From: Denis Rancourt <>
Date: Tue, May 10, 2011 at 4:10 PM
Subject: climate
To: gschmidt@giss.nasa.gov, mann@psu.edu, ammann@ucar.edu, rasmus.benestad@met.no, rbradley@geo.umass.edu, rahmstorf@ozean-klima.de, rahmstorf@pik-potsdam.de, steig@u.washington.edu, d-archer@uchicago.edu, rtp1@geosci.uchicago.edu, garidel@marine.rutgers.edu, jrbouldin@ucdavis.edu, wmconnolley@gmail.com
Dear Gavin Schmidt, Michael Mann, Caspar Ammann, Rasmus Benestad, Ray Bradley, Stefan Rahmstorf, Eric Steig, David Archer, Ray Pierrehumbert, Thibault de Garidel, Jim Bouldin, and William Michael Connolley,
Dear contributors to Real Climate,
Dear colleagues,
Re: A new article for your review
Please consider this new article:
"Radiation physics constraints on global warming"
http://activistteacher.blogspot.com/2011/05/radiation-physics-constraints-on-global.html
I believe this article contains proof of incorrect/unjustified assumptions and corresponding results published on the Real Climate web site.
I would welcome your reviews of my article for posting.
I will feature all your comments and criticisms on the same blog.
Sincerely,
Denis Rancourt, B.Sc., M.Sc., Ph.D. (Physics)
Former professor and environmental researcher, University of Ottawa, Canada
http://rancourt.academicfreedom.ca/blogs-etc/scientific-work.html
From: Raymond P.
ReplyDeleteDate: Tue, May 10, 2011 at 4:24 PM
Subject: climate
To: Denis Rancourt
Cc: allrc
Dear Mr. Rancourt,
Your discussion of energy balance starts off soundly, but then you get mired in a nest
of mistakes, the most critical of which is your misunderstanding of Kirchoff's Law.
Kirchoff's law only requires that emissivity and absorptivity be equal at the same
wavelength. Since Earth's incoming radiation is shortwave, but outgoing is
longwave (infrared), there is no contradiction between a surface emissivity
near unity and an albedo of around 0.3 . Your calculation erroneously
attributes the effect of atmospheric infrared opacity to surface emissivity.
By the way, climate models do not assume surface infrared emissivity to be unity.
The deviations from unity are not a major effect in the surface budget, but
the emissivity of common Earth materials can be easily measured, and
in full GCM's the emissivity is taken into account in the lower boundary
condition for radiation models.
Thank you for your interest in this subject.
--Ray Pierrehumbert
From: Michael Mann [mem45]
ReplyDeleteDate: Tue, May 10, 2011 at 4:10 PM
Subject: Re: climate
To: denis rancourt
I will be away from my email through May 14, 2011.
Any email sent before then may remain unread and be discarded. If your message
is important, you will need to resend after that date.
From: Denis Rancourt <>
ReplyDeleteDate: Tue, May 10, 2011 at 5:05 PM
Subject: Re: climate
To: "Raymond P."
Cc: allrc , gschmidt@giss.nasa.gov, mann@psu.edu, ammann@ucar.edu, rasmus.benestad@met.no, rbradley@geo.umass.edu, rahmstorf@ozean-klima.de, rahmstorf@pik-potsdam.de, steig@u.washington.edu, d-archer@uchicago.edu, garidel@marine.rutgers.edu, jrbouldin@ucdavis.edu, wmconnolley@gmail.com
Dear Mr. Pierrehumbert,
Thank you for your critique. I will post it. You are correct that Kirchoff's Law strictly applies for a given wavelength and that I took it to apply at all wavelengths for a given material. (I took albedo and emissivity to be wavelength-independent. This could indeed be rather off, depending on the material.)
Could you point me to a paper where shortwave albedo and longwave emissivity were measured in a common Earth material?
Do you believe that a correct longwave emissivity for Earth is 1 and that therefore the atmosphereless Earth would be at -19C? This is stated on the RealClimate web site.
Also, it would be useful if you could state what other errors you have found in the article, since you have already ascertained these errors.
Sincerely,
Denis Rancourt
From: Raymond P.
ReplyDeleteDate: Wed, May 11, 2011 at 12:11 AM
Subject: Re: climate
To: Denis Rancourt
Cc: gschmidt@giss.nasa.gov, mann@psu.edu, ammann@ucar.edu, rasmus.benestad@met.no, rbradley@geo.umass.edu, rahmstorf@ozean-klima.de, rahmstorf@pik-potsdam.de, steig@u.washington.edu, d-archer@uchicago.edu, garidel@marine.rutgers.edu, jrbouldin@ucdavis.edu, wmconnolley@gmail.com
Emission-weighted emissivity is one of the easiest quantities to measure. It is even routinely used
in engineering studies. Detaied spectrally resolved emissivity measurements are routinely
reported in Icarus and JSQRT, since they are crucial to the use of infrared spectroscopy
in estimating mineral composition of planetary surfaces. The literature is far too vast to
summarize, but an example of some typical emissivities at various temperatures for
common building and terrestrial materials is listed, for exampe, at:
http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Emissivity.htm&ID=254#anchor4
Also emissivity can be computed in a straightforward way from measured absorption
coefficients of condensed substances. Detailed data for water, water ice and CO2 ice
is given in Chapter 4 and 5 of my book, Principles of Planetary Climate. Data sets
and references are found on the book web site. (go to geosci.uchicago.edu/~rtp1 and
follow links to ClimateBook).
The emissivity of ice and water, which makes up most of the surface of the Earth,
is very accurately known. The emissivity of land varies more, especially
in response to vegetation cover, but it is known well enough for the purposes
of determining energy balance; there can be problems with microwave emissivity
of land surfaces which complicate doing microwave retrievals over land in
some circumstances.
I do not actually agree with the statement that the Earth's temperature would
be -19C if you removed the atmosphere. This is a true statement of what
you would get if you replaced the atmosphere with an IR-transparent
atmosphere (e.g. N2), which could still transport heat, and if moreover
you could prevent the ocean from freezing over. In reality, if you did that,
the oceans would freeze, and the mean temperature would be much
colder than -19C (see my AREPS Neoproterozoic review article for
numbers). But if the Earth had no oceans and you took away the
atmosphere, first of all, you would also take away the clouds (which
changes the albedo) and second of all you would take away heat transport.
In that case, the temperature distribution would be rather like the Moon --
100C at the subsolar point, maybe -100C on the night side. (Slightly
warmer than the Moon on the night side, because the Earth is more
rapidly rotating, so there's less time for the surface to cool down).
But there is absolutely zero question that removing CO2 from the
Earth's atmosphere would make it much colder than -19C, and
probably cause the Earth to turn into a snowball. The radiation
physics of this is unassailable, and based on more than a century
of work by some of the best physicists around, backed up by
thousands of laboratory and satellite measurements. You are
really barking up the wrong tree.
--Ray Pierrehumbert
From: Denis Rancourt
ReplyDeleteDate: Wed, May 11, 2011 at 8:40 AM
Subject: Re: climate
To: "Raymond P."
Cc: all-same
Thank you for your detailed response.
From now on, whenever I describe the simple radiation balance equations I will stress that the albedo is for shortwave whereas the emissivity is for longwave (and that Kirchoff's Law therefore is not relevant). That arbitrary step of setting emissivity equal to 1 in textbook descriptions (without explaining that water and vegetation emissivities are close to 1) always bothered me, since I was 18 in first year.
I will make a revised article and I will also correct others who may make the same error about Kirchoff's Law.
Thanks.
Denis Rancourt