Why Does The Atmosphere Heat Up During The Day?

Shortwave radiation passes largely unimpeded through the atmosphere. It strikes the ground and warms it. The warmed ground emits longwave radiation, some of which is absorbed by greenhouse gases, causing the atmosphere to warm.

If there were no greenhouse gases, almost all of the surface heat would radiate back into space without warming the atmosphere. A small amount of heat would transfer kinetically directly at the ground surface, but the atmosphere would be very cold. This is basically what happens in Antarctica, where there are very few greenhouse gases.

How could a weather model possibly work without a radiative transfer model which models the greenhouse effect?


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68 Responses to Why Does The Atmosphere Heat Up During The Day?

  1. James windham says:

    The solar heated surface heats the air by kinetic transfer as you say, but if the tiny amounts of CO2 traps irradiated heat, then why is it only trapping heat near the surface and letting the air get colder and colder the farther away from the surface that we measure it?

    • Most of the absorbed LW is by H2O which is most abundant near the surface.

      As elevation increases, the pressure decreases along with the temperature – i.e. the adiabatic lapse rate. Rising air expands and cools.

    • The mean free path length for CO2 is 33 meters. After about 500 feet, all the 15 micron IR is absorbed. This is called the altitude of extinction. The warming from CO2 happens right near the ground.

      Adding CO2 to the atmosphere does nothing but lower the altitude of extinction. It doesn’t cause any warming.

      • (33 meters…at sea level.)

        • policycritic says:

          Morgan, could you explain what you are talking about some more? I thought 15 micron IR absorbs at 193K. I can change 1000-1500 ft in altitude in my town in less than 60 minutes, with a mere 15° temp difference. I thought you wrote before that CO2 doesn’t absorb until the troposphere. Now I’m confused. Thx.

        • Policycritic, earth radiates between 7 and 100 microns. CO2 absorbs the 15 micron band which is right smack in the middle of earth’s radiation spectrum.

          study it

        • policycritic says:

          Morgan, I have but I don’t have your years of experience; I have your hyzercreek explanation parked on my desktop, and even though I’ve read it 20 times, I reread it every once in a while for the plain-speaking. But now I’m really confused because I thought the surfce emitted in the 220K to 320K N-band.

        • The chart shows Planck’s curve for 220 through 300 degrees (pole to equator)

      • Robert Austin says:

        I agree with your first paragraph but not the second. See my post further down.

      • higley7 says:

        You COMPLETELY ignore conductive heat transfer! This leads to convection and warm breezes. IR radiation is only about 15% of the energy budget from the surface. The rest is all conductive/convective and the heat of vaporization from evaporation (the latter is not sensible as heat).

        • usJim says:

          The rest is all conductive/convective and the heat of vaporization from evaporation (the latter is not sensible as heat).

          How does this ‘heat’ energy then leave the planet? Does it ever leave the planet? Your explanation is incomplete and implies it never leaves the planet.

        • daveburton says:

          higley7, he wasn’t suggesting that conductive heat transfer doesn’t occur, it just wasn’t the topic of that comment.

          usJim, evaporation and condensation works in a classic “refrigeration cycle” to cool the surface of the Earth. It starts with evaporative cooling at the surface. The moist air is lighter than dry air, so it rises. The lower temperature and pressure at altitude causes the moisture to condense out, forming clouds, and releasing its latent heat. The water then falls as rain, back to the surface.

          The process transports a lot of heat from the surface to the altitude of the clouds. But you are correct, it does not transport it all the way to outer space. However, the atmosphere is much thinner up there, and when the CO2 and H2O in the atmosphere radiate longwave radiation, the number of opaque molecules above them is much smaller, so quite a bit of the IR can leave the planet without being intercepted by other CO2 molecules.

          Note: as CO2 concentrations increase (e.g., from 300 ppmv to 400 ppmv), then the altitude needed for a photon to have an x-percent chance of leaving the planet also increases. (I don’t know what “x” value corresponds to the famous “Effective Emission Height” or EEH.)

      • daveburton says:

        Morgan Wright wrote, “After about 500 feet, all the 15 micron IR is absorbed [by CO2] … Adding CO2 to the atmosphere does nothing but lower the altitude of extinction. It doesn’t cause any warming.”

        Morgan, that’s not quite right. It doesn’t cause much warming, but it does cause some.

        It’s not much because, at 400 ppmv, we’re way past the point of diminishing returns w/r/t the greenhouse effect of CO2. MODTRAN Tropical Atmosphere calculates that just 20 ppmv CO2 would have fully half the warming effect of the current 400 ppmv.

        The NCAR radiation code says 40 ppmv, rather than 20, but, either way, it’s obvious that additional CO2 will have only a slight effect on temperatures. The NCAR radiation code says boosting CO2 to 600 ppmv would increase temperatures only about 1°C compared to the current 400 ppmv, and MODTRAN Tropical Atmosphere calculates it to have only about half that much effect, even with the amplification effect of water vapor included (see the MODTRAN link, above).

        Obviously, 0.5 to 1°C of warming is not worrisome, and my guess is that negative (stabilizing) feedbacks will reduce it even more. But it is not zero, either.

        So, why isn’t it zero? Well, at 15 microns, In the center of CO2’s primary absorption band, you’re nearly right: IR is so completely blocked already that adding more CO2 has little effect. However, at the fringes of CO2’s absorption bands, it’s a different story. Adding more CO2 does have substantial effect on the absorption of those wavelengths by the atmosphere.

        Additionally, even at 15 microns there’s an effect, albeit small, because it does matter how close to the surface the IR is absorbed. Lowering that altitude changes the temperature profile of the atmosphere, leading to (slightly) higher temperatures at the surface, and (slightly) lower temperatures at higher altitudes, as explained by Dr. Roy Spencer.

        Two months ago I attended a very interesting guest lecture by Princeton Prof. Wm. Happer, at UNC on this topic. There’s probably nobody in the world more expert on this topic than he is. Unfortunately, there was no video recording made of the lecture, but I made an audio recording, and Prof. Happer sent me his Powerpoint slides. With his permission, I put both on my web site, here:
        I suggest that you view the powerpoint slides while listening to the lecture.

  2. nickreality65 says:

    “any” or not very much?

  3. omanuel says:

    Thank you, Steven, for the explznation

    If NASA scientists had any interest in explaining changes in Earth’s climate they would show the public how the wavelength of solar radiation changes

    1. Over a typical solar cycle (22 yr)
    2. After the solar system’s birth 5Ga
    4. Abruptly in case of solar eruptions

    • omanuel says:

      The birthday of Climategate is a good time to start explaining principles of science to the public:


    • omanuel says:

      For example, as noted on page #3 of “Solar energy,” Advances in Astronomy [https://dl.dropboxusercontent.com/u/10640850/Solar_Energy.pdf ], the weakest nuclear force – neutron-repulsion – becomes the most important nuclear force in heavy atoms, some planets, ordinary stars and galaxies.

      1. Because neutron repulsion is the weakest nuclear force

      2. That is why the nuclear structure changes at ~150 amu

      3. Alpha-decay occurs above ~150 amu (atomic mass units), because alpha particles (i.e., He-4 nuclei, or pairs of n-p pairs) are on the nuclear surface and neutrons are confined to the core if the mass number is greater than 150 amu, A > 150 amu

      4. Spontaneous fission begins when the nuclear core has 52 neutrons surrounded by 45 alpha particles in Th-232, or 46 alpha particles in U-236, or 47 alpha particles in Pu-240.

      5.Neutron-induced fission is possible when one additional neutron is added to the 51-neutron core surrounded by 46 alpha particles in U-235 or 47 alpha particles in Pu-239 or 48 alpha particles Cm-243.

      6. Spontaneous fission is the dominant decay mode when the nuclear core has 58 neutrons surrounded by 48 alpha particles in Cm-250 or 49 alpha particles in Cf-254 or 50 alpha particles in Fm-258

      Thus neutron-repulsion usually determines the structure, stability and decay mode for every physical structure composed of neutrons and protons more massive than 150 amu (atomic mass units) – no matter whether the structure is a heavy atom, planet, star, galaxy, or the entire universe!

  4. Robert Austin says:

    Also, without the presence of greenhouse gases in the upper troposphere, the convection in our troposphere would be crippled. Similar to a vast thermal air conditioner, one can picture the evapourative (heat absorbing) end of the machine in the lower troposphere and the condensing end of the machine (heat releasing) in the upper troposphere. Indeed, the tropopause is defined by the altitude where the most of radiation occurs (within in the greenhouse gas emission bands) directly to space. Greenhouse gas radiative absorption and subsequent thermalization near the earth’s surface serves to boost the efficiency of the machine by enhancing the convective cooling loop. So the greenhouse gases do double duty in both heating and cooling of the atmosphere at differing locations.

  5. higley7 says:

    You COMPLETELY ignore conductive heat transfer! This leads to convection and warm breezes. IR radiation is only about 15% of the energy budget from the surface. The rest is all conductive/convective and the heat of vaporization from evaporation (the latter is not sensible as heat).

    It is a big mistake to follow Trenberth’s insistence on ignoring the conduction/convection of the system. That’s why Trenberth is always whining about the “missing heat.” It has already gone upward. Duh.

    • What do you mean by “the surface” ?

    • Curt says:

      Nobody’s ignoring conductive/convective heat transfer. Even the greatly simplified Kiehl-Trenberth diagrams show more power transmitted from the surface to the atmosphere by conduction/convection and evaporation than by (net) radiative transfer.

      But as I pointed out in an earlier thread, if the atmosphere were completely transparent to surface radiation, it could not, on average over the long term, absorb any power through these other means from the surface, because it would have no capability of transferring any of this power to space.

  6. Roy Spencer says:

    feeling frisky today, are we, Steve? 🙂

  7. Coldlynx says:

    I must object ;
    “Shortwave radiation passes largely unimpeded through the atmosphere.” Do not agree.
    Nasa say 23% of solar incoming is absorbed in the atmosphere.
    Link here:
    About half of what are absorbed by Earth surface of 47%. The rest is reflected to space.
    1/3 of total absorbed by atmosphere 2/3 by earth surface.
    “The warmed ground emits longwave radiation, some of which is absorbed by greenhouse gases, causing the atmosphere to warm”
    “If there were no greenhouse gases, almost all of the surface heat would radiate back into space without warming the atmosphere. A small amount of heat would transfer kinetically directly at the ground surface, but the atmosphere would be very cold.”
    Only 5% of total 17% or about 1/3 of outgoing thermal radiation from ground are absorbed by the GHG in the atmosphere. Only 5% of Earth total heat balance of 71% are radiation energy absorbed by GHG.
    Compare with 42% by thermal, evaporation and convection. Or 23% direct heating by sun.
    The atmosphere would still be heated even without GHG.
    But note that most of the energy leaving the planet earth is by the help of the GHG in the atmosphere. 59% are from atmosphere and by the GHG.
    Earth is cooled by the GHG in the atmosphere. Not heated by GHG.
    Without GHG would the atmosphere still be heated but not cooled until a energy balance point with higher average temperature would occure.
    Heat as defined by thermodynamics in a macroscopic view.

  8. Paul says:

    Absolutely no greenhouse gas is needed for the ground to heat the lower atmosphere. The natural convection does the job at 99%. That’s how the real greenhouse effect works when you suppress the external convection.

  9. nickreality65 says:

    If there is water, i.e. oceans, lakes, etc., there will be evaporation.

  10. hell_is_like_newark says:

    Request: Could this conversation be expanded to include the effect of air density on temperature?

    • jae43 says:

      More density means more molecules banging on everything, thus creating more heat.

      • Curt says:

        That’s more pressure, not more “heat”.

        The act of compression can increase the temperature of a gas, but it is a one-off affair. If the gas has any thermal interface to other bodies, the increase will not be maintained.

        • nielszoo says:

          In an atmosphere higher pressure means higher heat to volume equilibrium because you have diurnal energy input from the sun. Take the Australian Outback and Chilean Atacama Desert for examples. Both have similar terrain, precipitation, humidity (low) and are at the same latitude but Atacama, even though it gets more intense solar radiation, has colder surface air temperatures by 10°C in the summer. This due to the lower air pressure at Atacama’s altitude. The higher you get, the colder it is in any atmospheric system due to lower pressure as defined by ideal gas law and is calculated as the adiabatic lapse rate as air moves up the column to lower pressure.

        • Rosco says:

          However a whole atmosphere has only radiation to space to “release” the energy gained.

          The analogy of the temporary temperature increase when you inflate a tyre does not apply to the whole of the atmosphere – all the atmosphere does is redistribute “heat” to attempt to re-establish some equilibrium condition which the solar radiation is continually disturbing. The “pre-defined equilibrium” condition is obviously determined by the atmospheric constituents – pressure, volume, temperature and types of gases.

          There is still the issue of non greenhouse gases which have little interaction with infra-red which obviously change in temperature each day. Increasing in altitude and cooling is not energy release but conversion from kinetic energy measured as temperature to gravitational potential energy.

          There are hundreds of examples demonstrating this effect including the famous Chinook winds.

          I have difficulty in reconciling the inability of 99% of the atmosphere to release significant quantities of energy by infra-red radiation other than by transferring their kinetic energy (temperature) to infra-red radiating gases with the claim that increasing the reasonably rare chance of this occurrence (<2%) will result in a net trapping of energy.

          If 99% of the warmed atmosphere can only significantly transfer energy to space via GHGs logic says increasing the probability should increase the rate of radiation to space.

          And NASA data shows this is happening – http://earthobservatory.nasa.gov/Features/Nimbus/nimbus2.php

          This site shows a positive anomaly for radiation emitted to space from 1979 to 2005 with exception of brief periods following major volcanic eruptions.

          As I said I have difficulty in reconciling the increasing probability for 99% of the atmosphere to transfer its energy to space by more GHG interactions with "trapping heat".

      • hell_is_like_newark says:

        I was thinking along the lines (extreme example): Venus: much of the sunlight is reflected yet the planet is very hot, both on the sunny side and dark side (Venus spins very slow).

        • Venus is fairly dark even during the day, because of the thick cloud cover. Greenhouse effect at the surface is minimal, because there is very little incoming SW radiation.

        • nielszoo says:

          Atmospheric pressure on Venus is ~80 times that of Earth and that’s the main reason it’s hotter.

        • Rosco says:

          We think Venus absorbs little solar energy because a significant proportion of visible light is reflected.

          But the solar radiation also contains significant energy at other wavelengths and Venus’ atmosphere is comprised of gases which absorb these wavelengths.

          I think it is too simplistic to reject significant solar interaction with Venus’ atmosphere based on the reflection of visible light. We know surfaces can reflect visible light and yet absorb other wavelengths and increase in temperature – it happens every day as our vision confirms.

          After all the greenhouse effect is all about absorbing infra-red radiation and both the CO2 atmosphere and sulphuric cloud layers of Venus would absorb almost all the IR the Sun sends its way. I am not sure of how UV interacts.

          But there is almost certainly significant absorption of a significant amount of the solar radiation even though it is presumed to reflect 80% of visible wavelengths. The amount of absorption by Venus’ atmosphere could be as high as 55% of the solar constant of ~2614 W/sqm at Venus as quoted by NASA – perhaps 1450 W/sqm.

          This is significantly more than the oft quoted 132 w/sqm I see quoted as the insolation for Venus in University lectures.

        • But the surface temperature is controlled by the atmospheric pressure.

  11. jae43 says:

    Remember that about half the solar radiation is longwave which probably saturates all the IR-absorbing molecules at any given time when sun is shining.

    • Go Canucks!! says:

      You may be a great chemist but your knowledge of the global Energy Budget is lacking. 32% of absorbed radiation is LW or 22% if you use the TOA insolation.
      Also, the LW insolation has a different wavelength that is not absorbed as is the radiated LW from the earths surface.
      Secondly the use of “probably” is not a scientific statement but a belief.

    • daveburton says:

      There is no “saturation.” If molecules which absorb light at particular wavelengths became “saturated,” and couldn’t absorb more, then you couldn’t burn anything with a laser, because the first photons striking the target would “saturate” it, and the material would then cease absorbing energy from the laser.

      When a CO2 molecule absorbs a photon at 15 microns, in the lower atmosphere, it doesn’t keep that energy for long. The mean time for it to transfer that energy by collision with another molecule (usually N2) is only about a nanosecond. The mean decay time for a CO2 molecule to lose its absorbed energy by emission of another photon is nearly a second — almost a billion times as long. So except in the very ratified upper atmosphere, nearly all CO2 molecules lose the energy which they acquire by IR absorption almost immediately, through collisions with other gas molecules. Conversely, that’s also how they acquire the energy which they lose by IR emission — the downwelling longwave IR which heats up both the earth’s surface and many arguments.

      • Saturation means that all of the upwelling radiation is already being absorbed, and adding more GHG doesn’t increase the probability of a photon being captured.

        • daveburton says:

          I know, but that wasn’t what jae43 meant by his use of the word (which is why I put it in quote marks in my reply to him).

          Let’s switch topics, however, to the kind of saturation that you’re talking about…

          While it’s true that the atmosphere already has more than enough CO2 to saturate (block) the main 15 micron absorption band almost completely, the same is not true at the fringes of that band. That’s “where all the action is” w/r/t the warming effect of adding additional CO2 to the atmosphere, and that’s the main reason that adding additional CO2 does still have an effect, albeit small, even though the main absorption band is saturated.

          MODTRAN tries to calculate it, and, although it’s not clear that they’ve really got the line shapes right, it’s probably reasonably close.

  12. Tel says:

    The surface of the Moon is about the same distance from the Sun as we are, and roughly the same albedo, but it heats up to 100 degrees C during the day, which is significantly hotter than any desert on Earth.


    A small amount of heat would transfer kinetically directly at the ground surface, but the atmosphere would be very cold.

    On the Moon, the surface gets so hot precisely because it cannot transfer the heat away into the atmosphere. Since the lunar atmosphere is such a low pressure (low mass for a given volume compared with Earth), it has no capacity to take heat.

    As I’m sure I have mentioned, the primary effect of Earth’s atmosphere is to regulate the temperature, preventing both extreme highs and extreme lows. Any “heat trapping” effect is minor and largely irrelevant.

  13. Goodmongo says:

    “This is basically what happens in Antarctica, where there are very few greenhouse gases.”

    You can’t be claiming that the poles receive as much shortwave radiation as the equator?

  14. usJim says:

    I see “jae” a long time thermal radiation denier has joined the pack, albeit with a slightly different moniker this time. Be not deceived, this looks just like the jae of old …

    jae, how do long wave IR satellites work? You know, the sat images from NASA? Like the ones available here:


    • jae43 says:

      I don’t understand why you would say that I “deny” thermal radiation (it’s as dumb as calling someone a “climate denier”). In fact, I am a PhD chemist and have even used thermal radiation for molecule identification (IR spectroscopy). I deny that the “atmospheric greenhouse effect” is caused by thermal radiation, though. A recent PNAS article supports this: http://hockeyschtick.blogspot.com/2014/11/new-paper-changes-fundamental.html

      • usJim says:

        Your record is long and your tracks are many; You know this, I know this, and hopefully those who need to know your obfuscation tricks will recognize thos too.

      • usJim says:

        jae, how about the WV imagery available on that same webpage? How does that work? Are you aware of how that works or are you highly ignorant of such things?

      • usJim says:

        jae, I don’t know if this is you, but the ‘match ‘ looks pretty close:

        Jae Edmonds is a Chief Scientist and Laboratory Fellow at the Pacific Northwest National Laboratory’s (PNNL) Joint Global Change Research Institute, and Adjunct Professor of Public Policy at the University of Maryland at College Park .

        Dr. Edmonds is the principal investigator for the Global Energy Technology Strategy Program to Address Climate Change, an international, public-private research collaboration.

        His research in the areas of long-term, global, energy, economy, and climate change spans more than 25 years, during which time he published several books, numerous scientific papers and made countless presentations. He serves on numerous panels and advisory boards related to energy, technology and climate change. His received his Ph.D. from Duke University in 1975.

        I would expect you to be better informed on these topics than you have exhibited. Your performance here, and elsewhere appears sub par.

  15. gallopingcamel says:

    All these qualitative arguments prove absolutely nothing. You have to quantify which means solving equations.

    Fortunately most of the heavy lifting has been done by Robinson and Catling who can explain the temperature profiles in the atmospheres of all seven bodies in the solar system with significant atmospheres:

    I am trying to extend the work of R&C using engineering software (Finite Element Analysis) to include cloud layers. Their equations already work pretty well for Titan:

    • Rick Fischer says:

      Thanks for the informative links. Does any of your work bear on the quality of the treatment in the AGW computer models of the contributions of H2O and CO2? It would seem that the wild disagreement between the models’ output and reality means that there are errors in how those contributions are used, or they are missing significant other factors, or both.

      I don’t see how any scientist could defend these models, yet I don’t see any scientific criticism of the models either.

  16. Rick Fischer says:

    A very useful posting and comments. Would someone please comment if what I have read about the AGW computer models is correct, that they misrepresent or ignore the greenhouse contribution of H2O? And also that they are using an erroneous contribution of CO2 to the greenhouse effect?

    If true, how do the AGW acolytes support these errors?

    • Gail Combs says:

      “….If true, how do the AGW acolytes support these errors?”

      SEE: http://hockeyschtick.blogspot.com/2014/11/new-paper-changes-fundamental.html

      The paper jae43 linked to above.

      This paper is just a rehashing of the “CO2 is the climate control knob and increased water vapor/melted ice is a feedback” that allows the IPCC Climastrologists to increase CO2’s effects by a factor of three and make it into a catastrophic.

      The only problem is the earth has already proven that model wrong.

      ” ….these researchers say, the planet is likely to have less ice and the air will become more humid under climate change, both of which will act to absorb more shortwave radiation from the sun….”

      Except that is not what has happened.
      GRAPH: NOAA Specific Humidity with 37 Month Running Average from 1948

      % change in Albedo from Earthshine Project Note the inflection point at the time of the Super El Nino.

      And then there is the polar ice that is not melting. RACookPE1978 over at WUWT explains why the record high Antarctic Sea Ice is much more important to the climate compared to ‘melting’ Arctic Sea Ice.

      The second assumption about Arctic Amplification, and easily the second most important assumption in the entire CAGW religion, is how the CAGW dogma assumes the albedo change as the polar icecap reduces will affect future climate. Sea Ice vs Open Ocean albedo does matter, and, in truth, really deserves a long conversation in its own entire thread, but let’s look at few important things.

      One. Continuously increasing positive Antarctic Sea Ice anomalies between 70 south latitudes and 59 south latitudes every day of the year for the past 15 years DO affect the world’s heat balance, but Arctic sea ice declines since 1979 – which occur between 78 north and 85 north in September each year do NOT affect the earth;’s heat balance.

      Two. Arctic sea ice albedo DOES change routinely over the year, and is lowest during the yearly June-July-August melt season. Actual Arctic sea ice is NOT the pristine Wikipedia-approved laboratory values you so often see quotes: 0.95, 0.90, 0.86, etc) Actual measured Arctic sea ice (Curry, JGR 2001, Applications of SHEBA/FIRE Data to Evaluation of Snow/Ice Albedo Parametrization) is available for 13 years now, but seldom accurately called out. Figure 1 of Curry’s measurements shows the following:…..

      So, in September in the high Arctic when the solar elevation angle SEA is NEVER more than 8-10 degrees above the horizon at ANY time of the day when the sun is even visible, what is the measured clear sky open ocean albedo? Between 0.22 and 0.35.

      Not all that much different from the albedo of the “dirty sea ice” that is melting away. Yes, there is an increase in absorbed radiation in the Arctic above 78-82 latitude when sea ice is replaced by open ocean, BUT it is not very much difference in energy over the 12 hours of even potential sunlight!

      And, although the sun’s rays do heat the open water slightly during those daylight hours, the open water about 78-82 north loses MORE HEAT to the sky over the entire period of the 24 hour day through increased long-wave radiation, increased evaporation, increased convection, and increased conduction than does sea ice!

      Rather than an “arctic sea ice amplification” the numbers show that – during the late melting season under today’s conditions, every square meter of open ocean north of 76-82 north LOSES more heat on a daily basis than does sea-ice-covered arctic waters under the same air conditions!

      The exact opposite, unfortunate, is also true down south:
      Under today’s conditions at Antarctic sea ice extents between 60 south and 70 south latitudes, EVERY square kilometer of increased Antarctic sea ice at ANY time of year reflects more energy into space away from the planet, INCREASES total planet cooling!

      See the rest of that comment with the technical explanation and R. A. Cook’s other comments for why melting Arctic Ice is a red herring.

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