the change in percentage of absorption per degree of change in temperature. The graph shows a ~ 0.4% increase in absorption per °C of warming.

Finally, to convert this percentage change in absorption to a global average water vapor feedback in watts per square metre per °C, we simply need to multiply the average upwelling longwave (~ 399 W/m2) times 0.443%, which is the change in percentage per degree C. This gives us a value for the change in absorption of 1.8 ± .001 W/m2 per degree C.

Finally, recall what the authors said above, that “atmospheric water vapor amplifies warming by 2.2 plus or minus 0.4 watts per square meter per degree Celsius.” That means that the CERES data does not disagree with the conclusions of the authors above. However, it is quite a bit smaller—the Gordon et al. value is about 20% larger than the CERES value.

Which one seems more solid? I’d say the CERES data, for a couple of reasons. First, because the trend is so linear and is stable over such a wide range. Second, because the uncertainty in the trend is so small. That indicates to me that it is a real phenomenon with the indicated strength, a 1.8 W/m2 increase in absorbed TOA radiation.

Finally, according to Gordon et al. there is both a short-term and a long-term effect. They say

By forcing a radiative transfer model with the observed distribution of water vapor, we can understand the effect that the water vapor has on the TOA irradiance. Combining information on how global mean surface temperature affects the total atmospheric moisture content, we provide an estimate of the feedback that water vapor exerts in our climate system. Using our technique, we calculate a short-term water vapor feedback of 2.2 W m–2 K–1. The errors associated with this calculation, associated primarily with the shortness of our observational time series, suggest that the long-term water vapor feedback lies between 1.9 and 2.8 W m-2 K–1.

So … which one is being measured in this type of analysis? I would argue that the gridcells in each case represent the steady-state, after all readjustments and including all long-term effects. As a result, I think that we are measuring the long-term water-vapor feedback.

That’s the latest news from CERES, the gift that keeps on giving.

Best to all,

w.

NOTES:

Ut Solet

If you disagree with something I (or anyone) says, please quote my words exactly. I can defend my own words, or admit their errors, and I’m happy to do so as needed. I can’t defend your (mis)understanding of my words. If you quote what I said, we can all be clear just what it is that you think is incorrect.

Data and Paper

Press Release here.

Paywalled paper: An observationally based constraint on the water-vapor feedback, Gordon et al., JGR Atmospheres

R Code: CERES Water Vapor (zipped folder 750 mb)

CERES Data: CERES TOA (220 Mb) and CERES Surface (115 Mb)

[UPDATE]

An alert reader noted that I had simplified the actual solution, saying:

Since one of the feedbacks is T^4 it would probably come out as T^3 in a percentage plot and this curve has strong upwards curvature.

To which I replied:

Not really, although you are correct that expressing it as a percentage removes most of the dependence on temperature, but not quite all of the dependence on temperature. As a result, as you point out the derivative would not be a straight line. Here’s the math. The absorption as a percentage, as noted above, is

(S- TOA)/S

with S being upwelling surface LW and TOA upwelling LW.

This simplifies to

1 – TOA/S

But as you point out, S, the surface upwelling LW, is related to temperature by the Stefan-Boltzmann equation, viz

S = sigma T4

where S is surface upwelling LW, sigma is the Stefan Boltzmann constant, and T is temperature. (As is usual in such calculations I’ve assumed the surface LW emissivity is 1. It makes no significant difference to the results.)

In addition, the TOA upwelling longwave varies linearly with T. This was a surprise to me. One of the interesting parts of the CERES dataset investigation is seeing who varies linearly with temperature, and who varies linearly with W/m2. In this case TOA can be well expressed (to a first order) as a linear function of T of the form mT+b.

clear sky toa upwelling lw vs surface temperature ceres

This means that (again to a first order) I am taking the derivative of

1 – (m T + b) / (sigma T4)

which solves to

(4 b + 3 m T)/(sigma T5)

Over the range of interest, this graphs out as

variation in water vapor feedback with changes in temp

Recall that my straight-line estimate was 0.44% per degree, the average of the values shown above. In fact, the more nuanced analysis the commenter suggested shows that it varies between about 0.38% and 0.5% per degree.

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93 Responses to Water Vapor Feedback

  1. ATheoK says:

    Is good analysis Willis! Thanks!

  2. David, UK says:

    Would love for you to write straight, without the floweriness, sez I.
    d.

  3. markx says:

    Dumb question time (on a quick read)…..

    I presume fig 1 somehow takes into account the varied surface temperatures, which would be directly related to the amount of upwelling LW?

    How is the ‘absorbed upwelling LW’ calculated? (Is that by taking into account known surface temperatures and calculating theoretical upwelling vs measured upwelling LW?)

    Thanks
    Mark.

  4. Another Ian says:

    David UK

    A long way from “Inebriated with the eloquesence of his own verbosity” IMO

  5. Joel O'Bryan says:

    In Figure 3, what would happen to the linear trend line slope if data with points with T < -20C were dropped (truncated)? (that would truncate the polar data)

    The polar regions seem to me to have been confounding interpretations of the global climate data. The conventional wisdom has been (often parroted) as the poles are "canary in the coal mine", i.e. a leading predictor of where global climate is heading. But that doesn't fit with the fact that diurnal and coriolis mixing effects are least effective there. And the now the famous polar vortex, despite the recent displacements southward, belies the fact that generally polar atmospheric circulation and polar ocean currents are more isolated and stable, and thus it would seem the polar regions are actually lagging indicators of global climate.

  6. TimTheToolMan says:

    Sorry Willis, I dont think this is particularly valid improvement. CERES clear sky “measurements” are calculated values using a radiative transfer model and so you’re effectively reporting what the model says should be being absorbed rather what is actually measured.

  7. Rik says:

    Do water vapour increase because temperature increased or do temperature increase because water vapour increased? How can we differ?

  8. This posting would make a gem of a short paper for the reviewed literature.

    Two brief observations. First, Willis’ value of 1.8 Watts per square meter per 1 Celsius degree of warming is the same as that which Soden and Held (2006), cited with approval in IPCC (2007), find in response to a CO2 doubling (which drives a direct warming of 1 Celsius degree).

    Secondly,the ISCCP data since 1983 seem to disagree with the CERES data. ISCCP shows no change in column water vapor, except at the crucial 300 mB pressure altitude, where it is actually falling somewhat. Data are at isccp.giss.nasa.gov/products/otherDsets.html.

  9. jauntycyclist says:

    as the major greenhouse gas do we need to tax dihydrogen monoxide? Maybe banning it is better?

    “In February 2011, during the campaign of the Finnish parliamentary election, a voting advice application asked the candidates whether the availability of “hydric acid also known as dihydrogen monoxide” should be restricted. 49% of the candidates answered in favour of the restriction.”

    http://en.wikipedia.org/wiki/Dihydrogen_monoxide

    so we nearly there! another 2% and you would have a consensus and settled knowledge with no need for debate with ‘d eniers’.

  10. izen says:

    @- “This gives us a value for the change in absorption of 1.8 ± .001 W/m2 per degree C.”

    This seems to confirm that ‘widget’ claim of four Hiroshimas a minute or whatever the rate of energy accumulation measured by climate scientists is.

  11. JohnB says:

    Probably a dumb question, but apart from model estimates how do you calculate the upwelling surface longwave radiation in the first place? Where and how is it measured?

    If “X” is the USLR and “Y” is the measurement at TOA then “X-Y” gives the absorption, but how is “X” calculated?.

    Thanks.

  12. Baa Humbug says:

    I can see the Atacama desert, but Gobi not so much. Gobi is on the border of China and (mostly in) Mongolia I thought.
    Also. how come I can’t make out the vast deserts of Nth Africa, Arabia and Australia? Are there so much water vapour above these intense dry places? I’m confused.

  13. Will Pratt says:

    Every body knows that water vapour absorbs and transports LW radiation as latent heat, away from the surface to the top of the atmosphere.

    The assumption here is that the LW absorbed by water vapour causes GHE warming simply because some so called “GHG” has absorbed it. The truth however is the exact opposite. Water vapour removes LW IR or thermal radiation, if you prefer, as latent heat.

    The effect of latent heat removal, as we are all very well aware Willis, is cooling, not warming.

    Water vapour is a negative feedback mechanism.

    GHG cooling, if you insist.

  14. Espen says:

    Baa Humbug says:
    March 24, 2014 at 2:03 am
    I can see the Atacama desert, but Gobi not so much. Gobi is on the border of China and (mostly in) Mongolia I thought.

    Yes, the yellow-greenish area there is Tibet, not Gobi.

  15. eyesonu says:

    Good work Very well presented.

    Water vapor is the ultimate GHG AND the ultimate thermostat mechanism.

  16. Santa Baby says:

    Why does the graph stop at 25 deg C? Me would love to see the graph all the way to 35 or 40 ?

  17. Robert JM says:

    The end point at 2009 is during an El Nino, which have been to shown to produce a massive plume of water vapour in the atmosphere as part of their heat dissipation process.
    Strangely enough the world does’t explode when this happens but instead cools.
    This is because the earth warms and cools in a 24 hour cycle and of course when water vapour cools it condenses forming clouds that subsequently reduce incoming solar radiation.

    While El Nino initially involves some positive feedback due to disruption of the convective cycle and laminar cloud layers it eventually turns into a giant heat Vacuum cleaner!
    The Super El Nino of 97/98 was directly proceeded by a 5% decline in cloud cover in the mid to late 90s, the true cause of most of the observed global warming in the satellite era. Shown in the ISCCP data.

  18. tom0mason says:

    I’m so glad to see more information on water vapor and it’s planetary effect. Thanks Willis.
    I’ve also seen a good write-up at Friends of Science site –
    http://www.friendsofscience.org/index.php?id=710

    It is my favorite question to to the hardened but ignorant CAGW types I meet –
    So what is the most abundant (so called) greenhouse gas?
    They, of cause, reply ‘CO2’!

  19. Greg says:

    Very interesting once again, Willis. The proportional trick was a good idea.

    “Finally, to convert this percentage change in absorption to a global average water vapor feedback in watts per square metre per °C, we simply need to multiply the average upwelling longwave (~ 399 W/m2) times 0.443%, which is the change in percentage per degree C. This gives us a value for the change in absorption of 1.8 ± .001 W/m2 per degree C”.

    No, sorry you’ve transformed your variables. You’re applying the slope of the transformed variables to an average on the non transformed LW radiation.

    Now the average of any quantity is not the same as the average of it as a proportion or percentage.

    In fitting your straight line to the proportional rise you are effectively taking the geometric mean. You are then applying this result to the global arithmetic mean of LW. There may be some way to deal with that but it’s not valid as it stands.

    I would also observe that the part of the graph from 10 – 30 deg C is far from linear, especially for sea data.

    Since one of the feedbacks is T^4 it would probably come out as T^3 in a percentage plot and this curve has strong upwards curvature.

  20. Greg says:

    The tropical temp cut off is what is giving the up tick and this is a very non linear effect. There are probably too many things of a very different nature going on here. Below zero will be very different regime as well.

    The main issue is the problem of applying the average of the proportion to the straight average of LW.

  21. Richard says:

    Hmm the hottest places are the areas with the least water vapour.

  22. Greg says:

    Since you have all the data may be the fix is to find global average of the proportional change for 1 degree and than multiply by 0.443 , or whatever.

  23. Ed Zuiderwijk says:

    The feedback on water vapour absorption is small, it hardly affects the effective opacity of the atmosphere. Increased cloudiness gives a negative feedback. Hence the feedback is most likely neutral. This would mean that the Earth’s atmosphere is in homeostatic equilibrium with water vapour content acting as the thermostat.

    There is a hypothesis that says that if the atmosphere contains a volatile constituent (in our case water) then the equilibrium temperature will be somewhere between 10 and 20 degrees above its triple point. On Earth it is 16 degrees above it. On Titan, the other example in the Solar system, it is about 15 degrees above the triple point of Methane.

  24. mobihci says:

    this is all very useful info for a stationary planet without clouds. observations have shown that water vapour feedback is affected by more than just surface temperature.

  25. M Simon says:

    David, UK says:
    March 24, 2014 at 12:39 am

    Would love for you to write straight, without the floweriness, sez I.
    d.

    Love the flowers. See my avatar. If not here elsewhere.

  26. When I saw these clouds I thought of Willis.

  27. johnmarshall says:

    None of the above explains why dry deserts are HOTTER than water vapour rich rainforest.

  28. chemengrls says:

    Upwelling long wave surface radiation is obtained from Planck’s Law. Absorption of LW in CO2 and wv wavebands is also obtained from Planck’s Law by integrating the area under the curve. Traverse to extinction through the atmosphere is obtained from Steffan Boltzman knowing the emissivity for length of traverse and GHG concetration and equating it to the absorbed LW in W/m^2.

  29. richard says:

    http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap7.html

    7.5.2 Clouds

    Feedbacks associated with changes in cloud cover represent the largest uncertainty in current estimates of climate change. Clouds can provide considerable negative feedback to global warming. We find from Figure 7-14 that the radiative forcing DF from an increase DA in the Earth’s albedo is

    (7.24)

    An increase in albedo of 0.007 (or 2.6%) since preindustrial times would have caused a negative radiative forcing DF = -2.5 W m-2, canceling the forcing from the concurrent rise in greenhouse gases. Such a small increase in albedo would not have been observable. We might expect, as water vapor concentrations increase in the atmosphere, that cloud cover should increase. However, that is not obvious. Some scientists argue that an increase in water vapor would in fact make clouds more likely to precipitate and therefore decrease cloud cover.

    To further complicate matters, clouds not only increase the albedo of the Earth, they are also efficient absorbers of IR radiation and hence contribute to the greenhouse effect. Whether a cloud has a net heating or cooling effect depends on its temperature. High clouds (such as cirrus) cause net heating, while low clouds (such as stratus) cause net cooling. This distinction can be understood in terms of our one-layer greenhouse model. Inserting a high cloud in the model is like adding a second atmospheric layer; it enhances the greenhouse effect. A low cloud, however, has a temperature close to that of the surface due to transport of heat by convection. As a result it radiates almost the same energy as the surface did before the cloud formed, and there is little greenhouse warming .

    Surely as well then regarding the supposed warming effect of co2 -( A low cloud, however, has a temperature close to that of the surface due to transport of heat by convection. As a result it radiates almost the same energy as the surface did before the cloud formed, and there is little greenhouse warming) co2 would cause little warming within this range.

    NASA- clouds on average cause cooling.

  30. Henry Clark says:

    Using our technique, we calculate a short-term water vapor feedback of 2.2 W m–2 K–1. The errors associated with this calculation, associated primarily with the shortness of our observational time series, suggest that the long-term water vapor feedback lies between 1.9 and 2.8 W m-2 K–1.

    Any reader should keep in mind that so implying warming by increased LW absorption has not been shown to consider the net effect, where the net effect includes extra water vapor leading to extra clouds with increased SW reflection. For instance, as a thought experiment, if nearly no water vapor was entering the atmosphere, there would be nearly no clouds able to form either. Within temperature ranges above freezing, higher temperature tends to lead to increased SW reflection, with increased albedo via increased clouds.

    The overall reflectance (albedo) of planet Earth is about 30 percent, meaning that about 30 percent of the incoming shortwave solar radiation is radiated back to space. If all clouds were removed, the global albedo would decrease to about 15 percent, and the amount of shortwave energy available for warming the planet surface would increase from 239 W/m2 to 288 W/m2 (Hartmann 1994). However, the longwave radiation would also be affected, with 266 W/m2 being emitted to space, compared to the present 234 W/m2 (Hartmann 1994). The net effect of removing all clouds would therefore still be an increase in net radiation of about 17 W/m2. So the global cloud cover has a clear overall cooling effect on the planet, even though the net effect of high and low clouds are opposite

    http://www.climate4you.com/ClimateAndClouds.htm

    (Hartmann 1994 may be an old publication, but that’s a bonus in ways: usually the older the publication, the less likely it is to have intentional error in data).

    A runaway greenhouse effect doesn’t happen, and there isn’t just net positive feedback from additional evaporation of water vapor for:

    an increase in a GHG (e.g. CO2 or a fluctuation in water vapor) -> warming -> more GHG release from the warming -> more warming -> more GHG release -> etc.

  31. daveburton says:

    A couple of years ago I ran some MODTRAN tropical atmosphere calculations, and compared the predicted temperature change with “constant water vapor pressure” to “constant humidity.” (Note that constant humidity means water vapor pressure increases at higher temperatures.) It calculated a 1.65x greater temperature increase with constant humidity. In other words, water vapor amplification of CO2-induced warming was calculated to be only 65%.

    Even including that amplification by water vapor, MODTRAN calculated that a doubling of CO2 from pre-industrial levels should only cause about 1°C of warming (and additional CO2 has a diminishing effect, due to saturation of the associated IR absorption bands):
    http://www.burtonsys.com/climate/MODTRAN_etc.html

    Additionally, water-cycle cooling should contribute a strong negative (stabilizing) feedback mechanism. Higher temperatures increase evaporation, which removes large amounts of heat of evaporation from the surface and carries it to the middle troposphere, where the heat is released when the water vapor condenses into clouds, rain & snow. (This is a classic refrigeration cycle, just like what happens in your air conditioner, except that the refrigerant undergoing the phase changes is water instead of Freon, and it’s the wet surfaces of the Earth being cooled instead of the interior of your home.)

  32. Kirk c says:

    Of course a linear tend line will give you a very clean answer. (Fig 4) I think you need to draw two lines around the data. One will have the slope shown (1.8) and capture the lower bounding line of the points a second will be much steeper in order to capture the upper bounds of data. Therefore the two slopes will define your upper and lower limits… Probably 2.2 +\- 0.4. ..Or so.

  33. John West says:

    Does it matter whether it’s 1.8 or 2.2? Either way, it’s way less than the nearly 20 needed for alarm.

    “Taking the Measure of the Greenhouse Effect ” http://www.giss.nasa.gov/research/briefs/schmidt_05/
    “If, for instance, CO2 concentrations are doubled, then the absorption would increase by 4 W/m2, but once the water vapor and clouds react, the absorption increases by almost 20 W/m2 — demonstrating that (in the GISS climate model, at least) the “feedbacks” are amplifying the effects of the initial radiative forcing from CO2 alone.”

    Of course, giss.nasa.gov is down at the moment but the science has spoken, is clear, uncontrovertable, and settled! (lol) Ok, well perhaps not all that but the ballance of the evidence would suggest that there’s nothing to worry about, expect mild warming from the burning of fossil fuels. When can we move on?

  34. Steve Keohane says:

    johnmarshall says:March 24, 2014 at 3:46 am

    None of the above explains why dry deserts are HOTTER than water vapour rich rainforest.

    Isn’t it because the sunlight is not absorbed by the atmosphere and heats the surface and cools radically at night, a 50°F cycle. It is the water vapor giving more mass to the atmosphere that stabilizes the temperature.

  35. richard says:

    rain forest Vs desert – so effectively water vapour cools during the day and slows down cooling at night.

  36. milodonharlani says:

    The Atacama proper is in Chile. Its northern extension in Peru is the Sechura Desert.

  37. neillusion says:

    There’s a huge ball of fire in the sky throwing a tremendous amount of energy at the earth. There are things that affect the amount of energy that gets ‘in’. There are things which use or otherwise hold on to that energy.
    Given the (large) amount of energy available to get through, and a fact established from the start, that temp rise precedes CO2 rise, I can’t help but dismiss CO2 (1part in 2500 compared to water vapour 1part in 30,000 of atmsph mass) from the (long) lineup of suspects. It seems to me that the huge reflective area of clouds would have the biggest effect ‘at source’, so to speak, and clouds being clouds, there will be a link between clouds and water vapour.

    So the twist I see in this is that water vapour shows a link to temperature but only through its link to cloud cover, not its ability to hold a relatively tiny amount of the heat that does get through. As with CO2, I feel that water vapour is a result of warming. It can’t hold on to something that isn’t there in the first place.

  38. Kelvin Vaughan says:

    Brain in gear, questions coming.

    What happens to the ULWIR once it has been absorbed?
    At what height is it absorbed? Is it mostly in the lower atmosphere?
    Does the lapse rate change the amount reradiated After it has been absorbed?

  39. johnmarshall says:

    @ steve keohane

    It is the need for latent heat used in the evapouration of water and the cloud formation due to convection and cloud tops reflecting heat to space. Deserts have near zero water so zero latent heat requirement. Deserts also have a higher temperature range than rainforest. another reality fact not covered by the GHE theory.

  40. fhhaynie says:

    I’ve used a similar approach with the reannalysis data http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl. There is a highly correlated relationship between the dependant variable, difference between black body radiation at SST and OLR at TOA, and the independant variables of precipitation rate and precipitable water. I have observed that including CO2 concentrations with these factors in multi-regressions indicate an insignificant effect of CO2.

  41. Alex says:

    So all of this is cherry-picked on ‘clear sky’ data. How the f*ck do u get any reasonable, real life data from this. Is this some sort of surreal post? God, Willis, you can come up with better stuff than this.

  42. fhhaynie says:

    Richard says:

    March 24, 2014 at 2:58 am

    The least amount of water vapor in the atmosphere is in the Antarctic where the frost point is the lowest.

  43. Alex says:

    Was the ceres data gathered on the UN declared cloud free day? Or were they looking at gaps between clouds etc. and then extrapolating the results over 1200 kms?

  44. JohnB says:

    @chemengrls Thanks for that.

    Follow up question. As the upwelling surface radiation as calculated by Planck’s Law is dependent on the temperature of the body concerned, how is an accurate planetary temperature derived?

  45. Ulric Lyons says:

    So why does this water vapour distribution show regular gaps through the tropics?
    http://www.fourmilab.ch/cgi-bin/Earth

  46. Arno Arrak says:

    None of the above. According to the Miskolczi greenhouse theory (MGT) water vapor feedback is effectively negative. His theory applies to a situation where more than one greenhouse gas are simultaneously absorbing in the infrared. Arrhenius, Fourier, and IPCC cannot handle this. In such a case a common optimum absorption window exists that the gases present jointly maintain. In the earth atmosphere the gases that count are carbon dioxide and water vapor. From radiation theory it can be shown that the optical thickness in the infrared of their joint optimum absorption window is 1.87. This corresponds to a transmittance of 15 percent or absorbance of 85 percent. If you now add carbon dioxide to the atmosphere it will start to absorb just as Arrhenius says. But this will increase the optical thickness. And as soon as that happens, water vapor will start to diminish, rain out, and the optimum absorption window is restored. Miskolczi showed this empirically by using NOAA weather balloon database that goes back to 1948 by measuring the change in infrared transmittance of the atmosphere over time. It turned out that infrared transmittance stayed constant for 61 years while atmospheric carbon dioxide at the same time increased by 21.6 percent. Addition of this substantial amount of carbon dioxide to air had no influence whatsoever on the absorption of IR by the atmosphere.There goes that greenhouse effect of Hansen. More currently, this is the reason why there is no greenhouse warming now despite the fact that atmospheric carbon dioxide is higher than ever and is still increasing. Lets now take a note of how laws of nature operate. You can’t turn them on or off to magically create a temporary hiatus. If the greenhouse effect is inoperative today it has always been inoperative. You will naturally want to know how come that this all started only 17 years ago. The answer is that it did not start 17 years ago, it has always been like that. The reason people think there was greenhouse warming before is simply because any previous warming designated as greenhouse warming has been misidentified by over-eager pseudo-scientists anxious to point to their favorite warming. This includes Hansen whose claim that he identified greenhouse warming in 1988 is false. He had a poorly resolved temperature curve with one year temperature intervals. That was not enough to show him that there were three El Nino peaks between 1980 and 1988. His peak heights were also incorrect and his “100 year” high point turned out to be nothing more exotic than an ordinary El Nino peak, the 1987/88 El Nino to be precise.

  47. Steve Keohane says:

    johnmarshall says:
    March 24, 2014 at 6:57 am

    @ steve keohane

    Enthalpy.

  48. Eyal Porat says:

    Rik says:
    March 24, 2014 at 1:26 am

    Do water vapour increase because temperature increased or do temperature increase because water vapour increased? How can we differ?

    My thoughts precisely!

  49. Alex says:

    The whole GHG thing is a straw man. A spectroscope is a beautiful piece of instrumentation for determining the signature of molecules (IR range). It is not a thermometer. The term ‘absorption’ does not mean it is a heat sink. The term ‘emission’ does not mean it is a power source. These are terms that are applied to the spectrum. They have little to do with thermodynamic properties. The mechanics/optics are set up to ‘see’ extremely directional light, fractions of a degree. Any molecule between the source and the final sensor is going to ‘interfere’ (simplified) with the direction of photons, thereby appearing as an absorption band. The reality is that the photon comes from one direction, is ‘absorbed’ and emitted again in some random direction, not necessarily in the direction of the sensor. The emission is going to occur in any possible direction. Approximately 41,500 directions based on 1 square degree on a globular surface. So it is no surprise that a detector with limited view is going to see a blank space. This does not mean that the molecule has retained this energy for any appreciable time. Any retention time is measured in microseconds. A spectroscope could also measure emission lines , but it would have to be extremely sensitive because the emissions would have a 1 in 41,500 chance of hitting the sensor. That is why you have absorption spectroscopy in IR and not emission spectroscopy.
    If you were to have 2 spectroscopes set at 90 degrees to each other with a heating source in front of one and a cold source, say, liquid nitrogen cooled on the other. Then you would obtain an absorption and an emission spectrum at exactly the same time.
    Therein ends my basic physics and instrumentation lesson. The boys that played with spectrums over 100 years ago had fun. Unfortunately some had drawn the wrong conclusions. We are paying for it now

  50. A positive water vapor feedback of 1.8 +/- 0.001 W/C is actually a little higher than the IPCC AR 5 estimate of 1.6 +/- 0.3 W/C
    See table 9.5 http://www.climatechange2013.org/images/report/WG1AR5_Chapter09_FINAL.pdf

    This means that this calculation gives a higher contribution to climate sensitivity from water vapor than the IPCC models, which is inconvenient seen from a climate sceptics point of view

    Science sometimes gives surprising results. So I congratulate you Willis, with a good and honest job, good scientists do not silently throw inconvenient results away.

  51. Jeff Motsinger says:

    An excellent article, thank you. However, there are more significant digits in the error bar than the number (1.8 plus or minus 0.001 W/m^2).

  52. Jeff Patterson says:

    To my eye Figure 4 looks logarithmic which I think would be expected due to saturation.

  53. Willis Eschenbach says:

    TimTheToolMan says:
    March 24, 2014 at 1:16 am

    Sorry Willis, I dont think this is particularly valid improvement. CERES clear sky “measurements” are calculated values using a radiative transfer model and so you’re effectively reporting what the model says should be being absorbed rather what is actually measured.

    Thanks, Tim, but … no. There are two groups of CERES datasets. The TOA datasets are measured. The surface datasets are calculated from the TOA datasets, and validated against a variety of other sources..

    However, I’ve compared the CERES upwelling surface longwave dataset to the surface longwave calculated from the observed temperatures and guess what? They are very close, certainly close enough for our purposes.

    So while you are kind of correct (some of the CERES data is calculated not measured), it’s a difference that makes very little difference.

    Regards,

    w.

  54. Russ R. says:

    Willis,

    There appears to be an inflection point in the data. In your Figure 4, focusing in on the ocean data … the blue dots appear to turn upward right around 30C.

    Is there enough data to reliably estimate the relationship independently above and below the inflection point?

  55. chemengrls says:

    JohnB

    I don’t know and I’ve never tried to to work it out.

  56. rgbatduke says:

    I can see the Atacama desert, but Gobi not so much. Gobi is on the border of China and (mostly in) Mongolia I thought.
    Also. how come I can’t make out the vast deserts of Nth Africa, Arabia and Australia? Are there so much water vapour above these intense dry places? I’m confused.

    I have to agree. Where, exactly, is the water vapour above these intense dry places? The average humidity of the Sahara, for example, is around 25%, and most of that comes from its comparatively few rains (it is around 4 or 5% humid most of the time). I’m not certain what kind of average the 25% is, but there is nothing LIKE a 25% relationship between the nearly 100% humid equatorial ocean.

    Humidity is of course a questionable measure in and of itself, as it is usually expressed as relative humidity, water vapor content relative to saturation. Cold air and warm air with exactly the same water vapor content can have very different relative humidity. It is still surprising to me that the Sahara and Namib do not stand out like a sore thumb. Parts of the Namib dessert receive 19mm of rain and 35 mm of fog/dew precipitation per year — where in NC we get that much rain in a day and that much dew precipitation in a week or two. Yet NC is considered drier than the Namib as far as any of the maps above are concerned. Then there is the US midwest, considered to be much, much drier (as far as water-vapor-linked atmospheric absorption is concerned) than the Sahara.

    I have to say, Willis, that this fails mere common sense checks for data consistency. I’m not certain what is really being graphed here on the maps, but I’m pretty sure that it isn’t what any of these arguments claim it is.

    Indeed, one can compare the direct spectrographs provided in Petty’s book with this data to see the puzzle. He provides the spectrograph looking down over the Sahara, and in the dry air the CO_2 bands stand out but everywhere else the atmosphere is nearly transparent. He also provides direct spectrographs looking down over tropical ocean, where there is an overwhelming contribution from water vapor and even the CO_2 bands are reduced to perturbations on a broad background of absorption. The spectrographs just don’t seem consistent with the maps above, suggesting that the normalization isn’t being done right. I don’t know offhand how to fix it or how it is wrong, but I’d be very suspicious of any map that shows substantial water-vapor absorption above places that get less than 5 inches of total precipitation a year.

    I’ve long thought that the GHE can be better studied in places like the Namib and the Sahara than anywhere else on Earth, largely because they lack the confounding effect of water vapor. Water vapor is not a good direct proxy for the GHE because it is a dual contribution. Yes, it increases absorption and hence back radiation, but it also is the vehicle for direct transport of latent heat up from the surface to heights from which it can be radiated without passing through the greenhouse layer. Finally, it is the precursor to clouds, where the direct variation of the effective albedo usually trumps the variation of GHE. Altogether water vapor produces a mix of feedbacks from different, nonlinearly coupled processes that affect the total radiation being given off by any patch of surface and the pathways by which incident heat leave (humid air also absorbs and scatters more SW energy on the way down and prevent as much from reaching the surface in the first place, for example). That’s why deserts are good. All of this is turned off.

    rgb

  57. John Tillman says:

    rgbatduke says:
    March 24, 2014 at 9:23 am

    Short of going to the South Pole, as did the putative gravity-wave detecting BICEP2 team, the best place to study the GHE would be the Atacama Desert of northern Chile, where so many observatories are located, thanks to extreme dryness of the air above mountains there.

  58. Willis Eschenbach said:

    As the inimitable Ramanathan pointed out, the distribution of water vapor in the atmosphere is shown by the variations in the clear-sky atmospheric absorption of upwelling longwave.

    Finally, recall what the authors said above, that “atmospheric water vapor amplifies warming by 2.2 plus or minus 0.4 watts per square meter per degree Celsius.”

    As a result, I think that we are measuring the long-term water-vapor feedback.
    ———————

    Sam Cogar asks:

    Looking at the Figure 3 graphic, it is obvious that the H2O vapor ppm is the greatest at the Equator and decreases toward either Pole.

    And if I accept this as reasonably accurate figures, to wit:

    “The percentage water vapor in surface air varies from .01% at -42℃ (-44℉) to 4.24% when the dew point is 30℃ (86℉).” Src: http://en.wikipedia.org/wiki/Water_vapor

    And looking again at your Figure 3 graphic, I then have to assume that the H2O vapor ppm between the Equator and the extent of the Temperate Zones, … @ 66.5° north latitude & 66.5° south latitude, ……. should average between 4.24% at the Equator to say 1.5% in said Temperate Zones. And if expressed in ppm then the H2O vapor averages between 42,400 ppm and 15,000 ppm respectively.

    Now given the above stated fact about “H2O vapor amplification” then that means it requires a minimum average of 15,000 ppm to 20,000 ppm of H2O vapor (1.5 – 2%) to amplify atmospheric warming by 2.2 plus or minus 0.4 watts per square meter per degree Celsius.

    Now if the current atmospheric CO2 is at 0.040% ….. or 400 ppm, … then the H2O vapor at 15,000 ppm is 37.5 times greater than the CO2 ….. and at 20,000 ppm it is 50 times greater than the CO2. (106 > @ 4.24%)

    Now considering all the above, just how much would, could, does 400 ppm of CO2 amplify atmospheric warming in watts per square meter per degree Celsius.

    And if one is using a thermometer to measure near-surface temperatures then how does one know which one (1) of the gasses in the air is responsible for the increase in temperature and/or how much of the temperature increase during any given time frame?

    Or is my thinking totally FUBAR ….. and thus my question irrelevant?

  59. Keitho says:

    Is there a reason for the Sahara desert not responding in the same way as the Atacama and Gobi deserts?

  60. milodonharlani says:

    Keitho says:
    March 24, 2014 at 10:40 am

    The Namib & Atacama share cold eastern boundary currents flowing north from Antarctic waters, which produce fog but very little to no rain. The Gobi is not as dry, but suffers from a continental climate, with a rain shadow formed by the Himalayas’ blocking clouds from the Indian Ocean.

  61. Willis Eschenbach says:

    Greg says:
    March 24, 2014 at 2:51 am

    “Finally, to convert this percentage change in absorption to a global average water vapor feedback in watts per square metre per °C, we simply need to multiply the average upwelling longwave (~ 399 W/m2) times 0.443%, which is the change in percentage per degree C. This gives us a value for the change in absorption of 1.8 ± .001 W/m2 per degree C”.

    No, sorry you’ve transformed your variables. You’re applying the slope of the transformed variables to an average on the non transformed LW radiation.

    Now the average of any quantity is not the same as the average of it as a proportion or percentage.

    Not sure I follow this one.

    In fitting your straight line to the proportional rise you are effectively taking the geometric mean. You are then applying this result to the global arithmetic mean of LW. There may be some way to deal with that but it’s not valid as it stands.

    Mmmm … in fitting a straight line between the proportional rise and the temperature, I’m taking the derivative of the % absorbed WRT temperature. The percentage absorbed is:

    A = (S – TOA) / S

    where A is the percentage absorbed, S is the upwelling longwave surface radiation, and TOA is the TOA lw radiation.

    I’m not clear why taking that derivative dA/dT is equivalent to a geometric mean.

    I would also observe that the part of the graph from 10 – 30 deg C is far from linear, especially for sea data.

    Some non-linearity is always present in the real world. In this case, unlike most such graphs, the surprising thing was the linearity.

    Since one of the feedbacks is T^4 it would probably come out as T^3 in a percentage plot and this curve has strong upwards curvature.

    Not really, although you are correct that expressing it as a percentage removes most of the dependence on temperature, but not quite all of the dependence on temperature. As a result, as you point out the derivative would not be a straight line. Here’s the math. The absorption as a percentage, as noted above, is

    (S- TOA)/S

    with S upwelling surface LW and TOA upwelling LW.

    This simplifies to

    1 – TOA/S

    But as you point out, S, the surface upwelling LW, is related to temperature by the Stefan-Boltzmann equation, viz

    S = sigma T4

    where S is surface upwelling LW, sigma is the Stefan Boltzmann constant, and T is temperature. (As is usual in such calculations I’ve assumed the surface LW emissivity is 1. It makes no significant difference to the results.)

    In addition, the TOA upwelling longwave varies linearly with T. This was a surprise to me. One of the interesting parts of the CERES dataset investigation is seeing who varies linearly with temperature, and who varies linearly with W/m2. In this case TOA can be well expressed (to a first order) as a linear function of T of the form mT+b.

    This means that I am taking the derivative of

    1 – (m T + b) / (sigma T4)

    which solves to

    (4 b + 3 m T)/(sigma T5)

    Over the range of interest, this graphs out as

    Recall that my straight-line estimate was 0.44% per degree. In fact, the more nuanced analysis you suggested shows that it varies between about 0.38% and 0.5% per degree.

    Thanks for an interesting question,

    w.

  62. Duster says:

    rgbatduke says:
    March 24, 2014 at 9:23 am

    I’ve long thought that the GHE can be better studied in places like the Namib and the Sahara than anywhere else on Earth, largely because they lack the confounding effect of water vapor. Water vapor is not a good direct proxy for the GHE because it is a dual contribution. …

    I suspect that what is really clear from this discussion is that without water vapour there is no significant GHE. CO2 certainly traps a little LWIR energy, but only in proportion to its concentration, which is negligible on earth. Water vapour does the yeoman work in keeping the planet habitable. This question has some very important implications since, off the planet, we can trace some rough parallels between Earth and Mars for example over much of the solar system’s early history. Recently, one objection to the anthropic CO2 effect as a contributor to recent warming was that among other neighbors, Mars has also experienced observable warming during the last few decades.

  63. Curious George says:

    Richard says: “Inserting a high cloud in the model is like adding a second atmospheric layer; it enhances the greenhouse effect.”. How sure are you? During the day time, the cloud backscatters a substantial part of solar irradiance , which varies from 1321 W/m2 to 1412 W/m2. During the night it backscatters the upwelling IR (about 400 W/m2 – there are huge variations). Whether the overall effect is cooling or warming is far from clear. If you make assumptions like “the top of a low cloud has a temperature close to that of the surface due to convection”, you introduce a huge error – check with any glider pilot.

  64. Willis Eschenbach says:

    Alex says:
    March 24, 2014 at 7:10 am

    So all of this is cherry-picked on ‘clear sky’ data. How the f*ck do u get any reasonable, real life data from this. Is this some sort of surreal post? God, Willis, you can come up with better stuff than this.

    Alex, what I am investigating in this post is what is called the “clear-sky greenhouse effect”. Using clear-sky data is the only way I know of to investigate that, and no, that’s not cherry picking in any sense.

    w.

  65. Willis Eschenbach says:

    rgbatduke says:
    March 24, 2014 at 9:23 am

    I have to say, Willis, that this fails mere common sense checks for data consistency. I’m not certain what is really being graphed here on the maps, but I’m pretty sure that it isn’t what any of these arguments claim it is.

    Sorry, my friend, but you’ll have to get your common sense recalibrated. As I mentioned, I’m not the inventor of this idea that the distribution of the clear-sky GHE is a reasonable estimate of the distribution of the atmospheric water vapor. As far as I know, that was Ramanathan, here’s his graph:

    The source of the graph is here, it’s an interesting read. Note that his graph of the GHE, although displayed using much larger gridcells, is quite similar to my results.

    HOWEVER, if you still think that the variations in the atmospheric absorption of upwelling LW are from something other than variations in water vapor … then what might that something be?

    w.

  66. daveburton says:

    johnmarshall wrote, “None of the above explains why dry deserts are HOTTER than water vapour rich rainforest.”

    Steve Keohane replied, “Isn’t it because the sunlight is not absorbed by the atmosphere and heats the surface and cools radically at night, a 50°F cycle. It is the water vapor giving more mass to the atmosphere that stabilizes the temperature.”

    Close. Humid air is actually lighter than dry air, not heavier, because H2O vapor molecules have molecular weight of only 18, compared to 32 for O2 and 28 for N2.

    But surface moisture and vegetation do moderate temperatures. When water evaporates from open water and moist surfaces (mostly in the daytime), and by plant transpiration (only in the daytime for most plants), the process of evaporation removes “heat of evaporation,” cooling the surface from which it evaporates. So in the desert, where there’s little water to evaporate in the daytime, the day/night temperature swings are greater.

    The heat absorbed by evaporation is carried by the rising moist air into the middle troposphere (because the moist air is lighter!), where it is released when the water vapor condenses into clouds, rain & snow. The additional cloudiness also tends to cool the surface during the daytime, and reduce heat loss at night, both of which reduce surface temperature excursions. But that doesn’t happen much in deserts, either, because they have few clouds.

  67. daveburton says:

    Duster wrote, “…without water vapour there is no significant GHE. CO2 certainly traps a little LWIR energy, but only in proportion to its concentration, which is negligible on earth.”

    That’s incorrect. In fact, the reason that additional CO2 has so little GHG effect is that there is already so much of it in the atmosphere.

    MODTRAN calculates that 50% of the warming effect of current (400 ppm) CO2 level would be accomplished by just 20 ppm CO2 (for a tropical atmosphere w/ constant relative humidity). The NCAR radiation code says that 40 ppm CO2 would be needed to get 50% of the current CO2-caused warming, rather than 20 ppm, but, either way, the lesson is clear: we’re well past the point of diminishing returns w/r/t the warming effect of CO2.

    For a more intuitive approach, think of CO2 as a coloring agent. It tints the atmosphere in the infrared.

    It doesn’t take much of a coloring agent to dramatically color an otherwise clear fluid or gas. Just as the first drop of blue food coloring added to a bowl of water has a dramatic effect on its color, but additions of more drops of blue food coloring have a diminishing effects, so GHGs “color” the atmosphere in the IR region, and have diminishing effects as their concentrations go up. That’s why GHGs with very low concentrations are said to be more “potent” as GHGs: because the wavelengths (colors!) which they block are not already mostly blocked.

    By way of analogy, consider a liter of pure water in a clear, 10x10x10 cm cubic jar or box, and one drop of food coloring. Our (99% N2+O2) atmosphere is like the water, and CO2 is like the food coloring, except that the “color” of CO2 is from absorption in the invisible IR range.

    If you add one drop of food coloring to the liter of water, it will quite noticeably tint the whole liter. But one drop is only about 0.05 ml, so one drop in one liter is 0.05 / 1000 = 0.00005 = just 50 ppm.

    But consider: although the atmosphere is less dense than liquid water, it is miles thick. The full thickness of the atmosphere is about the same mass as a 30 foot deep layer of water.

    Your cubic jar of colored water is only about four inches thick. So to get an equivalent thickness to the Earth’s atmosphere, you’ll have to stack up 90 of those jars of colored water in a 30-foot-long row.

    Now, look through (or shine a light through) the row of 90 jars of colored water. Imagine how deep the color will be, from just 50 ppm food coloring.

    That’s why just a few ppm of a trace gas can significantly affect the spectrum of the light which passes through the Earth’s atmosphere, and have a potentially significant so-called “greenhouse” effect.

  68. Willis Eschenbach says:

    rgb, I thought further about the question I asked you, regarding what is causing the variation in absorption, viz:

    HOWEVER, if you still think that the variations in the atmospheric absorption of upwelling LW are from something other than variations in water vapor … then what might that something be?

    One possibility is that we are also seeing the variation in CO2 absorption with temperature, due to the location of the absorption bands … this is of course another possible source of feedback.

    However, it doesn’t change the underlying question or results. We want to find out what is happening with clear-sky absorption as temperature rises. Whether CO2 or water vapor or both are involved is not very significant, as the net feedback (change in % absorbed per degree of warming) is the main issue, not the sources of the net feedback.

    w.

  69. Steve Fitzpatrick says:

    Willis,

    Very interesting work

    The revised graphic of upwelling long-wave versus temperature (OLS slope of 1.93 watts/degree) implies a clear-sky sensitivity to CO2 forcing of ~3.71/1.93 = 1.9 C per doubling of CO2. But the data shows enough curvature to suggest warmer regions have a significantly greater increase in absolute (not percentage) clear-sky upwelling per degree of warming than do cold regions. It might be interesting to weight the average slope by surface area (that is, there is a lot more surface area in the tropics than above 60 degrees). The weighting could be just a multilication by the sine of the latitude for each cell. This would I think give a better estimate of the average sensitivity, and by eyebal, I would guess and area weighted clear sky sensitivity of about 1.7-1.8C per doubling. FWIW, this seems to be not far from empirical estimates of sensitivity.

    Of course, determining the net sensitivity requires and accurate estimate of the net influence of clouds…. both reflection of sunlight and blocking of upwelling longwave. No easy task.

  70. Ulric Lyons says:

    Given the relationship between temperature and absorption, is Figure 3 actually representing temperature more than water vapour distribution?

  71. @richard \at 3:52 am
    RE: cirrus clouds

    Does water vapor have the same IR absorption and emission spectra
    as do ice crystals (i.e. water vapor in solid state) in cirrus clouds
    and condensed water droplets in stratus clouds?

  72. Willis Eschenbach says:

    rgb, further to the possibility of variations in CO2 absorption, I took a look at MODTRAN. Using MODTRAN, I determined that in the absence of water, that the percentage of absorption by CO2 is indeed temperature dependent. The approximate relation is

    Percentage Absorption = .14 * Temperature (K) -24.7

    The range of interest in Figure 4 is perhaps -50°C to +35°C. At -50°C (Antarctic), CO2 alone absorbs only about 5% of the upwelling surface LW. On the other hand, at +35°C (Sahara desert), CO2 alone absorbs more than three times as much, about 17% of the upwelling LW.

    This may explain some part of the difference in Figure 3 between the atmospheric absorption in areas of dry and cold (Antarctic) versus dry and warm (Sahara).

    As always, my thanks for your contributions,

    w.

  73. daveburton says:

    markx asked, “How is the ‘absorbed upwelling LW’ calculated? (Is that by taking into account known surface temperatures and calculating theoretical upwelling vs measured upwelling LW?)”

    I have the same question.

  74. I need to ask some dumb questions:
    What is measured?
    What is calculated?
    And what keep us from engaging in a circular calculation in the analysis that is some other model’s assumptions?

    Willis (Fig 1): Absorption is calculated as the upwelling surface longwave radiation minus the upwelling top-of-atmosphere (TOA) longwave radiation. The difference between the two is what is absorbed.

    JohnB at 1:52 am
    Probably a dumb question, but apart from model estimates how do you calculate the upwelling surface longwave radiation in the first place? Where and how is it measured?

    Willis 8:58 am: The TOA datasets are measured. The surface datasets are calculated from the TOA datasets, and validated against a variety of other sources.

    At best the CERES instruments in the Terra, Aqua, Aura, TRMM satellites measures LW from TOA. It is supplemented with data converted from geostationary GOES. (From “Evidence That Clouds….” thread Oct. 8-10, 2013)

    A lot of calculations goes into making the CERES dataset with hourly data.
    How much of it is calculate using models? Are the models in some doubt?
    From where does the CERES dataset get its upwelling Surface LW?

    Surface fluxes derived from radiative calculations that utilize MODIS cloud and aerosol properties, meteorological assimilation data from the Goddard Earth Observing System (GEOS) -4 and -5 models, and aerosol assimilation data from the Model for Atmospheric Transport and Chemistry. In order to minimize the error in surface fluxes due to uncertainties in the input data sources, input parameters in the radiative calculations are objectively adjusted within their uncertainty to ensure calculated TOA fluxes are consistent CERES EBAF-TOA fluxes. CALIPSO and Cloudsat observations are used to derive a priori uncertainties in MODIS cloud and aerosol properties. AIRS data are used to remove biases in reanalysis upper troposphere temperature/humidity profiles. – NCAR Climate Data Expert Guidance

    When you subtract TOA LW from the upwelling surface LW, how do we know we aren’t just evaluating the assumptions NCAR used to generate the calculated upwelling surface LW?

  75. Will Pratt says:

    Willis, my question @ #comment-1597561, as seems usual, has gone missing.

    However I think it highly pertinent to the subject at hand so I will ask it again.

    How do you distinguish between spontaneous emission of IR from water vapour as a so called “GHG” and IR from latent heat emitted by the process of condensation of water vapour, at the TOA.

    Thanks.

  76. johnmarshall says:

    The humid air is heated by the surface and convects because of its reduced density imposed by the increased temperature. this air cools as it rises and forms clouds which increase albedo so reduce solar heating. Rainforest temperatures rarely go above 40C during the day or below 25C at night. Dry deserts have no such negative feedback and have to rely on the fixed albedo of the surface. this heats the air which will convect but without the water vapour will not form clouds. The sand surface in the Namibian desert has been measured at over 70C The air temperature at the standard height for temperature measurements is considerably cooler, 50+C. Night time temperatures can fall to below 10C.

  77. Kristian says:

    The only three ways more humid air above a surface will tend towards warming that surface in relative terms is 1) lowering the temp gradient going up from it (as soon as the water vapour condenses, it releases latent heat into the air – will happen mostly after the sun’s gone down), 2) allowing the air above the surface to take much longer to cool in the night because of its greater heat capacity, and 3) suppressing evaporation rates from the surface by moving the air mass above it closer to the saturation point.

    The radiative properties of H2O in themselves will in fact act towards cooling the surface, because they will let less solar energy per unit of time be absorbed by the surface. The air will also absorb more efficiently the IR coming off the ground, but since the air has so much higher heat capacity, then much more energy is also required before its temperature goes up as much. And as soon as it warms, it moves up anyway, away from the surface, through its heightened buoyancy.

    During the night it is in fact these radiative properties that allow the humid air to cool to space (or at least to higher levels of the atmosphere). The delay then stems rather from the air’s great heat capacity and the release of latent heat.

  78. Kristian says:

    Something to show you how the troposphere works:

    The easiest ‘experiment’ you could do to verify how radiation is only along for the ride in the troposphere is to hold your hand close to a candle flame out in the calm open air, let’s say 10-15 cm (4-6 inches) away from it to the side. Remember that the fire is incredibly hot compared to the surface of the earth (well, apart from fresh lava, that is*) and especially compared to the air surrounding it, so radiative heat transfer should be highly significant in this situation. And it is. But there’s another mechanism around that quite effortlessly negates its effect on the air around the candle. Just about 5 inches away from the flame, to the side, you can practically no longer feel its heat. Why not? Where did it go?

    It went UP. The radiation streaming out from the candle flame is quickly absorbed by the air around it, warming it. But as soon as this happens, the air expands, grows less dense and floats up. Convection. It happens instantaneously, automatically.

    Place your hand 5 inches above the flame instead and you will most certainly feel the heat. Most likely to the extent that you’ll soon have to pull it back.

    The energy warming the air comes from the radiation. But the mechanism transporting it up and away is convection.

    This is how the troposphere works.

    *Those of you that have flown above a field of fresh lava (or a bush fire) can testify to the power of the convective currents rising up from it.

  79. Frank says:

    Willis, RGB: Your map that quantifies water vapor in terms of “W/m2 absorbed” can’t be easily translated into more familiar units like humidity or total precipitable water. The water vapor over the Sahara desert certainly does not absorb more OLR than the water vapor over the US, because OLR emitted by the surface and passing through the atmosphere is more complicated than light passing through a sample in an infrared spectrophotometer. Remember that an average of only 10% (or less) of the photons emitted by the surface of the planet escape directly to space (40 W/m2). If all of the directly-escaping photons come through clear skies and about half of the skies are clear, then only 20% of the photons emitted from the surface escape directly to space (80 W/m2). We need an average 240 W/m2 of OLR to balance incoming SWR (and probably more to compensate for cloudy areas). Therefore at least 160 W/m2 of OLR is emitted from GHG’s IN those clear skies, not from the surface far below. Those areas showing the most “absorption of surface emission” are actually the areas where GHGs emit relatively few photons directly to space (than expected for the surface temperature far below) because they are very high, cold and dry. Your map is a better measure of the greenhouse effect itself (absorption combined with omni-directional temperature-dependent re-emission) than absorption alone.

    Lapse rate also plays a role, since it controls the temperature difference between the surface and GHGs high in the atmosphere emitting photons directly to space. When you analyze the data, you obtain the sum of water vapor and lapse rate feedbacks.

    The biggest limitation of this approach is that it produces water vapor feedback only from clear skies. In most places, the skies are clear when the air is descending and dry; and cloudy when the air is rising and humid. The is no reason to assume that water vapor feedback in clear skies is representative of “global” water vapor feedback. The red areas showing high water vapor feedback in some tropical areas should be producing the “hot spot in the upper tropical troposphere”, but it may be missing because of what is happening in cloudy skies.

    Ramanathan analyzed his data by subtracting the Planck feedback (5.5 W/m2/degK) from the total Planck-water vapor-lapse rate feedback that is observed directly from space.

    I’m not sure where you obtained your surface emission/temperature data. Is it surface temperature only under clear skies or all skies? Ramanathan plotted monthly average clear-skies OLR vs mean monthly global surface temperature under all skies.

  80. On the question of upwelling longwave radiation, to wit:

    Figure 3. As in Figure 1, showing the distribution of water vapor, but this time shown as the percentage of upwelling surface longwave radiation which is absorbed in clear-sky conditions.
    —————————-

    After I first looked at the Figure 3 graphic my first thought was … “WHOA”, … those desert areas should be showing up in “dark purple” if that is a per se “picture” of the upwelling longwave radiation from the surface.

    But then as I was pondering over what I might say about it in a post …… it dawned upon me as to what the problem was, ….. me thinks. I’m not going to state or claim anything too be a fact because I’m not a Degreed Climatologist or Physicist with published credentials so I will just offer my opinion and you experts can be the judges.

    First of all, Figure 3 is not a “snapshot” picture of the upwelling longwave radiation from the entire surface of the earth …… simply because that would be impossible to do.

    Secondly, it is obvious that Figure 3 is a “time-lapse” picture of the earth’s surface over a period of a minimum of 365 days … with the LW radiation being graphically expresses as an “average” and not as “actual”.

    Thus said, if the LW radiation is being expresses as a 24 hour/365 day “average” then the “color” of desert areas in question are correctly being shown in Figure 3.

    Or something close to that ….. or maybe farther away.

    ————

    Another question I have often pondered on the measurement of upwelling surface longwave radiation verses cloudy skies …… just how do the experts account for the effects of fogs relative to both the incoming solar irradiance and the upwelling longwave radiation from the surface?

    Like both daytime and night time mountain fogs, lowland fogs, valley fogs, coastal fogs, ocean fogs, lake fogs, river fogs, etc.

    If clouds have an effect …… then fogs surely do also.

    Lots of fog, ….. like here in The Great Smokey Mountains.
    Picture: http://www.abovebeyondcabin.com/87ef4640.jpg
    Source: http://www.abovebeyondcabin.com/greatsmokymountainsnationalpark.htm

  81. Norman Woods says:

    CERES proves the Infrared Cooling Model is the correct model for the earth’s climate.

    Infrared Warming is not and has not ever been the predominating mechanism for earth.

    In fact, the atmosphere’s infrared gases are responsible for reflecting almost a quarter of the sun’s energy out to space.

    When James Hansen started his computer climate modeling activities his own fellow employees spoke out about how his models were worse than inaccurate the were grossly mis-defining action of the earth’s atmosphere.

    They said his models didn’t have the atmosphere obeying Ideal Gas Law.

    Two award winning entrepreneurs and atmospheric chemists who founded the Ireland National Aquarium were doing research on atmospheres and chemistry related to oceanic life.

    They noticed the “concensus” claimants’ description of activity of CO2 didn’t match what they knew.

    One of them is a computer programmer. His name is Ronan Connolly.

    He took apart some climate models by educating himself on the history of climate models and found they are relatively simplistic.

    Idly the Connollys, father Michael who founded the Ireland National Aquarium and ran it’s research facilities, and atmospheric chemist-computer programmer Ronan

    checked to see if the modern GCI or Global Computer Model,

    models the atmosphere obeying Ideal Gas Law.

    They found they don’t.
    Not one of the modern Global Climate Models.

    Go check it out, Michael and Ronan Connolly, start at the very beginning of their combined introductions and overviews of their papers and read through it.

    I am old enough that I can remember hearing some people saying that those climate models were basically designed wrong, Hansen and “his friends in computer modeling” knew it.

    We see now that all along,,
    this falsehood in science has been driven by James Hansen and fellow computer modelers who everyone now realizes are crooks.

  82. Dr. Strangelove says:

    Willis
    Sorry you got it wrong. Your 1.8 W/m^2/C is not comparable to Gordon et al 2.2 W/m^2/C. First, you have to understand what water vapor feedback is. It is the change in TOA radiative balance per unit change in surface temperature. What you calculated is change in absorbed atmospheric longwave per unit change in geographic temperature.

    The key word is geographic. The change in temperature is due to different temperatures on different parts of the globe. Surface temperature is change in temperature of the same geographic area (or global) at different times. Another key word is absorbed longwave. The TOA radiative balance is not determined by absorbed longwave. It is determined by incoming TOA radiation minus outgoing TOA radiation. That you got a number close to 2.2 W/m^2/C is coincidental because the physics is different.

  83. eyesonu says:

    rgbatduke says:
    March 24, 2014 at 9:23 am

    =============

    Over the past couple of years mainly during hurricane season I have viewed satellite observations over Africa from a standpoint of curiosity. If I recall correctly there seems to be a prevalent air/cloud movement from the Indian ocean across to the Atlantic. Hurricanes often begin to develop off the coast of Africa in the Atlantic.

    A point to consider may be that very moist air from the Indian ocean crossing a desert region with a high heat or LWIR may not be likely to precipitate out as it crosses the continent but that moisture would still be in the air mass at high altitude. As you noted it is not likely that additional moisture would be added from the ground over a desert environment so actual convection from the ground would be limited as to what would occur over a warm ocean environment. Could it be that the hurricane formations off the Atlantic coast of Africa is actually influenced by Indian ocean moisture being carried at high altitude combined with hot low level air crossing into the Atlantic setting up the convection that would then be expected? This combination of “new” moisture/convection mixing with an air mass already containing a relatively high moisture content may be a determining factor for the formation of tropical storms in that region.

    That may also validate Willis’ observations over the Sahara region. Absent convection driven by evaporating ground moisture would the rapidly cooling desert at night cause the lower and mid atmospheric levels to rise and fall as if it were breathing? The lowering of the moisture bearing layers through the lapse rate could be just at the “sweet spot” that would warm enough to eliminate cloud formation at night. The LWIR absorbed in the day would keep it warm and reduce cloud formation.

    So using the reasoning as noted above I would not discount what Willis has done. He is doing groundbreaking work here and is doing so outside the box. That is the only way we will ever understand what is really happening with regards to the climate.

    Good work Willis.

  84. Mervyn says:

    The supposition of the positive water vapour feedback mechanism adopted by the IPCC is absolute rubbish, and here is why.

    The atmospheric carbon dioxide concentration has been increasing “alarmingly” because of human activity emissions of carbon dioxide, so they say! This increase in carbon dioxide absorbs infra red heat from the ground, then “back-radiates” infra red heat to the ground, adding to the heat from the sun, making the air hotter and causing more water to evaporate into the air, which then allows even more heat to be absorbed in the atmosphere.

    This supposition means that the total heat relating to the greenhouse heat effect can only increase one way… upwards. That’s what a positive feed back mechanism does… the effect only increases.

    Funny then, how the real world observational data on climate does not reflect that Mother Nature is actually obeying the IPCC’s positive water vapour feedback mechanism. The reason is simple… the mechanism is pure and simple crap, and most experts in thermodynamics give the IPCC a big “F” for FAIL.

  85. The way I seen the CAGW flim-flm scam unfolding was, to wit:

    James Hansen et el needed a “better story” every time Budget Funding came up in Congress. And every time it came up he gave them a “better story” to believe ….. and Congress believed it and kept giving him more n’ more money. And Al Gore was a member of Congress and was listening to those “better stories”.

    Then Al Gore ran for POTUS and lost, ….. and was out of a job and no prospects of getting one. Then he remembered all those “better stories” that James Hansen et el had been telling Congress and decided to produce his Documentary titled “An Inconvenient Truth” and based it entirely on all those “better stories” claiming they were all scientifically factual and TRUTHFUL

    And thus James Hansen et el was caught between “a rock and a hard place” and had to agree with and attest to everything Gore was claiming as scientific fact ….. otherwise Hansen et el would have been up the proverbial creek without a paddle.

    And it worked out great for Hansen et el because the public was duped into believing everything contained in said “An Inconvenient Truth” and Hansen et el began creating “better n’ better stories” for public consumption and thus even greater Congressional Funding.

    And thus “the race was on” ….. with everyone trying to get their fair share of “The CAGW Pie” that Congress was dumping BILLIONS of dollars into.

    And none of those “pie eaters” want you messin with the good deal they got going ….. and will fight you tooth n’ nail iffen you do.

  86. cba says:

    Some Items to Consider
    Water vapor is a log function when it comes to absorption. It tends to have a 2 – 3 times greater effect for a change than does co2 and is 2-3 times stronger in typical total amount.

    Relative Humidity, RH, is a linear scale showing the % of h2o vapor relative to the maximum amount the atmosphere will take at that temperature. Absorption by h2o vapor depends upon the total number of h2o molecules in your column of atmosphere, and has everything to do with Absolute Humidity, but not Relative Humidity. In other words, during the day, you might go from having 35% relative humidity in the afternoon and late at night having the RH hit 80% and have the same absolute humidity both times. Also, the humidity at the surface is not related to the humidity present at higher altitudes. There could be layers of moist air or dry air or both present.

    Absorption by molecules – like h2o and co2 are not very temperature dependent. However, emission is very temperature dependent as T gives one the conditions for filling more (higher) molecular energy states and that determines which wavelengths can be radiated. Absorption and emission are the flip sides of the same coin. Except for the emission temperature dependence making the sides different, they would be identical. If a parcel of gas were at the same temperature as an illuminating source behind it, there would be no molecular spectrum of absorption or emission visible. With a colder source, one would be seeing emission spectra from the parcel and with a warmer source behind the parcel, one would be seeing and absorption spectra.

    Also, molecules are colliding frequently with others of their kind and other kinds. There will exist a local temperature of the gas. A molecule capable of radiating in the IR can either radiate energy away or give it away in a collision with another molecule. A molecule can absorb a photon and be raised to a higher energy state or it can be raised to that higher energy state by a collision with another molecule. A higher energy state has a time for that state that is the average duration which that sort of molecule will stay in that state before radiation is emitted and the state changes to a lower one. If the time between collisions is much less than this time, it is likely that the molecule will give up its energy by a collision rather than be radiation. The term forbidden line comes from this – which is some astronomical emission lines occur in space due to the long times between collisions out there while the short times on the lab bench mean one never sees it happen in the laboratory.

    I don’t know about Willis’ paper on this thread as I haven’t had time to answer the questions that popped up when I skimmed through it. I have my doubts that it is meaningful, unlike much of his work and some of that may be due to those creating the dataset and other portions of the problem may simply be that it’s out of context with other factors that have greater influence.

  87. chemengrls says:

    Fig 1 makes no mention of temperature. Based on absorption figures which are quite low I would estimate a figure much less than 20 C maybe 10 to 15 C. I will check my calcs and come back with an estimate.

  88. chemengrls says:

    Surface T 5 C upwelling LWIR upto 340W/m^2. Absorbed LWIR by 23000ppm wv upto 200W/m^2.

  89. daveburton says:

    Mervyn wrote, “[The] increase in carbon dioxide absorbs infra red heat from the ground, then ‘back-radiates’ infra red heat to the ground, adding to the heat from the sun, making the air hotter and causing more water to evaporate into the air, which then allows even more heat to be absorbed in the atmosphere.
    This supposition means that the total heat relating to the greenhouse heat effect can only increase one way… upwards. That’s what a positive feed back mechanism does… the effect only increases.”

    That’s incorrect. Positive feedbacks amplify (and, if large enough, destabilize) systems. Positive temperature feedbacks amplify temperature changes. That is, they work in both directions: they amplify decreases in temperature just as much as they amplify increases in temperature.

    In the case of water vapor, warmer temperatures cause increased evaporation and higher H2O vapor partial pressure in the atmosphere, leading to increased “greenhouse effect.” But it works the other way, too: cooler temperatures cause decreased evaporation and lower H2O vapor partial pressure, leading to decreased “greenhouse effect.”

    Fortunately, there are also very fundamental negative feedback mechanisms also operating, which prevent extreme system instability. The most basic of these mechanisms is simply that heat losses go up with temperature. That’s why when you turn your electric stove burner on “high,” it doesn’t continue to get hotter and hotter for as long you continue to pour energy (electric power) into it. Rather, its temperature plateaus when the rate of heat loss balances the electric power that the stove burner is consuming.

    The IPCC modelers err by underestimating or ignoring negative feedbacks, and overestimating the magnitude of positive feedbacks. E.g., MODTRAN calculates that the amplification effect by water vapor is much smaller than the alarmists guess it to be.

  90. timetochooseagain says:

    of course water vapor depends positively on temperature in the present state. It does not follow, however, that one can use that relation, to predict the effect of a change in temperature as translates into a change in water vapor.

  91. Norman Woods says:

    Very well put. And now all the people who bowed down to the great concensus
    are having it shoved down their throats one bite at a time as the reality that every word they said is an inversion of the real situation – the earth operates on an infrared cooling model,

    Hansen’s models don’t have the atmosphere obedient to Ideal Gas Law

    Mann was just a dumb geologist when he tried computer crime he immediately got caught, and has had to bear that since the beginning.

    It was and is crime and those models do not have the Atmosphere operating according to Ideal Gas Law, is something I recall after becoming interested in it after many years away from this.

    The idea to all these people who were gobbling up James Hansen’s stories as reality based that they have been caught before their own careers ended is emotionally devastating to them from the first to the last but just like the people knew at N.A.S.A. when they laid down their reputations to defy the crime spree that was James Hansen

    the truth catches up a lot of times, a lot faster than people wish. Particularly in science. Because every single false witness to a whole suite of sophisticated lies, thinks because scientists are slow talkers and technology evolves slowly that’s the same thing as “this falsehood is going to last forever, and I’ll always be the darling of the crowd.”

    No, they won’t which is why civilization can roll over so many evils and keep on ticking. There’s always a new batch of criminal exploiters but civilization depends on there always being a new generation of innocent truth tellers

    who want their jobs. And will not stop until the right thing is the ruling thing again.

    And all that money winds up being wasted as men an women spread lies just for the power to spread something.
    Beats honest work!

    There was never any hope any of the magical gas coalition’s claims would have been true or there would have been a noted correlation between CO2 and water vapor which is most certainly missing.

    NOAA itself did a 10 + years study to see if back radiation predicted by green house effect thermostat claimants was occurring. They found out after eight hundred thousand measurements that not only was night time infrared radiation not growing,

    between 1996 and 2010
    they found out there is less infrared radiation than when they started the test.

    Why?

    Lowered water vapor.

    http://journals.ametsoc.org/doi/abs/10.1175/2011JCLI4210.1?journalCode=clim
    This was at the epicenter of NOAAs own claims of green house gas back radiation warming.

    Nothing anybody who believes in it
    is ever found to be true to the letter

    because it’s all built on the concept that the surface of the earth is warmed by the very gases that are responsible for cooling the surface: particularly

    *water.

    “Oh no it’s James Hansen’s darling of his computer modeling exploits CO2.”
    No,
    CO2 is the one cooling the upper atmosphere.

    NASA themselves released a study where once again truth arights the boat turned sideways by fraud, saying CO2 is the main coolant of the upper atmosphere.
    http://goo.gl/iBOJkL

    I shortened that url it’s just the search return for “NASA study proves CO2 cools upper atmosphere” which NASA released just a couple of years ago as honest scientists

    not feeding at the alarm gravy train trough
    simply

    stepped up to the plate and told the truth.

    Theres not enough CO2 in the lower atmosphere to overthrow the massive phase change cooling of water as it evaporates lifting heat from the surface to the 20,000 foot level to be spread out and radiate upward.

    The entire thing is a scam which is why everyone associated with it is estimated to have the intellectual capability of Bigfoot.

    The list of people whose scientific credibility approaches zero is directly related to the degree by which they stand with James Hansen’s inverted “Infrared heating model” his, and his modeler friends claim the earth operates by,

    and the actual earth model for climatic control which is ”infrared cooling model” response.

    In real science of the 20th century it was James Hansen’s ”infrared heating model” which was utterly ripped to shreds by hundreds of revelations like a burlap bag leaking water.

    They grew old an tired and were thinned out by passage of time and now what they were doing is revealed to all,

    shouted from the housetops. By too many truth lovers to intimidate and frighten and insult.

    And the lovers of truth will indeed bury these scammers in piles of literature for upcoming decades as their loyalty to the alarm gravy train and lying overrode every moral compunction they had.

    Samuel C Cogar says:
    March 26, 2014 at 8:58 am
    The way I seen the CAGW flim-flm scam unfolding was, to wit:

    James Hansen et el needed a “better story” every time Budget Funding came up in Congress. And every time it came up he gave them a “better story” to believe ….. and Congress believed it and kept giving him more n’ more money. And Al Gore was a member of Congress and was listening to those “better stories”.

    Then Al Gore ran for POTUS and lost, ….. and was out of a job and no prospects of getting one. Then he remembered all those “better stories” that James Hansen et el had been telling Congress and decided to produce his Documentary titled “An Inconvenient Truth” and based it entirely on all those “better stories” claiming they were all scientifically factual and TRUTHFUL

    And thus James Hansen et el was caught between “a rock and a hard place” and had to agree with and attest to everything Gore was claiming as scientific fact ….. otherwise Hansen et el would have been up the proverbial creek without a paddle.

    And it worked out great for Hansen et el because the public was duped into believing everything contained in said “An Inconvenient Truth” and Hansen et el began creating “better n’ better stories” for public consumption and thus even greater Congressional Funding.

    And thus “the race was on” ….. with everyone trying to get their fair share of “The CAGW Pie” that Congress was dumping BILLIONS of dollars into.

    And none of those “pie eaters” want you messin with the good deal they got going ….. and will fight you tooth n’ nail iffen you do.

  92. chemengrls says:

    chemengrls says:

    March 26, 2014 at 12:10 pm

    Surface T 5 C upwelling LWIR upto 340W/m^2. Absorbed LWIR by 23000ppm wv upto 200W/m^2.

    Correction @ Ts 5 C ppm wv is 8600ppm. Absorbed LWIR by 8600ppm wv upto 200W/m^2.
    Surface T (Ts) 20 C upwelling LWIR upto 400W/m^2.Absorbed LWIR by 23000 ppm wv upto 230W/m^2 .

  93. chemengrls says:

    The principal emission bands of water vapour are 2.55 to 2.84, 5.6 to 7.6 and 12 to 25 microns when compared with those of CO2 which are 2.64 to 2.84, 4.13 to 4.5 and 13 to 17 microns the potential for absorbing LWIR, judging by its wider third band (the other bands being negligible) is much greater for wv than for CO2 molecules. Bearing in mind that saturated or near saturated air at 25 C contains upto 31000 ppm ( compared with 380ppm CO2) of wv the potential for absorption is very much greater. Water vapour concentrations at this level of course are at fairly low altitudes but even so the contribution ( judging by Fig1) in keeping the biosphere habitable is largely due to wv swamping any cotribution from CO2. It would appear on this evidence that CO2 is largely a red herring along with emission controls and low carbon economies. Clearly CO2 at its present concentration pales into insignificance and the need to bankrupt our economies in an effort to reduce it is completely unnecessary

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