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Venus: Cool Greenhouse?

(originally published as “Venus Forecast” on Aug 17. 2007):

(first post in a series dedicated to the planet Venus as “example” of runaway greenhouse warming)
Venus post #1: Venus: Cool Greenhouse?
Venus post #2: Venus Warming Revisited
Venus post #3: Venus Missing Greenhouse Warming
Venus post #4: Venus and a Thicker-Atmosphere Earth

In a few years, the old ideas of Fred Singer will come back into fashion.

Venus’ retrograde rotation, incredibly massive atmosphere and relatively young (<500 million years) surface will be elegantly explained by the crash of a massive satellite half a billion years ago (with subsequent melting of much if not the whole crust, and humongous outgassing).

UPDATE FEB 28 2008: Space.com: Venus Mysteries Blamed on Colossal Collision

Current lead-melting surface temperatures will be just as beautifully explained by simple adiabatic processes.

The role of CO2 in the heating of the atmosphere via some “greenhouse effect” will be seriously reconsidered and almost completely dismissed.


Some quick computations:

Ratio of available solar energy Venus/Earth: 190%

Earth, surface pressure: 1000 mbar; temperature: 288K
Venus, 50km altitude pressure: 1000 mbar; temperature: 330K
330K/288K = 114% < 190%

Venus, surface pressure: 90,000 mbar; temperature: 735K
Temperature of terrestrial air compressed from 288K/1,000mbar to 90,000mbar: 887K
735K/887K = 82.9% < 190%

Far from showing any CO2-induced global warming, Venus is much cooler than expected, likely because of the high-altitude clouds that prevent us from looking at the surface.

  1. Carl Rooker
    2010/05/14 at 12:41

    I have been wondering about the possibility that Venus high atmospheric content and temperature might be caused by a large bolide colliding with it. I think you are correct, that such would explain the retrograde rotation, surface conditions, and the atmospheric conditions far better than the alledged “Green House” argument.

    • 2010/05/18 at 16:06

      Carl – We even know when that happened, as the Cytherean surface is no more than 500 million years old

  2. cmb
    2010/03/04 at 16:29

    Where are the sources for your numbers?

    • cmb
      2010/03/04 at 16:38

      Also, why are you comparing earth’s surface temp to Venus 20 miles up in the atmosphere?

      Earth surface: 288k Venus surface: 735k

      Blows 190% out of the water, doesn’t it? That’s due to heat trapped on the surface by – you guessed it – greenhouse effect.

      Next, why are you using the temporary heat produced by compression compared to an atmosphere at resting state? Compressing air makes it hotter – but temporarily. Let that compressed air temperature settle via radiative transfer like an atmosphere does and… 190% blown out of the water again!

      • 2010/03/04 at 17:01

        cmb – the sources of which numbers? There is a link for the 887k.

        The first comparison is isobaric and about Venus at 50km, not 20 miles.

        Not sure what do you mean by “settle via radiative transfer”? It well depends on the composition of the atmosphere (and the insulation of the compressed air’s container)

  3. Scott Brooks
    2009/10/23 at 17:59

    Hello Maurizio

    I believe you are right on about the cause of the Venus source of heating. Very intelligent observation.

    NASA has a publication back from the early days before Hansen came on board. It involves atmospheric modeling by computer.

    Models of Venus Atmosphere 1972
    SP- 8011

    Back in the days of real science they compared the research of computer models of the Venus Atmosphere to what several early Venus probes reported. They hypothesized that the troposphere layer lapse rate would be adiabatic and the probe, Venera 7, proved their results.

    You will find this publication quite interesting if you can still get it. I would like to hear your comments about it since most other sites cowtow to the Venusian heating effect as CO2 forcing coupled with the insulating properties of the sulfur dioxide clouds.

    One site states:

    About 80% of the incoming solar radiation is reflected back to space by the cloud layer, about 10% is absorbed by the atmosphere and only 10% manages to get through it and heat the surface. However, the thermal radiation emitted by the surface gets trapped by the same atmosphere. The result is an amazing 500 °C difference between the surface and cloud-top temperatures.

    Now I am not physicist enough to do the math on that but it makes me wonder about the claim of runaway green house effect and Venus as the poster child. But you seem to have a science background, I don’t know your CIV. I would be interested in your feed back.

    Here is another site that hints about the adiabatic heating effect:

    Venusian atmosphere:

    The atmosphere of Venus is composed of 97% CO2, 2% N2 and less than 1% of O2, H2O and CH4 (methane). There is also a substantial amount of sulfuric acid in the lower atmosphere.

    Understanding the pressure, density and temperature of an atmosphere means understanding the Ideal Gas Law. The Ideal Gas Law states that the pressure, density and temperature of a gas are all related by a simple formula.

    For example, if you increase the pressure of a gas, its temperature also goes up or its density goes down. If you lower the density, the pressure goes down or the temperature goes up.

    The formula to express this relation is: P = NkρT
    where ρ is the density (in gm/cc), T is the temperature (in Kelvins), P is the pressure (in bars), N is Avagadro’s number (a constant) and k is Boltzmann’s constant. Since there are two constants and three variables, it is often useful to express the ideal gas law as the ratio of the values. So, for example, the pressure, density and temperature of two planets’ atmospheres (planet 1 and planet 2) are expressed as: P1/P2 = (ρ1/ρ2)(T1/T2)

    The surface temperature of Venus is around 890 degrees F, the hottest average temperature in the Solar System. This is due to the rich amount of CO2 which leads to a runaway.

    But he lapses back to an enhanced greenhouse mantra concerning anthropogenic gases. It makes me wonder about falsifying science for grant grease. It seems to have become more common these days, like companies looking for federal stimulus like Cap and Trade regulations.

  4. Carl Rooker
    2009/05/01 at 14:52

    This is simple high school chemistry. Raise the gas pressure, raise the temperature.

    Also, the very high amount of gas in Venus atmosphere would hold much more energy (heat) than the Earth’s much less dense atmosphere.

    Add Venus’ proximity to the sun, and you have a very warm planet indeed.

    Very recently a certain proponent of anthropogenic global warming has said the Earth could end up like Venus.

    Maybe said proponent of anthropogenic global warming should go back to high school.

  5. Bill Illis
    2009/01/26 at 01:14

    Given the different densities of the atmospheres, are there calculations of how much “gravitational compression” would add to Venus’ temps versus Earth’s.

    The different densities of the atmosphere itself produce different temperature profiles.

    What is the greenhouse effect which allows a star to heat up, compress and begin nuclear fusion? Zero or less. Gravitational compression is the big missing factor.

  6. aaron
    2008/12/19 at 13:02

    ca va a tous, hi all. i have always been a proponent of runaway greenhouses tendacy to doom there selves. even when the inverse-square is considered, venus would not be much warmer than earth compared to what is now if it would have an atmosphere similar to our about 6 to 9c warmer. there are so many other parameters that lead to what happens to the conditions on a planet.
    never put much in to this whole “goldielocks” zone. i think in the past few years (since the late 1970s) we have seen SO2 fall drematically and that could mean a waning of volcanic activity. there would simply need to be considerable volcanic activity to maintain that 10km thick deck, also there is not enuf solar radiation getting to the surface to maintain the current greenhouse due to CO2’s absoption bands being well in the IR range. i think particular attention must be payed to the dematic changes that venus express witnessed during a 4 day period in the southern polar regions in january 2007. this repressed a massive sudden change in the morphology of the clouds(either a mass injection of SO2 of cooling to the dew point). what could this mean? abientot, aaron

  7. papertiger
    2008/03/01 at 12:19

    Here’s another post. This one might bring sparks because Dr Andrew Dessler of Tx A&M and Gristmill blog, one of Prof Hansen’s more vocal defenders, frequently uses the Chron SciBlog as a sounding board.
    (On the other hand, it’s posted late in the thread, so maybe it will be a big fizzle)

  8. 2008/02/28 at 21:22

    Earth’s orbit “radius”: 1 AU
    Venus’: 0.72 AU

    energy from the Sun decreases according to the square of the distance


    that is 1/0.05184=192.9% more energy at Venus’ distance than at Earth’s

    Since we have done several approximations, 190% seems as good a value as any.

    For reference, note that the Venus Express probe has solar panels managing to produce 806W at Earth’s orbit, and 1,425W at Venus’ orbit.

    That ratio 1425/806=177% is slightly lower than 190%, a fact that can be explained by a slightly lower efficiency in the harsher radiation and temperature environment around Venus.

  9. papertiger
    2008/02/28 at 18:54

    Hey Omni,
    I’m not content to wait a few years. Let the truth be known though the heavens fall.
    I intend to pound some bastions of science into dust with this information.

    Sciam, Nat Geo, Sky&Telescope, Astronomy mag, and any other institution or journal which has parroted the “runnaway greenhouse” on Venus story that I can think of (Wikipedia seems a likely place to start)- they are all going to hear from me.
    But first I need to cross some eyes and dot some tees. Could you give me the source for your Venus to Earth TSI ratio? I found some people using it in a second hand way on a “terraforming” forum, but haven’t found an original study reference (although why I would bother lending credence to “official” sources escapes me at this point – I still have to play the game from that angle for public pressure to build).

  10. papertiger
    2008/02/28 at 10:36

    Done . First, but not last, time I have used it. Link is to the fast comments of Lubos Motl’s The Reference Frame ; http://motls.blogspot.com/2008/02/unchained-goddess-global-warming-1958.html.

  11. 2008/02/28 at 08:53

    thank you papertiger. Yes the numbers are all mine. But of course others thought similarly before me. Feel free to use it, just hyperlink it here please, and drop me a note with the URL.

    Of course there might be something we are missing in all of this. Perhaps one day somebody will show what that is.

  12. papertiger
    2008/02/28 at 04:56

    Did you think of that yourself?
    I had been playing around with the surface pressure, retrograde motion and 9 month long “day” for months without pulling it all together in nearly as concise a newspaper comment friendly 100 word or less package as you have.

    And oh yes I will be stealing it!

  1. 2010/05/07 at 21:53
  2. 2008/03/06 at 00:20
  3. 2008/03/02 at 21:26
  4. 2008/03/02 at 00:25

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