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The Environment / Is Carbon Dioxide the real cause of an increase in Gobal Warming?
« on: 26/04/2011 18:11:32 »
On the thread “What does Iain Stewart's "CO2 experiment" Demonstrate (http://www.thenakedscientists.com/forum/index.php?topic=38723.25) JP and I had a brief chat about a book “Introduction to Atmospheric Chemistry” by Daniel J. Jacob, Princeton University Press, 1999 PDF version (http://acmg.seas.harvard.edu/publications/jacobbook/index.html), which is available for free viewing. CHAPTER 7. THE GREENHOUSE EFFECT (unlike Professor Stewart’s demonstration) makes it quite clear that
I have E-mailed Dr. Jacob about it and also suggested that he might be interested in taking a look at the analyses provided by Roger Taguchi on Professor Judith Curry's "Physics of the atmospheric greenhouse(?) effect" thread (http://judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-62506), which challenge Dr. Jacob’s analyses. Dr. Jacob has not yet responded but Roger has and here’s his comment
I’m sorry that this is not easy reading but that simply reflects the complexity of the subject itself. Further details are available on Professor Curry’s "Physics of the atmospheric greenhouse(?) effect" thread and in Roger’s revised article “Net Feedback Analysis - revised 2011_04_12”, which I can make available if anyone is interested.
Best regards, Pete Ridley
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.. By far the most important greenhouse gas is water vapor because of its abundance and its extensive IR absorption features ... It also gives a very even-handed description of that vexed question of feedback effects in Section 7.4 RADIATIVE FORCING, but this was off topic for that thread. It appears relevant to this one and could help to answer the question.
I have E-mailed Dr. Jacob about it and also suggested that he might be interested in taking a look at the analyses provided by Roger Taguchi on Professor Judith Curry's "Physics of the atmospheric greenhouse(?) effect" thread (http://judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-62506), which challenge Dr. Jacob’s analyses. Dr. Jacob has not yet responded but Roger has and here’s his comment
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.. In general, I agree with most of what's there. The main difference remains in their continued misconception about the atmosphere being able to emit black body radiation (the grey atmosphere model is wrong, what Judith Curry has called "kindergarten science"). It can't.
What the CO2 and other greenhouse gases do is absorb IR emitted BY THE WARM SOLID OR LIQUID SURFACE OF THE EARTH, and transfer by inelastic collision energy to N2 and O2 and Ar, gases, which CANNOT re-emit IR energy to outer space. At steady state, the IR that DOES manage to escape to outer space through the windows where there is no appreciable absorption by greenhouse gases must balance the net incoming Solar radiation which is mainly in the visible and near-IR. I was glad to see that the book quotes an
albedo of 0.28, which happens to be what I calculated after correction for truncation error (the IPCC numbers give an albedo of 0.24, a little on the low side).
The wrong idea that the atmosphere actually absorbs AND THEN RE-EMITS black body radiation (according to the Stefan-Boltzmann T^4 relation) I think results in their wrong factor of 1/2 in the temperature sensitivity
relation. Compare my simple, compact and true derivation of temperature sensitivity by simply differentiating the Stefan-Boltzmann law WHICH APPLIES TO A SOLID OR LIQUID EMITTING SURFACE, NOT THE ATMOSPHERE WHICH IS A GAS which cannot emit a continuous, i.e. black body, spectrum.
Because of a cancellation of errors the book actually got close to predicting the observed 0.7 degree (they call it 0.6 degree) rise in global temperature since about 1850. They got 0.8 degrees. Multiply this by a factor of 2 to correct for their mistake in using f/2 instead of f in the temperature sensitivity formula, and you get 1.6 degrees, which means they are a factor of 2 too high (my contention)
I’m sorry that this is not easy reading but that simply reflects the complexity of the subject itself. Further details are available on Professor Curry’s "Physics of the atmospheric greenhouse(?) effect" thread and in Roger’s revised article “Net Feedback Analysis - revised 2011_04_12”, which I can make available if anyone is interested.
Best regards, Pete Ridley