söndag 30 januari 2011

The hypothesis of Jelbring and the rebuttal by Erren and Dietze

In 2003, Swedish climatologist Hans Jelbring proposed a theory, based mostly on heuristic lines of argument, for explaining the atmospheric lapse rate and its heating impact on the surface. In a way it could be viewed as a modern rendition of the hypothesis of Herapath. The paper, published in E&E, had the title "Greenhouse Effect as a function of Atmospheric Mass". Below is a quote of the central hypothesis:

"In an ideal gas atmosphere, the adiabatic temperature lapse rate has to be –g/cp where cp is the heat capacity of the gas (ref 2 p. 49). Theoretical calculations are well confirmed by observational evidence in the atmosphere of Earth. The adiabatic temperature lapse rate on Earth is thus –9.81/1004 = –0.0098 K/m. As James R. Holton concluded after deriving this result: “Hence, the dry adiabatic lapse rate is approximately constant throughout the lower atmosphere.” The temperature lapse rate in our model atmosphere also has to be –g/cp, since its atmosphere is organized adiabatically."

The paper was followed by a fierce rebuttal  by Hans Erren and Peter Dietze entitled "The Greenhouse Effect should not be redifined" published in the same journal. I will quote parts of the text, hopefully capturing the essence of the message:

"Hans Jelbring titles his paper "The 'Greenhouse effect' as a function of atmospheric mass" though another term would be required as by definition the Greenhouse effect (GE) is a radiative effect, i.e. warming from back-radiation to ground, which is independent of atmospheric mass and adiabatic lapse rate and thus cannot be governed in its magnitude. The GE is from infrared (IR) absorption and thermal re-emission (see chapter "Radiative Forcing" of <http://www.john-daly.com/forcing/moderr.htm>) which occurs independently from the thermodynamic processes that Hans J considers to be the only relevant ones in the troposphere. His suspicion that IPCCs Global Warming (GW) models wrongly consider all the atmospheric energy transport being radiative only, is incorrect. The basic GE modelling copes with the radiative and convective part of the energy fluxes."

It is true that the basic GE modelling takes into account a convective overturning, but the radiative and convective processes are highly interacting, see the post "What is the greenhouse effect". Furthermore:

"In the atmosphere we find a combination of convective lapse (in regions where convection is strong), a gravity lapse plus the radiative lapse. The author seems to deny atmospheric radiation and to consider greenhouse scientists who base their theory on radiative physics as to foolishly believe in conventional radiative models and HITRAN spectra which he considers to be without scientific foundation. He simply redefines the GE as the difference in temperature between the surface
and a non-existent minus 18 degC black body reference shell at an arbitrary level of altitude, resulting from the magnitude of the adiabatic lapse rate. He concludes that this lapse rate is independent of the mass and the temperature of the model atmosphere. He further concludes that the GE expressed by the lapse rate is constant and independent of radiative properties (!) of the constituents. In particular we object his statement that "the atmospheric mass exposed to a gravity field is the cause of the substantial part of GW". Strong doubts arise whether the author has understood the radiative GE at all."

What they mean with "combination of lapses" remains obscure. Notably, they also write:

"If we would assume that no GHGs exist (as they are asserted to be irrelevant) and the Earth had a resting atmosphere which is fully transparent to radiation, the ground would turn to minus 18 degC to get into radiative equilibrium with the incoming solar 240 W/m² - no matter what mass the atmosphere has and to what extent a gravity lapse rate may cause a cooler (than minus 18 °C) upper atmosphere. Upper layers would be cooler because the vertical component of the thermal molecular speed is reduced. This "gravity lapse rate" may be similar to the lapse rate g/Cp that Hans J uses. But it cannot cause a warming (relative to minus 18 degC) of the atmosphere near ground and thus a warming of the ground itself. So the adiabatic lapse rate cannot explain the plus 15 degC ground temperature and thus replace any radiative basic and anthropogenic GE. Any ground warmer than minus 18 DegC would definitely mean a perpetuum mobile permanently producing energy out of gravity. Static air pressure cannot produce permanent heat in an open non-insulated system."

It should be emphasized that the greenhouse hypothesis is not ambiguous on the (average) temperature at any altitude, it is clearly defined for any absorption/emmision parameter. Compare with the wiew of Roy Spencer

3 kommentarer:

  1. Hi Anders,

    Just a quick note. The part of Jelbring's paper you quote above is not his 'central hypothesis'.

    It's just passing a restatement of the well known (century-old) calculation for the dry adiabatic lapse rate. Which doesn't depend at all on radiative heating or absorption - is in fact entirely independent of it.

    So it's kind of hard to see what your point is.

  2. You miss the point altogether. See my paper "Planetary Surface Temperatures. A Discussion of Alternative Mechanisms."

    The point you miss is that the assumption that the atmosphere would be isothermal (all at 255K) if it were 20% pure oxygen and 80% pure nitrogen is totally dependent upon assuming that the First Law of Thermodynamics can be violated by a parcel of air rising adiabatically. The laws of physics are not violated, hence the assumption of 255K is wrong, and calculations show it is more like a case of 300K being cooled to 288K because the wet lapse rate is less.

    Doug Cotton

  3. Doug,
    I haven't read your paper so I can't comment on it. I don't agree with what you say in your post.

    I didn't read anything that assumes the atmosphere would be isothermal if the GHG's are gone. In fact the quote attributed to Erren et. al. says the opposite:
    "Upper layers would be cooler because the vertical component of the thermal molecular speed is reduced. This "gravity lapse rate" may be similar to the lapse rate g/Cp that Hans J uses"

    What they are saying is the temperature of the surface would be simply computed from reflectivity and the emission coefficient of the surface and balancing incoming radiation from the sun, with outgoing radiation. They are assuming the albedo and emissivity is unchanged, so the surface temperature would be 255K. The adiabatic lapse rate would then be applied to this surface temperature to get a temperature profile.