CO2 global warming alarmism is based on a postulate of "radiative forcing" of 3.7 W/m2 from doubling of the concentration of atmospheric CO2 from preindustrial level of 300 ppm, with an associated warming effect of about 1 C, which after postulated positive feedback becomes an alarming 3 C. Without the radiative forcing of 3.7 W/m2, CO2 alarmism collapses to zero.
The radiative forcing of 3.7 W/m2 upon doubling of atmospheric CO2 is based on radiative transfer models based on models for absorption/emission spectra, but direct atmospheric experimental verification is lacking.
Even more conspicuously, laboratory measurements of absorptivity/emissivity of air with the low concentrations of CO2 present in the atmosphere which could support the 3.7 W/m2, are very sparse as evidenced here. The early work by Tyndall (1860s) and Arrhenius (1896) still remain as main references.
What is readily available on the web are many examples of school projects where young people are guided to supply the experimental evidence of CO2 warming which is lacking.
PS1 The main reference beyond Tyndall and Arrhenius is Hottel/Leckner with the following typical chart showing the emissivity of CO2 depending on temperature and partial pressure p_CO2 x L (atm-m), where p_CO2 = 0.00039 the partial pressure of CO2 at a total pressure of 1 atm and L is the optical thickness of CO2 which is about 1 m around the main resonance at wave number 667.
Th 3.7 W/m2 of "radiative forcing" from doubled CO2 may well be the biggest scientific "hockey stick" ever fabricated, so cleverly concocted that even prominent climate skeptics have been convinced.
PS2 Here are two Spectral Calc computation showing that the optical thickness of air with 390 ppm CO2 at a total pressure of 1 bar, is about 1 m at main resonance 667 (top graph: length = 1 m, bottom graph: length = 10 m), with a line broadening of about 2 cm^-1 in accordance with the near-resonance of Mathematical Physics of Blackbody Radiation.
I think you are wrong about data on carbon dioxide. The so-called climate scientists and incompetent physicists have just ignored the huge amount of research by engineers, and chemical engineers in particular. You have referred to Prof Nasif Nahle in one of your posts. In his article “Total emissivity of carbon dioxide and its effect on Tropospheric Temperature” he references Prof Hoyt Hottel’s book “Radiant Heat Transmission” 3rd ed 1954 and a paper by Lechner B “The Spectral and Total Emissivity of water vapour and carbon dioxide” Combustion & Flame vol 17 no 1, 1971. The Thesis by Ihab Honna Farag MIT 1976 (supervisors Prof Sarofim & Prof Hottel) titled “Radiative Heat Transmission from non-luminous Gases- Computational study of emissivities of water vapor & carbon Dioxide” has a large list of references (about 145) including research articles by a number of Germans such as K Schack “Berechnung der Stralung von Wasser dampf und Kohlendioxid” Chemie Ingenieur Technik vol 42 no2
SvaraRaderaSomething of Prof Hoyt Hottel can be found here http://web.mit.edu/newsoffice/1998/hottel-0926.html
He developed, from his research work, an equation to determine the emissivity of gases containing water vapor and CO2 based on partial pressures and path length. This can be found in chapter 5 (Heat and mass transfer) of Perry’s Chemical Engineering Handbook. Hottel also developed graphs shown in books on Process Heat Transfer based on the equation to aid design before the advent of computers.
Yes I know of Hottel and Leckner. Do they give support if 3.7 W/m2 of radiative forcing from doubled CO2?
SvaraRaderaNot in my calculations! The various factors in the equation to calculate absorptivity and emissivity are complicated. There are logarithmic factors. Three given calculated factors in Perry's Chemical Engineering handbook are for temperatures in furnaces (1000, 1500 & 2000K). It is stated the factors are valid over a 2000fold range and these need to be extended or interpolated. Prof Nahle takes a different approach and refers to graphs of Hottel etc. The graphs I have go down to 100F and need to be extended down to the lower temperature in the atmosphere.
SvaraRaderaI personally have made measurements of heat loss from surfaces (pipes) of temperatures in the range 25 to 350C to atmosphere, in furnaces where flame temperatures are in the range 2000 to 3200C and various heat exchangers with gases in the range 150 to 1200C.
My experience and calculations supported by experience indicate a) the absorptivity & emissivity of H2O vapor is much more important than CO2 - it is at least 10 times higher at the same path length and partial pressure. In the atmosphere the absorptivity of CO2 at 400pm is insignificant (my value is a little higher than Prof Nahle, however he may be correct)
b)in flames the major emissivity arises from particles.In gases flames to get high radiation it is necessary to have internal reducing conditions to crack CH4 to C*. I have improved flame emissivity from 0.45 (mainly from H2O) to 0.8 (mainly from C*) by design of gas burners
c) at surface temperatures of 50C and lower heat loss by convection is more important than by radiation. The alarmist assumptions about radiation is nonsense. Even in furnaces with flame temperatures of 3000C convection must be counted and can do damage with poor flame placement and control.
d) the term "radiative forcing" is meaningless. The driver of heat transfer is related to temperature difference. The absorption of a very small amount of radiant heat by the trace gas CO2 in the atmosphere has NO measurable effect on temperature. The heat of the atmosphere is eventually radiated to space at the top of the atmosphere by H2O (gas, liquid & solid), aerosols, particles & to a small extent by CO2. A cold atmosphere (say 220K) can not radiate back to a surface of higher temperature on earth (230 to 340K -supposed average 288K)
Your direct experience gives valuable support to the impression I get sitting in my chair and reading.
SvaraRaderaL is path length. Rather than set it to 1 meter, it would have a value of 1000m -10,000m (approx since pressure varies as well) as we look up into the sky (a slice of the troposphere).
SvaraRaderaThat 3+ order of magnitude difference is very significant and leads to emissivity near .2 rather than .01.
cementafriend, yes, these curves can be approximated with complex formulas found in engineering text books, but you have not argued anything remotely convincing to suggest the physicists are wrong. When you have a good argument, consider publishing it in a bona-fide physics journal. [Hint, prepare an argument that actually addresses the physics behind the greenhouse effect, eg, Ramanathan/Coakley 1978.]