Do greenhouse gases warm the planet by 33°C? Jinan Cao checks the numbers.

Jinan Cao has been dissecting the nature of the greenhouse effect and a key calculation that I normally just accept without questioning. This will set a few pigeons loose, but it will be interesting to see where they land.

The claims analyzed here are the oft repeated ones that the Earth’s greenhouse effect already warms us by 33°C and that a doubling of CO2 directly causes a 1.1°C rise (that’s with no feedbacks taken into account).

Jinan points out that these numbers, repeated as “fact”, are merely a result of misuse of the Stefan-Boltzmann equation. If Earth is not a perfect black body, but has an emissivity of 0.7 (as satellites suggest), then the temperature of the planet’s surface without any greenhouse effect would not be -18°C, but more like 5°C. That would mean the entire warming due to the greenhouse effect is only around 10°C, not the more impressive 33°C that is usually claimed. It means the greenhouse effect is probably less important than implied.

The 1.1°C direct rise that is predicted from doubling CO2 without feedbacks would also need to be recalculated. This paper does not try to do that, but if Jinan is right, that figure would be significantly lower too. Jinan looks at how that figure was derived. David Evans has been helping review Jinan’s work and writes the introduction below. – Jo

Jo Nova

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7 responses to “Do greenhouse gases warm the planet by 33°C? Jinan Cao checks the numbers.

  1. well we know the moon reaches 250 f in a few hrs in the daytime, seems to me like the earths atmos acts to cool in the daytime and at night slows down cooling, well apart from the desert at night
    where there is little moisture to do this.

  2. One point I have *never* seen discussed in the context of ‘global warming’ is the atmospheric heat capacity. That is a property of all matter that measures the amount of heat (energy) that is needed to raise the temperature of a specific amount of the material a given temperature increment. It takes significantly more energy to raise the temperature of a molecule fo CO2 by a degree than a molecule of N2 or O2. This means that more CO2 produces an atmosphere that is *less* sensitive to added energy in terms of temperature changes. The CO2-rich atmosphere acts like a thicker blanket to absorb and hold more energy with less heating, and to keep the energy from escaping as fast at night.

    • Tom, heat capacity change is small, but negative
      CO2 = 0.846 kJ/kgK
      O2 = 0.918 kJ/kgK
      N2 = 1.040 kJ/kgK

      Air is 79% N2 and 21% O2 = 1.014 kJ/kgK
      Should we enter a burn the world scenario and get 10,000 ppm CO2, this would be
      Air is 79% N2, 1% CO2, and 20% O2 = 1.0136 kJ/kgK

  3. Norm Kalmanovitch

    The question isn’t whether or not greenhouse gases cause a 33°C greenhouse effect as much as it is whether the increase in CO2 emissions gas caused this 33°C greenouse effect to be enhanced to by 2°C to 5°C as predicted by climate models.
    In my 1969 theoretical geophysics class we used the same 288 K minus 255 K to calculate the 33°C greenhouse effect as Hansen did in his 1981 paper ” Climate Impact of Increasing Atmospheric Carbon Dioxide”
    (http://pubs.giss.nasa.gov/docs/1981/1981_Hansen_etal.pdf ) In spite of the massive increase in CO2 emissions from the 14.2gt/year level in 1969 when we calculated the greenhouse effect to be 33°C to taday with emissions topping 34gt/year we still calculate the greenhouse effect to be the same difference between 288 K and 255 K giving us the same 33°C answer.
    If there is no enhancement of the greenhouse effect in our consistant 33°C calculation in spite of a 139% increase in CO2 emissions since 1969; there is no mechanism for increased CO2 emissions to cause the projected catastrophic global warmming which relies entirely on the validity of this mechanism.
    Unless the IPCC can actually demonstrate an enhanced greenhouse effect they have no mechanism for their claims and this is not possible because 32 years of OLR measurements by weather satellites incontrovrtably demionstrate that there has not even been a detectable enhancement of the greenhouse effect in spite of the 78.9% increase in CO2 emissions since 1978!!!

  4. Although the “greenhouse effect” term is imprecise, it is vivid and has some validity. The atmosphere does moderate Earth’s temperature enormously, as richard’s point about the Moon shows.
    If atmospheric scientists demonstrate that the “greenhouse effect” is much smaller than most people believe, then obviously the influence of human activity on the atmosphere is also less important.
    There are a lot of elements in the atmosphere that interact to moderate the temperature. There are other elements of the surface that affect temperature, of course. The vast majority of our atmosphere is of natural origin; humans produce small amounts of gases that are likely to affect the atmosphere’s heat budget. But nearly all JunkScience readers are clear that human activity does not significantly alter the Earth’s thermostat.
    Tom, I’m not sure I followed your comment correctly, but I agree that the role of various gases has been described inaccurately.

    • “If atmospheric scientists demonstrate that the “greenhouse effect” is much smaller than most people believe, then obviously the influence of human activity on the atmosphere is also less important.”

      The pisser is that the burden is on the skeptics, and not on the people who suggest Man has dominion over the atmosphere. We have to disprove that which is not proven.

      • Howdy Gamecock
        Yes. Accusers love to have the accusation itself pretend to be proof, which it is not.
        In science and the law, the one who makes the claim is supposed to carry the burden of proof. The more remarkable the claim, the higher the threshold is supposed to be. Nice theory but it’s been stomped on badly in the AGW debate.

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