Venus battle resolved?


Jeff Id took issue with Chris Colose for bringing up the high surface temperature at Venus in his SkS post

CO2 is a strong greenhouse gas, and it is important in impeding how efficiently our planet loses radiative heat to space.  We don’t often think of CO2 as a “pollutant” on Venus, yet it still allows the planet to support temperatures well above the melting point of lead or tin.

Jeff replied at his blog:

Venus does have a more reflective atmosphere but it is also closer to the sun than the Earth.  For the thinking mind, it is difficult to ignore that the atmosphere is a ridiculous 90 times more dense. (…) In fact, if you just used Nitrogen alone at the same mass you would get a ton of heat just by the insulating properties of a gas.

On a subsequent post he reiterates his thought that

the reason for Venus surface temeprature being so high was the pressure and that any gas would create a huge warming effect 

However, during the discussion he seems to be backpedaling:

#15, Chris, (…)

My reply was that it was the pressure and amount of gas which caused the temperature more than the specific greenhouse effect of some particularly powerful gas. I pointed out that even N2 would cause a ton of warming with wording that clearly recognized there would be less warming and a paper was referenced where even the 96.5 percent N2 atmosphere had 80C of warming. I was also careful not to claim that all gasses would definitely cause a hot Venus and intentionally phrased even that as a question. In other words, you are making assumptions of a point I didn’t state.

To be fair, I admit that a pure nitrogen atmosphere had less warming than I would have (but did not) guess.

Is it just me, or does that indeed sound like he agrees that the majority of the >500 degrees greenhouse effect on Venus stems from the radiative properties of its atmosphere (~96% CO2) rather than from its density/pressure? The impression I got from his post was that the opposite though. Makes me wonder what the argument is really about. So I asked:


It seems that you agree that the high temperature on Venus is due primarily to a strong CO2 greenhouse effect (few hundred deg) and secondarily (?) to the high surface pressure (the ~80 deg number that was mentioned upthread).

If so, then I don’t understand the beef you have with Chris’ take, where he uses Venus as an example that shows that CO2 is a greenhouse gas.  

Jeff replied:


I object to its comparison to Earth as a scare tactic in general. That’s all.

Argument resolved. Both agree that the greenhouse properties of Venus’ atmosphere are primarily responsible for its high surface temperature, and they disagree as to whether or how this could be mentioned in a discussion about Earth’s climate.

Quick rundown on Venus’ climate:

Venus is closer to the sun than the Earth, but its higher reflectivity more than compensates for that. Without a greenhouse effect Venus would actually be colder than the Earth would be without a greenhouse effect. In reality Venus is about 500 degrees warmer than this so called black body temperature (the greenhouse effect on the Earth is about 33 degrees). This is primarily due to the inception of infrared radiation by its thick atmosphere of almost pure CO2. The high density also helps, but is of secondary importance.

More reading:

Realclimate on Venus

SoD’s Venusian Mysteries

Brian Angliss at S&R

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25 Responses to “Venus battle resolved?”

  1. Chris Colose Says:

    Jeff was just being argumentative. There was absolutely no hint of “scare-mongering” in my original SkS piece; he just needed to create some talking point (and repeat it several times, as per skeptic tactics 101) to justify his original objection to my post.

  2. Jeff Id Says:

    “Jeff was being argumentative because it doesn’t belong in a discussion of Earth CO2. ”

    The Happer article was quite accurate in my opinion despite Chris’s portrayal. I’ve written many times that CO2 is a warming gas, even posted several times at WUWT on the subject. Much to the dismay of the less technical readers in the HUGE crowd there.

    While I do (and did) admit that the Nitrogen warming number is less than I expected, I used the wording that even just nitrogen would probably create a ton of warming indicating I knew it would be substantially less (read the post). Turns out that I wasn’t exactly wrong, right? I challenged people to find a g as which wouldn’t create much warming and received several replies.

    Actually one comment showed that if you put even a CO2-less verson of earth’s atmosphere on Venus some have shown that you would get similar warming to Venus just from the water vapor at 90 atmospheres.

    It was used by Chris Colose in a weak rebuttal of Happer’s accurate article. The warministas ate it up, I called it out. Like the hockey shtick garbage, Venus is an overused and useless example for anything other than demonstrating that the greenhouse effect exists (which Happer or i and most of my readers, don’t disagree with)- or possibly as scare tactics for the non-technical.

  3. Dana Says:

    I was going to say the same as Chris’ comment – Jeff says his objection is when Venus is used as a “scare tactic”, but Chris certainly didn’t do that. So apparently he has no objection to Chris’ post, which makes me wonder why he raised the criticism at all (as Chris notes, no doubt just being argumentative).

    It’s also worth noting that Venus is about twice as hot as Mercury despite being about twice as far from the Sun.

  4. Dana Says:

    “The Happer article was quite accurate in my opinion”

    Congratulations, you literally just made my jaw drop.

    I used the SkS Firefox add-on to add the Happer article to our database. This involves cataloguing each climate myth in the article. It took me close to an hour to accomplish this, because Happer managed to cram approximately 20 long-debunked climate myths into his article. It was a Gish Gallop that would have made Monckton proud. To call this thing “quite accurate” is just stunning. Quite literally jaw-dropping.

  5. Brian D Says:

    Is there a reason why, in response to the “Venus is hotter because it’s closer to the sun” canard, I don’t hear more people bringing up Mercury? Even closer to the sun, much lower albedo, but about 400 degrees cooler than Venus? I know it’s smaller (my astronomy is rather rusty, but back-of-the-envelope suggests Venus would get less energy from the sun too, before correcting for albedo. If I knew where to look I would have just used insolation figures.). I also know it’s an incomplete position (since it doesn’t address the canard’s close relative of “Venus is hotter due to pressure, not greenhouse gas”), but it would seem to be a solid way to expose the lie for what it is, especially to the sort of audience that thinks “Venus is closer to the sun” with no mention of albedo or radiative physics is convincing.

  6. Brian D Says:

    Well, while typing that up and doing said back-of-the-envelope estimations, I see Dana does in deed bring up Mercury…

    Btw, Dana, looking through that Happer article, you have the patience of a saint.

  7. Dana Says:

    Thanks Brian, it was painful to read the whole thing. For a supposedly prominent Princeton physicist to repeat so many baseless and long-debunked myths, it just makes you wonder what the heck he was thinking when he wrote that thing. It was about on par with Monckton’s articles, maybe even worse. As someone with a physics background myself, it just pains me to see this sort of thing, because I like to think physicists should be more adept at critical thinking. Then again, that same mindset may be why some physicists like Happer think they can be climate experts without actually putting in the time to research the subject.

    As for Venus, I usually bring up Mercury when it’s mentioned. I think it’s a useful comparison, and a simple one (twice as far, twice as hot).

  8. M Says:

    Its still not clear to me that even the 80 degree number for a pure nitrogen atmosphere has much credibility… it seemed to come from the Bullock thesis that showed that replacement of CO2 with N2 resulted in a 400 degree reduction, leaving 100 degrees.

    Quoting Jeff: “With no C02 (mostly nitrogen atmosphere) the surface temp in Carrick’s 82 link drops from about 480C (wiki) by 422.7C leaving a Nitrogen based surface temperature of 57C. This means we can estimate a 100C warming effect from a mostly nitrogen composition atmosphere.”

    However, the 100C warming effect remaining includes significant contributions by a number of other warming substances like H2O and clouds (see the Bullock thesis for calculations showing that replacement of H2O with N2, or making clouds IR transparent both cause reductions in temperature). So while a high-pressure pure N2 atmosphere might lead to some warming due to Rayleigh scattering, it isn’t clear that we have resolved exactly how much, and specifically I think that 80 is rather too large.

  9. Chris Colose Says:


    The Rayleigh scattering is a cooling effect through raising albedo, and the albedo on Venus without clouds is still a moderately high ~40% because of this (though CO2 is also a more effective Rayleigh scatterer at 90 bars than N2).

    I think I’m going to work out another SkS piece on this stuff…

  10. M Says:

    “I think I’m going to work out another SkS piece on this stuff…”

    What I would love to see is a “Venus surface temperature vs. CO2 concentration” plot, assuming a 1 to 1 swap of CO2 and N2. Actually, as a first step, perhaps a 1 to 1 swap of CO2 and a magic IR-transparent CO2, and as a 2nd step, CO2 for N2, because CO2 into N2 will change all sorts of other things about the atmosphere (heat capacity, phase transition temperature, etc.) which complicate a simpler picture that is only due to radiative changes. As an example, the Bullock study which made clouds IR-transparent had weird boundary effects where the clouds used to be (which may explain, partly, why the sum of all the various experiments that Bullock did seem to sum to more than the total Venus greenhouse effect, whereas the equivalent experiment for the Earth sums to less – see Schmidt et al. 2010 where single factor removal only deletes 73% of the total GHG effect when added together).

  11. Chris Colose Says:


    A lot of these “what if” kind of things are research-quality questions and require more sophisticated modeling than I know how to do (or have the time, I’m working at NASA GISS over the summer right now on paleoclimate stuff and have other things I need to be doing). A lot of the radiative transfer calculations you can get away with on Earth don’t work on Venus where a lot of new factors are introduced. There’s also a lot of uncertainty associated with a number of issues (for example, CO2 continuum absorption) when you move into these conditions, and where there is little spectroscopy data available. Downloading things like Ray Pierrehumbert’s ClimateBook-Python interface and playing with the coding and problem sets is a good first step to some of these issues.

    The problem with the Air Vent comments is everyone seems to have their own pet theories about climate, thermodynamics, radiation, etc and no one seems to actually understand the physical basis behind a number of these factors. Qualitatively, a lot of this is easy (although there’s always surprises and things you wouldn’t think of) but quantitatively it’s not.

    Sticking to rocky planets/moons, there’s also only a few atmospheres of substantial pressure (e.g., Venus, Titan, Mars to some extent) that we can actually use examples of for exotic conditions, so a lot of these thought-experiments are a bit too hypothetical and you can’t find much in the literature to validate hypotheses.

  12. Jeff Id Says:


    Run it with Earth’s atmosphere for fun – if you aren’t afraid of a higher number. I hate real climate because they wouldn’t even consider it.

    Someone pointed out at tAV that the condensation of Nitrogen would cause unexpected complexities also. Whatever, you all get my point whether you agree or not.

  13. Eli Rabett Says:

    If you want an example of the effect of compression without the sun, use Titan (the outer planets really don’t have a surface)

  14. Jeff Id Says:

    “The problem with the Air Vent comments is everyone seems to have their own pet theories about climate, thermodynamics, radiation, etc and no one seems to actually understand the physical basis behind a number of these factors.”

    I think that is common from a lot of blogs. Especially if you consider the less technical of the group. I know of no pet theories for many of tAV readers who live mostly with a bunch of unanswered questions. Derek is a non-regular who has been pounded on quite a bit.

    Over half the commenters at tAV hold PhD’s in my estimation. Most of us have a mutual tiredness of being talked down to by a some climatologists who don’t even hold up to my own meager math credentials. Too much certainty, too much exaggeration, to many claims unsubstantiated, and for me, too many stupidly unworkable solutions.

    [edit. Off topic and derogatory. BV]

  15. Chris Colose Says:


    First of all, the “climate science” community consists of thousands of people, with a number of groups working independently around the world on a number of topics– ranging from sensitivity studies, modeling, clouds, aerosols, tropical dynamics, radiation, polar dynamics, mid-latitude dynamics, planets, carbon cycling, paleoclimate (on a large number of timescales), etc, etc.

    If you have specific objections with a handful of them (or a handful of studies that came out), even if those objections are valid, the implications are likely to extend to only a very small community of people. For example, I have not followed Steig and the Antarctic stuff on the blogs at all, and have no particular desire to; whether a certain region of antarctica has actually warmed a couple degrees more than someone else’s analysis is minutia, and while it’s important people are studying this stuff, it has little bearing on the big picture climate questions, and little impact on most of everyone else’s field of study. I’m tired of these broad categorizations of “climate scientists,” and it’s this vague sort of accusation that ruined any semblance of credibility in the Happer article (among other things). And even if you feel “some” climate scientists are talking down on you, rather than attributing it to some superiority complex that they all must have, perhaps a good reflection on your own attitude is in order:

    Your (and your readerships) broad agreement with the Happer article is very telling that you are not in a position to judge the quality of climate science or the logic required to think like a scientist. I’m sure some of your readers know statistics or other topics much better than myself, but this clearly does not demonstrate any familiarity with the literature or physics of climate. It is certainly surprising to me that such well-educated people could be so gullible concerning some of the topics which are not necessarily “climate science” related, like the large degree of straw man attacks, irrelevancies, and personal attacks which bear no reflection on how science is actually done. PhD’s or not, it is quite clear that very little of your readership has decent exposure to climate literature, conferences, etc., and yet they all speak so confidently about how it is all done. This is what ruins your credibility on the subject, even if you have qualifications or have made a real contribution to Antarctic temperature trend data.

  16. Bart Says:

    – Chris brought up Venus as an example of the radiative properties of CO2 in a reply to Happer. Even though Happer in his article doesn’t deny the greenhouse effect and doesn’t bring up the saturation canard (hence no direct reason to bring up Venus), I don’t regard Chris’ quote as a ‘scare tactic’ at all.

    – Jeff writes “I used the wording that even just nitrogen would probably create a ton of warming indicating I knew it would be substantially less (read the post).” Reading back what you wrote, my impression is the opposite: “the reason for Venus surface temeprature being so high was the pressure and that any gas would create a huge warming effect” and calling Chris’ Venus example idiocy.
    The impression you left in your posts was that the greenhouse effect from CO2 was minor at Venus, a point from which you have since backpedaled. If I misunderstood you on that point, I can guarantee that I’m not alone because it was clear as mud.

    – Let’s focus the discussion on Venus’ climate and how that argument unfolded. The discussion is not about the Air Vent’s readership or most definitely not about climate scientists’ behavior. There’s still an open thread for that.

  17. scienceofdoom Says:


    Nice article (I think this is the first time I have commented here). I believe you got to the heart of the issue.

    Jeff’s original article sure confused me. I am glad he has clarified his point.

    Venus and Earth cannot be directly compared in a linear fashion. The equations of radiative transfer are highly non-linear.

    I suspect that many people would be surprised by the results of the excellent (mathematical) experiment suggested by M (June 8, 2011 at 00:42).

    I wouldn’t be (surprised) because I don’t know what to expect. If that makes sense. The only way to find out the answer to any question of radiative transfer is to do the calculations.

    But Chris Colose makes the valid point that these are not easy calculations (massive computational effort), and would come with some measure of uncertainty due to questions surrounding some spectroscopic properties.

    Given Jeff’s interest in the topic of CO2 in the atmosphere it would be nice to find out if he endorses the equations (as shown in Understanding Atmospheric Radiation and the “Greenhouse” Effect – Part Six – The Equations). And whether he believes the results that are calculated for given concentration of gases and temperature profiles through the atmosphere are correct – with what level of uncertainty.

    Some comment on this in Theory and Experiment – Atmospheric Radiation.

  18. bugs Says:

    I just want to know why Jeff Id is so quick to accept incorrect assertions such as Happer’s, but utterly ‘skeptical’ of science that does not agree with his prejudices.

    He is also quick to make conspiracy theory accusations against scientists at his own blog.

  19. Jeff Id Says:

    “I just want to know why Jeff Id is so quick to accept incorrect assertions such as Happer’s, but utterly ‘skeptical’ of science that does not agree with his prejudices.”

    Because I agree with them.

  20. Jeff Id Says:


    I recommend Bart’s blog to anyone. He’s honest in his presentation here and doesn’t snip comments (much). ;)

    I often read your blog as well, but am not sure if I have commented. I enjoy the math and presentation of text material to back up your points. Some of the flow calculations took be back a couple of decades. I read your article linked this morning and find nothing to disagree with. As far as uncertainty, the only uncertainty I noted was that of what is available for absorption at any given moment due to line broadening and the current energy state of each molecule. I can’t recall where you took the thread in the next post and don’t have time this morning.

    There are a few blogs I read regularly as of late, CA, Lucia’s, SOD and WUWT. There was an interesting discussion between yourself and DeWitt a couple of weeks ago that was fun to follow. Others I read less often including this one but they are still excellent and a good source of information. I tried to quit blogging for time reasons but found it very difficult as it is my favorite way to let off steam. It is frustrating these days as I don’t have any time to do the math I want to, but my business and kids have to come first.

  21. scienceofdoom Says:

    Jeff Id said on Happer’s assertions: “Because I agree with them“.

    I missed the start of the story. What are his assertions?

  22. scienceofdoom Says:

    Jeff Id said, on June 8, 2011 at 14:48:

    I read your article linked this morning and find nothing to disagree with.

    Thanks. This clears up my questions.

  23. Bob Brand Says:

    Hi Science of Doom,

    I missed the start of the story. What are his assertions?

    I guess the article by William Happer can be found here:

    I also have an opinion about this piece – and it is not very positive. There are only a few quantitative statements in there, just linear extrapolations of past trends. The paleoclimatology is treated in an incredibly off-hand manner, as though society and ecology could painlessly transition into the circumstances present during the Paleocene-Eocene Thermal Maximum.

    There is nothing in the piece about the Venusian atmosphere. Maybe the Venusians should be grateful.

    Anyway Science of Doom – your site is the absolute best, the cats’ meow. Please keep disregarding the rhetoric and the politics, and *DO* partake a bit in rest, relaxation and fresh air now and then. :)

  24. scienceofdoom Says:

    Bob Brand,
    Thanks very much.

  25. The Planetary Greenhouse Engine Revisited Says:

    […] effect on Venus that I made in passing-by (e.g., here, here, and Bart  Verheggen chipped in too).  I notice many issues still plaguing the web with regard to the basic physics […]

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