Do Global Energy budgets make sense. ???
04-22-2010, 03:39 PM
RE: Do Global Energy budgets make sense. ???
Then we have this to consider.
Post # 80:
80.Cement a friend said
April 21, 2010 at 4:47 am
Missed the timing of the post and have not read all the comments.
I will not enter into a discussion about what some people believe is the physics but let me point out a few things that may cause a little more thought on the subject.
Jeff’s figure 1 is old. It maybe be exaggerated. For CO2 look at figure 4. There is no absorption of radiant energy at a wavelength greater than 16 micron. Both figures 1 & 4 refer to 100% CO2 and show the absorption wavelengths for CO2 too wide. Have a look at the NIST (National Institute of Standards & Technology) database http://webbook.nist.gov/cgi/cbook.cgi?ID...9&Mask=200 and I think this is the spectra http://webbook.nist.gov/cgi/cbook.cgi?ID...=0#IR-SPEC It will be seen a) that absorption at 4.2 micron is very very narrow. I believe that it is distinct and is used to identify CO2 on other planets b) the absorption band between 14 and 16 micron is like the normal probability curve with a peak absorption of 70% (not 100%). The latter band is also occurs in the H20 vapor spectra. I understand from some article including discussion on updates of the HITRAN database. The many past measurements have been contaminated by water vapor and that new missing lines have been found for water vapor.
You many have noted in the past comments on some websites about the self cooking chicken in the microwave. Regardless of the actual mechanism of radiation absorption and re-emission energy can not be created from nothing.
There are two questions the radiant absorption by CO2 a) how much does it absorb and b) what amount is transferred to other molecules to heat the surrounds.
The first question requires two calculations which both have assumptions. Firstly, there is an energy balance
For temperature calculations only the net heat transfer counts. If there are two molecules of CO2 in container with 100% reflecting surrounds at the same temperature, there will be no heat transfer between them and their temperature will not change. There can be no heat transfer from a cool (negative degree C) troposphere to a higher temperature earth surface. If 170 W/m2 are received at the surface then a similar amount (with variations from time to time of surface absorption particularly the oceans and re-emission)must leave the surface. But at the surface there is heat transfer by convection (surely everyone has sen heat hases, mirages, willi-willis, eagles and other birds gliding on up-draughts etc). Books on heat transfer and my own many calculations have found a split of something like 50:50 on land between radiation and convection. Then there is evaporation of water over seas & oceans. (I have seen no paper in which anyone actually calculates these values or even mentions Nusselt,Prandtl,or Reynolds numbers)
Then one can make a calculation of the absorptivity of CO2 using for example the Hottel (5-145 in Perry’s Chemical Engineering Handbook) which includes partial pressures, temperature of source and receiver, beam length, the wavelength emissivities. I used and assumption of a beam length of 11 km (some only use 8km atmospheric height). I came up with an overall absorptivity for CO2 of 0.007 and for H2O vapor of 0.4 on a clear day. Then considering over laps and total heat flow. My assessment is that CO2 has a negligible effect on heat absorption. (I have seen no climate-related paper which makes the slightest mention of Prof Hoyt Hottel an recognised world expert on heat transfer by radiation)
Finally, there is the second question. People have made guesses at that. The AGW people seem to say CO2 does not radiate to space.
There are others (including John T Houghton in “The Physics of the Atmosphere) that say CO2 radiates a lot to space. If CO2 re-radiates all its absorbed energy then there will be no increase in temperature. Maybe it is somewhere between.
In the end actual measurements, properly separated into various components, has be be correct. The evidence (from icecores proxies and more recently measurement by varies accurate instruments) indicates that temperature leads CO2. This can be explained if CO2 as a negligible effect on atmospheric temperatures. The evidence can not be explained if it “guessed/assumed” that doubling of CO2 will cause measurable temperature increases of 1 to 3.5 degrees C
It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.
–William O. Douglas, U.S. Supreme Court Justice, 1952
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RE: Do Global Energy budgets make sense. ??? - Sunsettommy - 04-22-2010 03:39 PM
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