This is a guest post from talkshop contributor Ed Caryl. It is an expanded version of an article he had posted on Pierre Gosselin’s excellent ‘notrickszone’ website a while ago. I think this needs wider exposure. I’m not an expert in radiative physics, but I’d welcome the views of those who are in response to this interesting piece. If Ed is right, there’s some serious ‘splainin’ to do on the part of the atmospheric physicists. I’m not sure widened ‘wings’ on absorption frequencies are going to cover it. – TB.
UPDATE 22-9-2012: The latest version of Ed’s Article is here. He has rerun the online MODTRAN model with the ‘water vapour scale parameter modified in line with suggestions made in comments, and added some other further material and analysis.
Analyzing the Earth’s Heat Radiation Using MODTRAN
By Ed Caryl
The Climate Team has always claimed that a doubling of CO2 would add 3.7 Watts/m2 to the global climate budget and thus this would fry us all. This fate is their religion’s version of Hell, except we will all suffer this rather than just the “sinners,” thus giving them leverage to force us to do their will. Many bloggers, and some others, notably even the Berkley Earth Surface Temperature (BEST) study,[i] have pointed out that there are many locations that are cooling rather than warming. The warmists would have us believe that these cooling stations are just due to local phenomenon, such as albedo change, land use, site moves, or other changes, and that the warming stations are not due to UHI.
The greenhouse effect is described as an increase in downward infrared radiation due to water vapor, carbon dioxide, methane, ozone, and CFC’s in the atmosphere. But strangely, there are very few measurements of this radiation in the only way that tells us if this is true, measuring the spectrum. Each of the above gases absorbs and re-emits radiation at specific wavelengths. These emission lines should change when the mixture of gases changes. A Spectrometer designed to operate at these wavelengths will tell us if this is true.
MODTRAN is a computer program that was initially developed by the US Air Force in the late 1980’s that does a line-by-line analysis of the IR
spectrum transmitted by the atmosphere. An on-line version is available at the University of Chicago, here.[ii]
In the 24 year history of MODTRAN, the US Air Force and many other organizations, including climate scientists, have validated the software for their own purposes. The best way to prove that it is valid for climate studies, is to show comparable spectra from other sources.
Infrared astronomers are quite familiar with the problem of atmospheric IR. IR astronomy is not easily done on the earth’s surface because the lower atmosphere is nearly opaque to IR because of moisture in the air. Consequently IR astronomy is done at high altitudes, at very cold, or at very dry locations, or all three. The Atacama Desert in Chile, the top of Mauna Kea in Hawaii, the south pole, airborne observatories, or satellites are the favored locations.
The web was searched for any image of the back radiation spectrum. None were found for any temperate or tropical zone. The only spectra found are from the Arctic at -10°C, and the south pole at -30°C. From the spectral shape, it appears that the Arctic data was taken at Summit Camp on the Greenland ice sheet. Those are the next figures with the MODTRAN version for comparison.
Over most of the earth, figure 3 is the spectrum seen by a spectrometer looking at the sky. Only at very cold, very dry, and/or very high locations will any features be seen in the spectra. The available literature use either figure 1a or 2a over and over, as if those spectra represent the whole globe. They do not.
From the top of the atmosphere we have a similar situation. The available spectra are taken over deserts. The following figure is from the University of Chicago web site here,[v] and is a comparison of the IRIS Satellite spectra with MODTRAN set for desert conditions. IF MODTRAN hat been set for the exactly the same temperature and humidity as the satellite observed, the match would have been nearly exact.
Why CO2 Does Nothing
When I first began exploring MODTRAN, the numbers it produced for downward radiation at the surface, the “back radiation”, seemed to make no sense. It nearly always produced the same number, and I thought that part of the program was broken. On reflection, it became clear that the numbers were correct and that I had fallen into the warmist trap of believing that CO2 really does something to the Greenhouse effect. When the numbers in the very low humidities were charted, all became clear.
Here is what Modtran says about downward or “back” radiation at the earth’s surface for values of humidity from 0 to 90% and CO2 from 0 to 1000 ppm. The IPCC agreed translation of a change in radiation to a change in temperature is a change of 1 W/m2 = a change of 1°C.
Figure 6: You should notice that the legend cites six traces, but you see only five. That is because the 50, and 90% humidity traces are superimposed. There is very little change in the downward radiation for any humidity from 10% and above and for any CO2 concentration from zero to 1000 ppm, or indeed for any concentration of CO2 up to 10,000 ppm.
As you can see, only in the driest desert on earth will increasing CO2 increase the “back” radiation. Water vapor is by far the strongest greenhouse gas, but it is nearly saturated at 10% humidity. At 10% humidity and above, no amount of CO2 does anything. Most of the humidity on earth is in that area on the right where doubling CO2 will do nothing to increase the long-wave radiation from the sky. Yet another CAGW fail.
Why the Earth is Cooling
Here is the result of calculating the outbound long-wave radiation (OLR) at the top of the atmosphere (TOA) , or as it is labeled in MODTRAN, I out. The settings used were: CH4 – 1.8 pmm, Tropical Ozone 800 ppb, Strat. Ozone 1, Ground T offset – 0°C, hold water vapor – Relative Humidity, Water Vapor Scale – at 0, 10, 50, and 90 percent, Locality – 1976 U. S. Standard Atmosphere, No Clouds or Rain, Sensor altitude 100 km, Looking Down. These values are the best at representing a global average. The default temperature the program uses is 15°C. This produced the following table and chart for various CO2 and water vapor values. Lesser values mean less heat escapes the earth and the earth warms. This is the “greenhouse effect”.
Figure 10: A chart of the outbound radiation increase since 1948. There has been a more than 1 Watt/m2 increase in outbound radiation in that interval, despite rising CO2.
Humidity has been decreasing in the upper atmosphere over the last 60 years. That offsets the rising CO2. We saw the cooling in the 70’s but increased solar radiation along with ocean cycles held off the cooling over the last 20 years. That period has now come to an end.
None of the charts and graphs you will see in the climate literature touting global warming caused by CO2 will include considerations that atmospheric water vapor might change as well. If they do consider water vapor, the warmists believe that a warmer climate caused by CO2 will increase water vapor. First, it isn’t warming. Second, humidity is decreasing.
Mother Earth has an excellent thermostat system. Even if somehow average humidity should increase to 50% and CO2 goes to 1000 ppm, only about 0.55 Watts/m2 will be added. This is unlikely in the extreme, and might add a 0.5°C to warming. No one would notice. A more likely scenario is that humidity will fall further or stay the same, resulting in no warming or a rise of less than 0.4°C.
In light of figure 10, why have we not seen global cooling? We did in the period up to 1980. Since then, the answer is clouds and the sun (and constant temperature record adjustments by GHCN, GISS, UEA, etc.). If falling humidity at nearly all levels in the atmosphere, there are less clouds. This allows more solar radiation to reach the surface, compensating for the radiation leaving the TOA. It all balances out. A link to more reading on this, here.[vii]
My question is: Why have the professional “Climatologists” not done the simple work that I did on a lazy Saturday afternoon with my laptop? They must know that water vapor nearly wipes out CO2 in warming the earth, and that cloud and albedo changes do the rest. What’s their excuse for this massive “oversight”?
Edward B. Caryl worked in high technology for 50 years, as an Electronics Technician, Applications Engineer, Script Writer/Producer, and Product Marketing Manager. Ed started his career in the U. S. Air Force. During part of that time he maintained the weather instrumentation on Typhoon/Hurricane Hunter aircraft in the Pacific. He also worked as an Electronics Technician at Boeing Aircraft and for RCA Service Company at Thule Air Base in Greenland. Ed then majored in physics at the University of Washington for two years, also taking courses in math, chemistry, anthropology, sociology, economics, and creative writing. Ed spent the last 40 years of his career in research, product support, and marketing at Tektronix, Inc., a worldwide manufacturer of electronic test and measurement equipment. His work required understanding the measurement needs of a wide range of customers in the scientific community and assisting those customers in making and analyzing measurements. He has had a life-long interest in the sciences, reading on a wide range of subjects. He and his wife are now retired and living in New Mexico. His hobbies are woodworking, writing, and astronomy.