Monday, September 20, 2010

CO2 is a bit player in Global Warming

        An essay by Richard Petschauer, Carbon Dioxide Heat Trapping: Merely a Bit Player in Global Warming, shows that IPCC estimates of climate sensitivity to CO2 are greatly exaggerated. The author utilizes the Spectracalc spectral analysis program to determine the ability of the 'greenhouse' gas CO2 to absorb the long wave infrared energy emitted from the Earth's surface (a stepwise spectral line-by-spectral line "integral" of the area under the curve). He finds that at present CO2 levels, only 7.4% of heat radiated from the Earth is absorbed by CO2 and that the vast majority of heat absorption is due to water vapor. Furthermore, a doubling of CO2 levels only results in the absorption by CO2 increasing to 8.0%, a 4x increase to 8.7%, and 8x increase to 9.6%.
         As a first approximation to determine 'climate sensitivity' (change in temperature due to a doubling of CO2), one might assume the total so-called 'greenhouse effect' of 33C is correct, multiply that by the % change in absorption due to doubled CO2 (0.6%), to arrive at a climate sensitivity of only 0.198C. This is a far cry from the climate sensitivity figures of 2 - 4.5C claimed by the IPCC. The empirical data to date also supports a climate sensitivity of <1C (refs 1,2,3,4,5,6...)
Region of interest of CO2 LWIR (long wave infrared) absorption
Blowup of region of interest showing overlap between CO2 and water vapor
shaded area is absorbed by CO2 only

Blowup of above figure. Area with asterisk is absorbed by CO2 only.
ABSTRACT: New calculations show that doubling of carbon dioxide (CO2) will increase average global temperature by only about 1F (degrees Fahrenheit) or 0.55C (degrees Centigrade), much less than the range of 2C to 4.5C estimated by the United Nations International Panel on Climate Change (IPCC). These new calculations are based on NASA supported spectral calculations available on the Internet relating to greenhouse gases. The temperature increases are estimated to be somewhat more in winter in the colder climates because of reduced competing atmosphere water vapor, but smaller increases at other times and places. These calculations also estimate that a 10% increase of water vapor in the atmosphere, a stronger greenhouse gas than CO2, or a reduction in the average cloud cover of only about 2 percent, will increase global temperature about as much as doubling CO2 would. Each additional doubling of CO2 will cause further temperature increases about the same as that caused by the first doubling. Greenhouse gases, except water vapor, only trap heat at certain narrow wavelengths of infrared radiation related to their molecular structures. Data shows that present concentrations of CO2, a strong absorber, are already well above the saturation value at its principal wavelength, so increases in it have a relative small affect. These new calculations are based on atmospheric models of the energy absorption bandwidths of greenhouse gases coupled with Max Planck’s equations relating to infrared wavelength distributions. A new simple technique is also proposed in the appendix to measure actual trapped heat being radiated back from the atmosphere to the Earth. This can be used to evaluate validate various estimating models. It also indicates that the role of clouds and their height above the Earth may have a larger role than previously thought. Since clouds operate as both powerful heat-trapping agents, overriding others, and a reflector of the sun’s energy, they may be the key factor in the regulation of the average global temperature. At the present time, they are one of the least measured parameters in the computer models predicting future climate changes. Weather and climate forecasting considering all factors is very complex, thus this paper does not cover that subject. However it is felt that the simple role of long-term heat rises due to only CO2 changes is a much simpler process and better estimated by basic models as used herein. Certain shortcomings in the IPCC data and estimates, as reported by others, are also summarized. Based on this new information, recommendations are made regarding future U.S. energy policy. While it does appear that the recent years show a warming trend, the role of CO2 in this is very small, and perhaps beneficial in moderating winter temperatures in colder climates.

h/t comment by Scottar alerting me to this essay


  1. Thanks for posting this interesting discussion. The statement that heat transfer from the colder CO2 gas to the warmer surface is forbidden by the 2nd law of thermodynamics is not correct. The 2nd law forbids processes whose ONLY effect is to transfer heat from a colder to a warmer body in an isolated system. In the case of the CO2 in the atmosphere its density would be changed in the process (ie, work would be done on the gas, etc) and thus the warming effect is not the only energy transfer going on in this process. It is those other effects in this process that contribute to a reduced climate sensitivity to increases in CO2 concentration.


  2. 1. An "isolated system" is a theoretical concept that does not occur in nature.

    2. The second law applies to all systems in the universe
    3. 2nd law states heat cannot flow from cold to hot without work input. CO2 cannot add work input.
    4. Of course, radiation is not the only process that occurs, in fact adiabatic effects and convection probably outweigh radiative effects, but you won't hear that from any climate scientist.

  3. Tucano,
    I asked Dr. Claes Johnson [] to also reply to your comment and he emailed this reply:

    1. Of course everything is coupled to everything, and nothing is really isolated, but still we can view e.g. the Earth + atmosphere with given radiative forcing as an isolated system.

    2. Of course radiative transfer of heat energy is from warm to cold, as shown in

  4. The correct statement of The second law of thermodynamics is “The entropy change of any system and its surroundings, considered together, resulting from any real process is positive, approaching zero when the process approaches reversibility”. If one understands thermodynamics and entropy it is clear that heat can not flow from a cold source (low entropy) to a hot receiver (high entropy). Is it a big leap in logic to say that those who assume heat flows from cold to hot do not understand thermodynamics?
    keep strong Cementafriend

  5. Anonymous said:

    "Is it a big leap in logic to say that those who assume heat flows from cold to hot do not understand thermodynamics?"

    If you assume that is the only thing happening, yes. But if there is work being done in the system, no. Or am I to presume you live in a world without refrigerators and freezers?


  6. Tucano/Dalcio,
    As stated above, CO2 cannot provide work input, although climate scientists believe it does by flagrantly violating the 1st law:

    and the 2nd law:

    and please do study Dr. Claes Johnson's paper

    before getting back to us with your detailed critique.

  7. another fig showing how H20 almost completely overlaps CO2 absorption spectra