Greenhouse gases, such as carbon dioxide and water vapor, are gas molecules that absorb infrared radiation (net heat energy) emitted from Earth’s surface and reradiate it back to Earth’s surface, contributing to the greenhouse effect. These gases, like nitrogen and oxygen, are able to absorb and re-emit infrared energy, which is then circulated in the atmosphere and eventually lost to space.
The molecular structure of gases in our atmosphere determines their ability to absorb and re-radiate infrared energy. Once excited by absorbing infrared radiation, a greenhouse gas molecule can lose energy again by re-emitting radiation of the same wavelength or pass energy on to other molecules in the air. The bulk of the atmosphere is made up of nitrogen and other gases, such as CO2 and H2O.
Greenhouse gases increase in temperature and share that heat with the rest of the molecules in the air. The vibrationally excited molecules may radiate, some of which will be lost to space, and some absorbed by the Earth. If the concentration of greenhouse gases increases, more infrared radiation will be absorbed and emitted back toward Earth’s surface, creating an enhanced surface temperature.
The ability to absorb and re-emit IR energy makes a greenhouse gas effective in trapping heat. Not all gas molecules are able to absorb infrared radiation, but when they do, their temperature rises. This process is similar to coals from a fire that are warm but not glowing. When greenhouse gases absorb radiation, they distribute the acquired energy to the surrounding air as thermal energy, or the kinetic energy of gas molecules.
📹 Ott/Shula: Why is there back radiation but no greenhouse effect?
About Tom Shula: • Academic training in theoretical physics. Disillusioned with the community and left with a M.S. to work in tech …
What happens to greenhouse gases when they absorb infrared radiation?
Greenhouse gases, such as carbon dioxide (C2H12), cause the Earth to warm by absorbing infrared radiation. This process causes gas molecules to move and vibrate faster, resulting in warmer air and the ability to re-emit the radiation. This slight effect shifts the equilibria of greenhouse gases, amplifying the effect. The main issue with $ce(CO2)$ is an indirect effect, which slightly warms the Earth, increasing the amount of water vapor in the atmosphere.
Water is a more potent greenhouse gas than $ce(CO2)$ and absorbs at different wavelengths in the IR. This is problematic because the amount of IR radiation absorbed is close to saturation. Increasing the amount of $ce(CO2)$ does not necessarily mean doubling the amount of IR radiation absorbed and redirected back towards Earth. This relationship is closer to logarithmic than linear, and introducing more water vapor allows for a wavelength of IR radiation that may not be saturated. The atmosphere is a complex system, and understanding the mixing of gases and their duration is crucial.
How infrared radiation interacts with a greenhouse gas molecule?
The natural greenhouse effect is a phenomenon where Earth’s atmosphere absorbs longer wavelengths of infrared radiation from the sun, causing it to emit infrared radiation in all directions. This process, combined with visible radiation from the sun and infrared radiation from the atmosphere, causes Earth to be warmer than it would otherwise be. The sun’s visible wavelengths pass easily through the atmosphere, reaching Earth, with approximately 51 percent of this sunlight being absorbed by land, water, and vegetation at Earth’s surface. This process keeps Earth’s average global temperature at approximately 15°C (59°F).
How do infrared rays cause the greenhouse effect?
The correct answer is IR rays, which are responsible for the greenhouse effect, which occurs when infrared radiation from the Sun is absorbed by water vapor and certain gases in the atmosphere, increasing Earth’s temperature. The MP Police Constable 2023 PET Admit Card has been released, and the second phase of selection examination will be conducted from 23. 09. 2024 to 09. 11. 2024. The Madhya Pradesh Professional Examination Board (MPPEB) announced the MP Police Constable Vacancy 2023 on June 23, 2023.
What happens to molecules when infrared radiation is absorbed?
Covalent bonds vibrate in different vibrational modes, such as stretching and bending, with a characteristic ground state frequency that corresponds to the frequency of the infrared region (10-13 to 10-14 Hz, or 2. 5 to 17 μm in wavelength) of the electromagnetic spectrum. When exposed to infrared radiation, a molecule absorbs radiation that matches the frequency of its bond vibration. This absorbs the radiation, increasing the bond’s vibration amplitude but maintaining the same vibrational frequency.
In an infrared spectrophotometer, a beam of IR radiation passes through a sample, with some absorbed and the remaining going through. A blank cell with no sample passes through the cell, and the detector records and compares the radiation transmitted through the sample with that transmitted in the absence of the sample. The computer plots the result as a graph showing transmittance vs frequency.
When a greenhouse gas molecule absorbs an infrared photon what happens next?
Carbon dioxide (CO2) molecules can absorb and re-emit infrared (IR) radiation, making them an effective heat-trapping greenhouse gas. This ability allows CO2 molecules to vibrate in ways that simpler nitrogen and oxygen molecules cannot, allowing them to capture the IR photons. In a complex real-world process, a CO2 molecule might bump into several other gas molecules before re-emitting the infrared photon. The faster motion of a molecule that results from the IR photon increases the temperature of the gases in the atmosphere.
Not all gas molecules can absorb and re-emit IR radiation, as nitrogen and oxygen, which make up over 90% of Earth’s atmosphere, do not absorb infrared photons. CO2 molecules can vibrate in ways that simpler nitrogen and oxygen molecules cannot, allowing them to capture the IR photons. This makes CO2 an effective heat-trapping greenhouse gas. In summary, CO2 molecules are able to absorb and re-emit infrared energy, making them an effective heat-trapping greenhouse gas.
What happens when a molecule absorbs infrared light?
The absorption of infrared radiation by a molecule gives rise to vibrational transitions as a consequence of the existence of low-energy gaps. Furthermore, this process enables the molecule to undergo rotation, as the requisite energy for rotational levels is minimal.
Do greenhouse gases trap solar radiation or infrared radiation?
Greenhouse gases are atmospheric gases that absorb long-wave infrared radiation from the Earth’s surface, contributing to the Earth’s warming. They absorb infrared light and re-radiate it in all directions, including back to Earth, while capturing little or no incoming solar radiation. This process, known as the Greenhouse Effect, is a naturally occurring phenomenon. Without greenhouse gases, the Earth’s average temperature would be lower and much of it frozen.
However, pollution is increasing the levels of these gases, potentially leading to severe warming and dangerous climate changes in the future. Natural greenhouse gases include water vapor, carbon dioxide, methane, and nitrous oxide, while man-made greenhouse gases include CO2, CH 4, N 2, and chlorine and bromine-containing compounds like sulphur hexafluoride and chlorofluorocarbons.
What is the relationship between infrared photons and greenhouse gases?
Greenhouse gases, including water vapor, carbon dioxide, methane, nitrous oxide, and ozone, readily absorb infrared photons, exhibiting a similar optical behavior to that of glass in a greenhouse. These gases are transparent to visible light but can also absorb infrared radiation.
What happens when a molecule absorbs IR?
The IR theory explains that molecule vibrational frequencies are measured using the IR technique, which involves passing polychromatic light through a sample and measuring the intensity of the transmitted light at each frequency. When molecules absorb IR radiation, they transition from a ground vibrational state to an excited vibrational state. To be IR active, a molecule must change its dipole moment, which is a vector quantity based on the orientation of the molecule and the photon electric vector.
Absorption occurs for vibrations that displace the dipole along a molecular axis, while completely polarized vibrations are absent. In heteronuclear diatomic molecules, the dipole moment is an uneven distribution of electron density between atoms, with one atom having a net negative charge. The relationship between IR intensity and dipole moment can be mathematically expressed.
What is the greenhouse effect of infrared heat?
Greenhouse gases in the atmosphere absorb and re-radiate infrared radiation, which is energy radiated from Earth’s surface as heat. This process impeds the loss of heat from the atmosphere to space. Solar radiation, shortwave, high-energy, including visible light, is absorbed and transfers its energy to Earth’s surface or atmosphere, increasing the temperature of land, air, or water. Earth’s cooler temperature causes it to re-radiate energy as longwave, lower-energy wavelengths than it absorbs, resulting in infrared radiation, which we feel as heat.
The amount of heat re-radiated from Earth’s surface is influenced by factors such as the amount of solar radiation absorbed at that location. Most of the heat is reabsorbed and re-radiated in the atmosphere multiple times by greenhouse gases and clouds.
What happens when infrared radiation is absorbed?
The Earth’s surface absorbs visible light and high frequency infrared radiation, increasing its internal energy and causing it to heat up. This energy is transferred to the atmosphere through conduction. All objects emit and absorb radiation, with the hotter the body, the more infrared radiation it emits and the greater the proportion of visible light emitted. The temperature of a body is linked to this balance.
📹 Astronomy – Ch. 9.1: Earth’s Atmosphere (7 of 61) How a Gas Molecule Absorbs Energy
In this video I will explain how a gas molecule absorbs energy through 1) molecular collisions-fast molecule collides with a slow …
This is absolutely brilliant! I thought I had a pretty good understanding of the GHG mechanism and the quantisation involved. But I’ve never seen anyone set out the impact of thermalisation like this. So, this is a double killer blow to climate change. At 15um, CO2 absorbs 100% of upwelling IR within 10 to 50 metres (meaning climate sensitivity is close to zero). But this article shows that the reality of thermalisation kills climate change before you even need to worry about radiative absorption and re-emission.
I think the point is not that there is no green house gas effect. Rather that the effect is not a purely radiative one, although radiative models appear to have good agreement with satellite measurements (right answer for the wrong reason perhaps). The alarmists claim that more CO2 will cause more warming is not threatened by the thermalisation theory. Instead we get back to the point that there is already sufficient CO2 in the atmosphere to absorb much of the emitted radiation of the appropriate wavelength (then thermalise it) so adding more CO2 will have a small effect (diminishing returns).
Thank you I suppose someone needs to TAKE the FEAR out of Greenhouse! Perhaps we should use the more correct terminology thereby reducing the Fear connotation from the dialogue? All the great greenhouses I’ve ever been in are filled with the MOST amazing plants and creatures – so where’s the fire?!! And the irony is, they are covering our beautiful, fertile lands, which live & breathe and even produce FOOD, with hideous GLASS solar panels and plastic & concrete wind turbines.. Talk about a man-made crisis.
Excellent work. While not news to me I am glad you gathered it in one comprehensive article for others and more. If I may I would like to point out that Earth mean temp is due to specific heat capacity of it’s surface (water) and it’s rotation period (1 day). The atmosphere with the water cycle is mostly a cooling mechanism as far as I can tell, but I may be slightly wrong on the magnitude of this one claim. This became obvious while computing the temperature of the Moon if it’s rotation period got shortened to 1 day instead of the current 29 days.
nice presentation. Thinking it can be simplified further for the pols. WE live in the lower atmosphere (about 10 m/30 feet). This is the only area we need to be concerned about. The sun is the source of heat for the Earth. Sunlight is converted to infrared radiation. This amount is constant. 99.4% is absorbed by current levels of Co2 and converted to heat. Adding CO2 has essentially no effect because there is essentially a no more infrared radiation to absorb and convert. This is the “CO2 saturation effect’. Measuring OLR is not useful as a proxy for ‘the greenhouse effect” is the OLR is decoupled from the heating of the lower atmosphere (where we live).
Dear Markus, to further clarify for you, I will here give an example of how flow of energy through a system is not adequately accounted for by the oversimplified paradigm that you rely on on your talk of the second law. Much energy is transported from equatorial to polar regions, partly by ocean currents, partly in the atmosphere. In a polar winter region, radiation from the condensed matter surface to outer space is much easier than it is in equatorial regions, because the polar air is drier. In a polar winter region, there is a temperature inversion, so that the condensed matter surface is colder than the troposphere above it. Thus, in a polar winter region, there is substantial net transport of energy as heat from troposphere to condensed matter surface, contrary to your overgeneralisation that the net transport is always from condensed matter surface to troposphere. This is not the only reason why your oversimplified narrative for the second law is astray, but it is a simple example of one way in which it can go astray. To cover the process globally overall, instead of the static oversimplification that you rely on in your appeal to the second law, a thoroughly dynamic approach is needed.
Dear Markus, perhaps it may help if I explain in more detail why your attempt to apply the second law is mistaken. Strictly, the second law refers to a scenario of two bodies, starting with each in its own state of internal thermodynamic equilibrium, separated by a rigid wall that is impermeable to heat. The wall is then made permeable to heat, conductive and radiative. The law then says that heat will pass from the hotter to the colder. You effectively rely on this simple scenario. Such is not the scenario of the earth’s energy transport process, the system of present interest. The latter scenario is always far from thermodynamic equilibrium, with substantial amounts of heat entering and leaving as radiation, the heat being supplied by a hot body, the sun, and being passed out to cold surroundings, outer space. That there are substantial energy flows through the system calls for analysis beyond that of the simple scenario on which you rely.
There is no GH effect because the IR energy transfer between the surface and the atmosphere is the difference between the upward IR flux (from the surface towards the atmosphere but not in the atmospheric window) and downward IR flux (from the atmosphere towards the surface). This IR energy transfer = 17W/m² (according to the NASA) and is upward so it can’t warm the surface (which is indeed warmer than the atmosphere). Moreover, these same active gases in the IR spectrum emit 170W/m² (according to the NASA, and 160W/m² from the top of the troposphere according to the IPCC) into the space, with a negligeable backward flux, so that the IR energy transfer is 170W/m² (or 160 W/m² at the top of the troposphere). The global effect of those gases (with the contribution of convection/advection cells) on the atmosphere is the difference of the 2 IR energy transfers (what is emitted into space minus what is absorbed from the surface by the atmosphere) and result is that those gases cool the atmosphere by 170 – 17 = 153Wm² (and they cool the troposphere by 160-17 = 143W/m²). “GHG” should be named “active gases in the IR spectrum” or “ACG” for “air conditioning gases” or “Atmosphere Cooling Gases”. P.S. : – data from the K&T Energy budget showed at 18:35 are similar and the result is the same. – the “trick” of the backradiation in those energy budget is that the bac radiation is a simple flux, not an Energy transfer. With respect to energy transfers (which are the aim of the energy budget diagrams) the 2 radiative fluxes between the surface and the atmosphere HAVE to BE substracted on to the other to give ONE single upward energy transfer = 17W/m² in the NASA energy budget, and = 350 – 324 = 26 W/m² in the K&T energy budget diagram.
My favorite article on the Tom Nelson podcast so far! I feel stumped that I could have ever ‘fallen for’ the idea that heat transport from the surface of the earth to the top of atmosphere (ToA) could be (modelled as) purely radiative, when all human experience, plus my extensive industrial ditto, point clearly to convection as the dominant heat transfer mode. It was right in front of me the whole time… Anyway, CO2 does capture some radiation, which had it not been for CO2, would have radiated into space. What is not true is that it matter a lot whether 99.9% is absorbed within the first 5, 10 or 20 m of the troposphere.
Roy Spencer did an experiment with an IR thermometer. He measured a clear sky temperature of 27 deg F and pointing at a cloud a temperature of 41 deg F. The current temperature was 78 deg F. How this can be explained with the thermalization process, as measured radiations are just coming from 50 meters up? You can find Roy’s experiment on his blog of April 2013.
That sounds a little bit different, as in your other articles. Where you tell us, there is no Backradiation because of Thermalisation. Now you say, if i understand it right, yes there is backradiation, but not from interaction with Photons rather from thermally excited emission. That means collisions with other Moleculs, right? But in one of your other articles you calculate that only ca. 3% (at See level) of all air molecules have enough kinetic energy to excite a CO2 Molecule. That cannot explain the Measurments of the backradiation. If they measure right.
The only section I violently disagree with here is the discussion of the IPCC energy flow diagram, at about the 19 minute mark. 1. The diagram is bad conjecture. It is not empirically based, and I believe it will fail any attempt to validate it. Convenient for the IPCC that there’s no way to validate their averaged energy diagram as such a world imagined by the modellers does not exist. In the real world : we have day and night. Earth has a titlt giving seasons. the amount of incident radiation recieved at the ground varies because earth is a sphere and the sun rays hit that sphere almost as straight lines. I believe no empirically derived energy balance system exists. But correct me if I’m wrong – is there a whole earth real energy balance system? – to check the silly “flat earth” IPCC model against? 2. Warmists miss-apply the Stefan-Boltzmann Law, as explained by Yong Tuition. There should be 2 terms a Source term and an absorber term. both T^4. The absorber has a lower temperature, so that term is lower than the source term. The absorber term is subtracted from the source term to get a value for radiance flow. When radiation only travels a short distance before it is absorbed by CO2/H2O radiatively active gases, the absorber term will be quite high as the temperature difference between temperatures of the surface and atmosphere above it are small. I suppose the absorber term for the fraction of emissions making their way out to space will use 3K : 3^4 – the supposed temperature of the background radiation of the universe?
If the theory presented here is true, you would measure one or more orders of magnitude (50.000 times less?) less radiative flux in the 15 um band when moving away from the surface, but pointing towards the surface. Because the flux that originates from the surface of the Earth (locally) would be thermalized than thus ‘disappear’, only to ‘re-emerge’ at ToA (top of atmosphere), specifically the height where thermally stimulated emission starts to outweigh thermalization. Has such an experiment been carried out?
Dear Markus, it is a mistake of logic to try to define the greenhouse effect as you seem to do at 0:13, as ‘a thing caused by back radiation’. The mistake of logic is to try to define something just by one of its several constituent mechanisms. As if to try to define the wood by one of its trees (or, in American parlance, the forest by one of its trees). Back radiation is one of the several constituent mechanisms of the greenhouse effect, but it is not its sole defining feature. The proper definition of the greenhouse effect is as an overall effect of the presence of greenhouse gases relative to their absence.
With respect to my previous question; If the back radiation is a near ground effect only, then why is the downwelling thermal radiation increased by clouds ? “Question on downwelling radiation ; In his presentation Happer shows a graph of measurements of DWR (using a pyrgeometer) at 12 minutes youtu.be/60nJOKGU3Ks?si=efcO8joACEgTsa-R .”
The claim that the GHE is in violation of the 2nd law of thermodynamics is predicated on the fact that the person making this claim is using a strawman argument! And seeing that there is so many of these arguments, i’m not going to go into details about them. Rather, detail what the GHE is: The GHE is predicated on the fact that temperature at the surface is dependent on energy balance: If energy in is = to energy out, you have no temperature change. If energy in is > than energy out, then temperature rises. If energy in is < energy out, then temperature decreases. GHG's like Co2 and Water Vapor slow the loss of energy into space, thus creating a buildup of energy near the surface. (Temperature rises)
Dear Markus, you are not using a proper or natural definition of the greenhouse effect. The natural meaning of the term ‘greenhouse effect’ is ‘the difference between the condensed matter surface temperatures in the presence and absence of greenhouse gases’. You confuse yourself by trying to define it in terms of your notions of the several contributory mechanisms of energy transport in the atmosphere. The greenhouse effect is properly defined by the overall effect, not by consideration of its several contributory mechanisms. It is natural and substantial, roughly 33°C. Those of us, such as you and me and Tom, who say that man-made carbon-dioxide-emissions global warming is practically nothing, are saying that added man-made CO2 adds practically nothing to the natural greenhouse effect.
Is it possible that the process you identify, thermalization, or rather the reverse of it ‘thermally excited emission’ is in fact the cause of the back radiation. You state that “very few” co2 molecules get to re radiate due to 7×10 to the 9 interactions per second. Maybe those very few are sufficient enough to be the cause of back radiation. In fact the large number of interactions per second may cause enough excitations of co2 molecules, that some will radiate faster than the 0.5 half life stated. Or that the constant collisions will ensure that the co2 molecule is excited for a long enough period that it will then indeed emit a photon. This would mean the back radiation is dependent on the amount of GHG molecules, logarithmic relationship. The additional heat from clouds would then make sense if that heat results in greater thermalization of the co2 molecules by oxygen and nitrogen and inevitably more thermally excited emissions and therefore more back radiation?
Dear Markus, we value your opinion, but here you are mistaken. The temperatures of the bodies that are affected by the earth’s energy transfer process are governed by the nets of various substantial flows of energy, so that the system is always substantially out of thermodynamic equilibrium, though it can, suitably averaged, at times be transiently in a more or less steady state. The balance of energy at the earth’s condensed matter surface is the algebraic sum of the following several substantial flows of energy: of the rate of absorption of directly impinging sunlight on the condensed matter surface (+), of the rate back radiation from the atmosphere (+), of the rate of surface emitted radiation passing straight through the atmosphere to outer space (–), of the net rate of absorption of the surface’s emitted radiation by the atmosphere (–), of the net rate of transfer of energy from the surface to the atmosphere by evaporation (–), of the net rate of transfer of energy from the surface to the atmosphere by conduction (–), and of net storage rate of energy by the condensed matter surface (+). Though it is never violated, the second law of thermodynamics does not directly govern this net algebraic sum because the second law, exactly stated, refers to completed transfers between bodies in mutual and respectively internal thermodynamic equilibrium, which is a state of zero rates of energy transfer, not a state of substantial rates of flow of energy. It is a matter of rates of flow of energy.