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

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Climate Hustle

How do we know more CO2 is causing warming?

What the science says...

Select a level... Basic Intermediate Advanced

An enhanced greenhouse effect from CO2 has been confirmed by multiple lines of empirical evidence.

Climate Myth...

Increasing CO2 has little to no effect
"While major green house gas H2O substantially warms the Earth, minor green house gases such as CO2 have little effect.... The 6-fold increase in hydrocarbon use since 1940 has had no noticeable effect on atmospheric temperature ... " (Environmental Effects of Increased Atmospheric Carbon Dioxide)

Predicting the Future

Good scientific theories are said to have ‘predictive power’. In other words, armed only with a theory, we should be able to make predictions about a subject. If the theory’s any good, the predictions will come true.

Here’s an example: when the Table of Elements was proposed, many elements were yet to be discovered. Using the theory behind the Periodic Table, the Russian chemist Dmitri Mendeleev was able to predict the properties of germanium, gallium and scandium, despite the fact they hadn’t been discovered.

The effect of adding man-made CO2 is predicted in the theory of greenhouse gases. This theory was first proposed by Swedish scientist Svante Arrhenius in 1896, based on earlier work by Fourier and Tyndall. Many scientist have refined the theory in the last century. Nearly all have reached the same conclusion: if we increase the amount of greenhouse gases in the atmosphere, the Earth will warm up.

What they don’t agree on is by how much. This issue is called ‘climate sensitivity’, the amount the temperatures will increase if CO2 is doubled from pre-industrial levels. Climate models have predicted the least temperature rise would be on average 1.65°C (2.97°F) , but upper estimates vary a lot, averaging 5.2°C (9.36°F). Current best estimates are for a rise of around 3°C (5.4°F), with a likely maximum of 4.5°C (8.1°F).

What Goes Down…

The greenhouse effect works like this: Energy arrives from the sun in the form of visible light and ultraviolet radiation.  The Earth then emits some of this energy as infrared radiation. Greenhouse gases in the atmosphere 'capture' some of this heat, then re-emit it in all directions - including back to the Earth's surface.

Through this process, CO2 and other greenhouse gases keep the Earth’s surface 33°Celsius (59.4°F) warmer than it would be without them. We have added 42% more CO2, and temperatures have gone up. There should be some evidence that links CO2 to the temperature rise.

So far, the average global temperature has gone up by about 0.8 degrees C (1.4°F):

"According to an ongoing temperature analysis conducted by scientists at NASA’s Goddard Institute for Space Studies (GISS)…the average global temperature on Earth has increased by about 0.8°Celsius (1.4°Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade."

The temperatures are going up, just like the theory predicted. But where’s the connection with CO2, or other greenhouse gases like methane, ozone or nitrous oxide?

The connection can be found in the spectrum of greenhouse radiation. Using high-resolution FTIR spectroscopy, we can measure the exact wavelengths of long-wave (infrared) radiation reaching the ground.

 

Figure 1: Spectrum of the greenhouse radiation measured at the surface. Greenhouse effect from water vapour is filtered out, showing the contributions of other greenhouse gases (Evans 2006).

Sure enough, we can see that CO2 is adding considerable warming, along with ozone (O3) and methane (CH4). This is called surface radiative forcing, and the measurements are part of the empirical evidence that CO2 is causing the warming.

...Must Go Up

How long has CO2 been contributing to increased warming? According to NASA, “Two-thirds of the warming has occurred since 1975”. Is there a reliable way to identify CO2’s influence on temperatures over that period?

There is: we can measure the wavelengths of long-wave radiation leaving the Earth (upward radiation). Satellites have recorded the Earth's outbound radiation. We can examine the spectrum of upward long-wave radiation in 1970 and 1997 to see if there are changes.

 

Figure 2: Change in spectrum from 1970 to 1996 due to trace gases. 'Brightness temperature' indicates equivalent blackbody temperature (Harries 2001).

This time, we see that during the period when temperatures increased the most, emissions of upward radiation have decreased through radiative trapping at exactly the same wavenumbers as they increased for downward radiation. The same greenhouse gases are identified: CO2, methane, ozone etc.

The Empirical Evidence

As temperatures started to rise, scientists became more and more interested in the cause. Many theories were proposed. All save one have fallen by the wayside, discarded for lack of evidence. One theory alone has stood the test of time, strengthened by experiments. 

We know CO2 absorbs and re-emits longwave radiation (Tyndall). The theory of greenhouse gases predicts that if we increase the proportion of greenhouse gases, more warming will occur (Arrhenius).

Scientists have measured the influence of CO2 on both incoming solar energy and outgoing long-wave radiation. Less longwave radiation is escaping to space at the specific wavelengths of greenhouse gases. Increased longwave radiation is measured at the surface of the Earth at the same wavelengths.

These data provide empirical evidence for the predicted effect of CO2.

Basic rebuttal written by GPWayne


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 1 August 2015 by MichaelK. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

A good summation of the physics of radiative forcing can be found in V. Ramanathan's Trace-Gas Greenhouse Effect and Global Warming.

Comments

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Comments 301 to 350 out of 358:

  1. Tom Curtis @300.  Thank you.  Can you tell me if the basic equation is a curve-fitting equation (ie, without the sensitivity factor), or is it derived from fundamental physics?  I can't seem to locate something that ought to be related, say, to the partial derivative of enthalpy wrt T at constant p, (∂H/∂T)p.  Have you seen something of the sort?  My apologies if this is a duplicate.  The page did not update with my submission.

    Response:

    [JH] Your prior two duplicate posts have been deleted.

  2. Tom Curtis @300. Thank you. Can you tell me if the formula for radiative forcing is a curve-fitting equation (ie, without the sensitivity factor), or is it derived from fundamental physics? I can't seem to locate something that ought to be related, say, to the partial derivative of enthalpy wrt T at constant p, . Have you seen something of the sort? My apologies if this is a duplicate. The page did not update with my submission, until I took the symbols out.

    Response:

    [JH] They all appeared. Two of the duplicate posts have been deleted.

  3. Tom Curtis @ 300  I've been trying to post a physics question, but the page won't update with my submission, so I'll just use English. Does the forcing equation arise from fundamental physics to your knowledge, or is it something from curve-fitting efforts?  Is it possible to put partial differential equations in this text-box?

    Response:

    [JH] All of your prior posts were visible. 

  4. Is this post system working?  My last three tries have not produced a post after Tom Curtic @ 300.

    Response:

    [JH] Yes, the system is working. All of your comments have appeared.

    [RH] What's probably happening is, he's posting at the end of one page and the comments is showing up on the new following page. That one trips people up from time to time.

  5. DrBill@304,

    Please show a bit more respect to Mr Curtis by taking care to spell his name correctly. The fact that Mr Curtis in one of the most accomplished commenters on this site calls for even more care.

    Then people will show more respect to you and your comments, reciprocally.

  6. chriskoz @305 while I agree that correct spellings of names is a matter of courtesy, DrBill spelled my name correctly in three posts prior to that @304, so it is reasonable to assume that that mispelling was entirely inadvertent.  Further, "most accomplished" is a compliment that suggests significant acheivement in a scientific field, whereas I lack even a BSc.  I take that as a compliment to my depth of understanding of the topic, for which thankyou.  However, while I think is deserved, that depth is limited, especially relative to anybody with a PhD in atmospheric physics.

  7. DrBill @301, the formula for radiative forcing was not directly derived from fundamental physics.  Rather, the change in Outgoing Long Wave Radiation at the tropopause, as corrected for radiation from the stratosphere after a stratospheric adjustment (which is technically what the formula determines), was calculated across a wide range of representative conditions for the Earth using a variety of radiation models, for different CO2 concentrations.  Ideally, the conditions include calculations for each cell in a 2.5o x 2.5o grid (or equivalent) on an hourly basis, with a representative distribution and type of cloud cover, although a very close approximationg can be made using a restricted number of latituded bands and seasonal conditions.  The results are then have a curve fitted to it, which provides the formula.  The same thing can be done with less accuracy with Global Circulation Models (ie, climate models).  

    The basic result was first stated in the IPCC FAR 1990.  That the CO2 temperature response (and hence forcing) has followed basically a logarithmic function was determined in 1896 by Arrhenius from empirical data.  The current version of the formula (which uses a different constant) was determined by Myhre et al (1998).   They showed this graph:

     

    The formula breaks down at very low and very high CO2 concentrations.

  8. Just a quick thanks to Tom CurtiS, JH and RH.  FWIW, I tried several ways to make the page show up and not until this evening did I try to quit and relog in, and that seemed to work.  I agree with chriskoz about courtesy and thank Tom for recognizing a typo.  If JH/RH don't mind, I wouldn't mind seeing my 302,3,4 deleted; 301 had all I had in mind to ask, as it had reference to the partial derivatives that result in Cp.  It's late here, for me, and I'll post a new submission tomorrow.

  9. The free energy change of a process is the sum of energy and entropy*temp, and is generally regarded as happening spontaneously when the sum is <0. A version of free energy is that of Helmholtz, whose summation is ΔF (or ΔA) = ΔE -TΔS, but another is the Gibbs ΔG=ΔH-TΔS. The difference between the two expressions is that ΔE and ΔH are not the same thing: ΔE, as I've been used to thinking of it, is now named ΔU, while ΔH = ΔU + Δ(pV).  In short, Gibbs Energy includes PV work, while Helmholtz does not when evaluating the possibility of a spontaneous process.  A view of this, which I hold, is that the ΔE portion emphasizes the radiative changes, while the ΔH portion includes pV work.

    Since the atmosphere not only radiates energy in trying to come to equilibrium, but also does substantial pV work, I believe a model that seems to rely on radiative transfers is not sufficient to explain the climate.

    In support of this, I refer the reader to the 1962 and 1976 editions of The U.S. Standard Atmosphere.  Google links lead to pdf's and I don't know if anyone wants to wade through dozens of derivations and perhaps 60 pages of notes and explanations, so I won't burden this post with the links themselves, unless someone wants them.  In summary, the NASA, NOAA, and a host of other sponsors and contributors determine a model of the atmosphere based on gravity and Cp ((∂H/∂T)p [see @301], and regard CO2, methane and NOx as "trace gases" with no significant impact on temperature.  Similarly, the lapse rate -g/Cp suggests the derivation from Gibbs.

    The dichotomy is strong enough to get out the old slide rule, imo, and attempt to recognize something fundamental like Cp in the forcing equation.  I have not so far.

  10. DrBill @309, radiation models are not climate models.  They determine the transfer of radiant energy within the atmosphere given a set of conditions which include well mixed greenhouse gases present, water vapour present, clouds present, and atmospheric density and temperature profiles.  They were first developed for the US Airforce as part of its effort to develop infrared guided missiles (Sidewinders), and were later used for the development of FLIR systems, for interpreting microwave radiation from the atmosphere as temperature, and of course, for determining IR radiation from the atmosphere.  As such, they can determine the change in Outgoing Infrared Radiation given a change in atmospheric profile, where such changes at the tropopause are also the change in atmospheric forcing.

    In 1970, LBL radiation models could produce results as accurate as this if fed detailed atmospheric profile data gathered by a weather balloon:

    By 2008 they could produce results with accuracies like this with more approximate profile information:

    Further, for determining radiative forcing, the models are generally set with a temperature profile determined by radiative/convective equilibrium in the troposphere (ie, one that follows the adiabatic lapse rate), and with a radiative equilibrium above the tropopause, and therefore complies with the requirements of the laws of thermodynamics (including that for Gibbs free energy).

    Of course, radiative models only determine forcing, and not the temperature response to forcing within the troposphere.  (They can be used to calculate the initial temperature responce in the stratosphere and above were radiative equilibrium obtains.)

    Global Circulation Models, which determine temperature responce as well as radiative response, also include approximations to the laws of thermodynamics governing movement of gases under gravity.  (Approximations only given the limits of cell size required to make the models able to operate on modern super computers.)

    Response:

    [JH] Spencer Wart has detailed the history of General Circulation Models here

  11. Tom Curtis at 11:04 AM on 20 April, 2017
    " the formula for radiative forcing was not directly derived from fundamental physics. Rather, the change in Outgoing Long Wave Radiation at the tropopause, as corrected for radiation from the stratosphere after a stratospheric adjustment (which is technically what the formula determines), was calculated across a wide range of representative conditions for the Earth using a variety of radiation models, for different CO2 concentrations."

    This seems very odd to me. You use a formula for radiation, not based on fundamental physics?

    And the changes in Outgoing Long Wave Radiation is corrected for radiation in the stratosphere, after you adjust the stratosphere in what way?

    This is then used to calculate surface temperature, or some influence on it?

    Isn´t that an example of doing radiation physics backways? To me it seems like you use the effect as a cause if you start at the last point where radiation leaves the climate system.

    Do I understand it right that you adjust stratospheric radiation to co2 concentration, then correct Outgoing Long Wave radiation to that, then use that information as a cause, or part of the cause, of surface temperature?

    Is the infrared radiation of the stratosphere the cause of infrared radiation in the tropopause, and the infrared radiation of the tropopause is the cause of infrared radiation from the surface? I see you write radiative forcing, but as I understand it, radiative forcing is still a change of infrared radiation.

    Can you connect that to solar radiation? I guess this chain reaction stops at the surface since it is not possible for the surface to have an effect on heat from the sun. I thought a model had to be done in the other way around, you start with the heat source and find the amount of absorbed heat in the surface. Then continue to estimate the heat absorbed by the atmospheres different layers and then it leaves the system. That´s how I learned in school, but that is a long time ago, I guess something has changed.

    But I think it is counterproductive to not use fundamental physics to explain temperature, or Outgoing Longwave Radiation. When we learned about solar radiation and the temperature of the atmosphere, our teacher used a basic model for heat. He used the surface temperature and the inverse square law. He said that the solar heat is absorbed and emitted according to the inverse square law and the difference in temperature, or heat flux, is the way to describe earth as a steam engine. That is fundamental physics and it gives the right amount of infrared radiation observed by satellites. Just use the difference and divide whats left by four.

    When you say that you use a model doing it backways, in my view, and that it doesn´t use fundamental physics that describe heat, why is your way of doing it better?

  12. I had a look at the link to general circulation models. After reading that my conclusion is that it seems like we are not much wiser

    "For all the millions of hours the modelers had devoted to their computations, in the end they could not say exactly how serious future global warming would be. They could only say that it was almost certain to be bad, and unless strong steps were taken soon, it might well be an appalling catastrophe."

    This does not convince me that climate models are doing it right by using backwards calculations where emitted radiation is causing the temperature of layers below.

    After reading this I don´t get much wiser either:

    https://pubs.giss.nasa.gov/docs/2011/2011_Hansen_ha06510a.pdf

    It seems like he is saying that if the thermal radiation emitted from the atmosphere, it causes the temperature to increase?

    He says that observed heat from the earth is not in balance, the heat flux from the sun that heats earth is larger than the amount of heat that earth emit to space. I find that logical, the earth is not equally warm throughout, and then it has to emit less energy. Only when the system is equally warm in every point inside, it emits as much heat to space as it receives. If we compare to a steam engine and the troposphere is the waterfilled cylinder, then it has to have an even temperature from the surface all the way up to the tropopause before the heat flux is equal to what the sun deliver to the surface. 

    I really don´t understand this radiative forcing and radiative imbalance, how does it work? How can less heat emitted from the atmosphere cause more heat elsewhere? The more I read about it, the more confused I get.

    Hansen wrote about satellite measurements showing an imbalance of 6.5W/m^2 averaged over 5 years. Then he says it was thought to be implausible and they made instrumentation calibrations to align the devices with what the models say, 0.85W/m^2. 

    He says that the forcings is known accurately, but when measured it is corrected to follow the models. They don´t correct the models according to measurements?

    How can forcings be known accurately if they are not a result of measurements? Not any of the studies show how any numbers of forcing has been achieved. And I can´t find any descriptions of the heat flow the way I think it should be done, or rather, the way I like it. Just using measured temperature to find out how much heat there is in the different parts, and from there you can describe the heat flow. That is how we always have done it, and it works. Steam engine, it works perfectly for earth, why use anything else? My teacher must have been very smart, or dumb enough to keep it simple. I was directed here after talking to people in the march and they couldn´t answer my questions. I thought it was strange, so many people marching for science, but no one knew anything about heat, but they all carried signs about temperature increasing and climate problems. I always thought that the issue was about the atmosphere getting so hot that it came near to surface temperature, from top to bottom, because that is what it takes to heat something up usually. But this is just strange and now I think that it must be a good thing Trump won the election. I thought he said some stupid things, but he seems to act like he knows what he´s doing.

    I guess I won´t be coming back here anymore. Good Luck with your campaign, you are going to need it.

  13. It was supposed to say 

    -It seems like he is saying that if the thermal radiation emitted from the atmosphere decrease, it causes the temperature to increase?

  14. vatmark... It's rather interesting that you don't grasp this very simple concept but seem to believe that reflects poorly on the science and Hansen rather than you. It's not uncommon, though. We see a fair number of people who come here in a similar state and post extensive comments on how the entire global scientific community doesn't understands this stuff. People here patiently attempt to explain the science to the best of their abilities, and usually the person questioning the science either storms off, never to be heard from again, or gets so absurdly beligerent that we have to block them from posting.

    At some point, in their early education, surely all these folks had to take some science classes. Or, perhaps, many of these people have children who have to take science. If they go through a section and tell the teacher they're wrong, and mark the wrong answers on the tests... They fail the class. Everyone, I believe, generally would find this to be unacceptable. The child needs to learn the materials and understand the current science. And even the child, I would assume, would also understand when they didn't study hard enough or put in enough effort to pass the class.

    But somewhere these people grow into adults who, it seems fairly deliberately, choose to not accept the scientific materials, like vatmark here. He's seemingly concluding that the experts in this scientific matter are stating things wrong, even though he doesn't comprehend fundamentally simple science.

    So, at some point in their lives, there has to be a transition. A point or a period of time over which they move from understanding they don't understand the science to rejection of the science in order to avoid understanding or cover for the incapacity to understand it.

    I just find this whole process perpetually fascinating.

  15. vatmark @312, sorry for my delayed response.  I am suffering from poor health at the moment, and am finding it difficult to respond to involved posts in a timely manner.  Unfortunately this may mean a further delay in responding to two other posts directed to me by you on another thread, for which I also apologize.

    1)

    "This does not convince me that climate models are doing it right by using backwards calculations where emitted radiation is causing the temperature of layers below."

    I should hope not, as that is not what General Circulation Models (GCM) do.  Rather, they divide the ocean and atmosphere into a number of cells, and for each time step solve for all energy entering, absorbed and emitted from that cell, including energy transfers by radiation, latent heat, diffusion and convection.  In doing so, they maintain conservation of energy and momentum (or at least as close an approximation as they can maintain given the cellular rather than continuous structure of the world).  When they do this, properties of the simplified models of the greenhouse effect used primarilly for didactic purposes are found to emerge naturally, thereby showing those simplified models to capture essential features of the phenomenon.

    2)

    "He says that observed heat from the earth is not in balance, the heat flux from the sun that heats earth is larger than the amount of heat that earth emit to space. I find that logical, the earth is not equally warm throughout, and then it has to emit less energy. Only when the system is equally warm in every point inside, it emits as much heat to space as it receives."

    You have taken a reqirement for a body, heated externally, and equally from all directions and assumed it is a universal condition.  It is not.

    To take a simple example, if a spherical body having the same thermal conductivity throughout, bathed in a fluid of uniform temperature, but having a significant heat source at the center.  According to you it must have the same temperature throughout before energy in can equal energy out.  But, based on Fourier's law of conduction, if there is no temperature gradient, there is no movement of energy by conduction.  If follows that based on your theory, the heat from the heat source at the center can never leave, which must result in an infinite energy build up at the center.

    Your assumed requirement does not even describe such very simple models.  It has been falsified, in fact, since Fourier's experiments that led to his seminal work.  It certainly does not apply to the complicated situation of an atmosphere, or a large, massive rotating sphereoid heated intensely from one side, and situated in a heat bath of near zero degrees absolute, ie, to the Earth.

    Your claim is also refuted by the Earth itself, which has existed for long enough, with a very stable energy source, that it is in near thermodynamic equilibrium.  If your supposed condition held, then there would be no significant difference in temperature with altitude.  Despite that, ice has existed at altitude in the tropics for hundreds of thousands of years. 

    3)

    "Hansen wrote about satellite measurements showing an imbalance of 6.5W/m^2 averaged over 5 years. Then he says it was thought to be implausible and they made instrumentation calibrations to align the devices with what the models say, 0.85W/m^2."

    Satellite measurements currently suffer a disadvantage, in that while they are very accurate in showing relative changes in Total Solar Irradiance (TSI) and Outgoing Long Wave Radiation (OLR), they are fairly inaccurate in showing absolute values.  This was known from design specifications, and also by comparison of the data from instruments of the same, or different design over the same period, as here:

    That means, while we can know the annual change in the energy imbalance quite accurately, we cannot know it's absolute value from satellites alone.  Two different methods are used to compensate for this.  In the past, the values from climate models were used of necessity.  Since the advent of Argos, the rise in OHC is sufficienty well known that it can be used to calibrate the absolute energy imbalance.  Hanson discusses both methods (which approximately agree, and certainly agree far better than does either with the value from the satellites).  Further, the specific use of computers you mention was not Hanson's, but that of Loeb (2006).

    4)

    "How can forcings be known accurately if they are not a result of measurements? Not any of the studies show how any numbers of forcing has been achieved."

    Hanson does not say the forcings are known accurately.  Rather, he shows the Probability Density Functions of the forcings:

    As can be seen, the 95% confidence limits of the greenhouse gas forcing amount to a range of about 1 W/m^2, or approximately a third of the best estimate forcing.  In constrast, the aerosol forcing has a 95% confidence limit range of about 3 W/m^2, or just over twice the best estimate.

    5)

    "And I can´t find any descriptions of the heat flow the way I think it should be done, or rather, the way I like it."

    Given the level of understanding of thermodynamics shown by you in your claims about equal temperature, it is neither a surprise nor a problem that you cannot find descriptions of heat flow the way you like.  GCMs do use, however, the standard laws of thermodynamics, and of heat flow in its various forms.

  16. vatmark @311:

    1) 

    "This seems very odd to me. You use a formula for radiation, not based on fundamental physics?"

    The radiation models used to calculate radiative forcing are based on fundamental physics (ie, basic physical laws).  The actual radiative forcing, however, depends on things like extent and type of cloud cover, type of ground cover, surface temperature, etc.  These conditions cannot be directly calculated from fuandamental physics, but must be observed.  It follows that the radiative forcing also cannot be directly calculated from fundamental physics.

    2)

    "And the changes in Outgoing Long Wave Radiation is corrected for radiation in the stratosphere, after you adjust the stratosphere in what way?"

    Given a change in atmospheric concentration of a greenhouse gas, or of incoming insolation, the stratosphere will establish effective thermal equilibrium very quickly.  As a result it is convenient to define radiative forcing with the stratospheric adjustment.  You can do it differently.  The Instantaneious Radiative Forcing is calculated without a stratospheric adjustment, for example.  However, the values cited in the IPCC are for the adjusted Radiative Forcing.

    The stratospheric adjustment would be made by adjusting the stratospheric temperature by successive approximation until energy into the stratosphere equals energy out of the stratosphere, and the various levels of the stratosphere are in local thermodynamic equilibrium.  As noted above, I have seen an explicit technique for doing this, but do not currently remember it.

    3)

    "Isn´t that an example of doing radiation physics backways? To me it seems like you use the effect as a cause if you start at the last point where radiation leaves the climate system."

    You appear to be confused.  A change in radiative forcing can as easilly be due to a change in insolation (your forwards effect) as from a change in green hous gas concentration.  The radiative forcing is used because the tropopause is an easilly defined and measured energy boundary.  As such, it must satisfy the definition of conservation of energy - ie, that if more energy goes in than out, energy must be stored in some form within the boundary.  Given that the energy levels involved are not sufficient for large scale energy to matter conversion, the energy will be stored as heat, and consequently will result in an increase in temperature.  It is that fact that makes it possible to calculate the effects of changes in GHG concentration by using the concept of "radiative forcing".

    I will note that GCMs and radiative transfer models do not use "radiative forcing" to calculate the consequences of changed GHG concentrations, or solar irradiance.  They follow all the energy transfers in a step by step process as described in the preceding post.  It is only when we do not have access to GCMs (or in specific contexts radiative transfer models), or we want to calculate approximate results without waiting for the several days or weeks of a GCM run that we make use of radiative forcing.  

  17. ""Isn´t that an example of doing radiation physics backways?"

    I suspect you may be getting confused by the technical definitions here.

     

    The simple definition is:

    "The rate of energy change per unit area of the globe as measured at the top of the atmosphere"

    It is used as way to put the various sources of radiative change (GHG, aerosols, albedo, change in solar insolation) onto an equal footing (more or less). Dont confuse the way in how the change in a particular forcing is actually measured with how it is recalculated to express it as a change in TOA radiative forcing.

  18. The whole reason is that CO2 is the GHG that we can do something about. Even if not the main cause. The discussion is entertainment.

  19. There’s no such thing as the radiative greenhouse effect. I accept it’s a rather bold statement, so let me explain why;

    Do you agree that the heat flow equation (for plane parallel) is: Q = sigma * (T1^4 – T2^4) ?

    The net difference between the radiative ENERGY which is emitted from both surfaces will result in HEAT being transferred to the surface of the cooler object and this will result in the TEMPERATURE of the cooler surface increasing. It may also result in the TEMPERATURE of the warmer surface decreasing (if the warmer object does not have it’s own power source). Either way, HEAT will continue to be transferred to the cooler object until thermodynamic equilibrium is achieved, when Q =0. At this point no further HEAT is transferred, although both surfaces continue to emit ENERGY. The TEMPERATURE of both surfaces will thereafter remain constant.

    When confronted with this statement of truth, many climate experts will revert to the “restricted emissions” argument where the back radiation from the shell inhibits the warmer object from emitting it’s internal ENERGY thus causing the warmer object to HEAT itself and thus cause an increase in TEMPERATURE of the warmer surface.

    If this is your claim, show me the part in the HEAT FLOW equation where it states that the primary object, T1, stops emitting because it is prevented from doing so by the secondary object, T2?

    The heat flow equation states that T1 emits fully, at: sigma * T1^4, all of the time; it never has its energy “stopped up” inside of itself. And, the ENERGY from the 2nd body (if it's cooler than the 1st body) can’t act as HEAT. The 2nd body does not stop the 1st one from emitting. The 2nd body never sends back more ENERGY to the first than the first sends to the 2nd, hence the 2nd can never HEAT the 1st.

    Photons don’t act like electrons. Photons are bosons. Bosons stack upon themselves and can share the same space. They are waves, not particles. Normal matter is particulate and can NOT stack upon itself…if you try to shove matter together it takes up more space. Much confusion is caused by a misunderstanding between particulate material and photon waves. The waves from the secondary (cooler) object don’t suddenly become part of “the commitment” from the primary (warmer) object…photon waves don’t add up like that. If you take two equal waves and pass them through each other, at some point in the phase overlap the amplitude of the combined wave will double…and also at some point during the overlap the two waves will cancel each other out. But the effect is on the amplitude. The effect is not on the frequency. You would need a change in the frequency in order to increase temperature, but when identical waves combine they do not change their frequency. This is why the waves from the secondary object only resonate and scatter…they can’t do anything to the frequency of the existing vibrations in the primary object.

    That’s the plane parallel scenario dealt with.

    Now to move to a steel shell around a sphere where the sphere has it’s own internal power source.

    If you agree that only net ENERGY can cause HEAT transfer, and providing that you also agree that the only object which experiences HEAT (and thus experiences a TEMPERATURE increase) is that object where, on it’s surface, Powerin > Powerout i.e. if the power received by an object is greater than the power emitted by that object, then the [positive] difference will be manifested as HEAT upon the surface of that object, and this HEAT will increase the TEMPERATURE of that object, then we can proceed as this the essence of the 2nd LoT.

    The model that we are now considering is slightly more complicated than the plane parallel model because of the distance between the outside of the sphere (say having radius 1m) and the inside surface of the shell (say having radius 2m): the surface areas of the two objects are not identical. I therefore suggest that it is more convenient to use power densities (with units of W/m2) rather than absolute power values, so we can say HEAT will be transferred across the [single] boundary between the two objects when PowerDensityin > PowerDensityout and that HEAT will be experienced only by that object where the net difference is positive.

    When the temperature of the sphere is Tsphere then, at the surface of the sphere, the PowerDensitysphere = sigma * Tsphere4

    When the temperature of the shell is Tshell then, at the surface of the shell, the PowerDensityshell = sigma * Tshell4

    Let's consider what happens at each surface;

    At the surface of the shell, all of the sphere's emissions are received by the shell. However, due the inverse square law, the PowerDensity of the sphere's own emissions are dissipated over the larger area of the shell (and on the dimensions provided we conveniently know that the surface area of the shell is four times that of the sphere). Nevertheless, if at the surface of the shell PowerDensityin > PowerDensityout then the shell will receive HEAT.

    At the surface of the sphere, due to the angle of view from the surface of the shell, not all of the shell's emissions are received by the sphere (some will radiate onto another part of the shell's own surface, again without transferring HEAT). Only if Rshell = Rsphere , will 100% of the shell's PowerDensity leaving the inside surface of the shell be received by the surface of the sphere. Nevertheless, if at the surface of the sphere, PowerDensityin > PowerDensityout then the sphere will receive HEAT.

    Hopefully, we can still agree on all of the above, because it's still 2nd LoT. If we do agree, then;

    If Tsphere is greater (warmer) than Tshell then HEAT may (depending upon the respective PowerDensity values at the inside surface of the shell) be transferred to the shell (and no HEAT will be transferred to the sphere). Conversely, if Tshell is greater (warmer) than Tsphere then HEAT may (depending upon the two respective PowerDensity values at the surface of the sphere) be transferred to the sphere (and no HEAT will be transferred to the shell).

    For a sphere with no internal power source of it's own, the concept of introducing a shell around the sphere actually does decrease the rate of cooling experienced by the sphere (than it would otherwise do as is dissipates it's ever decreasing ENERGY into a 0K environment) but unless the shell was warmer than the sphere at the point the shell was introduced, the sphere will never get hotter.

    For a sphere with it's own internal power source, the concept of introducing a shell around the sphere does not change the rate at which the sphere dissipates it's ENERGY to satisfy it’s Stefan-Boltzmann commitment i.e. the temperature of the shell does not impair the sphere from radiating it's ENERGY and so the TEMPERATURE of the sphere does not increase (unless the shell was warmer than the sphere at the point it was introduced - but even then, the increase in TEMPERATURE would be transient).

    The (false) argument that the introduction of the shell around the sphere prevents the sphere from radiating it's due power density of: sigma * T4 (and so gets warmer from it's own heat) appears to be derived from the erroneous belief that the net energy difference is calculated as the difference between PowerDensityin - minus zero (being the amount it would have received had the shell not been present). This can be shown to be a fallacy if we let the radius of the shell be diminished to it's minimum value i.e. the radius of the shell is reduced to be that of the sphere. In this scenario, the "restricted emissions" argument says that at thermal equilibrium, the PowerDensityshell = PowerDensitysphere and because the shell radiates this on both surfaces, the surface of the sphere also receives PowerDensityshell as HEAT. If this were indeed true, the Sphere would have it's own constant power source of Psphere plus that which receives from the shell (PowerDensityin minus zero), which is Pshell (which is also Psphere) i.e. this is 2*P. But the original model only generates 1 * P. The incorrect "restricted emissions" logic has resulted in the creation of energy (by a factor of two, no less) - something that the 1st LoT says is not possible.

    If you now substitute the sphere with internal power source for the Earth and it’s constant ENERGY from our sun and substitute the steel shell for greenhouse gases at the top of the atmosphere then you will now see that the whole radiative Greenhouse effect story has been mathematically busted – the Earth’s surface does not get hotter from back-radiation from the atmosphere.

    Response:

    [PS] This is an absurd travesty of the actual physics. You would possibly benefit from detailed look at the physics at scienceofdoom assuming you want to understand the problem as opposed to trying to convince yourself that you are justified in opposing climate action.

  20. Lampacres @319 , you have tied yourself into a knot, with your "spherical steel shell".  To simplify, go back to your "parallel plates" which is a decently fitting approximation of the planetary surface for heat/energy flow per square mile.

    Two questions, Lampacres :-

    Q1 : How exactly does the high-school physics you mention . . . show any disagreement with mainstream climate science?

    Q2 : Have you posted earlier, under the name Cosmoswarrior (etc) ?

    Response:

    [PS] Nice thought but I think it best left to moderators to hunt sockpuppets. Lampacres appears to be someone who stumbled on skydragon nonsense. Hopefully can work through textbook.

  21. Lampacres @ 319:

    I will only discuss paragraphs 2 and 3.

    Paragraph 2: correct equation for the net exchange between the two plates, but you forgot the other two sides of the plates. What are the inputs/outputs on those sides? Or are you assuming/imposing zero energy flux in any direction other than back and forth between the two plates?

    Paragraph 3: you state "...if the warmer object does not have it’s own power source...".

    If you are making an analogy with earth, then there is a power source: the sun. It's an impoprtant source, hence my comments about paragraph 2. You're forgetting something.

    The other thing you're forgetting, if you are trying to make an analogy with the earth, is that the cooler plate is also losing energy to space. It is also important. Plates have two sides, last I looked.

    Try looking over at Eli Rabbet's The Green Plate Effect to see the math done correctly. Also his follow-up post Green Plate Challenge. (If you find yourself agreeing with Betty Pound, then you're in deep physics denial.)

    Frankly, I stopped reading closely after you got into the sphere case. You've got the fundamentals of the lane parallel case so wrong that it wasnt worth it. Same mistakes in the sphere section.

    Response:

    [PS] Frankly, I would like Lampacres to answer SoD two questions (and do it on the SoD site) to see whether there is any point to further discussion here. (Another imaginary law of thermodynamics disciples responded to the challenge with this head-vice required answer rather than answering the questions. We dont to go there). The Green plate challenge is another good place to start.

  22. My apologies to Moderators — and to Lampacres, for the insinuation.  (The content's validity, and the lengthy style, seemed to bear some similarity.)

    The parallel plate analogy needs some improvement.  Perhaps try with one plate being semi-transparent.  For starters.  And possibly the Sun might come into it somewhere, too.

  23. I agree with the statement that CO2 is one of the main driven of climate changes. But it’s not the only one. There are some other things or other gases that can cause climate changes. Actually it’s no matter what can cause climate change more or less we have to prevent it. However, we have to concern on what can cause climate change the most. So, we can find a way to prevent it.

    Response:

    [TD] You are correct that there are other drivers of climate change, but human-caused increase of CO2 is the most important cause of the current warming. Please read the post "CO2 Is the Main Driver of Climate Change."

  24. In Figure 2 comparing spectral absorbtion of outbound radiation 1970 till 1996 why doesn't the O3 absorbtion decrease as the amount of O3 in the atmosphere decreased over that period I expected to see the opposite effect to the CO2 but it seems to be the same effect for a decrease in concentration. I found a chart showing a fall of around 5% O3 over that period: Ozone depletion graph

  25. User 1001,

    I could not find a reference that exactly matched your question.

    Most (90%) of the atmospheric ozone is in the stratosphere.  It blocks incoming UV radiation and protects the Earth's surface.  This ozone has degraded in recent decades from attack by chlor-flouro chemicals.  The Montreal Protocol has strated the healing process for stratospheric ozone.

    At the surface of the Earth (the troposphere) the situation is different.  Here ozone is created by pollutants humans release into the atmosphere.  The concentration of ozone in the troposphere is increasing.  Wikipedia says:

    "Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe. However, the most widely accepted scientific assessments relating to climate change (e.g. the Intergovernmental Panel on Climate Change Third Assessment Report)[47] suggest that the radiative forcing of tropospheric ozone is about 25% that of carbon dioxide."

    Ozone in the troposphere absorbs outgoing IR radiation.  Thus at the same time as overall concentrations of ozone decreases (causing more UV radiation to reach the surface), there is more ozone in the troposphere causing less UV radiation to get out (the basis of the green house effect).  We get screwed both ways.

  26. In the last paragraph of the previous post it should say "causing less IR  radiation to get out"

  27. I dont actually believe you guys are scientists because "actual scientists" such as nasa have proven that climate change is real and that the sun is not too blame and that co2 is the problem

    Response:

    [JH] Your comment seems to be in response to the denier meme statement which the article rebuts. Please read the article.

  28. It makes no sense that satellites should record a lessened flux of radiation to space within the emission band of CO2 when the concentration of CO2 is increasing in the atmosphere. If half of all emissions from CO2 go upward to space, then a higher atmospheric CO2 concentration should result in a greater, not a lesser, flux of radiation to space. The latter should not be at all affected by the storage of IR within Earth's atmospheric system. That only involves the half of radiation that is directed downward. A decrease in flux recorded by satellites is most likely due to an error in recording outward flux. I'd welcome some comments on this. Tx.

  29. davidbennettlaing,

    Your argument is an argument from increduility.  You need to provide data to support your claim.  Since experienced atmospheric chemists and physicists agree that increasing CO2 results in lowered emissions at the CO2 emission bands, it seems more likely that you are incorrect than they are.

    The Earth emits black body radiation upward.  CO2 absorbs in the same bands that it emits.  Energy is re-emitted upward and downward (as you state).  The energy emitted upward is reabsorbed at a higher altitude.  Energy is re-emitted up and down.  Eventually the energy emitted upward escapes to space.   This is called the escape altitude.  The satalite measures the energy that escapes.

    The energy that escapes is emitted from much higher in the atmosphere  that the original energy that was emitted from the surface of the Earth.  Since as you increase in altitude in the atmosphere it is colder, the energy is emitted from molecules that are colder than the surface molecules.  When molecules are colder less energy is emitted.  This difference in energy is what the satalite measures.  It relates to the difference in temperature between the surface and the atmosphere at the escape altitude.

    Increasing the amount of CO2 in the atmosphere causes the escape altitude to increase.  That results in lower emissions of energy since it is colder at higher altitudes.  The change in temperature with altitude is called the lapse rate.  The lapse rate is about 6C per kilometer of altitude.  Thus an increase of 100 meters in altitude results in a shift of about 0.6C in emission temperature.

    Since this decrease in energy has been measured, it makes no sense for you to object to measured data.  An explaination for the change is required.

  30. davidbennetlaing:

    You are thinking in terms of "CO2 changes, but nothing affecting emission else does". This is not correct.

    Temperature is also a factor. As the temperature profile changes, cooler temperatures tend to cause less IR emission. Also, as the increase in CO2 increasing emissivity, you can get the same emission with a cooler temperature.

    At any point in the atmosphere, the upward flux of IR is a combination of what is emitted locally, plus whatever was emitted upwards from lower layers that has not yet been absorbed.

    What is seen from space is a rather complex integration of emission from all atmospheric layers, less any absorption by overlying layers. You cannot think of it as a single "emit half up, half down" event. In mathematical terms, it is not a single equation, but a rather large system of equations.

    Doing the full math indicates that the lower atmosphere will warm, and the stratosphere will cool, and the view from space will be affected as indicated by the observations michael sweet has indicated.

  31. One of my friends conducted this backyard experiment.

    Could anyone explain what the error was with her approach, and whether or not there is a backyard-style experiment that she could do to observe the reradiating properties of CO2.

    "So, what I did was take two clear 6L ziplock bags, two cheap thermometers, 2 CO2 cartridges, and a seltzer bottle.

    The first bag, I taped the thermometer to the upside of the bag, then filled with normal air using a balloon pump, then measured the temperature (19.4 deg).

    The second bag, I taped the thermometer to the upside of the bag, then measured (19.8 deg - remember, they're shit $2 thermometers - note slightly warmer than "control"), then I filled it by releasing two CO2 chargers into it. I then measured the temperature again (19.0 deg) and again a few minutes later (18.7 deg).

    I then took them outside and placed them in the sun and measured each over a ten or so minute period. The bag containing CO2 was always colder - between 0.4 to 1.0 degree (it measured 1.4 colder, but I reject that because I was blocking the sun just before I measured).

    Each of the two CO2 cannisters has 7.8 g. The density of CO2 at STP is 1.98 kg/m3. For the 2 x 7.8 = 15.6 g, this equates to a volume of 7.88 L. The seltzer bottle holds 1.25 L. So total 7.88 + 2 x 1.25 = 10.38 L Total. The proportion of CO2 in that mix is 7.88/10.38 = approx 76%.

    So as you can see, I significantly increased the CO2 content of the air, and the results came back slightly negative re. its effect on temperature."

  32. (Thanks to anyone with the time to respond)

  33. Tristan @331,

    I'll hav a bash at an explanation for you.

    If we ignore problems of calibration & measurement errors (hearing of the shading of one of the samples is a bit of a worry), the flaws in the as-described experiment are surely quite profound.

    If we consider that a bag of gas in a transparent (to visible light) plastic bag will be heated through radiative transfer and thus measuring its temperture will give some indication of that radiative transfer, we are this comparing an Atmosphere bag heated both by sunlight plus terrestrial IR with a CO2 bag containing predominantly CO2. If one bag absorbs more radiation than the other, if the experiment is sensitive enough to show the effect, the more absorption would therefore register a higher temperature.

    However, to expect the High-CO2 bag to absorb more radiation is asking a bit much. The sunlight will be warming the oxygen/ozone and any water vapour in the Atmosphere bag. And additionally terrestrial IR will also be warming the atmosphere's CO2, CH4, N2O and again any water vapour in the Atmosphere bag. With the CO2 having replaced pretty-much all these absorbing gases and with all but a small part of sunlight absorbed by CO2, the comparison is asking whether the narrow CO2 IR absorption band when saturated with CO2 will absorb more or less than the atmospheric gases. In full sunlight, I would be surprised if CO2 was that absorbent. This graphic (usually 2 clicks to 'download your attachment') gives some indication of the absorbtion of various atmospheric gases. (I'd doubt whether the scales allow the various areas to be totted up.) But note that, while sunlight-in & IR-out will balance over a 24-hour period, sunlight operates for a shorter time than IR so at midday the sunlight could be four-times more powerful than the IR.

    While the experiment isn't ever going to properly reproduce the mechanisms that result from higher CO2 in the atmosphere, as a measure of CO2 absorbtion of IR, the experiment would have a better chance if conducted at night with the thermometers under the bags.

  34. I will try to add to MA Rodger's commentary.

    Tristan:

    Keep i mind that the only thing that the thermometer tells you is the temperature of the thermometer. Although this may seem a triviality, it is essential to start with this understanding. The next stage in trying to use the thermometer for any practical purpose is to try to get the temperature of the thermometer to match the temperature of the thing you are really interested in. In your experiment, you are interested in the gas inside the bag (comparing air-filled vs. CO2).

    A good way to think of the behaviour between the thermometer and its surroundings is to describe the energy balance of the thermometer. What are all the energy flows in and out of the thermometer, and under what conditions will the temperature of the thermometer match the gas in the bag?

    The thermometer can have three methods of energy exchange with its surroundings:

    1. Radiation. It can absorb visible (solar) radiation, absorb IR radiation, and emit IR radiation. The end result can be either a net gain or a net loss, or zero if all radiation terms balance.
    2. Exchange of thermal energy with its surroundings. If warmer than its surroundings, the thermometer will lose heat. If colder, it will gain heat. The goal is to get this term to zero, to match the gas in the bag.
    3. Loss of energy through evaporation. Changing liquid water to gas requires energy (latent heat of vaporization). That energy has to come from somewhere, and it will tend to cool the thermometer (energy loss). This is easily avoided by keeping the thermometer dry.... keeping it wet turns it into a psychrometer.

    So, in your experiment, you want terms 2 and 3 to equal zero to make sure you have the thermometer at the same temperature as the gas in the bag. This only happens if the radiation term is also zero.

    If the radiation term is positive, and the evaporation term is zero, then the positive radiation input will make the thermometer warmer than its surroundings. It will heat up until the radiation input is exactly matched by the thermal loss (energy moving from warm thermometer to cooler gas).

    Now, how can you get the radiation term to zero when your goal is to see the effect of increased absorption due to CO2? If the CO2-filled bag is absorbing IR radiation in greater quantities than the air-filled bag, then initially it will warm, but after it has warmed the bag/thermometer will also be emitting more IR - which you hope will balance the extra absorbed IR.

    There are two catches to this:

    1. The bag also has an energy balance. It's really the bag absorbing more IR that you want to detect, so you need to double-up on the energy balance description, tracking both the thermometer and the bag.
    2. The radiation term also includes absorption of sunlight (visible light). In order to isolate the IR effects, you need to make sure that the two bags/thermometers are not absorbing different amounts of solar radiation. Any solar absorption messes up the energy balance, creating an error (higher temperature) in the thermometer, but at least if the two bags are exactly the same, the error will be the same in both and you can still make a comparison.

    Catch #2 is the experiment-killer. You said you performed this out "in the sun". You haven't mentioned a time of day or location, but direct beam solar radiation usually approaches 1000 W/m2 on a nice clear day, and very slight differences in absorbed solar radiation will overwhelm the IR effect you want to see (maybe 1 W/m2?). My guess would be slight differences in the angle of the thermometers, or reflectivity of the system. Perhaps the plastic bag surface reflects a bit of sunlight at certain angles, so slight differences in shape or orientation alter the amount of solar radiation hitting the thermometer.

    Controlling for solar radiation error is a critical factor for weather observations of air temperature. Thermometers are usually housed in a Stevenson Screen or other radiation shield. They are also typically well-ventilated (strong air circulation).

    You can't "well-ventialte" the air and CO2 in your bags, because that defeats the purpose of getting the elevated CO2 to absorb IR. That leaves a very large factor of solar radiation error, which makes it difficult in your experimental setup to know if you are looking at an IR effect. (You are most likely not.)

  35. Thanks a ton MA And Bob. I appreciate it. I don't have the physics comprehension to address queries regarding that aspect of climate change.

    Hopefully my friend pops in herself if she has any follow-ups to your repsonses.

  36. Tristan, adding some points.

    When the CO2 is released from the spritzer, the gas will come out somewhat cooled, so that may explain the lower CO2 temperature in the bag. How good an insulator is the plastic, that may impact how easily any temperature difference due to this corrects?

    Better would be to set up the entire setup outside in the same environment, and take measurements before you add any gas. Then look at how the temperatures change immediately after you add the gases. Then monitor how they change subsequently after that.

    Next, although CO2 absorbs infrared, most of that absorption in the atmosphere takes 100's to 1000's of meters to be 100%. How much will be absorbed over inches?

    Next, what is the transmissivity of the plastic - how much radiation passes through the bag? The bags may be transparent to visible light (very high transmissivity) but most materials behave very differently for infrared light. Most naturally occuring materials have extremely low transmissivity to infrared. You would need to research the properties of the plastic involved. Otherwise you are effectively carrying out the experiment with an opaque (to infrared) bag.

    The greenhouse effect depends on the behaviour of the entiure atmosphere over vertical distances of many kilometers. Extra absorption by CO2 at the surface is only a small part of any change in the GH effect. The big changes involve how much emission by CO2 changes at high altitude - 10 km or so. It is very hard to model the GH effect with small, surface based setups.

  37. Hi MA and Bob,

    Thanks for your responses re. my "plastic bag" study.

    I have a few follow-up questions:

    MA:

    I agree with the general point that there is no calibration. It is backyard science - I did it to try to understand what the effect is at all, not to measure it accurately.

    > However, to expect the High-CO2 bag to absorb more radiation is asking a bit much. ... while sunlight-in & IR-out will balance over a 24-hour period, sunlight operates for a shorter time than IR so at midday the sunlight could be four-times more powerful than the IR.

    Let me clarify that what you're saying here is that the other gases are better absorbers of sunlight, but CO2 is a better absorbed of terrestrial IR. Does this mean that you believe that the effect of adding CO2 would be a negative effect on temperature in the day and a positive effect at night?

    > While the experiment isn't ever going to properly reproduce the mechanisms that result from higher CO2 in the atmosphere, as a measure of CO2 absorbtion of IR, the experiment would have a better chance if conducted at night with the thermometers under the bags.

    Can you please explain why the effect would be different with the CO2 in the atmosphere as opposed to in the bag? Is there more to it than simply more CO2 content in the air in a specific location? Are there additional macro-effects whe the CO2 is in the atmosphere that the bag experiment would not be able to emulate?

    Also, please clarify "under the bag", not "in the bag"?

    Bob:

    Would the fact that both thermometers are enclosed in the bag act as a control?

    If there is a difference to the thermometer reading itself, due to it's being enclosed in CO2 rather than air, how significant do you think that would be? I.e. How many degrees influence?

    Also, if there is an influence, isn't it highly unlikley that it would be exactly equal to the influence that the CO2 is having on warming the bag, resulting in a net zero reading?

    Thanks for taking the time to return your answers.

    Regards,

    Jessica

    P.S. If someone caould confirm what the expected temperature change per increased unit of ppm of CO2 (or "doubling of CO2") is, that would be great. Thankyou.

  38. Hi MA,

    FYI, I am repeating the study again, at night, as you suggested. So far there is no noticeable difference.

    Thanks for the advice,

    Jessica

  39. Hi Glenn,

    Thanks for your response. 

    >When the CO2 is released from the spritzer, the gas will come out somewhat cooled, so that may explain the lower CO2 temperature in the bag. How good an insulator is the plastic, that may impact how easily any temperature difference due to this corrects?

    The temperature did drop immediately (by about 1 degree) as you suggested as the CO2 comes out colder. I monitored the two bags for probably an hour or so so I imagine that would have corrected - also, when I took them outside, the temperatures of each rose by about 5 degrees, so I assume this would not have happened if the bags were good insulators.

    >Next, although CO2 absorbs infrared, most of that absorption in the atmosphere takes 100's to 1000's of meters to be 100%. How much will be absorbed over inches?

    Do you mean that it takes 100s to 1000s of meters at present CO2 levels to absorb all of the radiation available to it? I don't think this should matter. I am simply increasing the amount of CO2 in one particular point which will have a given amount of radiation, this should theoretically have a temparature effect (if the mechanism is as simple as add more CO2, absorb more radiation, get more heat).

    > Next, what is the transmissivity of the plastic - how much radiation passes through the bag? The bags may be transparent to visible light (very high transmissivity) but most materials behave very differently for infrared light. Most naturally occuring materials have extremely low transmissivity to infrared. You would need to research the properties of the plastic involved. Otherwise you are effectively carrying out the experiment with an opaque (to infrared) bag.

    Here is the infrared spectrum of polyethylene:
    https://azom.com/images/Article_Images/ImageForArticle_12386(1).jpg

    As you can see, here:
    https://webbook.nist.gov/cgi/cbook.cgi?Spec=C124389&Index=1&Type=IR
    The infrared spectrum of CO2 is different, there may be some overlap, but the bulk of what CO2 absorbs should pass thorugh the polyethylene plastic.

    > The greenhouse effect depends on the behaviour of the entiure atmosphere over vertical distances of many kilometers. Extra absorption by CO2 at the surface is only a small part of any change in the GH effect. The big changes involve how much emission by CO2 changes at high altitude - 10 km or so. It is very hard to model the GH effect with small, surface based setups.

    I can see that adding more CO2 to the atmosphere would have an overall effect if CO2 causes temperature to change. For example, if CO2's primary source of heat-producing radiation is terrestrial IR, and you add more CO2 to the atmosphere generally, the CO2 might absorb more of the IR closer to the Earth's surface, leaving less to be absorbed at higher altitudes, so temperatures might be warmer at low altitudes and cooler at high altitudes (at, say, 10 km up). But this is a prediction of how the atmosphere would respond given that CO2 has this effect. It's jumping the gun because I'm trying to prove the effect to begin with. I don't see why a pocket of air with more CO2 (as in the experiment) would not generate any noticable heat difference. The radiation available to it is the same, you are simply adding more CO2, which should theoretically result in a higher temperature locally (just as if you added CO2 at any particular point in the atmosphere, you should generate a higher temperature locally).

    Thanks for your response,

    Jessica

  40. jesscars @337,

    CO2's main absorption wave-length is at 12 microns. This is at the peak of the Earth's IR emissions but is an irrelevant part of sunlight. Thus a High-CO2 bag would be pretty-much transparent to sunlight as well as to the Earth's IR except at that 12 microns wavelength.  This transperancy is because in the bag world, the CO2 has purged all the other GHGs and thus reducing the warming from those other GHGs. This one-step-forward-one-step-back doesn't happen under AGW. Indeed, a CO2-warmed world results in elevated water vapour, another GHG. AGW is operating day & night but the night-time temperatures will be boosted more than the day-time ones.

    The actions of CO2 as a GHG is not that of a simple insulation layer (although the circulations in the atmosphere are far less leaky than the leaks in any greenhouse). One (simplistic) mode of warming concerns the altitude at which the IR at 12 microns can get a clear-shot out into space. As more CO2 enters the atmosphere, the clear-shot altitude increases and the temperature at that clear-shot altitude drops. The lower the temperature, the less IR energy the clear-shot gases can shoot out into space. The bag world cannot demonstrate such AGW mechanisms.

    One mechanism (the significnt one, we are told) concerns the breadth of the 12-micron band. At the flanks, only whizzy-whizzing CO2 molecules can catch the IR and as CO2 levels increase, so the whizzy-whizzing CO2 becomes denser & the flanks expand. This is the logorithmic 1ºC of warming for double CO2 (without feedbacks). With the High-CO2 bag, there are perhaps 10X doublings? and if we run with this back-of-fag-packet calculation, that would suggest the High-CO2 bag would see 10X 1ºC warming while the Atmosphere bag would have the planet's GHG warming which is usually reckoned to be about 30ºC. This suggests that the extra warming from the High-CO2 bag would not compensate for the GHG warming purged relative to the Atmosphere bag. Mind, the humidity will play a big big part in any such calculation.

    And under the bag? was simply to mirror the atmosphere being above the AGW-warmed surface. In the bag? would do as well if the position of the thermometer can be precise.

    Hope this blather has addressed your queries.

  41. I would emphasis what others are saying here:

    1/ what you are trying to do is demonstrating the radiative properties of CO2 which is central to the GHE, but you cannot demonstrate the GHE in a simple column of gas.

    2/ Getting the experimental setup right is difficult as it is easy to overwhelm the CO2 radiative effect with other spurious influence. Have a look at this setup to make a better attempt.

    Spend some time looking at the basic mechanics of how the GHE really works. Eg here or Science of Doom It's a lot more subtle in the full mechanism than a naive approach would expect. I would throughly recommend Wearts history of discovery of the global warming for its insight into the how experiments have helped and hindered the development of the science.

  42. Another point about Tristan/jesscars experiment that has only occurred to me reading the later comments. In the orignal description, the comparison is between a bag filled with normal air, and a bag filled with CO2.

    • The air-filled bag would have water vapour in it - in whatever amount is present in the air at that time. (Probably at most a few percent.)
    • The CO2-filled bag would be dry - i.e. no water vapour.

    As water vapour is also a greenhouse gas, the comparison is actually between two bags filled with different amounts of two different IR-absorbing gases. My first guess is that the CO2 would be a considerably greater IR absorber, due to its greater concentration, but You'd have to do the math. It does illustrate that there are a lot of fine details that need to be tracked.

    In experimental design, you really have to make sure that the variable of interest is indeed the main variable.

  43. Hi MA,

    Thanks for the response.

    > CO2's main absorption wave-length is at 12 microns. This is at the peak of the Earth's IR emissions but is an irrelevant part of sunlight. Thus a High-CO2 bag would be pretty-much transparent to sunlight as well as to the Earth's IR except at that 12 microns wavelength. This transperancy is because in the bag world, the CO2 has purged all the other GHGs and thus reducing the warming from those other GHGs. This one-step-forward-one-step-back doesn't happen under AGW. Indeed, a CO2-warmed world results in elevated water vapour, another GHG. AGW is operating day & night but the night-time temperatures will be boosted more than the day-time ones.

    I can agree that the bag purges the other gases, so doesn't experience warming from those gases, but if they have a higher heat-producing capacity than the CO2 that replaces them, why would the net effect of adding more CO2 to air be to increase temperatures? I repeated the same experiment at night (indoors) and again, there was no notcieable difference in temperatures.

    > The actions of CO2 as a GHG is not that of a simple insulation layer (although the circulations in the atmosphere are far less leaky than the leaks in any greenhouse). One (simplistic) mode of warming concerns the altitude at which the IR at 12 microns can get a clear-shot out into space. As more CO2 enters the atmosphere, the clear-shot altitude increases and the temperature at that clear-shot altitude drops. The lower the temperature, the less IR energy the clear-shot gases can shoot out into space. The bag world cannot demonstrate such AGW mechanisms.

    I agree with this too, that if CO2 has a warming effect, the effects of CO2 in the bag do not represent what will happen in the atmosphere. But why wouldn't the bag show any warming at all? I don't see why adding more CO2 to the atmosphere should effect temperatures, but adding CO2 to the bag has no effect on temperature. If there is a global or atmospheric effect of adding CO2, why isn't there a local one (in the bag)?

  44. Hi Bob,

    Thanks for your response:

    > The air-filled bag would have water vapour in it - in whatever amount is present in the air at that time. (Probably at most a few percent.)
    The CO2-filled bag would be dry - i.e. no water vapour.
    As water vapour is also a greenhouse gas, the comparison is actually between two bags filled with different amounts of two different IR-absorbing gases. My first guess is that the CO2 would be a considerably greater IR absorber, due to its greater concentration, but You'd have to do the math. It does illustrate that there are a lot of fine details that need to be tracked.

    H20 appears to be a more effective GHG by comparing at the infrared spectrums, here and here. The CO2 filled bag would have approx 1/4 the amount of normal air. I suppose I would have to do the maths, though I would have to know how effective the additional CO2 is and how effective the H2O is at creating heat. It does seem strange though that there is no real noticeable difference in the temperatures either indoors or outdoors or at night - it seems unlikely that these would always balance out.

  45. Hi scaddenp,

    Thanks for the response.

    > 1/ what you are trying to do is demonstrating the radiative properties of CO2 which is central to the GHE, but you cannot demonstrate the GHE in a simple column of gas.

    Why not? I am not sure why the warming effect of CO2 would not be seen in a local pocket of high-CO2 air.

    > 2/ Getting the experimental setup right is difficult as it is easy to overwhelm the CO2 radiative effect with other spurious influence. Have a look at this setup to make a better attempt.

    Thanks for the comment. I have seen a similar experiment done on youtube, but my problem is that CO2 is what's being added to the atmosphere, there is no additional radiation other than what is there naturally. So using a heat lamp, unless it emulates only natural radiation variations does not a represent what will happen when CO2 is in the natural atmosphere.

  46. Why not?

    Perhaps you should tell us how you think the GHE works? Check those references. An isothermal column will not have a GHE.

    Any scientific experiment depends on controlling the variables in the experiment. As has been pointed out to you, your design has all sorts of issues with that. If you want to do this outside, then you need to do it at night really. The radiation that the CO2 is interacting with (IR) comes from heat re-radiating from the surface and that being re-radiated from GHG in the atmosphere all the way up. Not easy to control. Direct measurement of the GHE in the atmosphere is a complex experimental design, not for amateurs. See this paper for instance on how to really do it.

    Using heat lamp as proxy for IR being irradiated surface allows you some control and at level which makes it measurable.

  47. Hi All,

    I have another question re. temperature predictions.

    If the expected warming is an increase of 1 degree per doubling of CO2, why is this not matched by the Vostok Ice Core samples? These show about a 1 degree per 10 ppm linear relationship. 

    Why would the historic linear trend be replaced by a logarithmic one? At what level of CO2 does this happen?

    Thanks,

    Jessica

  48. Hi scaddenp,

    My understanding is that CO2 molecules absorb terrestrial IR then reradiates it as heat. I'm not sure why it should matter if that's a bag with a higher concentration of CO2 or CO2 molecules in the atmosphere. I don't see why there should be a difference. Are you able to explain this to me? I will also check the papers.

    OK, so you acknowledge that the warming, when under natural sources of radiation is insignificant. I understand that adding radiaton would increase temperatures, but the GHG of the atmosphere will only ever face natural sources so it doesn't represent what will ever actually happen.

    I have tried the experiment at night, indoors, and outdoors, and with differnt concentrations of CO2. There is never a significant difference - definitley not 1 degree per doubling.

    Also, can you please confirm the 1 degree per doubling and where this comes from? This is not matched on the Vostok Ice Core samples, which show a linear relationship of about 1 degree per 10 ppm. I am not sure why the discrepancy in the science.

    Thanks,

    Jessica

  49. jesscars @343,

    The relative strength of CO2 as a GHG is dependent on the logarithmic nature of its forcing. The first doubling will, molecule for molecule, be twice as 'forceful' as the second doubling and a thousand times more 'forceful' than the tenth doubling. So the 'forcefulness' you measure in the High-CO2 bag will be mainly a thousand-times weaker than the CO2 'forcefulness' involved in AGW. And while the ten doublings of CO2 together will provide a very 'forceful' GHG effect at 15 microns, (By-the-way, I note my 12 microns @340 is wrong - it is 15 microns.) this is achieved by stripping all GHG from everywhere else. This one-step-warmer-one-step-cooler effect for the bag world could well explain the non-result although there could be many other contributing reasons.

    jesscars @347,

    Your comparison of the 1ºC of warming for double CO2 (without feedbacks) with the Vostok Ice Core temperature/CO2 graph doesn't properly hold. Firstly, the Vostok temperatures will be subject to polar amplification and Ice Ages result from other non-CO2 'forcings' (CH4, ice albedo) and their feedbacks. The direct CO2 contribution (without feedbacks) to the Ice Age cycles (which are globally some 5ºC) is probably something like 0.5ºC, which fits in with the logarithmic relationship. With feedbacks, the CO2 'forcing' is responsible for about a third of the Ice Age wobbles.

    The logarithmic nature of CO2 forcing holds certainly for 180ppm to 2,000ppm. (See for instance Etminan et al 2016.) At very low concentrations it will presumably be more linear (like CH4) but the point of change from logarithmic is not something I have met. Persumably the level is well below any CO2 levels ever seen on Earth.

  50. Jesscars — as an average reader here, I am puzzled why you persevere in trying to "fix" your backyard experiment set-up intended to replicate the already-demonstrated empirical evidence of CO2 "greenhouse".

    (A) Firstly, there is the empirical evidence from experimentation during the past 150+ years, showing CO2 absorption of (some) Infra-Red radiation.    (B) During the past century there is the empirical evidence of the CO2-related global Green House Effect [GHE] : evidence provided by both expensive and (relatively) cheap experimentations & observations.  (Admittedly, "greenhouse" is a poorly-named term — but historically we are now stuck with it, and it is now a widely-understood useful label.)

    Your experiment is inappropriate because of its lack of sensitivity and specificity (too many confounding variables in your experimental set-up).

    Not only do you need to address the question of IR absorption by CO2 gas, but secondly you need to address the mechanism of the planetary GHE (a mechanism which is completely unconducive to backyard experimentation, I think).

    And your later questions indicate that you have not grasped the essentials of global-scale surface temperature changes.   Climate is a complex matter, and you must not expect to understand all the science of it, by means of a few paragraphs of explanations — You owe it to yourself to undertake basic self-education by extensive reading (and/or by some of the excellent video-tutorials available.  And if you want to be entertained humorously by videos while self-educating, then seek out the series of Potholer54 videos — they educate indirectly, by amusingly debunking the numerous scientific errors committed by the anti-science brigade i.e. denialists.   Potholer54 also does a series on evolution-deniers . . . but you probably won't have time for that sort of humorous entertainment sideline.)

    The more you learn, the better you will be able to ask appropriate questions.   Start from the basics, and then you can usefully re-visit Vostok and global warming response curves.   As MA Rodger has implied, you have been trying to put the cart before the horse.

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