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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 51 to 75 out of 175:

  1. Berényi Péter, in your comments about Venus, I think you may be neglecting Venus's albedo.
  2. Will writes: 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. This is just absolute rubbish. Sorry, but there's no better way to put it. Thermal infrared radiation is merely a subset of the electromagnetic spectrum at wavelengths from around 3 to 1000 micrometers. The label "thermal" comes from the fact that this is the range in which the peak emittance occurs from objects at normal earth-surface temperatures. This is important because thermal infrared radiation is the only significant mechanism by which the Earth loses heat to space. If your claims were correct and longwave infrared radiation were unable to propagate through a vacuum, the Earth would rapidly heat up to the point where the oceans boiled away. Your willingness to write articles dismissing the greenhouse effect and accusing scientists of "fraud" when you don't understand even the most basic relevant physics is frankly shocking. It's far and away the best demonstration of the Dunning-Kruger Effect that I've seen in a long time.
  3. I'm glad to see people talking about simple experiments that attempt to illustrate the infrared absorptance of CO2. But there are two larger points in danger of being neglected here: (1) There is a very extensive literature on laboratory measurements of the spectral properties of CO2. (2) It's not really possible to completely replicate the real-world greenhouse effect in the lab. Part of the physical process involves an increase in the effective radiating height of the earth's atmosphere, something most labs aren't really set up to simulate. But there are many scientific processes that are similarly unsuited for laboratory replication -- plate tectonics is a great example. The fact that we're logistically incapable of recreating plate tectonics in a laboratory doesn't in any way invalidate it as a scientific theory. Like plate tectonics, we're able to make predictions based on the theories involved in anthropogenic global warming, and verify those predictions using observations. Some of those observations can be made under controlled conditions in the lab, but others can only be done in the real world environment. That's perfectly OK.
  4. Will at 03:30 AM on 26 August, 2010 I think we all need to understand what we mean by “atmosphere” and “heating” at these altitudes and appreciate what is meant by “bulge” and temperature profiles. We are talking about Solar UV radiation “heating” the rarified atmosphere between around 100 and 200km up (and also geomagnetic interactions). The temporarily increased kinetic energy allows (on average) more molecules to move “upwards” away from the effect of gravity, thus leading to a redistribution of density, and an increased density above a few hundred km up. This variation in density of atmospheric gases at low earth satellite orbit heights (around 300km), or so called “diurnal bulge” caused periodic variations in drag which were investigated in the early satellite era. For some historical context see Moe 1977. In terms of temperature, we are referring to the kinetic energy of atoms or molecules, rather than temperature in the sense that most people understand. Figure 1 in Johnson 1967 shows typical “temperature” variations (night time minimum sunspot cycle of around 430 degrees C to daytime maximum sunspot cycle of around 1530 degrees C) associated with the “bulge”. A more detailed graphic, from here, shows your “top down heating” suggestion has a rather obvious problem at around the (arbitrary) Thermosphere/Mesosphere boundary around 90km up (approx -90 degrees C), and again towards the lower Stratososphere. More independent measurement based evidence against your suggestion is that daytime temperatures do not measurably rise in periods of intense radio and magnetic solar activity when the “bulge” and “heating” can increase dramatically. Average UV activity has also tracked overall solar activity over recent decades of direct measurement (ie small average decline).
  5. #52 Ned at 19:00 PM on 26 August, 2010 you may be neglecting Venus's albedo I do. As I'm also neglecting the probable huge increase in Earth's albedo due to more clouds if it were put on a Cytherean orbit and also the increase in thermal IR opacity due to the same warm high clouds. The usual practice to ignore changes to albedo when discussing the greenhouse effect is admittedly a silly one. Like Earth with neither an atmosphere nor a hydrosphere but still retaining its present day albedo of 0.3 somehow, making its equilibrium temperature -18°C and comparing it to the actual average surface temperature of +15°C, calling the difference (33°C) the "greenhouse effect". As an exercise, calculate average surface temperature of a perfect blackbody "Earth" with no atmosphere at all for two cases.
    1. it's made of a perfect heat conductor material (uniform heat distribution along the surface is attained instantaneously)
    2. or it is made of a perfect heat insulator (each point on its surface is in radiative equilibrium, independent of its surroundings)
    There is neither greenhouse nor albedo effect in these cases, still, the difference in average equilibrium temperature is huge. You can also play with different heat capacities from zero up to very high values and see what happens.
  6. Berényi Péter @46 "That is, if a gas does not absorb thermal radiation (like nitrogen) it can't get rid of heat by radiation either." Really? So 79% of the atmosphere is cooled by what process? Does the majority of the atmospheric mass have to transfer its energy through a bottle neck of 0.0385% CO2 in order to radiate to space? Or is their a secret mechanism that only clever people know about? Of course nitrogen emits radiation, at light speed. Therefore it must also absorb at the same rate or become frozen.
  7. Berényi Péter, it was your choice to move the Earth to Venus's orbit and make a quantitative prediction ("5 C") of the magnitude of the increase in temperature associated with the greenhouse effect. That prediction ignored the fact that Venus's albedo is much higher than Earth's. All else being equal, if you put Earth and Venus at the same distance from the sun and gave them the same albedo, Earth would be much colder due to the lower concentration of greenhouse gases in its atmosphere. If you now want to say "Well, there are all these other complications" that's fine -- I agree completely -- but let's note for the record that your initial remarks were just plain wrong. There doesn't seem to be an article on this site specifically about the greenhouse effect on Venus; perhaps that would be a good subject for a post some day. In the mean time, I'd refer anyone who's interested in that subject to: * Goddard’s World by Chris Colose * Venusian Mysteries and Venusian Mysteries – Part Two over at Science of Doom.
  8. Will writes: Of course nitrogen emits radiation, at light speed. Therefore it must also absorb at the same rate or become frozen. OK. At what wavelengths does nitrogen absorb and emit radiation? Berényi Péter provided a nice illustration of the absorption bands for other gases. Can you please give us a link to something that shows the equivalent spectrum for nitrogen? Thanks.
  9. Peter Hogarth @55 The problem lies in the lack of understand of the fact that the atmosphere both radiates and insulates at the same time. This is the cause of the temperature gradient inversion profile of which of course your graph represent averaged figures day/night winter/summer. The temperature gradient inversions are caused by the fact that as the atmosphere thins it looses more energy via radiation, yet at the same time it still has an insulating effect. You have to consider this effect of insulation and radiation as three dimensional while at the same time incoming EMR is heating top-down unidirectional. Air is a top insulator and also a top radiator. The gradient inversions are caused by the imbalance between insulation, radiation and top-down heating. Claiming that the atmosphere is very thin at such high "Thermosphere" altitudes and therefore temperature is not relevant, is simply viewing this situation backwards. The bulge would not exist in the first place were it not for incoming EMR causing massive violent top-down atmospheric heating.
  10. (sorry, #57 was a mistake, I hit the wrong button and hit it early) #51 Tom Dayton at 13:04 PM on 26 August, 2010 there are many more successful such experiments The one you have shown us is not one of them. The child in the video says: "This graph shows my results. The red line shows the temperature of the jar with the CO2 and the blue line shows the control jar. In the morning I put the heat lamp on for a few minutes and as you can see the jar with the CO2 heated up faster. Then, while I was at school they both cooled down, but the CO2 jar stayed warmer. When I got home I turned the heat lamp on again and the same thing happened. From this I concluded the jar with the CO2 in it heated up faster, cooled down slower and maintained the difference." And here is the graph: The two graphs are identical except for the initial divergence and a constant offset later (I have copied a portion of the red curve made yellow onto the blue one to show it). There is no way a difference in emissivity/absorptivity between two objects can produce such a result. What is more, the carbon dioxide in jar B has much lower absorptivity than the thermometers themselves, so one would expect no difference between the two jars whatsoever. And even if there were a difference, jar B would have had cooled faster, not slower, as higher absorptivity goes along with higher emissivity. But as I've said, there were no such difference in absorptivities, at least none within the bounds of measurement errors. So what has happened? As you can see jar B has started from a somewhat higher temperature right in the morning, then this difference increased fast, then stayed the same for the rest of the day irrespective of the radiation source was on or off. Probably there was heating in the room that was turned off for the night and switched back in the morning just before the experiment started. It developed then maintained a temperature gradient between the positions of jar A and B on the table. We would never know for sure, because the kid missed the most basic control experiment. He has failed to switch places of the jars. The child may be cute, but it does not make his propositions valid. His final conclusion "We expect the Earth to act the same" has nothing to do with the "experiment", in his case it is based on pure belief and indoctrination. It is a huge disservice to kids to let them embarrass themselves in public like that instead of teaching them proper scientific methodology by pointing out all the obvious errors.
  11. #58 Will at 20:58 PM on 26 August, 2010 So 79% of the atmosphere is cooled by what process? Does the majority of the atmospheric mass have to transfer its energy through a bottle neck of 0.0385% CO2 in order to radiate to space? Not only CO2, there are others, the one major player being H2O. There is also an "atmospheric window" between 8 and 14 μm and another one called "Arctic window" above 16 μm, which is only "open" if there is very little moisture in the atmosphere. Through these windows radiation from the surface can escape to space directly. At ambient temperatures the only way for nitrogen to cool down is by frequent collisions with other stuff. If the atmosphere of a planet were made of pure N2 with no trace amount of anything else (it also has to be made of a single isotope of N, lets say 14N), it would not get cooler with increasing elevation. But you also have to make sure the surface was absolutely dry and dust free to make it work like that.
  12. #59 Ned at 21:05 PM on 26 August, 2010 All else being equal, if you put Earth and Venus at the same distance from the sun and gave them the same albedo Albedo is not a free parameter that you can simply give. Especially for atmospheres with a stuff that can condense to droplets provided it gets cool enough (both Earth and Venus have one). Also, with a practically infinite supply of GHG (the store is called ocean) the response of terrestrial climate to an increased opacity in a narrow IR band may be pretty counter-intuitive. The system as a whole does not have to get warmer to maintain power flux balance, it is enough to redistribute water vapor slightly. Not even average upper troposphere humidity has to decrease in order to decrease effective photosphere height (that is, bringing down the place radiation can escape to space from to a lower, therefore warmer level). It is quite enough to let humidity distribution getting a bit more uneven.
  13. BP writes: Albedo is not a free parameter that you can simply give. Of course not. But your initial comment that claimed only a "5 C" increase in temperature was based on a particular assumption about the Earth's albedo. You assumed it would stay constant, which is (a) not realistic, and (b) a misleading comparison to Venus, which has a much higher albedo. I would repeat everything I say in my comment above, but for simplicity's sake I'll just link to it
  14. Okay, BP, the child's experiment was not airtight. (For folks whose first language is not English, that was a pun.) So for the next child let's bring in professional help from scientists and the MythBusters!
  15. #64 Ned at 23:33 PM on 26 August, 2010 You assumed it would stay constant, which is (a) not realistic, and (b) a misleading comparison to Venus, which has a much higher albedo It is just as arbitrary and misleading as constructing an "Earth" with neither atmosphere nor hydrosphere but with the same albedo as it actually has, considered as a baseline to the "greenhouse effect".
  16. Berényi - On the contrary, changing a single variable is an essential method for conveying the effect of that variable. You could be more realistic in describing end-point conditions by looking at all the parameters, the interactions, feedbacks, etc. - but if what you wish to show (as in The Hoover Incident) is that current conditions could not hold true if that variable was changed, a single-variable approach is more than sufficient as a reductio ad absurdum proof.
  17. Will at 21:34 PM on 26 August, 2010 Heating in Thermosphere, as in increased kinetic energy per molecule or atom?, yes. Massive top down?, no, hardly any molecules (or mass) here. Further down, the UV is quite efficiently filtered by Stratospheric components such as Ozone (Ozone level peak around 20-25 km up - where it is cold?) - so that only 1-3% of total UV (mainly longer wavelength UVA) reaches the surface. You state: "as the atmosphere thins it looses more energy via radiation, yet at the same time it still has an insulating effect" How? I'm not sure what physical processes you are trying to communicate here. Approx 99.999% of the atmosphere is below the Thermosphere. Approx 99.9% is in the Troposphere. What substance exactly is providing insulating properties where? I suspect you may be stretching the definition of "air" a little thin...
  18. #55 "For some historical context see Moe 1977." On the webpage we've been referred to by Will is this statement: The Governments of the world and the various space agencies such as NASA have conspired to stay quiet about the Diurnal Atmospheric Bulge In addition to the reference cited by Peter Hogarth, here's Harris and Priester 1965. Both were NASA scientists at the time. I found that by googling 'diurnal atmospheric bulge'; it was the 4th hit on the 1st search result page. Without opening a can of political worms, how is the existence of this phenomenon being kept secret? Note that I ask how, not why. And also note this reference further down the same search. One of the great things about skepticalscience is that you can quickly find a more reasoned explanation. Note: Any rumors that I have started a 'Ned Fan Club' are categorically false.
  19. muoncounter at 03:17 AM on 27 August, 2010 To be fair, some of the relevant information was only declassified in 1971 (if memory serves).
  20. muoncounter at 03:17 AM on 27 August, 2010 For some more updated classic science on the Thermosphere and Mesopause, UV heating, upwelling IR and radiative balance, see States 2000.
  21. Berényi Péter @61 Probably there was heating in the room that was turned off for the night and switched back in the morning just before the experiment started. It developed then maintained a temperature gradient between the positions of jar A and B on the table. Hmm, heating that is turned on about 8.00am, and then is left on all day while he's out at school(as his caption says) and is kept on until at least 8.00pm. I thought the kid said he was worried about global warming ! But at least his experiment is missing some of the glaring errors in Will's version.
  22. Will at 21:34 PM , when you say that air is both a good insulator and a top radiator, does it not depend more on the movement of the air rather than it's inherent properties? Still air is indeed a very good insulator of heat, however moving air is a very efficient dispersant of heat.
  23. Will writes: The problem lies in the lack of understand of the fact that the atmosphere both radiates and insulates at the same time. Insulates what? From what? The only way that the Earth loses heat is by radiating to space. The only way that I can see the word "insulation" being relevant in this process is ... the effect of greenhouse gases repeatedly absorbing and re-radiating energy from the surface, slowing its outward flux and raising the temperature of the Earth system. But that's exactly the process you claim doesn't occur, so you presumably mean something else, right? In addition, I'm still curious about this remark from an earlier comment of yours: Thermal radiation is heat. Vibrating matter. Gas molecules are vibrating matter. [...] In the vacuum of space full spectrum EMR produces no thermal radiation, heat. Thermal infrared radiation is just another part of the electromagnetic spectrum; it's called "thermal" because it's the range at which normal Earth-surface objects radiate. It obviously does propagate through space (we use thermal sensors operating in the 8-14 micrometer window to measure this from satellites). Oh, and not to overload you with questions, but it would be nice if you could answer the questions from this comment. At what wavelength ranges does nitrogen in the Earth's atmosphere absorb and emit radiation? Thanks. muoncounter writes: Note: Any rumors that I have started a 'Ned Fan Club' are categorically false. Hey, I like that idea.
  24. Tom #65 The Mythbusters experiments sufferers the same problem than invalidates many Mythbusters experiments. The lack of replication and randomisation of placement of the treatments. I'd love to see someone do the experiment properly, but none that I have seen on the internet so far come close to a properly controlled, replicated and statistically analysed experiment. It's odd really. You'd think that every natural history museum in the World would have this sort of thing as a permanent installation.
  25. I just looked at the CO2 candle and tube demonstration of the so called greenhouse effects of absorbing heat when the CO2 fills the tube. What is not shown and is important is the spectral sensitivity of the sensor tube. Also, I would like to see the same experiment with water vapor being pumped in. I really don't think this is much of a relevant experiment concerning what is happening in our atmosphere. It seems to me that the results may be more stunning with water vapor and we should reduce that too.

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