tisdag 26 april 2011

The IPCC Trick: Climate Instability from Backradiation 2

The red curve in the above picture shows the spectrum of the outgoing longwave radiation
(OLR-spectrum) from the Earth including atmosphere, in the form of radiation intensity as a function of wavenumber/frequency. The background curves show the blackbody spectra for different temperatures. The picture gives the following information:
  • The area under OLR-spectrum is the total radiation ~ 240 W/m2.
  • The OLR-spectrum for wavenumbers larger than 800 represents radiation from the Earth surface at 285 K, which is not absorbed by the atmosphere (radiation through the atmospheric window).
  • The dip of OLR-spectrum around 700 represents radiation from the top of the troposphere at 220 K after absorption to saturation by atmospheric water vapor and CO2.
  • The red curve for wavenumbers smaller than 600 represents radiation from different levels of the troposphere at higher temperatures than 220 K after partial absorption by mainly water vapor.
  • An increase of CO2 can be have the effect of widening the dip which would require a compensating increase of the radiation outside the dip.
  • The area of the dip represent 10% of the total area ~ 24 W/m2.
  • The change of the width of the dip by increased CO2 may represent 10% of the dip ~ 3 W/m2.
  • Altogether, doubled CO2 may correspond to a "radiative forcing" of ~ 3 W/m2, which is also the number given by IPCC, and represents a 1% perturbation of the total outgoing radiation = total incoming radiation absorbed by the Earth including atmosphere ~ 240 W/m2.
The key question is now the effect on the surface temperature of a 1% change of the atmospheric absorption/radiation properties. There are two possible answers:
  • The first is the IPCC answer: The surface temperature is 288 K and 1% of 288 K is about 3 C = IPCC climate sensitivity.
  • There is another answer: The total effect of the atmosphere is to raise the temperature from the blackbody temperature of 255 K to the observed of 288 K, thus by 33 C, and 1% of 33 C is 0.3 C.
The alternative climate sensitivity is 0.3 C, ten times smaller than that given by IPCC. The trick by IPCC is to introduce backradiation to allow working with gross flows and corresponding gross temperatures, instead of net flows and temperature change. By introducing backradiation IPCC is able to inflate a climate sensitivity of 0.3 C, which is not alarming, to 3 C which is alarming.

The trick used by IPCC is thus to create gross two-way flows of energy by backradiation from the atmosphere to the Earth surface, and from a 1% perturbation of the gross flows obtain a climate sensitivity of 3 C, which is ten times as big as an estimate from net flows and temperature change.

The trick used by IPCC is now brought into light and it is up to you to decide its value as the scientific basis for CO2 climate alarmism:
  • Is 0.3 C a realistic upper bound on climate sensitivity?
  • Is 3 C a non-realistic artificially inflated sensitivity obtained by a trick of backradition creating something substantial from nothing?
What do you say?

Recall that the IPCC value of 3 C is obtained by feedback from a no-feedback value of 1 C according to the following definition of climate sensitivity used by IPCC as expressed by Gavin Schmidt:
  • “Climate sensitivity” is *defined* as being the equilibrium response of the global mean surface temperature to a change in radiative forcing while holding a number of things constant (aerosols, ice sheets, vegetation, ozone) (c.f. Charney 1979, Hansen et al, 1984 and thousands of publications since). There is no ambiguity here, no choice of metrics to examine, and no room for any element of belief or non-belief. It is a definition.
This definition allows IPCC to assign (no-feedback) climate sensitivity a value of about 1 C by a direct application of Stefan-Boltzmann's radiation law in its differentiad form dQ ~ 4 dT, with dQ ~ 4 W/m2 and dT ~ 1 C. This is the starting point for the IPCC value of 3 C, which is obtained by various feedbacks from the no-feedback value of 1 C.

You cannot argue about the truth of a definition, but a definition says nothing about reality, only something about language. The no-feedback sensitivity of 1 C looks like a statement about reality, but is in fact only a definition because global climate is not at all captured by Stefan-Boltzmann's radiation law alone.

Without the no-feedback value 1 C the IPCC climate sensitivity has nothing to feed on, and the the 3 C has to create itself as a 1% perturbation of gross temperature resulting from a 1% perturbation of gross energy transfer by backradiation.

A more detailed argument also leading to an upper bound on climate sensitivity of 0.3 C, is presented in a previous post.

1 kommentar:

  1. Claes, did you know that the window for radiation to space is actually 66 W/m2 and not 40 W/m2 as in the K&T paper and in the T,F&K paper and further it seems that Trenberth actually knows it see slide 26 of this link http://climategate.nl/wp-content/uploads/2011/02/CO2_and_climate_v7.pdf but he has not made a correction only expressed concerns in the climategate emails about the missing heat.
    keep strong cementafriend