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Climate Hustle

The runaway greenhouse effect on Venus

What the science says...

Venus very likely underwent a runaway or ‘moist’ greenhouse phase earlier in its history, and today is kept hot by a dense CO2 atmosphere.

Climate Myth...

Venus doesn't have a runaway greenhouse effect
Venus is not hot because of a runaway greenhouse.

In keeping with my recent theme of discussing planetary climate, I am revisiting a claim last year made by Steven Goddard at WUWT (here and here, and echoed by him again recently) that “the [runaway greenhouse] theory is beyond absurd,” and that it is pressure, not the greenhouse effect that keeps Venus hot.  My focus in this post is not on his alternative theory (discussed here), but to discuss Venus and the runaway greenhouse in general, as a matter of interest and as an educational opportunity.  In keeping my skepticism fair, I’d also like to address claims (sometimes thrown out by Jim Hansen in passing by) that burning all the coal, tars, and oil could conceivably initiate a runaway on Earth.

It is worth noting that the term runaway greenhouse refers to a specific process when discussed by planetary scientists, and simply having a very hot, high-CO2 atmosphere is not it.  It is best thought of as a process that may have happened in Venus’ past (or a large number of exo-planets being discovered close enough to their host star) rather than a circumstance it is currently in.

A Tutorial of Present-Day Venus

Venus’ orbit is approximately 70% closer to the sun, which means it receives about 1/0.72 ~ 2 times more solar insolation at the top of the atmosphere than Earth.  Venus also has a very high albedo which ends up over-compensating for the distance to the sun, so the absorbed solar energy by Venus is less than that for Earth.  The high albedo can be attributed to a host of gaseous sulfur species, along with what water there is, which provide fodder for several globally encircling sulfuric acid (H2SO4) cloud decks.  SO2 and H2O are the gaseous precursor of the clouds particles; the lower clouds are formed by condensation of H2SO4 vapor, with SO2 created by photochemistry in the upper clouds. Venus’ atmosphere also has a pressure of ~92 bars, nearly equivalent to what you’d feel swimming under a kilometer of ocean.  The dense atmosphere could keep the albedo well above Earth’s even without clouds due to the high Rayleigh scattering (the effect of clouds on Venus and how they could change in time is discussed in Bullock and Grinspoon, 2001). Less than 10% of the incident solar radiation reaches the surface.

Observations of the vapor content in the Venusian atmosphere show an extremely high heavy to light isotopic ratio (D/H) and is best interpreted as a preferential light hydrogen escape to space, while deuterium escapes less rapidly.  A lower limit of at least 100 times its current water content in the past can be inferred (e.g. Selsis et al. 2007 and references therein).

The greenhouse effect on Venus is primarily caused by CO2, although water vapor and SO2 are extremely important as well.  This makes Venus very opaque throughout the spectrum (figure 1a), and since most of the radiation that makes its way out to space comes from only the very topmost parts of the atmosphere, it can look as cold as Mars from IR imagery. In reality, Venus is even hotter than the dayside of Mercury, at an uncomfortable 735 K (or ~860 F). Like Earth, Venusian clouds also generate a greenhouse effect, although they are not as good infrared absorbers/emitters as water clouds.  However, the concentrated sulfuric acid droplets can scatter infrared back to the surface, generating an alternative form of the greenhouse effect that way.  In the dense Venusian CO2 atmosphere, pressure broadening from collisions and the presence of a large number of absorption features unimportant on modern Earth can come into play (figure 1b), which means quick and dirty attempts by Goddard to extrapolate the logarithmic dependence between CO2 and radiative forcing make little sense.  The typical Myhre et al (1998) equation which suggests every doubling of CO2 reduces the outgoing flux at the tropopause by ~4 W/m2, although even for CO2 concentration typical of post-snowball Earth states this can be substantially enhanced.  Figure 1b also shows that CO2 is not saturated, as some skeptics have claimed.

 

 Figure 1: a) Radiant spectra for the terrestrial planets.  Courtesy of David Grisp (Jet Propulsion Laboratory/CIT), from lecture "Understanding the Remote-Sensing Signatures of Life in Disk-averaged Planetary Spectra: 2" b) Absorption properties for CO2. The horizontal lines represent the absorption coefficient above which the atmosphere is strongly absorbing.  The green (orange) rectangle shows that portion of the spectrum where the atmosphere is optically thick for 300 (1200) ppm.  From Pierrehumbert (2011)

 How to get a Runaway?

To get a true runaway greenhouse, you need a conspiracy of solar radiation and the availability of some greenhouse gas in equilibrium with a surface reservoir (whose concentration increases with temperature by the Clausius-Clapeyron relation).  For Earth, or Venus in a runaway greenhouse phase, the condensable substance of interest is water— although one can generalize to other atmospheric agents as well.

The familiar water vapor feedback can be illustrated in Figure 2, whereby an increase in surface temperature increases the water vapor content, which in turn results in increased atmospheric opacity and greenhouse effect.  In a plot of outgoing radiation vs. temperature, this would result in less sensitive change in outgoing flux for a given temperature change (i.e., the outgoing radiation is more linear than one would expect from the σT4 blackbody-relation). 

 

Figure 2: Graph of the OLR vs. T for different values of the CO2 content and relative humidity.  For a fixed RH, the specific humidity increases with temperature. The horizontal lines are the absorbed shortwave radiation, which can be increased from 260-300 W m-2.  The water vapor feedback manifests itself as the temperature difference between b’-b and a’-a, since water vapor feedback linearizes the OLR curve.  Eventually the OLR asymptotes at the Komabayashi-Ingersoll limit.  Adopted from Pierrehumbert (2002)

 

One can imagine an extreme case in which the water vapor feedback becomes sufficiently effective, so that eventually the outgoing radiation is decoupled from surface temperature, and asymptotes into a horizontal line (sometimes called the “Komabayashi-Ingersoll” limit following the work of the authors in the 1960’s, although Nakajima et al (1992) expanded upon this limiting OLR in terms of tropospheric and stratospheric limitations).  In order to sustain the runaway, one requires a sufficient supply of absorbed solar radiation, as this prevents the system from reaching radiative equilibrium.  Once the absorbed radiation exceeds the limiting outgoing radiation, then a runaway greenhouse ensues and the radiation to space does not increase until the oceans are depleted, or perhaps the planet begins to get hot enough to radiate in near visible wavelengths.

 

Figure 3: Qualitative schematic of how the ocean reservoir is depleted in a runaway.  From Ch. 4 of R.T. Pierrehumbert’s Principles of Planetary Climate

 

On present-day Earth, a “cold trap” limits significant amounts of water vapor from reaching the high atmosphere, so its fate is ultimately to condense and precipitate out.  In a runaway scenario, this “cold trap” is broken and the atmosphere is moist even into the stratosphere.  This allows energetic UV radiation to break up H2O and allow for significant hydrogen loss to space, which explains the loss of water over time on Venus.  An intermediate case is the “moist greenhouse” (Kasting 1988) in which liquid water can remain on the surface, but the stratosphere is still wet so one can lose large quantities of water that way (note Venus may never actually encountered a true runaway, there is still debate over this).  Kasting (1988) explored the nature of the runaway /moist greenhouse, and later in 1993 applied this to understanding habitable zones around main-sequence stars.  He found that a planet with a vapor atmosphere can lose no more than ~310 W/m2, which corresponds to 140% of the modern solar constant (note the albedo of a dense H2O atmosphere is higher than the modern), or about 110% of the modern value for the moist greenhouse.

 

Earth and the Runaway: Past and Future

 

Because Earth is well under the absorbed solar radiation threshold for a runaway, water is in a regime where it condenses rather than accumulating indefinitely in the atmosphere.  The opposite is true for CO2, which builds up indefinitely unless checked by silicate weathering or ocean/biosphere removal processes.  In fact, a generalization to the runaway threshold thinking is when the solar radiation is so low, so that CO2 condenses out rather than building up in the atmosphere, as would be the case for very cold Mars-like planets.  Note the traditional runaway greenhouse threshold is largely independent of CO2 (figure 2 & 4; also see Kasting 1988), since the IR opacity is swamped by the water vapor effect.  This makes it very difficult to justify concerns over an anthropogenic-induced runaway.

 


Figure 4: The H2O–CO2 greenhouse. The plot shows the surface temperature as a function of radiated heat for different amounts of atmospheric CO2 (after Abe 1993). The albedo is the fraction of sunlight that is not absorbed (the appropriate albedo to use is the Bond albedo, which refers to all sunlight visible and invisible). Modern Earth has an albedo of 30%. Net insolations for Earth and Venus ca. 4.5 Ga (after the Sun reached the main sequence) are shown at 30% and 40% albedo. Earth entered the runaway greenhouse state only ephemerally after big impacts that generated big pulses of geothermal heat. For example, after the Moon-forming impact the atmosphere would have been in a runaway greenhouse state for ∼2 million years, during which the heat flow would have made up the difference between net insolation and the runaway greenhouse limit. A plausible trajectory takes Earth from ∼100 bars of CO2 and 40% albedo down to 0.1–1 bar and 30% albedo, at which point the oceans ice over and albedo jumps. Note that CO2 does not by itself cause a runaway. Also note that Venus would enter the runaway state when its albedo dropped below 35%.  Se e Zahnle et al 2007

 

This immunity to a runaway will not be the case in the long-term.  In about a billion years, the sun will brighten enough to push us into a state where hydrogen is lost much more rapidly, and a true runaway greenhouse occurs in several billion years from now, with the large caveat that clouds could increase the albedo and delay this process.

Interesting, some (e.g.. Zahnle et al 2007) have argued that Earth may have been in a transient runaway greenhouse phase within the first few million years, with geothermal heat and the heat flow from the moon-forming impact making up for the difference between the net solar insolation and the runaway greenhouse threshold, although this would last for only a brief period of time.  Because the runaway threshold also represents a maximum heat loss term, it means the planet would take many millions of years to cool off following such magma ocean & steam atmosphere events of the early Hadean, much slower than a no-atmosphere case (figure 5).

 

Figure 5: Radiative cooling rates from a steam atmosphere over a magma ocean. The radiated heat is equal to the sum of absorbed sunlight (net insolation) and geothermal heat flow. The plot shows the surface temperature as a function of radiated heat for different amounts of atmospheric H2O (adapted from Abe et al. 2000). The radiated heat is the sum of absorbed sunlight (net insolation) and geothermal heat flow. The different curves are labeled by the amount of H2O in the atmosphere (in bars). The runaway greenhouse threshold is indicated. This is the maximum rate that a steam atmosphere can radiate if condensed water is present. If at least 30 bars of water are present (a tenth of an ocean), the runaway greenhouse threshold applies even over a magma ocean. Note that the radiative cooling rate is always much smaller than the σT4 of a planet without an atmosphere

Conclusions

Venus likely underwent a runaway or “moist greenhouse” phase associated with rapid water loss and very high temperatures.  Once water is gone, silicate weathering reactions that draw down CO2 from the atmosphere are insignificant, and CO2 can then build up to very high values.  Today, a dense CO2 atmosphere keeps Venus extremely hot.

Last updated on 11 April 2011 by Chris Colose.

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Comments 251 to 266 out of 266:

  1. JC @250,

    You ask "Why would strong pressure prevent CO2 from having a greenhouse effect ?" It is actually the other way about. On Mars we see ten times the CO2 but very low atmospheric pressure and a very low GH-effect resulting from that CO2.

    You may have noted in the OP above the use of the term "pressure broadening." The absorption of radiation by a greenhouse gas occurs at very distinct wavelengths. These are usually bunched into a series of lines resulting from the quantum spins a gas molecule can have. But as the pressure of the gas increases (for instance, resulting from mixing in 800mbar of N2 and 200mbar of O2) these distinct wavelengths become broadened out. The result is that the greenhouse gas can more completely absorb a wider wavelength. (In the analogy @242, it's a bit like the "hat and gloves" becoming a full balaclava & arm-length gloves.) The graphic below is taken from a Science of Doom page, one of a series which explains the ins-&-outs of how GH-effects work.SoDoom Pressure Broadening

    The result of pressure broadening is a more effective GH-effect from a single gas operating in a particular wave-band.

  2. JC @250,

    You ask "Why would strong pressure prevent CO2 from having a greenhouse effect ?" It is actually the other way about. On Mars we see ten-times the CO2 but very low atmospheric pressure and a very low GH-effect resulting from that CO2.

    You may have noted in the OP above the use of the term "pressure broadening." The absorption of radiation by a greenhouse gas occurs at very distinct wavelengths. These are usually bunched into a series of lines resulting from the quantum spins a gas molecule can have. But as the pressure of the gas increases (for instance, resulting from mixing in 800mbar of N2 and 200mbar of O2) these distinct wavelengths become broadened out. The result is that the greenhouse gas can more completely absorb a wider wavelength. The graphic below is taken from a Science of Doom page illustrates what can happen to a single line under presure broadening.SoDoom Pressure Broadening

    The result of pressure broadening is a more effective GH-effect from a single gas operating in a particular wave-band. (In the analogy @242, it's a bit like the "hat and gloves" becoming a full balaclava & arm-length gloves.)

  3. Calculation of the greenhouse effect of CO2 on Venus, Mars and Earth:

    My starting hypothesis is as follows : energy from the greenhouse effect is proportional to the total amount of CO2 present in the entire atmosphere.

    Step 1 : To verify this hypothesis, take the case of Venus where the greenhouse effect is in total of CO2:
    Irradiance of Venus: 2613,9 W / m2.
    On Venus, at the top of the atmosphere 2613,9 / 4 = 653,475 W / m2 from the Sun penetrate the atmosphere.
    Since the albedo is 80% or 522,78 W / m2, only 130,7 W / m2 reaches the surface of Venus, the equivalent of a temperature of T = ∜ 130.7 / 5,67.10^ -8 = 219.12 ° K = -54 ° C
    The average surface area of Venus is 460 ° C, ie 733.15 ° K or E = (733.15)^ 4 × 5,67.10-8 = 16 381.5 W / m2.
    From 130,7 W / m2 to 16 381,5 W / m2 from the CO2 greenhouse effect, a total greenhouse effect of: 16 381,5 - 130,7 = 16 250,8 W / m2.
    Now we know that in the total atmosphere of Venus there is a total amount of CO2 equal to 4.72 × 10 ^ 20 kg.
    4,72.10 ^ 20 kg of CO2 therefore produced a greenhouse effect equivalent to 16 250,8 W / m2.

    Step 2 : Application of the hypothesis:
    If there is a proportionality between the amount of CO2 and the energy produced by the greenhouse effect, then on Mars we should obtain a greenhouse effect equivalent to B W / m2.

    Calculation of B :
    We know that in the total atmosphere of Mars there is a total amount of CO2 equal to 2,165 .10 ^ 16 kg.
    4,72.10 ^ 20 kg of CO2 corresponds to: 16 250,8 W / m2
    2,165 .10 ^ 16 kg corresponds to: B W / m2
    So B = (2,165 .10 ^ 16 x 16 250,8) / 4,72,10 ^ 20
    B = 0,745 W / m2
    If there is a proportionality between the amount of CO2 and energy produced by the greenhouse effect, then on Mars we should get a greenhouse effect equivalent to 0,745 W / m2.

    Step 3 : Verifying the hypothesis:
    Irradiance of Mars: 586,2 W / m2.
    On Mars, at the top of the 146,55 W / m2 atmosphere from the Sun penetrate the atmosphere.
    Since the albedo is 25% or 36,64 W / m2, only 109,91 W / m2 reaches the surface of Venus, the equivalent of a temperature of T = ∜ 109,91 / 5,67.10 ^ - 8 = 209.82 ° K = - 63.33 ° C
    The average surface area of entrances is - 63 ° C, ie 210,15 ° K or E = 210,15 × 4 × 5,67.10^ -8 = 110,586 W / m2.
    We thus go from 109,91 W / m2 to 110,586W / m2 by the CO2 greenhouse effect, ie a total greenhouse effect of:
    110,586 - 109,91 = 0,676 W / m2.
    What did we predict by proportionality? : a greenhouse effect of 0,745 W / m2

    Conclusion : Since the two values (0,676 and 0,745) are very close we can consider the proportionality hypothesis as true.

    Step 4 : Apply the hypothesis to the Earth:
    The atmosphere of the Earth contains 3,128.10 ^ 15 kg of CO2.
    Proportionally with Venus, the greenhouse effect of the Earth's CO2 should be:
    4,72.10 ^ 20 kg of CO2 corresponds to: 16 250.8 W / m2
    3,128.10 ^ 15 kg corresponds to: B W / m2
    B = (3,128.10^15 x 16 250,8) / 4,72 × 10
    B = 0,1077 W / m2
    The greenhouse effect of the 400 ppm CO2 of the Earth's atmosphere should be 0,1077 W / m2.

    The Giec gives a value close to 30 W / m2 for the greenhouse effect of the 400 ppmv of CO2 of the terrestrial atmosphere !


    How can we find these 30 W / m2 by the calculation ????

  4. JC,

    You are trying to do a seat of the pants calculation for something you do not understand.  It is impossible to do the calculation by the process you describe.  you must use the Modtram software that was referred to you upthread.

    We have already discussed that pressure effects make it impossible to compare Mars to Venus in the way you are attempting to do.  The calculations at Goddards site are worthless and deliberately misleading.

    I recommend that you GOGGLE scientific publications on the greenhouse effect on Venus and Mars.  There is a lot of material on Venus.  You can also use the search function at the top of the page to find related articles.

  5. JC @253,

    I wasn't aware that the IPCC (Geic) gave any value for total CO2 forcing. Perhaps you can give the reference to the IPCC (Geic) document.

    Beyond that, you tread a path that is very close to the ridiculous.

    As a test of your grand method, perhaps you can calculate the GH-effect for the Earth's moon. Our Moon of course has no atmosphere so this will test both you grand method as well as your data on average albedo and average surface temperature. (The average temperature you may find difficult to track down. I do have a calculated value if you need it.)

    And once you have passed that test, prehaps we can address the big big problems you need to overcome in assessing the size of a real GH-effect with your grand theory.

  6. I do not understand your test since I try to put in parallel the quantity of CO2 of an atmosphere and its greenhouse effect, but on the moon there is no atmosphere and therefore no greenhouse effect.

    For the radiative part of CO2 : "The second most important greenhouse gas is CO2, which 32 W m-2 in agreement with Charnock and Shine (1993) goal differing from Kandel's (1993) estimate of 50 W m-2. (in : LINK)

  7. JC @256,

    Thank you for your link to Kiehl and Trenberth (1996). (You will note it is not a publication of by Geic-IPCC). The paper does demonstrate the complications in establishing Earth's CO2 GH-effect within Earth's total GH-effect but does show it is something like 32Wm^-2, and a little higher for the CO2-effect without the other GH-effects overlapping. I suggested up-thread @249 the value 40Wm^-2 as an all-sky modern value,

     

    As for my suggestion that you test your grand method by using it on the Moon, I strongly advise that you do not dismiss it.
    My reason is because Mars has such a small GH-effect that other considerations will make your calculation useless. The strength of the Martian GH-effect is very like the Moon's, at or close to zero.

    Sadly, there is not a great deal of work published that calculates this Martian GH-effect (certainly not in recent years) but among these publications you will find Haberle (2013) 'Estimating the power of Mars’ greenhouse effect' which unfortunately is not directly available in full on-line. This paper suggests that the apparent GH-effect on Mars is actually negative, with the Martian temperature as-measured being Ts=~202K while the blackbody temperature calculates to Te=~208K. (Note this blackbody temperature Te is the value you use, as is made plain within Covey et al 2012. And note also I am minded not to go further into this situation with respect to Mars as it is somewhat complicated.)

    The same problem with Te & Ts occurs on the Moon. If you use your grand method to calculate the blackbody temperature you would obtain Te=270K. This can also be calculated using the as-measured amount of long-wave radiation emitted by the Moon (which is how they calculate the albedo). But because the Moon has such a large spread of day-night temperature and equator-polar temperature (these spreads resulting from it having (1) such a long day and (2) no atmosphere), this method is hopeless for calculating the arithmetic mean temperature of the Moon surface. Ts and Te are wildly different.

    The Moon's equatorial temperature range should give some indication of the Moon's average temperature by setting an upper limit. That provides a value of 243K, well below Te. The Moon's equator actually averages 216K (the noon-day maximum is far narrower than the midnight minimum) and for the Moon as a whole Ts=200K, these from my own calculation based on Fig9a of Williams et al (2017) (This calculation would be difficult to accept as there is no properly quoted Moon average to compare it to. Yet if I average the blackbody radation calculated for each portion of the Moon and then calculate temperature, the resulting Te=270K). Thus on the Moon the Ts-Te mismatch is very large.

    I would suggest there is a similar but smaller Ts-Te mismatch on Mars as suggested by Haberle (2013) and this is of great relevance to your choice of grand method to test the GH-effects of CO2.

  8. LINK

    Here page 11 you have an estimate of the average temperature of the Moon: 197,35 +/- 0,9 ° K. This corresponds to your 200 ° K!

    I think for the rest of your remarks (review the value of the Moon albedo ?).

    Response:

    [DB] Shortened and hyperlinked URL breaking page formatting.  Please learn to do this yourself using the Insert/Edit Link tool.

  9. JC @258,

    Thank you for finding Nikolov & Zeller (2015). These exoplanet scientists often come up with interesting work but it is not an area I follow. You will note their Appendix B providing a calculation of the Martian average global temperature based on measurements taken from Martian probes.

    The lunar temperature they use is reliant on Volokin & ReLlez (2014) who check their modelled value against the Diviner Lunar Radiometer Experiment data which is also the data presented by Williams et al (2017) which I mention @257 as the source of my calculated average lunar temperature.

  10. MAR@259 , the Nikolov & Zeller / a.k.a. Volokin & ReLlez joke is getting a bit old these days.   Is it still considered to have some instructive elements to it? 

  11. Eclectric @260,

    My personal position is that I do not recall reading Nikolov & Zeller before. There are certainly within it some worrying constructions within their model, that is worrying for a science faced by deluded AGW contrarians. (It may be diferent if you are researching exoplanetry climate.) Particularly worrying is the idea of the density of an atmosphere being a (or indeed 'the') contributing factor to the greenhouse effect. There is also the acceptance of the 37% result from Volokin & ReLiez which I consider to be badly wrong. (That is the idea that all airless rocky planets, if without an atmosphere like our Moon would have an average surface temperture 37% less-than a temperature calculated globally using the S-B equation j=σT^4.)

    But Nikolov & Zeller do present good accounts of the literature of lunar and Martian temperatues and also calculate a Martian temperature in a reasonable manner, something I've not seen elsewhere.

    Volokin & ReLiez I do remember as I did some simplistic calculations to unpack their 37%. I can repeat these with more confidence since Williams et al (2017). What I don't recall is their use of the Diviner Lunar Radiometer Experiment data (as used by Williams et al) to check their Moon calculations. That is a useful calculation.

    -----

    Setting out the simplistic calcs that show the 37% value is misused for the Earth (& Mars as well):-

    The 37% does occur on the Moon. Thus using S-B to calculate the lunar average temperature yields 270K, an over-estimation of some 70K. Only a small portion of this 70K is due to the zonal temperature range (hot tropics, cold poles), perhaps 5K of the 70K. The rest is due to the diurnal range. The Moon with a 708 hour 'day' has a very large diurnal range. Averaged across all zones, the range is 90K to 360K. It is this diurnal range that drops the remaining 65K below the S-B estimate. An Earth stripped of its atmosphere with a 24 hour day will have a smaller diurnal range (perhaps 40% of the lunar range). This is the point where Volokin & ReLiez "briefly explore" the issue. They examining the heat storeage of the planet surface thro the night, feeding conclusions back into their simplified modelling and find hardily any difference (0.3K) due to the 24 hour day. Somewhere they have forgotten Hölder’s Inequality (errors due to averaging a non-linear function) from which that 65K derives. The Moon's temperature between any single 29½ hour period (those used by Williams et al) varies up to a maximum of 114K while the Moon over the full 708 hours varies 267K, thus the 114/267=40%. If the Earth's 24 hour 'day' waggles temperature by only 40% of the Moon's 708 hour 'day', the Hölder’s Inequality shrinks massively, back-of-fag-packet perhaps from 65K to 10K.

    Now, magically, add on the zonal 5K and subtract the 15.7K non-greenhouse zonal-heat-transfer effect (this value from Volokin & ReLiez) and the Earth non-GHG temperature returns to the S-B estimated value. This then magically returns us to a 255K non-GHG Earth and thus the 33K GH-effect we all know & love.

  12. MAR@261 , my concern with Zeller / Rellez and his partner Nikolov / Volokin was more to do with the accuracy of the data they provide.

    Since the retraction of their 2015 paper (a jocular scandal, at minimum) and pointed criticisms from Gavin Schmidt, as well as by David Grinspoon [re some fudging of Mars temperature and pressure data], it casts even more of a shadow on their 2014 paper ~ which in one sense was a re-run of the unphysical ideas of Gerlich & Tscheuschner.

    I am not sure how much of the N&Z/V&Z business was an elaborate leg-pull.  Or perhaps they have simply "gone emeritus" and become denialist.

  13. Correction to last paragraph :-

    N&Z/V&R

  14. Eclectic @262,

    I'm not sure whether you want (1) an appraisal of the various Nikolov & Zeller papers or (2) an appraisal of Nikolov & Zeller. (Note we move further off-topic.)

    On the first point, the V&R/N&Z (2014) Moon temperature doesn't seem controversial. Their Mars temperature has been involved in criticism from David Grinspoon but I would ask that if the Mars temperature results of Nikolov & Zeller (2015)(withdrawn) are in error, I would be interested to see the results that demonstrate that error.

    Of coure, their grand theory of a pressure-driven global temperature is so much cods-wallop. Yet published cods-wallop is not unknown and can at times be a useful exercise. Note Grinspoon's comment here:-

    Rather than aiming to be a universal paradigm-buster, Grinspoon said the study is better served as a handy mathematical approximation. “It’s a kind of clever, back-of-the-envelope way to calculate planet temperatures,” Grinspoon said. Should scientists find themselves with limited exoplanet data, something like the Volokin and ReLlez model could be a simple way to approximate distant temperatures.

    On the second point, the record shows that up to 2006 the pair have a history of publication but not in climatology. They turned climate skeptics in about 2010 and their first attempts at overturning AGW were dreadful enough to give them a reputation of swivel-eyed lunatics, apparently preventing publication of later work. The the pseudonyms were an attempt to overcome this rejection. It worked. Their 2014 paper has not been withdrawn. Their 2015 was published bu then withdrawn. Today they have a publisher who will publish any old crap of a denialist persuasion (described with others here), thus facilitating the publication of the dubious Nikolov & Zeller (2017).

  15. Hello there :) Does it also debunk this theory here? It also take into account pressure and distances ratio beetween sun and venus, earth, also claiming no greenhouse effects.   

    http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html

    His claims "Venus's atmosphere DOES absorb 1.91 times the power that Earth's atmosphere does, as their temperature ratio shows--and that ratio is precisely that predicted simply from the ratio of their distances from the Sun" 

    I'm really curious about your opinion. Is there an error in his math? 

    PS I suppose this is the right place to ask this question if not direct me to the proper one please. 

  16. Sarmata @265,

    His (that is one Harry Dale Huffman) claim is that "Venus's atmosphere DOES absorb 1.91 times the power that Earth's atmosphere does" only holds if the reflectiveness of Earth & Venus are identical. The webpage does in an up-date acknowledge reflectiveness (albedo) and sets out to correct for it but makes the mistake of assessing albedo as being "the same fraction (f)"  on both Venus & Earth. Yet they are not even similar as this NASA Fact Sheet shows. Venus receives 2601.3Wm^-2 solar radiation and Earth 1361.0Wm^-2, a ratio of 1.91-times. But the albedo's are vastly different, Venus 0.77  and Earth 0.306. This means the absorbed solar radiation is 601Wm^-2 on Venus and 948Wm^-2 on Earth (these values over the disc of the planet). The true ratio is thus not 1.91-times but 0.63.

    And the fancy use of the 1.91 ratio (which is wrong so has no merit) only works over the Earth's troposphere and a portion of the Venus atmosphere. If it were some grand theory, you would expect it to work throughout these atmospheres and indeed throughout all atmospheres. So Jupiter the Harry Dale Huffman theory would give a 1bar atmospheric temperature on Jupiter of 55K (that's ignoring albedo which is similar to Earth's) and not the measured 168K.

    Planetary temp-pressure graph

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