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The runaway greenhouse effect on Venus

What the science says...

Select a level... Basic Advanced

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

"I bought off on the “runaway greenhouse” idea on Venus for several decades (without smoking pot) and only very recently have come to understand that the theory is beyond absurd." (Steve Goddard, WUWT)

At a glance

Earth: we take its existence for granted. But when one looks at its early evolution, from around 4.56 billion years ago, the fact that we are here at all starts to look miraculous.

Over billions of years, stars are born and then die. Our modern telescopes can observe such processes across the cosmos. So we have a reasonable idea of what happened when our own Solar System was young. It started out as a vast spinning disc of dust with the young Sun at its centre. What happened next?

Readers who look up a lot at night will be familiar with shooting stars. These are small remnants of the early Solar System, drawn towards Earth's surface by our planet's gravitational pull. Billions of years ago, the same thing happened but on an absolutely massive scale. Fledgeling protoplanets attracted more and more matter to themselves. Lots of them collided. Eventually out of all this violent chaos, a few winners emerged, making up the Solar System as we now know it.

The early Solar system was also extremely hot. Even more heat was generated during the near-constant collisions and through the super-abundance of fiercely radioactive isotopes. Protoplanets became so hot that they went through a completely molten stage, during which heavy elements such as iron sank down through gravity, towards the centre. That's how their cores formed. At the same time, the displaced lighter material rose, to form their silicate mantles. This dramatic process, that affected all juvenile rocky planets, is known as planetary differentiation.

Earth and Venus are the two largest rocky planets. But at some point after differentiation and solidification of their magma-oceans, their paths diverged. Earth ended up becoming habitable to life, but Venus turned into a hellscape. What happened?

There's a lot we don't know about Venus. But what we do know is that the surface temperature is hot enough to melt lead, at 477 °C (890 °F). Atmospheric pressure is akin to that found on Earth - but over a kilometre down in the oceans. The orbit of Venus may be closer to the Sun but a lot of the sunlight bathing the planet is reflected by the thick and permanent cloud cover. Several attempts to land probes on the surface have seen the craft expire during descent or only a short while (~2 hours max.) after landing.

Nevertheless, radar has been used to map the features of the planetary surface and analyses have been made of the Venusian atmosphere. The latter is almost all carbon dioxide, with a bit of nitrogen. Sulphuric acid droplets make up the clouds. Many hypotheses have been put forward for the evidently different evolution of Venus, but the critical bit - testing them - requires fieldwork under the most difficult conditions in the inner Solar System.

One leading hypothesis is that early on, Venus experienced a runaway water vapour-based greenhouse effect. Water vapour built up in the atmosphere and temperatures rose and rose until a point was reached where the oceans had evaporated. In the upper atmosphere, the water (H2O) molecules were split by exposure to high-energy ultraviolet light and the light hydrogen component escaped to space.

With that progressive loss of water, most processes that consume CO2 would eventually grind to a halt, unlike on Earth. Carbon dioxide released by volcanic activity would then simply accumulate in the Venusian atmosphere over billions of years, creating the stable but unfriendly conditions we see there today.

Earth instead managed to hang onto its water, to become the benign, life-supporting place where we live. We should be grateful!

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

Venus may have experienced a runaway greenhouse effect in the geological past. To use the term 'runaway' is to refer to a highly specific process when discussed by planetary scientists. Simply having a very hot, high-CO2 atmosphere is not it. So let's start with a tutorial on Venus at the present day.

Venus’ orbit is much closer to the sun, which means it receives almost twice the solar radiation at the top of its atmosphere than Earth. Venus also has a very high albedo which ends up over-compensating for the closer distance to the sun. The result is that less than 10% of that incident solar radiation reaches the surface. High albedo can be attributed to sulphur-bearing compounds, along with minor water vapour (around 20 ppm). These substances form globally encircling sulphuric acid-dominated cloud decks (fig. 1). Venus’ atmosphere also has a surface pressure of around 92 bars (or if you like, 92,000 millibars), equivalent to what you’d feel on Earth beneath more than a kilometre of ocean.

Venus in its shroud of clouds.

Fig. 1: Venus in its shroud of clouds - a false colour composite created by combining images taken using orange and ultraviolet spectral filters on the Mariner 10 spacecraft's imaging camera.The images used to create this view were acquired in 1974; the RH one has been enhanced to bring out texture and colour. Image: NASA.

Observations of the water vapour content in the Venusian atmosphere show a high heavy to light hydrogen isotopic ratio (D/H). This is best interpreted as the product of a preferential light hydrogen escape to space: deuterium escapes less easily. Venus is considered to have had at least 100 times its current water content in the past (e.g. Selsis et al. 2007 and references therein).

The greenhouse effect on Venus today is primarily caused by CO2, although water vapour and SO2 are important as well. 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 in infra-red (IR) imagery. In reality, the surface of Venus (Fig. 2) is even hotter than the dayside of Mercury, at a deadly 477 °C (890 °F).

Like Earth, the Venusian clouds also generate a greenhouse effect. However, they are poor IR absorbers and emitters compared to water clouds. The sulfuric acid droplets forming the clouds can also scatter IR radiation back to the surface, producing another form of the greenhouse effect in that way. In the dense Venusian CO2-rich atmosphere, there are IR-handling processes at work that are unimportant on modern Earth.

The Soviet Union's Venera 14 probe.

Fig. 2: The Soviet Union's Venera 14 probe captured two colour panoramas of Venus's surface in 1982. This panorama came from the rear camera. Image: Russian Academy of Sciences. More images can be seen at:

How to get a Runaway?

To get a true runaway greenhouse effect on Venus, you need a combination of solar radiation and the presence of a greenhouse gas. That gas has two key requirements. It must be condensable and it needs to be in equilibrium with its surface reservoir. In addition, its concentration must increase with temperature, as explained by the Clausius-Clapeyron relation. For Venus to enter a runaway greenhouse state, the greenhouse gas of interest is water vapour, plus its liquid reservoir, the water making up the oceans.

The greenhouse effect on any planet involves impeding the flux of outwards longwave radiation to space. Water vapour is very good at this so can potentially lead to a positive feedback runaway scenario. That works as follows: higher temperatures cause ever more water to evaporate and then drive temperatures even higher and on and on it goes - while there is an available liquid water reservoir.

Through water vapour's effectiveness at blocking IR, the outward longwave radiation flux eventually flatlines. If the incoming Solar flux is constantly greater than that outgoing flatline value, the planet is tipped out of radiative equilibrium and we have that runaway. If you like, it has a fever. The reservoir for water vapour - the oceans - is vast. That means the system may only be able to return to radiative equilibrium once the runaway process has stopped. In the extreme runaway greenhouse effect, that cessation may only happen at the point when the whole ocean has evaporated.

On present-day Earth, there is a strong temperature inversion, called the tropopause. It is situated between the troposphere and stratosphere. You can see it on thundery days when the tops of storm-clouds spread out beneath it to form the familiar anvil-shapes. The tropopause thus forms an effective barrier to moisture getting into the stratosphere. At the height of the tropopause on Earth, in any case, it's already too cold for water to remain in the vapour phase. The wispy clouds making up thunderstorm anvils consist of ice crystals. This impediment to water vapour's ascent is often referred to as a 'cold trap'.

In a runaway scenario, such as that proposed for Venus, no such impediment exists. This means the upper atmosphere would have become moist too. On Venus, the troposphere extends to a much greater height than on Earth. There is no stratosphere - we're talking about a very different situation here. That is critical because water vapour, upon reaching such great heights, has energetic Solar ultraviolet (UV) radiation to contend with. The UV is effective at splitting the H2O molecule into its constituent elements. Once that has happened, the hydrogen in particular is easily lost to space. One can envisage that once a runaway greenhouse effect got going, Venus' water content got steadily depleted in this manner through time. If Venus ever had oceans, they must have evaporated into oblivion. Because of the 'cold trap', this form of water-depletion is of very little significance on Earth - thankfully.

Once that water was lost, the chemical processes that lock up carbon in rocks on Earth could not operate. All of them involve water somewhere. Thereafter, every addition of carbon to the atmosphere, large or small, stayed up there. Most CO2 was probably of volcanic origin. The result was the 96.5% CO2 atmosphere and hellish surface temperature of Venus today.

Earth and the Runaway: Past and Future

Currently, Earth is well under the absorbed solar radiation threshold for a runaway greenhouse effect to occur. Its water condenses and is recycled back to the surface as rain, rather than accumulating indefinitely throughout the atmosphere. The opposite is true for CO2, which builds up and up through our emissions, only checked by natural removal processes. Note here that the runaway greenhouse threshold is largely independent of CO2 since the IR opacity is swamped by the water vapour effect. This makes it difficult to justify concerns over a CO2-induced runaway on Earth.

However, this immunity to a runaway greenhouse effect will not last forever. The most realistic scenario for Earth entering a runaway occurs a few billion years in the future, when the sun's brightness has substantially increased. Earth will then receive more sunlight than the outgoing longwave radiation escaping to space. A true runaway greenhouse effect is then able to kick in. Caveats apply, though. For example, greater cloud cover could increase planetary albedo and delay this process.

Interestingly, 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 of its existence. Geothermal heat and the heat flow from the moon-forming impact would have made up for the difference between the net solar insolation and the runaway greenhouse threshold. But if this happened it could only have lasted for a relatively short period of time - since we still have plenty of water on Earth.

For further reading, a recent review paper (Gillmann et al. 2022) explores the various hypotheses concerning the evolution of the Venusian atmosphere over geological time. There's also an excellent book chapter (Arney & Kane. 2020, currently available as a PDF at arXiv). As might be expected, difficulties in fieldwork are plural on Venus and designing a probe that survives touchdown and can go on to do the required data-collecting is still some time away. The key piece of evidence we need to confirm the existence of a runaway greenhouse effect in deep time would be for free water having once been present. But it is apparent that large parts of the surface were covered with lava flows from monster volcanoes at some point. Is that evidence nowhere to be seen, or is it just hiding? Time will tell.

Last updated on 21 January 2024 by John Mason. View Archives

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Comments 26 to 50 out of 267:

  1. Rosco - try using the search button up top and posting on topic. But first read the articles - you need to learn some science to make sense. If what you post isnt relevant to venus, then I guess it will be deleted. If you want your articles read, then stick to the rules.

    [DB] "But first read the articles"

    I can think of no better advice to give someone who is not yet doing so.  Thank you.

  2. Rosco - you seem to disagree on the possibility that CO2 makes it more difficult for energy entering the climate system to leave that system. These energy forms are at different wavelengths and so CO2 affects one over the other. CO2 doesn't create energy on its own (nobody has ever suggested this), it just reduces the ability of the whole system to shed energy effectively. Since the only way the Earth's (or Venus') climate system can shed energy is by radiation, that is rather important. Please be courteous and read the links you were provided with earlier. Based on your postings I suspect you haven't. What temperature would Earth be, if the atmosphere was unable to trap any of the outgoing longwave radiation?
  3. Watch that word "trap" sky--it's a denialist deviation point. I prefer "lengthen the path" of OLR. Rosco, what power are you assigning to convection? And are you implying radiative transfer has nothing to do with the average temperature of the Venusian atmosphere? Let's see some specifics on Venus, or take your theory over to the Colose article I linked earlier . . . please.
  4. 28, DSL, Rosco, I agree. I just looked around and came up with the same thread. The Planetary Greenhouse Interestingly, there's nothing better. No one else in the history of creative denial ever seems to have tried to argue that the greenhouse effect isn't relevant because convection + conduction does it all. Rosco, if you post a clear and concise argument on that thread (leaving out all of your observations that prove that conduction and convection exist, which is a strawman -- that is to say, an argument against something which no one is really contesting, and so of no value in advancing the discussion) then I will post a clear and reasoned response.
  5. There has never been any demonstrated mechanism of trapping heat - it is the engineer's dream to achieve this and increase efficency of machines. Even the stars have an energy input through gravity and if the assertions about Venus albedo being so reflective that almost no radiation reaches the surface there must be some source of heat that we don't know about. I think Earth's temperature would be about what it is plus or minus a degree or two. We would still have the sun's input and water.

    [DB] "There has never been"

    Never?  In over 150 years of scientists researching the greenhouse effect?

    Honestly, you betray your extreme lack of knowledge with comments like this.  You are not doing well, here.

  6. Heard of insulation? Plain ordinary convention physics with 100 of years of experimental evidence has no trouble calculating the temperature on the surface of venus without any mysterious energy source. By contrast, your misunderstanding has a problem. If you look at the energy diagram you see the breakdown, but most importantly, this energy flows are measured. In your understanding, you could not account for these measurements. Do you agree that the test of whether the science is right is measurement? By all means come up with alternative physics but your alternative theory in which the GHE is missing must be able to account for what we actually observe.
  7. DSL - point taken! Word-play is always dangerous ground. #30: Estimates of Earth's temperature without GHG's come in at well below freezing (IIRC ~-18C), mentioned in Chris Colose's article. The Sun does not provide enough energy this far away from it.
  8. 30, Rosco,
    There has never been any demonstrated mechanism of trapping heat
    Even the stars have an energy input through gravity
    Misleading or misunderstood. See Kelvin-Helmholtz timescale. See nuclear reactions, the true source of energy in stars. But in a nutshell, for the potential energy of gravity to be converted to another form, work must be done, meaning the object must compress, which it cannot do indefinitely (for a star, it would "burn out" in mere 18 million years). Otherwise it is a perpetual motion machine that is creating energy and violating the First Law of Thermodynamics.
    ...there must be some source of heat that we don't know about.
    I think...
    Fuzzy thinking of no value. What you think does not make it true. It does not create facts or truths, and is not a valid argument.
    We would still have the sun's input...
    Yes, about 241 W/m2 of solar input, which would bring the planet to 255K, when it is in fact at 288K. The question is how do we get that extra 33K? Answer: The Greenhouse Effect This is all very, very basic science. Please follow the links and read before posting further comments.
  9. Rosco, did you read the paper I linked to? Did you? I recall you saying, "I'm more than open to listen." Reading is "listening" when writing is the primary means of communication. You are not arguing from a physical model. You're arguing from what seems to be right to you. If you accept "seems to be right" as an argument, then we are at an impasse, because then my word becomes as good as yours, and we're all right. If you don't accept "seems to be right" as an argument, then start describing your physical model. Everything you've said so far suggests that you don't believe that CO2 absorbs and emits at specific frequencies (broadened by pressure). That might be a good place to start understanding. What are the emission/absorption spectra of Earth's (or Venus') ten most populous atmospheric gases? If you don't know, then you're not prepared to enter the discussion. While some here might tell you to go away (either directly or in tone), I won't.

    [DB] "While some here might tell you to go away (either directly or in tone), I won't."

    I think you speak for everyone in that our sincerest wish is for Rosco to be able to express himself more ably by addressing the science directly, uncomplicated by feelings and fuzzy thinking.

  10. Again, a Climastrology button is needed for Rosco. These sorts of creative science perception discussions need a thread of their own, because they really don't belong anywhere, and hence tend to wander about willy-nilly. Rosco barely met the requirements of this thread by rather randomly throwing the word "Venus" into his post. This sort of Alice-through-the-looking-glass discussion has been happening just far too often in recent months.
  11. I hope you will consider posting this - it is an analysis of energy input to a planet's atmosphere that is surely a starting point for discussion. You wanted a concise analysis well this may meet your requirements. The solar constant TOA Earth is ~1368 W/sq m agreed ? The solar constant TOA Venus is ~1.91 times that ~2612 W/sq m agreed ? I will talk about earth initially because we have better knowledge. The sun's radiation is approximately parallel. When it hits an atmosphere at 90 degrees to the tangent it will be absorbed at the maximum. When it hits at an angle to the tangent some will be reflected and some will pass into the atmosphere. The maximum component of the radiation that enters at 90 degrees to the tangent is the cosine of the latitude of the point - hence at the mid point the angle is 0 cos 0 = 1. Let’s stop the planet rotating - the solar constant is still 1368 W/sq m. The earth presents approximately a hemisphere to the sun's insolation. At the midpoint of the hemisphere the tangent to the atmosphere is at 90 degrees to the insolation and the angle between the incident radiation and the normal is zero - at the poles the tangent to the atmosphere is parallel to the radiation and the angle to the normal is 90 degrees. The tangent to the atmosphere at any point North or South is the cosine of the latitude. The insolation at any point varies as the cosine curve of the latitude. So let’s stop the earth at midday on a point on the equator when the sun is vertical to the equator and consider a line from north to south. At the mid point the insolation is 1368 W/sq m minus the albedo minus absorption by the atmosphere. If not, why not ? If you consider any other point on the hemisphere the angle the sun's parallel rays make to the tangent is the cosine of the latitude. Therefore the factor to reduce the insolation incident on the atmosphere is the cosine of the latitude – that is it varies from 1 at the midpoint to zero at the “pole”. So at the equator the insolation is ~ 684 W /sq m - 1368/2 - additional source is IPCC - Chapter 1 Historical Overview of Climate Change Science P115 -"About half the solar radiation is absorbed by the Earth's surface and warms it." This energy is capable of causing a maximum temperature of 331 K or ~58C which if my memory serves me well is approximately the highest temperature recorded. If the albedo were uniform over the earth - which it isn't - the maximum insolation should vary as a cosine curve from the midpoint north or south. For example consider Baghdad - ~ 33 N (why choose Baghdad ? - A well known desert location with "normal albedo low cloud and a well documented temperature record) - the maximum insolation is cos 33 x 684 = ~573.65 W/sq m. Maximum temperature for this insolation is ~317 K or 44 C. Meterological records show Baghdad's maximum temperatures are ~ 44 C in summer. So how does this even matter ? It demonstrates that maximum is different to average - obvious. It demonstrates that Earth and Venus may possibly receive more radiation and hence have higher temperatures than is calculated by reducing solar insolation to ~240 W/sq m to calculate the average temperature on Earth or to ~132 W/sq m on Venus. Again, I have not denigrated anybody's opinion simply proposed some discussion points.
  12. Oh dear. 'Discussion' here is a bit (not very much, but a bit) like discussing an English or history topic at an educational institution. Reading the material first is an unavoidable requirement of talking or writing on the item in question. You've been given quite a few excellent references. Stop writing, thinking, discussing for a while and do some reading. You only need to choose a couple of those offered to start with. But you do need to get started.
  13. What is wrong with the exchange of ideas and analysis ?
  14. Sphaerica said "false" to my assertion that "There has never been any demonstrated mechanism of trapping heat". OK - what is it ? Sphaerica said "Misleading or misunderstood" to my assertion that "Even the stars have an energy input through gravity" Are you denying it was gravity which initiated all the fusion reactions in the stars through increasing pressure resulting in increasing temperatures which eventually reach the point where fusion reactions can take place ? If you do assert this then I think you will find yourself at odds with every theory about the universe. From what I remember from my studies gravity is credited with the formation of virtually everything after the big bang - our rocky planets are thought to have accreted from the dust and gases of space until they achieved sufficient mass that this accretion process accelerated because gravity exerts a force proportional to mass - F = mass X acceleration. The core of Earth is hot due to gravity which is ultimately responsible for vulcanism and our magnetic field. Sphaerica accuses me of "Fuzzy thinking of no value". OK - well demolish the arguement posted above. The fact is you cannot unless you reduce the solar insolation to ~342 W/sq m then again by the albedo to achieve ~240 W/sq m. You must justify this by reasoned argument. What you need to demonstrate is why this reduction is valid when at any point in time no matter what the undeniable truth is that at TOA Earth the solar constant is 1368 W/sq m and at any time the insolation on the Earth's surface is the radiation normal to the atmosphere minus the albedo and whatever is absorbed by the atmosphere. All climate scientists agree with the value of the solar constant as 1368 W/sq m. If the earth only receives 240 W /sq m whare did the other 1128 W/sq m go ? The IPCC state ~50% makes it to the surface - this is broken down to 30% reflected (albedo) 20 % absorbed by atmosphere - and don't tell no insolation is absorbed because it is shortwave because there are plenty of bands available to absorb the > 50 % of insolation that isn't visible light - ~ 44% of the insolation is in the infrared wavelebghts while ~ 8% is ultraviolet which is the most energetic. There is indisputable proof that the radiation TOA Earth is capable of raising the temperature much higher than minus 18 C. NASA quotes the maximum temperature on the moon as in excess of 120 C. This explains what a fantastic shield our atmosphere is.
    Response: You continue to refuse to get a basic education. You are derailing this thread. All other readers, I suggest you simply stop responding to him.
  15. PS - I am not arguing from what seems to be right to me. I have a degree in Environmenta health Science and a degree in Engineering Technology. I was a professional Environmental Health Officer whose principal role was to enforce Environmental legislation especially prosecuting individuals or businesses responsible for pollution. I have retired. My last University attendance was in 1994 when I completed the Engineering degree. Basic physics involves breaking down a force into its components for example using the sine and cosine of the incident angle so there is plenty of precedent for the use of this concept.
  16. I've read the response. I've quoted the IPCC. I've made valid calculations using Stefan-Boltzman to arrive at maximum temperatures for different radiation levels and I have provided 2 example that demonstrate actual recorded temperatures correlate almost exactly with what was calculated. I am simply proposing something to think about. I am certainly not uneducated - I achieved honours in nearly every subject I undertook in my 2 degrees.
  17. Rosco @39:
    "Are you denying it was gravity which initiated all the fusion reactions in the stars through increasing pressure resulting in increasing temperatures which eventually reach the point where fusion reactions can take place ?"
    The gravitational force is not consumed by the production of energy in stars. Therefore, regardless of the fact that it is essential for establishing the conditions of fusion, it is not the source of the energy. The energy in fact comes from the conversion of mass to energy by fusion in that the daughter elements in fusion are very slightly lighter than the parent particles.
    "The core of Earth is hot due to gravity which is ultimately responsible for vulcanism and our magnetic field."
    The Earth was heated to a molten state by impacts early in its history, but the heat from those impacts escaped to space in approximately 10 million years of the earths 4,500 million year history. It remains molten because of the energy released by fission of radioactive isotopes (primarily Uranium) in the core, along with a small amount of energy from tidal friction. Again in fission, the combined mass of the daughter isotopes (and particles) is slightly less than that of the parent isotopes, the difference being released as energy. Gravitation is completely irrelevant to this process. These may seem like minor points to you, but what they show to me an others on this site is a casual disregard for accuracy which permeates your posts and turn them into scientific garbage. As others have done, I cannot recommend highly enough that you sit down and read before continuing to post this nonsense online.
  18. Rosco @39:
    "What you need to demonstrate is why this reduction is valid when at any point in time no matter what the undeniable truth is that at TOA Earth the solar constant is 1368 W/sq m and at any time the insolation on the Earth's surface is the radiation normal to the atmosphere minus the albedo and whatever is absorbed by the atmosphere. All climate scientists agree with the value of the solar constant as 1368 W/sq m. If the earth only receives 240 W /sq m whare did the other 1128 W/sq m go ? "
    Basic Education: Area of a circle = pi r^2 Area of a sphere = 4 pi r^2 Ratio of the area of a sphere to the area of a circle of identical radius = 4 Total energy flux from sunlight intercepted by the Earth = 1368 W/m^2 * pi RE^2, where RE is the radius of the Earth. Total area energy flux is distributed over = 4 * pi RE^2, where RE is the radius of the Earth. Therefore, average energy flux of sunlight intercepted per square meter of the Earh's surface equals 1368/4 = 342 W/m^2. And the average energy flux of sunlight intercepted after albedo on the Earth's surface equals 342 * 0.7 = 239.4 W/m^2. What is the value of an education if you just assume any time that you disagree with a climate scientist that the PhD heavily published climate scientists have simply forgotten basic facts of geometry, and not one of the thousands of climate scientists world wide have managed to notice? Because that is what you have done. Your automatic assumption that because you have a bachelors degree in engineering, the PhDs in physics must have got it wrong would be hilariously funny if it where not so sad, and the issue serious.
  19. 43, Tom Curtis, You're wasting your breath. Look at his comment here, where he says:
    Why is it valid to reduce solar insolation by a factor of 4 to calculate the "effective blackbody temperature" of a planet - especially Venus with it 200 odd earth day long day ? I get the geometry I just think it isn't relevant for a dynamic system.
    It's really hopeless, and pointless.
  20. Rosco: "PS - I am not arguing from what seems to be right to me." Rosco: "I get the geometry I just think it isn't relevant for a dynamic system." Eh?
  21. Sphaerica @44, I get that he won't get it. But perhaps some reader will not be familiar with spherical geometry, and will now see for themselves that Rosco is spouting complete and utter tripe.
  22. You still have not demonstrated how the solar constant is reduced from 1368 to 342. How do you explain the temperature on the moon ?
  23. Rosco @47, I have explained it in steps so small a grade 9 education is sufficient to follow, as proved by my explaining it to my daughter (who will no doubt have a good laugh if I show her this conversation). If you have not understood it, read again with care. It is not too hard. You have not raised any interesting questions about the moon. You have merely cited a vaguely remembered maximum temperature. Apparently you base all your reasoning on the assumption that the maximum temperature is the only relevant temperature, but I am disinclined to follow you in that absurdity.
  24. You still have not demonstrated how the solar constant is reduced from 1368 to 342
    Rosco, this is very, very, very simple. The amount of energy that strikes the earth is 1.748310 x 1017 W. [1368 W/m2 times the area of the earth that intercepts the sunlight, or 1.2780049 x 1014 km2]. Because the earth is rotating, this energy is distributed over the entire surface, not just one hemisphere. [Due to the geometry of a sphere versus the relatively linear approach of the sunlight the energy is not distributed evenly, but that issue is not yet a factor and is addressed later, we're only looking for the average energy per square meter. Note that your lengthy previous discussion of cosines and angles was wrong, and should be abandoned.] Albedo is not yet a factor. That is also considered later. We are simply looking for an average W/m2 to use for trivial calculations. The surface area of the earth is 5.1120196 x 1014 square meters. So we can compute the W/m2 as total energy received divided by total area receiving that energy, or 1.748310 x 1017 W / 5.1120196 x 1014 m2 = 341.99986 W/m2. It has now been explained to you. If you are incapable of following this simple logic, then you should simply stop posting. If you feel that you can dismiss this simple logic, merely because you want to but without a valid reason, then you are in serious denial and should perhaps apply some introspection to evaluate the cognitive dissonance that prevents you from rationally using your faculties to solve the very simplest aspects of the problem at hand, the foundation of which is accepted by every single actual climate scientist on the planet, including those who are also in serious denial about the final conclusions.
  25. That arguement is simply wrong. It takes 24 hours to distribute the energy over the earth and during that time the earth has completed one rotation and the whole of the earth is irradiated. Therefore reducing the insolation by a factor of four is not valid. Remember, a watt is a joule/sec so considering any point on earth at a single point in time is valid. If a watt did not involve time the geometric analysis, though simplistic, may have some validity. Tom Curtis @ 48 says "You have not raised any interesting questions about the moon. You have merely cited a vaguely remembered maximum temperature. Apparently you base all your reasoning on the assumption that the maximum temperature is the only relevant temperature, but I am disinclined to follow you in that absurdity." I think we can agree that 342 W/sq m results in ~278.7 K or about ~5.5 C. Obviously you insist the geometrical analysis is the correct analysis. The moon has no atmosphere and is obviously about the same distance from the sun therefore exposed to the same radiation level. The moon's temperature during the day is not ~278.7 K or about ~5.5 C. Obviously we have an anomaly that I find very interesting.

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