13 Sep (PRINCIPIA-SCIENTIFIC) – This article shows that at least THREE TIMES as much heat is radiated back into space by CO2 in the upper atmosphere as is ‘back-radiated’ to the Earth’s surface at this wavelength.
by Bevan Dockery
On January 1st 1989 the nations of the world took action, via the Montreal Protocol on Substances that Deplete the Ozone Layer, to eliminate the production of certain atmospheric pollutants; the man-made chlorofluorocarbons (CFC’s) and hydrochlorofluorocarbons (HCFC’s), because they caused ozone depletion in the stratosphere. This depletion allows excessive ultraviolet-B (UV-B) from the Sun to reach the Earth’s surface where it increases the risk of skin cancer, cataracts, and suppresses the immune system for humans and also damages other life forms.
The action of ozone is to absorb the radiance from the Sun across a number of different frequency bands including the damaging UV-B band. An extensive database of the infrared absorption spectra for gases is maintained on the HITRAN Web site by the Harvard-Smithsonian Centre for Astrophysics, Cambridge, MA, USA, in conjunction with the V.E. Zuev Institute of Atmospheric Optics, Tomsk, Russia. It includes the absorption spectra for water vapour, carbon dioxide (CO2), methane, (CH4), nitrous oxide (N2O), and the halocarbons which the UN’s Intergovernment Panel on Climate Change (IPCC) has stated are, in order of importance, the main ‘greenhouse gases’ in the atmosphere.
While we have been told that ‘greenhouse gases’ are a cause of dangerous surface global warming, climate scientists have failed to tell us that they also absorbs radiation from the Sun in the upper atmosphere thereby protecting the Earth in a similar fashion to the protection given by ozone. For the case of absorption by CO2, the most prominent spectral line is at a wavelength of 4.3 microns.
Applying Planck’s Law this gives us a spectral radiance of no more than 0.73 Watts per (steradians metre squared) per micron. This is for an Earth emitting at a temperature of 288 degrees Kelvin, dependent on the emissivity at the time. For the incoming Sun’s spectral radiance at the Earth’s orbit, the figure is 2.24 W/(sr m^2)/micron for a Sun temperature of 5780 degrees Kelvin.
These numbers mean that at least THREE TIMES as much heat is radiated back into space by CO2 in the upper atmosphere as is ‘back-radiated’ to the Earth’s surface at this wavelength.
Clearly, absorption and re-radiation of the sunshine in the upper atmosphere at this wavelength cools the Earth and is going to cause additional cooling as the concentration of CO2 increases.
Recent alarm about the release of methane gas from areas of permafrost failed to recognise that the main absorption peak for methane is at a wavelength of about 3.3 microns.
At this wavelength the radiant flux from the Sun is of the order of 85 times greater than that from an Earth at 15 degrees Celsius. This must result in about 85 times as much infrared radiation from the Sun, at 3.3 microns wavelength, being sent back into space by the absorption and re-radiation from methane molecules in the upper atmosphere as could be re-radiated into the lower atmosphere for infrared radiation sourced from the warmed Earth.
Furthermore as the Sun’s radiation is re-emitted into space before reaching the Earth’s surface, that surface will be colder than the assumed 15 degrees Celsius and thus will release even less radiation at all wavelengths.Next in order of importance, with regard to global warming potential, is nitrous oxide. The absorption peak for this gas is at 4.5 microns at which point the incoming radiant flux from the Sun is about three times the emission from the Earth’s surface.
Once again, an increase in the concentration of this gas may cause cooling of the Earth, not warming. While the IPCC claims confidence at levels of 95% or 98% in their attribution of global warming to ‘greenhouse gases’ in the atmosphere it appears as though they are only dealing with half of the story. There does not seem to be any recognition of the ‘back-radiation’ of the incoming Sun’s radiant flux out into space by the so-called greenhouse gases.
It is little wonder that the forecasts from the climatologists’ General Circulation Models have always been incorrect if they do not take account of this effect.
Add to that a lack of consideration of the variation in the emission from the Sun and the claimed confidence levels become unsustainable.An attempt to use the HITRAN site to determine the effect of doubling the concentration of CO2 for the IAO model for a tropical atmosphere from 333 ppm to 666 ppm, balancing the inward sunshine with the outgoing Earth radiation, gave a result that was insignificant relative to the possible errors in the assumptions involved. It certainly did not accord with the extravagant claims of warming made by the IPCC and their cohort. This approach may warrant a far more detailed investigation.
The origin of a failure to comprehend the problem may go back to the mantra of the Green movement of “shortwave in, long wave out”. This completely misrepresents the actual situation whereby the Sun’s spectrum is a continuum covering a large range of wavelengths and includes within it the range of emissions from the Earth.To conclude, the correlation of increasing Earth temperature with increasing CO2 concentration (between circa 1975-1998) was not a causal but a chance statistic.
Physical science would seem to indicate that a negative correlation should exist. Either ‘back-radiation’ of sunshine keeps the Earth cooler than it might otherwise be without greenhouse gases or there is no such back-radiation in which case there is no greenhouse heating effect.