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The greenhouse effect and the 2nd law of thermodynamics

What the science says...

Select a level... Basic Intermediate

The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.

Climate Myth...

2nd law of thermodynamics contradicts greenhouse theory


"The atmospheric greenhouse effect, an idea that many authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist." (Gerhard Gerlich)


At a glance

Although this topic may have a highly technical feel to it, thermodynamics is a big part of all our everyday lives. So while you are reading, do remember that there are glossary entries available for all thinly underlined terms - just hover your mouse cursor over them for the entry to appear.

Thermodynamics is the branch of physics that describes how energy interacts within systems. That interaction determines, for example, how we stay cosy or freeze to death. You wear less clothing in very hot weather and layer-up or add extra blankets to your bed when it's cold because such things control how energy interacts with your own body and therefore your degree of comfort and, in extreme cases, safety.

The human body and its surroundings and energy transfer between them make up one such system with which we are all familiar. But let's go a lot bigger here and think about heat energy and its transfer between the Sun, Earth's land/ocean surfaces, the atmosphere and the cosmos.

Sunshine hits the top of our atmosphere and some of it makes it down to the surface, where it heats up the ground and the oceans alike. These in turn give off heat in the form of invisible but warming infra-red radiation. But you can see the effects of that radiation - think of the heat-shimmer you see over a tarmac road-surface on a hot sunny day.

A proportion of that radiation goes back up through the atmosphere and escapes to space. But another proportion of it is absorbed by greenhouse gas molecules, such as water vapour, carbon dioxide and methane.  Heating up themselves, those molecules then re-emit that heat energy in all directions including downwards. Due to the greenhouse effect, the total loss of that outgoing radiation is avoided and the cooling of Earth's surface is thereby inhibited. Without that extra blanket, Earth's average temperature would be more than thirty degrees Celsius cooler than is currently the case.

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one form to another it can be neither created nor destroyed. The Second Law does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. That qualifier term, 'net', is the important one here. The Earth alone is not a "closed system", but is part of a constant, net energy flow from the Sun, to Earth and back out to space. Greenhouse gases simply inhibit part of that net flow, by returning some of the outgoing energy back towards Earth's surface.

The myth that the greenhouse effect is contrary to the second law of thermodynamics is mostly based on a very long 2009 paper by two German scientists (not climate scientists), Gerlich and Tscheuschner (G&T). In its title, the paper claimed to take down the theory that heat being trapped by our atmosphere keeps us warm. That's a huge claim to make – akin to stating there is no gravity.

The G&T paper has been the subject of many detailed rebuttals over the years since its publication. That's because one thing that makes the scientific community sit up and take notice is when something making big claims is published but which is so blatantly incorrect. To fully deal with every mistake contained in the paper, this rebuttal would have to be thousands of words long. A shorter riposte, posted in a discussion on the topic at the Quora website, was as follows: “...I might add that if G&T were correct they used dozens of rambling pages to prove that blankets can’t keep you warm at night."

If the Second Law of Thermodynamics is true - something we can safely assume – then, “blankets can’t keep you warm at night”, must be false. And - as you'll know from your own experiences - that is of course the case!

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

Among the junk-science themes promoted by climate science deniers is the claim that the explanation for global warming contradicts the second law of thermodynamics. Does it? Of course not (Halpern et al. 2010), but let's explore. Firstly, we need to know how thermal energy transfer works with particular regard to Earth's atmosphere. Then, we need to know what the second law of thermodynamics is, and how it applies to global warming.

Thermal energy is transferred through systems in five main ways: conduction, convection, advection, latent heat and, last but not least, radiation. We'll take them one by one.

Conduction is important in some solids – think of how a cold metal spoon placed in a pot of boiling water can become too hot to touch. In many fluids and gases, conduction is much less important. There are a few exceptions, such as mercury, a metal whose melting point is so low it exists as a liquid above -38 degrees Celsius, making it a handy temperature-marker in thermometers. But air's thermal conductivity is so low we can more or less count it out from this discussion.



Figure 1: Severe thunderstorm developing over the Welsh countryside one evening in August 2020. This excellent example of convection had strong enough updraughts to produce hail up to 2.5 cm in diameter. (Source: John Mason)

Hot air rises – that's why hot air balloons work, because warm air is less dense than its colder surroundings, making the artificially heated air in the balloon more buoyant and thereby creating a convective current. The same principle applies in nature: convection is the upward transfer of heat in a fluid or a gas. 

Convection is highly important in Earth's atmosphere and especially in its lower part, where most of our weather goes on. On a nice day, convection may be noticed as birds soar and spiral upwards on thermals, gaining height with the help of that rising warm air-current. On other days, mass-ascent of warm, moist air can result in any type of convective weather from showers to severe thunderstorms with their attendant hazards. In the most extreme examples like supercells, that convective ascent or updraught can reach speeds getting on for a hundred miles per hour. Such powerful convective currents can keep hailstones held high in the storm-cloud for long enough to grow to golfball size or larger.


Advection is the quasi-horizontal transport of a fluid or gas with its attendant properties. Here are a couple of examples. In the Northern Hemisphere, southerly winds bring mild to warm air from the tropics northwards. During the rapid transition from a cold spell to a warm southerly over Europe in early December 2022, the temperatures over parts of the UK leapt from around -10C to +14C in one weekend, due to warm air advection. Advection can also lead to certain specific phenomena such as sea-fogs – when warm air inland is transported over the surrounding cold seas, causing rapid condensation of water vapour near the air-sea interface.


Figure 2: Advection fog completely obscures Cardigan Bay, off the west coast of Wales, on an April afternoon in 2015, Air warmed over the land was advected seawards, where its moisture promptly condensed over the much colder sea surface.

Latent heat

Latent heat is the thermal energy released or absorbed during a substance's transition from solid to liquid, liquid to vapour or vice-versa. To fuse, or melt, a solid or to boil a liquid, it is necessary to add thermal energy to a system, whereas when a vapour condenses or a liquid freezes, energy is released. The amount of energy involved varies from one substance to another: to melt iron you need a furnace but with an ice cube you only need to leave it at room-temperature for a while. Such variations from one substance to another are expressed as specific latent heats of fusion or vapourisation, measured in amount of energy (KiloJoules) per kilogram. In the case of Earth's atmosphere, the only substance of major importance with regard to latent heat is water, because at the range of temperatures present, it's the only component that is both abundant and constantly transitioning between solid, liquid and vapour phases.


Radiation is the transfer of energy as electromagnetic rays, emitted by any heated surface. Electromagnetic radiation runs from long-wave - radio waves, microwaves, infra-red (IR), through the visible-light spectrum, down to short-wave – ultra-violet (UV), x-rays and gamma-rays. Although you cannot see IR radiation, you can feel it warming you when you sit by a fire. Indeed, the visible part of the spectrum used to be called “luminous heat” and the invisible IR radiation “non-luminous heat”, back in the 1800s when such things were slowly being figured-out.

Sunshine is an example of radiation. Unlike conduction and convection, radiation has the distinction of being able to travel from its source straight through the vacuum of space. Thus, Solar radiation travels through that vacuum for some 150 million kilometres, to reach our planet at a near-constant rate. Some Solar radiation, especially short-wave UV light, is absorbed by our atmosphere. Some is reflected straight back to space by cloud-tops. The rest makes it all the way down to the ground, where it is reflected from lighter surfaces or absorbed by darker ones. That's why black tarmac road surfaces can heat up until they melt on a bright summer's day.


Figure 3: Heat haze above a warmed road-surface, Lincoln Way in San Francisco, California. May 2007. Image: Wikimedia Commons.

Energy balance

What has all of the above got to do with global warming? Well, through its radiation-flux, the Sun heats the atmosphere, the surfaces of land and oceans. The surfaces heated by solar radiation in turn emit infrared radiation, some of which can escape directly into space, but some of which is absorbed by the greenhouse gases in the atmosphere, mostly carbon dioxide, water vapour, and methane. Greenhouse gases not only slow down the loss of energy from the surface, but also re-radiate that energy, some of which is directed back down towards the surface, increasing the surface temperature and increasing how much energy is radiated from the surface. Overall, this process leads to a state where the surface is warmer than it would be in the absence of an atmosphere with greenhouse gases. On average, the amount of energy radiated back into space matches the amount of energy being received from the Sun, but there's a slight imbalance that we'll come to.

If this system was severely out of balance either way, the planet would have either frozen or overheated millions of years ago. Instead the planet's climate is (or at least was) stable, broadly speaking. Its temperatures generally stay within bounds that allow life to thrive. It's all about energy balance. Figure 4 shows the numbers.

Energy Budget AR6 WGI Figure 7_2

Figure 4: Schematic representation of the global mean energy budget of the Earth (upper panel), and its equivalent without considerations of cloud effects (lower panel). Numbers indicate best estimates for the magnitudes of the globally averaged energy balance components in W m–2 together with their uncertainty ranges in parentheses (5–95% confidence range), representing climate conditions at the beginning of the 21st century. Figure adapted for IPCC AR6 WG1 Chapter 7, from Wild et al. (2015).

While the flow in and out of our atmosphere from or to space is essentially the same, the atmosphere is inhibiting the cooling of the Earth, storing that energy mostly near its surface. If it were simply a case of sunshine straight in, infra-red straight back out, which would occur if the atmosphere was transparent to infra-red (it isn't) – or indeed if there was no atmosphere, Earth would have a similar temperature-range to the essentially airless Moon. On the Lunar equator, daytime heating can raise the temperature to a searing 120OC, but unimpeded radiative cooling means that at night, it gets down to around -130OC. No atmosphere as such, no greenhouse effect.

Clearly, the concentrations of greenhouse gases determine their energy storage capacity and therefore the greenhouse effect's strength. This is particularly the case for those gases that are non-condensing at atmospheric temperatures. Of those non-condensing gases, carbon dioxide is the most important. Because it only exists as vapour, the main way it is removed is as a weak solution of carbonic acid in rainwater – indeed the old name for carbon dioxide was 'carbonic acid gas'. That means once it's up there, it has a long 'atmospheric residency', meaning it takes a long time to be removed. 

Earth’s temperature can be stable over long periods of time, but to make that possible, incoming energy and outgoing energy have to be exactly the same, in a state of balance known as ‘radiative equilibrium’. That equilibrium can be disturbed by changing the forcing caused by any components of the system. Thus, for example, as the concentration of carbon dioxide has fluctuated over geological time, mostly on gradual time-scales but in some cases abruptly, so has the planet's energy storage capacity. Such fluctuations have in turn determined Earth's climate state, Hothouse or Icehouse – the latter defined as having Polar ice-caps present, of whatever size. Currently, Earth’s energy budget imbalance averages out at just under +1 watt per square metre - that’s global warming. 

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one component to another it can be neither created nor destroyed. Self-evidently, the "isolated" part of the law must require that the sun and the cosmos be included. They are both components of the system: without the Sun as the prime energy generator, Earth would be frozen and lifeless; with the Sun but without Earth's emitted energy dispersing out into space, the planet would cook, Just thinking about Earth's surface and atmosphere in isolation is to ignore two of this system's most important components.

The Second Law of Thermodynamics does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. To reiterate, the qualifier term, 'net', is the important one here. In the case of the Earth-Sun system, it is again necessary to consider all of the components and their interactions: the sunshine, the warmed surface giving off IR radiation into the cooler atmosphere, the greenhouse gases re-emitting that radiation in all directions and finally the radiation emitted from the top of our atmosphere, to disperse out into the cold depths of space. That energy is not destroyed – it just disperses in all directions into the cold vastness out there. Some of it even heads towards the Sun too - since infra-red radiation has no way of determining that it is heading towards a much hotter body than the Earth,

Earth’s energy budget makes sure that all portions of the system are accounted for and this is routinely done in climate models. No violations exist. Greenhouse gases return some of the energy back towards Earth's surface but the net flow is still out into space. John Tyndall, in a lecture to the Royal Institution in 1859, recognised this. He said:

Tyndall 1859

As long as carbon emissions continue to rise, so will that planetary energy imbalance. Therefore, the only way to take the situation back towards stability is to reduce those emissions.

Update June 2023:

For additional links to relevant blog posts, please look at the "Further Reading" box, below.

Last updated on 29 June 2023 by John Mason. View Archives

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Comments 1526 to 1550 out of 1613:

  1. Gootmud @1522... There is an entire body of research related to precisely this topic known as attribution research. Your lack familiarity of the science shouldn't lead to the conclusion that "we can't explain causally." On the contrary, the overall causality of the shift in distribution is extremely well-known. The only place uncertainties appear are the chances that any given indivual weather event is driven by human causation. But even there, attribution research is demonstrating increasingly how much more likely these are to be primarily a result of the rise of CO2 concentrations in the atmosphere.

  2. Gootmud:

    Discussions of extreme events are probably better placed on this thread (after reading the original post):

  3. Wading through over 1,500 comments covering 12 years is a difficult and daunting task. So is reading almost 100 pages of Gerlich & Tscheuschner’s paper. There is so much misinformation and misunderstanding filled with distractions, red herrings, and wild geese, all mixed in with the good information, that it is hard to distill and address the fundamental problem. One hardly knows where to begin. But the core misunderstanding, equilibrium, is revealed in the quote from the abstract of G&T’s paper as shown above in the statement of the myth, as well as in Figure 32 of their paper.

    Increasing greenhouse gas (GHG) concentrations causes global warming by reducing radiant energy loss to space. The global energy balance is upset, and the planet warms until the balance is restored. The myth about the 2nd law is based upon an incorrect description of the global energy balance. As GHG increases, the atmospheric system, including the surface of the Earth, is not “radiatively equilibrated” until after warming occurs. Global warming is in accordance with both the 2nd law and the 1st law of thermodynamics - conservation of energy - as the atmosphere changes.
    Input = Output + Accumulation

  4. I am confused, of course.  According to greenhouse effect theory, about 50% of the radiation from the earth that CO2 captures is re-radiated back to the earth or somewhere in the atmosphere and recaptured.  I didn't know an object could be made hotter by reflecting its own radiation back on it.  Can someone explain that to me, please? Thanks.


    [BL] Yes, you certainly are confused, and your pattern of posing questions without reading the material available to you is very tiresome.

    First, I suggest that you read up a bit on radiative transfer, and learn about how reflection is not the same things as absorption followed be re-radiation. Mixing up reflection and re-radiation is a pretty basic error, and tells me that you have a very poor understanding of some basic physics.

    For the specifics about the greenhouse effect, scaddenp's comment (second after yours) points to a good post.

    As to your "an object could be made hotter" comment - does it occur to you that the earth's surface  receives heat from the sun at a pretty constant rate, and you can heat it up by reducing the rate that heat is lost back up through the atmosphere? Scaddenp's question about how a blanket can help keep you warm is a good starting point.

    If you really want answers, you would be far better off explaining what you do understand (or think you understand), rather than asking the kind of questions you've been asking. Unless you engage in serious discussion, expect to see moderation applied to your posts.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts or intentionally misleading comments and graphics or simply make things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.


  5. Likeitwarm 

    It sounds like the energy captured by greenhouse gases changes the Earth's energy balance. Without the greenhouse gases, Earth would freeze. From the page, "he Second Law does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. That qualifier term, 'net', is the important one here. The Earth alone is not a "closed system", but is part of a constant, net energy flow from the Sun, to Earth and back out to space. Greenhouse gases simply inhibit part of that net flow, by returning some of the outgoing energy back towards Earth's surface.

    The myth that the greenhouse effect is contrary to the second law of thermodynamics is mostly based on a very long 2009 paper by two German scientists (not climate scientists), Gerlich and Tscheuschner (G&T). In its title, the paper claimed to take down the theory that heat being trapped by our atmosphere keeps us warm. That's a huge claim to make – akin to stating there is no gravity."

    More though, it seems that melting albedo on the  Arctic Sea allows solar radiation to warming the ocean, which is something else to consider. I'm not a scientist, just interested.

  6. "Can someone please explain that to me?" Um, I would assume that you put a blanket on your bed at night to keep warm? How do you think that works? (Your body is irradiated in infrared). Since there are explanations here (the article) and plenty of others around the internet (eg here is a very good one), then I wonder how much you want to know the answer.

  7. scaddenp at 07:01 AM on 7 June 2023
    2nd law of thermodynamics contradicts greenhouse theory

    I've forgotten  how to use this board and answer. I'm not clear on what you don't understand. The blanket analogy is a common metaphor because the Earth's heat is being trapped by greenhouse gases, not unlike Venus.

    I understand that the Earth warms and cools, primarily, by the Malankovich Cycles and trapped greenhouse gases. Is someone saying otherwise, and if so, how do they explain worldwide glacier melt and sea level rise?

  8. EddieEvans 1530 & scaddenp 1531
    My question was simply; can an object be made warmer by reflecting its own radiation back on it?
    It has nothing to do with all the other stuff you mentioned.

    scaddenp 1531
    I do want to know the answer.
    A blanket works by preventing convection of air near and heated by conduction from my body. My body generates heat due to its life processes. In the summer I might want that convection to occur in order to cool my body.
    CO2 does not stop convection of the air. So, it does not act as a blanket.

    EddieEvans 1530
    CO2 does not hold on to that energy. It loses it within milionths of a second by conduction of heat or emission of IR, most likely conduction via collisions, to get back to equillibrium with the air around it. Water vapor on the otherhand can hold on to it for a comparatively long time, at least until it rises via convection due to being heated and condenses at a higher altitude releasing the heat. The amount of energy, possibly returned to earth, if it makes it all the way to the surface, is but a fraction of what was originally emitted from the surface, especially with CO2 being only .04% of the air. CO2 emits much better than oxygen and nitrogen, so CO2 has a cooling effect. Emissivity is necessary for things to cool. Low emissivity makes thing have to get hotter in order to emit IR. I would be inclined to say oxygen and nitrogen having much lower emissivity are the real greenhouse gasses as they would hold on to the heat longer. The other things you mention may be. But, I digress. First, I just want to hear/read the answer to my question.



    [BL] I have already tried to correct you on your confusions between "reflection" and "absorption and re-emission". Clearly you are not willing to let go of your misunderstandings.

    The answer to your question does indeed have very much to do with the things that people are telling you. You are refusing to listen to anything that is outside the mental box you have put yourself in. That leaves you blind to the correct answers to your questions.

    Your comments about CO2 vs. water vapour only further illustrate your poor understanding.

    Before you can learn an answer to your "question" there is much you need to unlearn.


  9. Sysop 1529

    Why can no body just answer my simple question?  Seems that thisis getting blown way out of proportion.  Sorry my question was so offensive.


    [BL]  You were pointed to a thorough explanation of how adding an object that absorbs and re-radiates IR radiation will heat an object that is being primarily heated by the sun. Here is is again:

    If you are not willing to read the references that people are providing - references that clearly answer your question and clarify your misunderstandings - then you are only wasting people's time.


  10. Likeitwarm @1529
    It’s easy to understand how one could be confused by this myth. It takes some serious study to sort through all of the distractions that are posed by Gerlich & Tscheuschner’s paper and discussed in over 1500 posts in this thread, especially since the little understood 2nd law of thermodynamics is invoked incorrectly as one of the main distractions.

    As I mentioned @1528, the 1st law of thermodynamics - conservation of energy – is applied.
    Input = Output + Accumulation

    For the global system of the surface and atmosphere, conservation of energy is:
    Solar in = Solar reflected + Radiant Energy Out from greenhouse gases + Radiant Energy Out from Earth’s surface + Accumulation

    When input = output, the energy is balanced and accumulation = zero. As EddieEvans @1530 mentions, it’s all about changes to the energy balance. The blanket analogy is an example of affecting the energy balance, although it does not describe the mechanism of radiant energy.
    Increasing greenhouse gas concentrations reduce radiant energy loss to space from the cold upper atmosphere. That upsets the global energy balance. Warming occurs until the energy loss to space, including radiant energy from the surface at specific wavelengths that are transparent to greenhouse gases, increases and the energy balance is restored.

    The 2nd law of thermodynamics describes limitations on how energy can be used in forms of heat and work. The problem with the myth is that it is based on an incorrect description of global warming. G&T’s paper describes modern global warming theory as “radiatively equilibrated”. It claims that the atmosphere acts as a perpetual heat pump that transfers heat from the cold stratosphere to the warm surface. G&T introduce distraction with a long discussion about the technical distinction between heat and energy, and a very long misrepresentation of global warming theory. However, since the energy balance is upset by increasing greenhouse gas concentrations, it is not equilibrated. Neither is global warming perpetual. The external energy source is the sun. Additional warming will stop when greenhouse gas concentrations stop rising and the equilibrium energy balance is restored at an elevated surface temperature.

  11. Likeitwarm @1533
    You are correct that CO2 does not hold onto the radiant energy that it absorbs. By Kirchoff’s law, absorptance = emittance. But Kirchoff’s law has a caveat – at thermal equilibrium, which involves the collisions between molecules. However, your description about the importance of water vapor is not correct. The radiant energy mechanism for water vapor is similar to CO2, but the energy emitted to space is greater because it is emitted at warmer temperatures of the troposphere. By Beer’s law, the low concentration of CO2 is sufficient to create a cold emitting layer in the tropopause. Your discussion of emissivity gets lost in descriptions of cooling, getting hotter, and oxygen and nitrogen being the real greenhouse gases. I suggest that you review the “Intermediate” rebuttal of the 2nd law myth. It has a very good description of the radiant energy mechanism of global warming.

  12. Leaving aside the exact mechanism of a blanket, it keeps you warm by slowing the heat loss from you body. The earth is exactly the same - it is warmed by sun more than internally because atmosphere is largely transparent to incoming radiation and opaque to outgoing radiation. You dont have to dance around complicated explanations. You can simply measure it. And Eli succinctly explains how in that link, yes , a body can be made hotter by reflecting radiation back.

    I'm curious - you have repeated myths all over the place which suggests somehow you got impression the science is wrong and then went searching for confirmation. Right back when you first heard about global warming, what made you decide that the science must be incorrect?


  13. Likeitwarm @1534,

    You ask "Why can no body just answer my simple question?"

    Your "simple question" was posed up-thread asking (as presented @1533 "Can an object be made warmer by reflecting its own radiation back on it?") to which the simple answer is "Yes" although your question is so poorly framed and using such inexact terminology that the "simple" answer is pretty meaningless. That is why you don't "just" get an answer to your "simple question."

    An object's temperature is defined and defined by the energy it emits to its surroundings. Also, emitted energy cools the object while energy absorbed warms it. If an object has its radiation somehow reflected back to itself while also still receiving energy that has been maintaining its temperature, it will "be made warmer."

    The interesting phenomenon in all this is the cause of the "reflecting its own radiation back" if the physics creating that energy flux is not actually 'reflection', which it isn't in this case. Such circumstance will require the "reflecting" agent to itself be "warmer" so what causes that. There in lies the cause of the greenhouse effect.

  14. @ Likeitwarm #1533

    Your dismissal of the blanket analogy  - "a blanket works by preventing convection of air near and heated by conduction from my body", demonstrates a gross misunderstanding of how the human body loses heat.

    If you lie outside with no clothes on on a cold day or night, your body will lose little heat due to conduction. Air is an utterly useless conductor of heat. Instread the human body loses almnost all heat by radiation - look up "radiative cooling". Then when you've done that, contemplate how frequently on winter mornings you've noticed cars covered in frost crystals but no grass frost. Some things are better at radiative cooling than others. Conduction within the metal body of the car makes sure it cools more evenly, but the cooling mechanism with respect to the surrounding air IS radiative.

    Anything that blocks that radiation through the surrounding air - by any mechanism - will give you a chance of survival - hence space-blankets, carried by many outdoor folks. It's also why we wear clothes and why on a hot summer's day we wear less of them.

  15. Likeitwarm @1533... You might want to take note that the earth does not shed heat to space via convection. It does so through radiation. 

  16. Also @1533... "CO2 does not hold on to that energy."

    CO2 does, though, slow the rate at which energy is emitted to space. Essentially, what greenhouse gases do is raise the altitude at which energy is emitted to space. In turn, it is the resulting thermal incline which determines the rise in surface temperature.


  17. To all who posted in response to my question in #1529,

    Thank you all for tolerating my ignorance.  I came here to learn and that I have.

    What I thought was a simple question was maybe not one and the answer required more thoughtful study than I gave it to begin with.

    I did read the post at and have a much better understanding of radiative heating, now.  I think I understand that you can add streams of radiation to heat a warmer object with a colder one, if that in fact is part of what Eli is teaching.

    On my original question, I was thinking an object isolated from the universe(not receiving radiation from another source) and surrounded by some imaginary material that somehow returned the objects own radiation to it.  I was thinking conservation and being in thermal equillibrium with itself that it would not get warmer. I see because of scaddenp's answer in #1537 that that is not true or I was not clear in #1529.

    @scaddenp #1537 "what made you decide that the science must be incorrect?"

    I don't know that I thought the science was wrong, I just did not understand how an object could increase its temperature with no other input.  I'm still puzzled somewhat.  I will require more study. Eli shows steady input of new energy to the plates and I meant an object with no other inputs. 

    I owe all a big apology to all for not being clear in #1529.

    Thank you all for the lessons.  I will study more before asking more questions.  Maybe I'll just ask for references if I can't find info on my own.


    [BL] Thank you for following that link, reading the material and having the honesty and courage to return to this site and and providing this feedback.

  18. Likeitwarm - wanting to learn is great - and frankly why this site exists. I was making assumptions about your priors on climate science because of multple posts in different topics. I am very curious about what leads non-scientists into "the science is wrong" mindset (fairly critical people that people dont do that in my own field) and how that originates. If this doesnt apply to you, then my apologies. No shortage of other people to ask.

  19. I know this post will technically be off topic, but is a direct answer to scaddenp's inquiry.

    scaddenp 1543 - I see there are many who claim their science is right on both sides of the climate argument and everyone presents what appears to be good arguments to support their position.  I know that it is normal human behavior to have some bias toward one's own argument.  This is the opinion of all that I talk to in the non-scientist group.  Many don't know who to believe and pay any attention to what can be a confusing subject.  Myself, not being a well educated physicist, feel at a disadvantage.  My math is only basic, algebra 2 in high school.  Someone very good with math could easily pull the wool over my eyes with complex formulas involved in this science.  I am a machine designer/cost anayizer/production programmer/personel manager for the production of an old product who got there by the seat of my pants.  I have been retired now 6 years.

    I just could not believe a trace gas of .04% of the atmosphere could have such an effect, especially with the history of CO2 volumes and estimated historic atmospheric temperatures not jiving with each other.  There are so many factors that have different affects, it is hard to discern which are reasonable  causes.  With "global" temperatures reportedly being fairly flat since 1998 and CO2 continuing to rise at a steady rate and the U.S. Government spending $375B, recently, towards climate initiatives(some is my tax money and yours if you pay U.S. taxes), I am still seeking the truth to inform my congress of the truth that I see.  I do not believe we should be destroying the world economies and spending vast amounts of the public treasure when there is so much disagreement on what is causing climate change.  That was the opinion of Dr. Allen Carlin of the EPA in 2009.  He called the evidence for AWG incomplete.

    I know you guys that support this site put a lot of time and effort into the science and site.  That's why I come here to investigate.

    If there is a better place to have this conversation, please let me know.


    [BL] For the "it's a trace gas" discussion, go to this post.

    To learn why measuring CO2 as a percent of the total gases is not the correct method when it comes to radiation transfer, go to this post. There is a certain level of mathematics in some of that, but the simple experiment with the dye in solution should be easy to follow.

    For the "it hasn't warmed since 1998" canard, go to this post.

    In general, the next time you find yourself wondering about a new topic, you should probably go to the Most Used Climate Myths section in the left sidebar of every page here. If it's not on the top 10 ("It hasn't warmed since 1998" is #9 there), then click on "View All Arguments" to get the entire list.

    You can also use the search box to search all the myth rebuttals, blog post, and (with an extra click) all the comments for the search terms you enter.


  20. There is no scientific source claiming that temperatures have been "fairly flat" since 1998.

  21. Likeitwarm... On the 0.04% topic, looking from space to the surface, a concentration of 0.04% is essentially opaque.

    You can think of it this way... a square of 1000x1000 molecules = 1 million molecules. Right? At 0.04% that means 400 will be CO2 randomly distributed. Add the next layer of 1M molecules, and 400 more randomly distributed CO2 molecules. And so on.

    It doesn't take very long before there is a near 100% chance that every one of the positions in that 1000x1000 grid will end up being a CO2 molecule.

    When you're talking about the full vertical profile of the atmosphere, 400ppm is a very significant concentration, significant because of the specific radiative properties of CO2.

  22. Likeitwarm... Not sure what you mean by "especially with the history of CO2 volumes and estimated historic atmospheric temperatures not jiving with each other."

    CO2 volumes and global temperature actually corrolate very well. It's one of the key reasons why we know our human emissions of CO2 are responsible for modern warming.

  23. Likeitwarm @1544

    How about signing-up for our free online course (MOOC) "Denial101x - Making sense of climate science denial"? The course - created in collaboration with the University of Queensland - explains the basics of climate science and which techniques are at play to sow doubt about human-caused global warming. The MOOC is offered in self-paced mode and is open until end of February 2024.

    Another helpful MOOC is "Climate Change: The Science and Global Impact" also offered on the edX platform in self-paced mode. I wrote a blog post about it when I "binge-watched" all the lectures in January 2021 and can really recommend it if you want to dig deeper.

  24. LikeitWarm. Thanks very much for your response and I hope the moderators wills tolerate me continuing thediscussion. So you think what sounds like a very small amount of gas triggered your skeptcism? You also state "I do not believe we should be destroying the world economies..." That is also an interesting statement. What do you think informs your opinion that transitions from fossil fuels would destroy the world's economies? If you can think back to when that idea first formed, it would be good.

    Also, since you are without a physics background, can ask you what your intuition would be about how far a photon of appropriate wavelength would travel up through the atmosphere on average before encountering a CO2 molecule. Please dont look it up or attempt to calculate it- I am really interested in your intuition on this, not your knowledge.


    [BL] Although we try to keep discussions on topic, we will allow some latitude here.

    In order to maintain a bit of on-topic discussion, I would suggest that likeitwarm also provide a bit more of an indication of how his intuition (or materials he read elsewhere) led to his initial statement "I didn't know an object could be made hotter by reflecting its own radiation back on it. "

    In particular, since the process of reflecting radiation (or absorbing it and re-emitting it back towards the original object) requires that energy be directed back to the object, what did likeitwarm think would happen to that energy?

  25. Rob Honeycutt 1547 Unrelatedness of co2 and temp does look like CO2 did not affect temperatures much at all.  looks like 1998 was a peak high temp and now it's back up to that peak 25 years later.  shows that averaged raw temperatures have been fairly flat since 2015.  The 2 groups of warm in 2015 & 2016 are summer months.  I know that's only 8 years, fairly short, but I would have expected temps to reflect the increase in CO2 of about 2.5 ppm per year.

    These things are put out there by people I don't think are dummies.  I wonder if they would put them out there if they knew they were wrong?


    [RH] Activated links

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