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Harris research on outgoing IRs--and cirrus/gaia; his study is flawed

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  • Mike Doran <mike@usinter.net>
    Increases in greenhouse forcing from outgiong longwave radiation spectra of the Earlth in 1970 and 1997 John E. Harris et a Nature (v.410, p.355, 15 March
    Message 1 of 1 , Jan 20, 2003
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      Increases in greenhouse forcing from outgiong longwave radiation
      spectra of the Earlth in 1970 and 1997
      John E. Harris et a Nature (v.410, p.355, 15 March 2001)

      " . . . broad-band difference signals could occur of aerosol or
      cloud 'contamination' rmains in the notaionally clear fields of
      view. Using availabe aerosol data,24 we have shown that ice cloud,
      paritcularly if composed ofsmall crystals, does exhibit stronger
      absorption in the 800-1,000cm-1 than the the 1,100-1,200 com-1
      window. It is quite possible that small residual amounts of ice
      cloud absorption remian in both sets of data. Owing to the larger
      field of vie, the IRIS spectra have a much higher probability fo
      being contaminated their IMG counterparts. The observed 1 K or so
      enhancement of the 800-1,000 cm'1 difference signal would be
      consistent with this, and could also arise from change in the mean
      cirrus microphysical properties. We cannot separate these two
      effects, but we do conclude that the observed window difference
      spectra strongly indicate an effect involving residual small ice
      crystal effects, incompletely cleared from the data. R.J.B. has
      performed further calculations, following on earlier work26, which
      confirm that the window difference specta of the magnitude observed
      can easily arise from small changes in the amount, size or shape of
      small ice crystals: these studies also indicate that the difference
      spectrum should be larger belwo 920 cm-1, which is consistent with
      the observed data, especially the global case (Fig.1b). Further work
      on these and other cloud effects in the data will be performed
      separately: for the present, we believe wehave demonstrated a
      sufficient udnerstanding of he observations to give confidnece to the
      principals finds of this work regarding radiative forcing due to CH4,
      CO2, O3 and chlorofluorocarbons.
      Third, we must also take into account inter-annual variability as a
      possible cause of the observed difference spectra. In the window
      region, the brightness temperature difference is strongly modulated
      by short-term fluxtuations, such as inter-annual variablity (specific
      concern involves teh 1997 warm El Nino/Southern Oscilation, ENSO,
      event). Our studies show that, while this could account of an
      uncertainty of 1 K in the position of the zero line in the spatially
      and temporally averaged differecne spectra used, it could not account
      for the sharp spectral features observed, nor the differential window
      signal just discussed."

      24. Shettle, E.P. in Atmospheric Propagation in the UV, Visible, IR
      and MM-wave Region and Related Systems Aspects 15-1-15-12 (AGARD-CP-
      454, Air Force Geophysics lab., Bedford, Massachusetts, 1990).
      25. Ackerman, S., Smith, W., Spinhirne, J. & Revercomb, H. The 27-8
      October 1986 FIR IFO cirrus cloud study: spectral properties of
      cirrus cloud in the 8-12 um windo., Mon. Wealth. Rev 118 2377-2388
      (1990).
      26. Bantges, R., Russell, & Haigh, J. Cirrus cloud top-of-atmosphere
      rediance spectra in the thermal infrared. J. Quant. Sepctroc. Radiat.
      Transfer 63, 487-498 (1999).

      See also http://www.vision.net.au/~daly/smoking.htm

      Comment:

      Daly is partially correct--and the third point of Harris is incorrect
      to NOT attribute the change in cirrus behavior to ENSO. Yet again,
      it isn't really SSTs we are talking about--although that is how the
      change in cirrus distribution manefests itself. For it isn't the
      SSTs that force the cirrus but more how the EMFs force the cirrus--
      which vary the SSTs and yes there is some aspect of warmer SSTs as
      more conductive that are interesting as causal of some movement on
      the cirrus.

      Correlations from solar activity to ENSO do come from the fact that
      flaring distributes EMF more diffusely compared to the coriolis
      driven temperatures of less activity--which cause the SSTs to warm
      more west--but, the primary mover is biological changes in
      conductivity of the oceans that oscillate given wind induction and
      other electrical aspects . . . of a living earth.
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