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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Has the greenhouse effect been falsified?

What the science says...

Select a level... Basic Intermediate

The greenhouse effect is standard physics and confirmed by observations.

Climate Myth...

Greenhouse effect has been falsified

"[T]he influence of so-called greenhouse gases on near-surface temperature - is not yet absolutely proven. In other words, there is as yet no incontrovertible proof either of the greenhouse effect, or its connection with alleged global warming.

This is no surprise, because in fact there is no such thing as the greenhouse effect: it is an impossibility.  The statement that so-called greenhouse gases, especially CO2, contribute to near-surface atmospheric warming is in glaring contradiction to well-known physical laws relating to gas and vapour, as well as to general caloric theory.' (Heinz Thieme)

At a glance

Did you know that in the late 1700s, astronomers calculated the Earth-Sun distance to within 3% of the correct average value of 149.6 million kilometres? That was an incredible feat for the time, involving painstaking measurements and some pretty serious number crunching, with no help from computers.

Why is that mentioned here, you might ask. It's because not long afterwards, in the 1820s, French physicist Jean Joseph Baptiste Fourier made another crucial calculation. He worked out that at this distance from the Sun, Earth should have been an uninhabitable iceball.

Fourier suggested there must be some kind of insulating 'blanket' within the atmosphere. By the end of that century, Eunice Foote and John Tyndall had proved him quite correct through their experiments with various gases and Svante Arrhenius quantified matters in 1896, even calculating the effect of doubling the concentration of CO2. They had it largely figured out all that time ago.

If you are still sceptical about the existence of a greenhouse effect on Earth, there's something you can do in order to double-check. Go to the moon.

Well, you don't have to go personally, thanks to remote sensing and lunar landings by both unmanned and manned craft. Such intrepid expeditions mean we have a stack of data regarding lunar properties. The moon is pretty much the same distance from the Sun as Earth, but the lunar atmosphere is so thin it may as well not exist at all. There's virtually nothing to inhibit heat transfer, in or out.

In addition, the Moon turns but slowly on its axis compared to Earth. While a mean Solar day here lasts 24 hours, on the Moon it lasts just under a month. You get the best part of a fortnight of relentless Solar heating followed by a similar period of cooling in the long lunar night. So what's the temperature?

In the vicinity of the Lunar equator, daytime temperatures eventually reach a boiling hot 120oC. During the lunar night, that temperature drops away to -130° C. No atmosphere so no greenhouse effect. All that heat accumulated in the long lunar day just shoots straight back out into space. Nights on Earth may be much shorter, but nevertheless in the absence of a greenhouse effect they would be brutal.

Our approximately Earth-sized near neighbour, Venus, closer to the Sun, is different again. It has a massive dense atmosphere mostly consisting of CO2 with a side-helping of sulphur dioxide. Surface atmospheric pressure on Venus is so great that on Earth you would need to go a kilometre down in the ocean to find similar values. The planet rotates very slowly on its axis so days and nights are even longer than on the Moon. But unlike the Moon, Venus is always a hot place. Its surface temperature is over 450oC, day or night. An extreme greenhouse effect maintains that heat.

Remember: no atmosphere, no greenhouse effect and unimaginably cold lunar nights - but the example of Venus shows you can also have too much of a good thing. Earth really is a Goldilocks planet.

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

Some climate science deniers dispute the existence of the ‘greenhouse effect’. This is where their arguments lurch from silly - to beyond silly. The greenhouse effect keeps the surface temperature of Earth approximately 33oC warmer than it would be if there were no greenhouse gases in the atmosphere. In other words, without the greenhouse effect, Earth would be effectively uninhabitable.

attacking the wrong greenhouse effect

Fig 1: The greenhouse effect is an analogy not meant as a scientific model of effect; hence, detractors have attacked the wrong model. (source: jg)

How do we know for sure this effect is real? The principle is demonstrated through basic physics, because a bare rock orbiting the Sun at the Earth-Sun distance (mean = 149.6 million kilometres) should be far colder than the Earth actually is. This was realised by Jean Joseph Baptiste Fourier in the 1820s, but the explanation why it was the case was not forthcoming for a few more decades. Fourier considered it to have something to do with the atmosphere having the properties of a kind of insulating blanket.

The existence of Fourier's hypothetical 'blanket' was confirmed by the experimental studies done by Eunice Foote and John Tyndall, working independently on either side of the Atlantic in the 1850s. Foote's results were announced at the 1856 meeting of the American Association for the Advancement of Science, and published in the American Journal of Science and Arts in the same year. The paper was entitled, ‘Circumstances Affecting the Heat of the Sun’s Rays’, with an excellent recent review by Ortiz and Jackon (2020). A key passage is as follows:

“The highest effect of the sun’s rays I have found to be in carbonic acid gas. An atmosphere of that gas would give to our earth a high temperature; and if as some suppose, at one period of its history, the air had mixed with it a larger proportion than at present, an increased temperature from its own action, as well as from increased weight, must have necessarily resulted.”

In his 1861 paper, “On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction” (PDF here), Tyndall stated:

“Now if, as the above experiments indicate, the chief influence be exercised by the aqueous vapour, every variation of this constituent must produce a change of climate. Similar remarks would apply to the carbonic acid diffused through the air; while an almost inappreciable admixture of any of the hydrocarbon vapours would produce great effects on the terrestrial rays and produce corresponding changes of climate.”

Tyndall had in his own words identified methane as an even more potent greenhouse gas than CO2. Later that century, Swedish scientist Svante Arrhenius put the numbers on the relationship between greenhouse gas concentrations and surface temperatures. He was able to calculate the effect of doubling the CO2 concentration in the air. The result was a globally-averaged figure of 5-6°C of warming, not that dissimilar to modern values.

Empirical Evidence for the Greenhouse Effect

We only have to look to our moon for evidence of what the Earth might be like, without an atmosphere and greenhouse effect. It's not as though we're short of data about our satellite. While the moon’s surface reaches 120oC (248oF) in direct sunlight at the equator during the long lunar day, when it gets dark the temperature drops down to a frigid -130oC (-202oF).

Since the moon is virtually the same distance from the sun as we are, it is reasonable to ask why at night the Earth doesn’t get as cold as the moon. The answer is that, unlike the Earth, the moon has no insulating blanket of greenhouse gases, because it has virtually no atmosphere at all. Without our protective atmosphere and its greenhouse effect, the Earth would be as barren as our lifeless moon. In the absence of the heat trapped overnight in the atmosphere (and in the ground and oceans) our nights would be so cold that few plants or animals could survive even a single one.

Conclusive evidence for the greenhouse effect – and the role CO2 plays – can also be seen in data from the surface and from satellites. By comparing the Sun’s heat reaching the Earth with the heat leaving it, both things we can measure with great accuracy, we can see that less long-wave radiation (heat) is leaving than arriving. Since the 1970s, less and less radiation is leaving the Earth, as the levels of CO2 and other greenhouse gases build up. Since all radiation is measured by its wavelength, we can see that the frequencies being trapped in the atmosphere are the same frequencies absorbed by greenhouse gases.

To conclude, disputing that the greenhouse effect is real is to attempt to discredit centuries of science, the laws of physics and indeed direct observation. Without the greenhouse effect, we would not even be here to argue about it.

Last updated on 26 November 2023 by John Mason. View Archives

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Comments 26 to 50 out of 66:

  1. You're right, Will, I should not have pointed you to Wikipedia for the definition of thermosphere. So let's use NASA. Or you could just search the internet for "thermosphere" and look at hundreds of definitions of it as a layer of the atmosphere.
  2. Will, glass is transparent to near-infrared wavelengths. It's opaque to thermal infrared wavelengths. See figure 2-3 here for an example. Lots of people get confused about this distinction, but if you're going to write about the earth's radiation budget you absolutely have to understand it.
  3. Will writes: As for Photosynthetic efficiency which is just one part of the effect I'm referring to, 2% is a stab in the dark. While it is claimed that crops such as wheat may achieve low efficiency of between 1-4%, sugar cain can achieve 7%, but photosynthesis is just one process plants use energy for. Oxygen production is another. Photosynthesis is how plants produce oxygen. It's the same process! A moment ago you were claiming that "40-50% of the incoming sunlight hitting the leaves is locked in by photosynthesis and the rest is reflected as short-wave". Healthy green plants absorb 90% or more of visible wavelengths of light, quite a bit less in the near-infrared. Only a small part of that, less than 10%, is converted by photosynthesis. The remainder warms the plant, and indirectly warms its environment. This is all irrelevant, though, since the analogy to a glass greenhouse is not intended as (nor appropriate as) a description of the physical mechanism by which CO2 warms the earth system.
    Response: Indeed. Will, in the post at the top of this page, see the section titled "The Term 'Greenhouse.'"
  4. Berényi - So, you are just talking about the lapse rate here? Your comments seemed to involve nitrogen as a greenhouse gas, which I found quite confusing. Certainly, if you remove half the atmosphere, the dynamics and equilibrium of the Earth would be different - much as it would be if you removed all of it. I was under the impression, however, that we were discussing greenhouse gasses and the greenhouse effect, with only a few % of the atmosphere in question. Not wholesale planetary engineering or hypothetical worlds...
  5. Just an overall note on topics, Berényi - your half/double N2 comment really represents a red herring with respect to a conversation on the greenhouse effect. It's not helpful, and doesn't advance the discussion in any way.
  6. Will writes: Please don't "Science of Doom" me. I'm not sure what you mean by that. Science of Doom offers admirably lucid, accurate, and detailed explanations of the physical basis for the greenhouse effect. They also manage to do so in a polite and respectful environment. It's hard to imagine a more appropriate resource for this particular thread.
  7. Will, The article on your web site that you've linked to includes serious factual errors. Diffusion of light by the atmosphere does not cause "the molecules also absorb some of that energy from the photon", and does not cause the molecules to vibrate. This is because, as has been explained to you above incoming solar radiation does not match the vibrational frequencies of the IR active vibrations - in visible light is too high a frequency for any molecular vibrations. Electron transitions do occur due to UV light, but the atmosphere is largely transparent to visible light. O2 and N2 are completely inactive to IR radiation, except for the tiny amount of isotopic variation which, as your own graphs show, are 1x10-30 less powerful than CO2 and are the wrong frequency for both incoming solar and outgoing earthlight. You should also be aware that the energy in photons is related to their frequency, not as you seem to assume, their intensity. Or do you really not believe Albert ? You are wrong to say all substances absorb IR radiation: use the search engine of your choice to look for "Dipole Moment" and "Vibration" and take your pick
  8. Hey Will, still no answer to post #3 & 4. At least the hypotheses put forward by climate scientists match real world observations and measurements. Which is kind of the whole point isn't it?.
  9. Ned "Will, glass is transparent to near-infrared wavelengths. It's opaque to thermal infrared wavelengths. See figure 2-3 here for an example." Lets just look at this statement for a minute. Thermal radiation is heat. Vibrating matter. Gas molecules are vibrating matter. They cannot pass through solid glass. You are confusing matter with energy. It is the energy which passes through the glass not the vibrating molecules which cause heat. In the vacuum of space full spectrum EMR produces no thermal radiation, heat. It is you who is confused or rather attempting to confuse. As for your comment about healthy green plants absorbing 90% of visible wavelengths, this is yet another stab in the dark generalisation. Some leaves are highly glossy/reflective and others are completely mat. It depends on the plant. Above all plants do not warm environments, they cool them, as per the urban heat island effect. Even in direct sunlight the top canopy of leaves on any plants will be much cooler than bare earth, and that is my point. So the point is, according to the bottom-up warming "greenhouse effect" hypothesis, an empty greenhouse should be considerably warmer than a full one, as attested to by the urban heat island effect, but this is not the case. With regards to false analogies, try implementing cap and trade without using the words "greenhouse gas emissions".
  10. Will, your experiment that you describe on your web site is not novel. Students have been doing similar experiments for years. Maybe there is a flaw in your experimental design, or the effect you created was too small to be detectable by your temperature measuring apparatus. I've got relevant links on this comment.
  11. Phil "This is because, as has been explained to you above incoming solar radiation does not match the vibrational frequencies of the IR active vibrations - in visible light is too high a frequency for any molecular vibrations. Electron transitions do occur due to UV light, but the atmosphere is largely transparent to visible light. You have contradicted yourself here.
  12. Will, you are incorrect. Thermal radiation is not vibrating matter, because "radiation" is not vibrating matter, it is instead electromagnetic energy. Use the internet to search for definitions of "thermal radiation." An example is a definition by the University of California San Diego Center for Astrophysics and Space Sciences.
  13. Tom Why don't you try it for yourself. The point is not to take my word for it. Its a simple test and yes children have done it and achieved the same results as I do.
  14. #34: "Above all plants do not warm environments, they cool them" And here in plain English is why: Plants give off water through tiny pores in their leaves, a process called evapotranspiration that cools the plant, just as perspiration cools our bodies. On a hot day, a tree can release tens of gallons of water into the air, acting as a natural air conditioner for its surroundings. And that's why plants cool their surrroundings, which has nothing to do with UHI. But here is why this may be a new problem: "There is no longer any doubt that carbon dioxide decreases evaporative cooling by plants and that this decreased cooling adds to global warming," says Cao. "This effect would cause significant warming even if carbon dioxide were not a greenhouse gas." Its a double-whammy. CO2 traps heat requiring plants to do more evaporative cooling, but CO2 acts to decrease a plant's ability to cool itself.
  15. Will - in your experiment you lack the black cardboard representing the Earth. Therefore you don't have the visible light changing to IR and attempting to leave back through the air or CO2, hence your experiment isn't set up correctly, and hence your results aren't going to show anything. I'm also not certain you're going to have sufficient CO2 in your quite small sample from soda water fizz; I would try it with an empty soda bottle full of air, and another where you fill it with CO2, either from a tank or using a piece of dry ice (vented until the ice sublimates, to keep pressure the same). Otherwise the effect may be too small to show up on simple (and rather inaccurate) thermometers like the liquid crystal ones you show.
  16. Tom I should have said "caused by" vibrating matter are you happy now? The point I am making is that Ned is wrong about glass being opaque to thermal radiation because if it were, why would we need double glazing with reflective coatings?
  17. Will #36 Read it again; the first sentence refers to molecular vibrations, and visible radiation, the second to electronic absorbtion and UV (i.e non-visble) radiation. No contradiction
  18. KR You are wrong, I have conducted these experiments on multiple surfaces. The CO2 bottle contains almost pure CO2. Enough to extinguish a burning match, see here: spinonthat.com/CO2.html At the end of the last video at the bottom of the page I demonstrate how much CO2 with a burning match. Still I am impressed at how you can convince yourself of almost anything based on pure guess work. Well done to you!
  19. Just to expand a bit more on my previous post. Molecules absorb EM radiation (sometimes loosely called "light" by lazy people like me - gulp!) by three mechanisms 1. Changes to Rotational Quantum states - in the microwave and low infra-red EM region. Molecules need a permanent dipole moment to absorb radiation. (N2 for example cannot, neither can CO2) 2. Changes to Vibration (of the nuclei against each other) - in the infra-red region. The vibration needs to change the dipole moment to absorb radiation (The one vibration in N2 cannot, 3 of the 4 vibrations in CO2 can) 3. Changes to Electron orbits - in visible and UV EM region. Again a change in dipole moment is required for absorption. This will depend on the lower and upper orbit, some N2 transitions will be allowed, and these occur in the UV region
  20. #30 KR at 05:50 AM on 26 August, 2010 your half/double N2 comment really represents a red herring with respect to a conversation on the greenhouse effect. Not really. For example World Book at NASA - Venus has the following "explanation": "Most astronomers believe that Venus's high surface temperature can be explained by what is known as the greenhouse effect". Surface temperature on Venus is about 458°C and if an astronomer believes it is so high because of the greenhouse effect, he is not an astronomer at all, but a crackpot. It is a shame National Aeronautics and Space Administration of the US disseminates such nonsense. At the 1 atm level temperature of Venus is only 71°C, that is, 387°C cooler than at the surface. If you'd put the Earth at the same orbit, its average surface temperature would go as high as 66°C. The difference is only 5°C, that could be called the additional greenhouse effect due to an atmosphere almost entirely made of CO2 and covered by clouds of sulfuric acid droplets above haze of the same stuff. You get it for doubling the amount of CO2 almost 11 times relative to Earth. The rest is pressure (92 bar at the surface), this is what makes Venus so hot, not the "greenhouse effect".
  21. #34 Will at 06:50 AM on 26 August, 2010 Even in direct sunlight the top canopy of leaves on any plants will be much cooler than bare earth That's true. Not because they reflect much light, but because of evaporation of water through pores on the back of leaves called stomata. If this vapor laden air rose high enough, it would cool by adiabatic expansion releasing the latent heat eventually by phase transition, producing rain and (relatively) hot dry air which leaves the cloud and radiates this heat into space. Cooling itself this way it sinks again, ready to take up some more moisture. GHGs are very important ingredients in this process, for due to Kirchhoff's law of thermal radiation in local thermodynamic equilibrium (which holds up tu 50 km in the atmosphere) emissivity of stuff is the same as its absorptivity. That is, if a gas does not absorb thermal radiation (like nitrogen) it can't get rid of heat by radiation either.
  22. I suggest a new way of trying to start a learning dialogue with Will. Assume he is right in the findings of his backyard experiment. What, then, happens to our scientific understanding and the engineering that has been developed from that science? What do we have to unlearn about the universe due to Will's discoveries? Will, you seem very invested, psychologically, in your experiments. I wonder if you are capable of accepting constructive criticism. If not, then you are incapable of actual dialogue, and it would be worthless for anyone here to continue to engage with you. A number of posters have challenged your understanding of physics, and they have presented research that has been done with much greater rigor and care than has yours, yet you reject their findings out of hand. And then you expect them to accept your findings without question.
  23. Hmm. So we have expensive experimental setups for quantifying greenhouse response of various gases to high degree of precision being invalidated by backyard experiement with cheap thermometers. I dont think so. I think this is a common experiment but the setup is difficult so you get "prove" or "disprove" greenhouse gas theory from physical processes that dont actually have anything to do with it. I prefer this setup for eliminating other possible effects.
  24. Will @23 - "At my site you find direct reproducible experimental evidence that pure CO2 causes less warming than ordinary air." Interesting, this experiment indicates otherwise
  25. In addition to that video linked by Dappledwater, there are many more successful such experiments, Will. Look at the sample at the right side of the YouTube page after you click on Dappledwater's link. Here's an example of a child's experiment:

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