This would imply that human caused global warming from a few extra parts per million was debunked and settled in 1982. Something is wrong.
It appears mainly in your understanding of how GW theory works.
The direct radiative effect of CO2 on earth's surface is a logarithmic function of concentration and is only on the order of 0.2oC per doubling of CO2. AGW hypothesis requires strong atmosperic feedbacks to achieve its trick.
http://www.meteor.iastate.edu/gccourse/model/direct/direct_lecture_new.html
Water-vapor/greenhouse feedback.Relative humidity is reasonably constant despite variations in absolute humidity. That is, an increase in temperature leads to more evaporation and increase in the absolute amount of water vapor in the air (increase absolute humidity). But since the warmer air has a higher saturation vapor pressure (can hold more water vapor), the relative humidity stays approximately constant. The increased absolute humidity, however, increases absorption of infrared radiation by the atmosphere and hence increases the greenhouse effect. Note that this increased greenhouse effect raises the surface temperature, which further increases evaporation. This feedback mechanism is not self-regulating, so we call it a positive feedback.
Cloudiness / surface-temperature feedback.As temperature increases, evaporation and absolute humidity both increase leading to more cloudiness. But the increase in clouds leads to increased reflection of solar energy and also leads to more trapping of infrared energy from the surface of the earth. The net effect (which depends on the altitude of the clouds) is thought to lead to a cooling, which makes this a negative feedback process.
as quantified by Ramanathan:
"the direct radiative effects of doubled CO2 can cause a maximum surface warming [at the equator] of about 0.2 K, and hence roughly 90% of the 2.0-2.5 K surface warming obtained by the GCM is caused by atmospheric feedback processes described above.
--- "Increased Atmospheric CO2: Zonal and Seasonal Estimates of the Effect on the Radiation Energy Balance and Surface Temperature"
(V. Ramanathan and M. S. Lian), J. Journal of Geophysical Research, Vol. 84, p. 4949, 1979.
That in a nutshell is the core hypothesis for the "greenhouse effect" as it applies to earth. By the way an actual greenhouse operates mainly by restricting convection not as a radiative forcing environment as the term is misapplied in planetary atmospheres. Old ideas of a hot house, watery Venus are where the "greenhouse" reference to global warming come from. Even for its early theories, the real story on atmospheric warmn has not been CO2 as much as the capacity of water vapor response to change in temperature at the liquid gas phase interface. When you have liquid water the amount of water vapor in the atmosphere is predominately a function of temperature at the gas/liquid surface interface by the Clausius-Clayperon relation.
For example the 2007 Version of The Encarta Encyclopedia
>>The atmosphere of the planet consists of 97 percent carbon dioxide (CO2) and is so thick that the surface pressure is 96 bars (compared with 1 bar on Earth). The surface temperature on Venus varies little from place to place and is extremely hot, about 462°C (736 K/864°F), or hot enough to melt lead. The high surface temperature is explained by an intense greenhouse effect. Even though only a small percentage of the solar energy that falls on Venus reaches the surface, the planet stays hot because the thick atmosphere prevents the energy from escaping.<<
While not "wrong" what is notible is that it fails to mention the role of Venus's cloud structure in achieving it's "greenhouse" effect. Clouds are very much the major workhorse in the Venesian atmosphere.
You see the problem with Venus is there is no liquid water at the surface to fuel a feedback effect & insufficient water vapor in its atmosphere to act as the multiplier to keep it hot if it weren't for sulfuric acid in its high altitude clouds. There would be gaping holes in its IR spectra to allow its trapped heat to escape it it weren't for the sulfuric acid aerosols in High level clouds to perform the function of essentially a dirty one way mirror to achieve the majority of its high degree of heating.
At a distance of 108.2 million km, Venus is closer to the Sun than the Earth by a factor of about Ö2, and so has about twice the incidence of solar energy. It is also much hotter at the surface, nearly 2 times more than the terrestrial mean of about 300 K. These facts are not simple to reconcile, however, because the ubiquitous and highly reflective cloud cover on Venus reflects 76% of the incoming solar flux and this results in a smaller net solar constant for Venus than for Earth. The high surface temperature must, therefore, be due to ‘greenhouse’ warming produced by the thick, cloudy atmosphere, possibly augmented by a contribution from the internal heat of the planet.
It is not simple to prove that the observed atmospheric conditions can in fact generate such a large ‘greenhouse’ effect. The problem is that the massive amounts of carbon dioxide are very effective at blocking the emission of thermal infrared radiation, but only at those wavelengths where the gas has absorption bands, which are far from covering the entire spectrum. Moderate amounts of water vapour are also required, and even then considerable spectral gaps or ‘windows’ remain. These could be blocked by the clouds, since liquid or solid absorbers present some opacity at every wavelength, the details depending on composition and particle size. The problem for early theorists was that using clouds to ‘close’ the greenhouse also tended to block the incoming sunlight, so that the calculated equilibrium temperature of the surface remained well below that observed.
This problem began to be resolved when it was realised that the clouds are made of sulphuric acid droplets, at least in the higher, most easily measured layers. These have the property of being highly absorbing at thermal infrared wavelengths, while being nearly conservative scatterers in the visible and near infrared. Thus, the clouds tend to diffuse downwards those of the incoming solar photon that they do not reflect to space, while blocking thermal emission from the lower atmosphere and surface. This explains the result, surprising at the time, that the Venera landers in the 1970s were able to photograph the surface in natural light. It also means that radiative transfer models, involving weak as well as strong bands of CO2 and H2O, plus those of the minor constituents CO, HCl and SO2, can account for the high surface temperatures by careful incorporation of the scattering and absorbing properties of the clouds.
The total solar energy diffusing through the cloud cover on Venus corresponds to about 17 watts per cm2 of surface insolation on the average, about 12% of the total absorbed by the planet and the atmosphere. The high opacity of the gaseous atmosphere and cloud at longer wavelengths requires the surface to reach temperatures high enough to melt zinc before the upwelling flux is intense enough, and at shorter wavelengths, so that equilibrium is attained. An airless body with the same albedo and at the same distance from the Sun as Venus would reach equilibrium for a mean surface temperature of only about 230 K. This 500K greenhouse enhancement of the surface temperature compares with only about 30K on Earth and 10K on Mars.
Popular descriptions that you find in encyclopedias rarely say all there is to be said about of subject by the way, they are not immune to political correctness and have been known fudge explainations by omission.
in any case this is intriguing, thanks for finding that. I'm waiting for three different servers to finish running three different programs so I'm happy to have something to research.
Try this google search string: venus water vapor H2SO4 clouds infrared OR microwave - Google Search I suspect you will run into some eye opening articles ;O)
For a more complete understanding of what atmospheric warming is actually about and the sensitivity of global warming models to CO2 in comparison to H20:
Here's an interesting study regarding LBL radiative transfer analysis of atmospheric GHG forcings versus the parameterization of the IPCC suite of AOGCMs has been documented in Collins et al. 2006, it provides useful insight as to the relative contributions of H2O forcings vs CO2 as implemented in global climate models:
Radiative forcing by well-mixed greenhouse gases:
Estimates from climate models in the
Intergovernmental Panel on Climate Change
(IPCC) Fourth Assessment Report (AR4)
http://www.agu.org/pubs/crossref/2006.../2005JD006713.shtml
http://pubs.giss.nasa.gov/abstracts/2006/Collins_etal.html
http://pubs.giss.nasa.gov/docs/2006/2006_Collins_etal.pdf
Collins, W.D., V. Ramaswamy, M.D. Schwarzkopf, Y. Sun, R.W. Portmann, Q. Fu, S.E.B. Casanova, J.-L. Dufresne, D.W. Fillmore, P.M.D. Forster, V.Y. Galin, L.K. Gohar, W.J. Ingram, D.P. Kratz, M.-P. Lefebvre, J. Li, P. Marquet, V. Oinas, Y. Tsushima, T. Uchiyama, and W.Y. Zhong 2006. Radiative forcing by well-mixed greenhouse gases: Estimates from climate models in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). J. Geophys. Res. 111, D14317, doi:10.1029/2005JD006713.
The radiative effects from increased concentrations of well-mixed greenhouse gases (WMGHGs) represent the most significant and best understood anthropogenic forcing of the climate system. The most comprehensive tools for simulating past and future climates influenced by WMGHGs are fully coupled atmosphere-ocean general circulation models (AOGCMs). Because of the importance of WMGHGs as forcing agents it is essential that AOGCMs compute the radiative forcing by these gases as accurately as possible. We present the results of a radiative transfer model intercomparison between the forcings computed by the radiative parameterizations of AOGCMs and by benchmark line-by-line (LBL) codes. The comparison is focused on forcing by CO2, CH4, N2O, CFC-11, CFC-12, and the increased H2O expected in warmer climates. The models included in the intercomparison include several LBL codes and most of the global models submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In general, the LBL models are in excellent agreement with each other. However, in many cases, there are substantial discrepancies among the AOGCMs and between the AOGCMs and LBL codes. In some cases this is because the AOGCMs neglect particular absorbers, in particular the near-infrared effects of CH4 and N2O, while in others it is due to the methods for modeling the radiative processes. The biases in the AOGCM forcings are generally largest at the surface level. We quantify these differences and discuss the implications for interpreting variations in forcing and response across the multimodel ensemble of AOGCM simulations assembled for the IPCC AR4.
:
Comparative results of this study show the relative contributions of H2O & CO2 to the anthropogenic global warming hypothesis under IPCC scenarios using the IPCC suite of AOGCMs used in the of their coming AR4 report.
vs the H2O column water vapor increase of 20%.
demonstrating the the dependancy of the IPCC suite of models to water vapor and the forcing water vapor and CO2 contributes in a relative comparison. Note the more than 10 to 1 forcing of water vapor over CO2 at the surface where global climate change has its most meaningful effect on us poor surface dwelling creatures.
Which is in the ball park of the DOE rough estimates in discussing the the efficacy of water vapor as a GHG relative to CO2:
http://www.eia.doe.gov/cneaf/alternate/page/environment/appd_d.html
"Carbon dioxide adds 12 percent to radiation trapping, which is less than the contribution from either water vapor or clouds. By itself, however, carbon dioxide is capable of trapping three times as much radiation as it actually does in the Earth's atmosphere. Freidenreich and colleagues[106] have reported the overlap of carbon dioxide and water absorption bands in the infrared region. Given the present composition of the atmosphere, the contribution to the total heating rate in the troposphere is around 5 percent from carbon dioxide and around 95 percent from water vapor."
[106] S.M. Freidenreich and V. Ramaswamy, “Solar Radiation Absorption by Carbon Dioxide, Overlap with Water, and a Parameterization for General Circulation Models,” Journal of Geophysical Research 98 (1993):7255-7264.
The work of Jack Barret provides the results of HITRAN line-by-line integration of the significance of water vapor as a green house gas in comparison to CO2, CH4 & N2O, in their respective concentrations in the atmosphere near the surface also clearly supports the above statements:
Energy & Environment, volume 16 No. 6 2005
"Greenhouse molecules, their spectra and function in the atmosphere"
by Jack Barrett, PhD (Physical chemistry, Imperial College, London)The infrared (IR) spectra of the four main GH gases over a 100 metre path length are presented in Figure 6, their concentrations being those that pertain to the atmosphere at sea-level, and in the case of water that which amounts to 45% humidity. *** SNIP ***
|
Table 1: Contributions to the absorption of the Earth's radiance
by the first 100 meters of the atmosphere |
| GHG |
% Absorption |
Absorption relative
To water vapor = 1 |
| Water Vapor |
68.2 |
1.000 |
| CO2 (285 ppmv) |
17.0 |
0.249 |
| CO2 (570 ppmv) |
19.0 |
0.271 |
| CH4 |
1.2 |
0.180 |
| N2O |
0.5 |
0.007 |
| Total [water, CO2, CH4, N20] |
86.9 |
|
| Combination with 285 ppmv CO2 |
72.9 |
1.069 |
| Combination with 570 ppmv CO2 |
73.4 |
1.076 |
Some idea of the relative contributions to global warming by the GHGs at the Earth’s surface may be calculated from the spectral data. Percentage absorption values are useful; they are calculated as %A = 100 – %T (T = transmission). The values for CO2 in the atmosphere in the pre-industrial era of 285 ppmv and double that value, so crucial to the IPCC arguments, are given in Table 1, together with the contributions from water vapour, N2O and methane. The absorption values for the pre-industrial atmosphere add up to 86.9%, significantly lower than the combined value of 72.9%. This occurs because there is considerable overlap between the spectral bands of water vapour and those of the other GHGs. If the concentration of CO2 were to be doubled in the absence of the other GHGs the increase in absorption would be 1.5%. In the presence of the other GHGs the same doubling of concentration achieves an increase in absorption of only 0.5%, only one third of its effect if it were the only GHG present. Whether this overlap effect is properly built into models of the atmosphere gives rise to some scepticism. The GHGs absorb 72.9% of the available radiance, leaving 27.1% that is transmitted of which an amount equivalent to 22.5% of the total passes through the window and the other parts of the spectral range transmit only 4.6%. For the doubled CO2 case this small percentage decreases slightly to 4.1%. These small percentage transmissions are reduced by 72.9% and 73.4% respectively by the second layer of 100 m of the atmosphere so that only ~1% in both cases is transmitted to the region higher than 200 m. |
As is readily determined from Dr. Barret's results, even with doubled CO2 concentration, water vapor constitutes more than 100*1/1.076 = 92% of the total radiative greenhouse effect in just the first 100meter column of air near the surface.
That's >92% not counting the additional radiative capacity in the troposphere above that level nor counting IR absorption of H2O in its particulate form as rain and ice content of clouds which contibute additionally to the atmospheric feedback processes discussed above.
Recalling the statements of Dr. Lindzen regarding the importance of H2O,
"Even if all other greenhouse gases (such as carbon dioxide and methane) were to disappear, we would still be left with over 98 percent of the current greenhouse effect."
Cato Review, Spring issue, 87-98, 1992;
speaking of the role of H2O as a GHG responding to thermal inputs from solar insolation, not even accounting for the additional effects of solar activity in the modulation of ionizing radiation affecting aerosol chemistry and the cloud formation processes of the atmosphere as well it is clear that we can establish that H2O contibution to total heating rate in the troposphere of water vapor as compared with CO2 gas, it is clear 92% < H2O% < 98%.
Given the DOE statement "the contribution to the total heating rate in the troposphere is around 5 percent from carbon dioxide and around 95 percent from water vapor."
We can turn other studies in the field that show why CO2 has such a low forcing at earth's surface:
Kiehl, J. T. and V. Ramanathan, 1982: Radiative Heating Due to Increased CO2: The Role of H2O Continuum Absorption in the 12-18 mm Region . J. Atmos. Sci., 39: 2923-2926.
Introduction:
Within the 12-18mm region, both H2O and CO2 absorb and emit radiation giving rise to the so-called "overlap." This study examines the role of this H2O-CO2 overlap in the CO2-climate proble. The H2O absorpotion, within the 12-18mm region, that has been traditionally included in climate models (Manabe and Wetherald, 1980; Ramanathan, 1981) is the line absorption due to the pure rotational band of H2O. In addition to the pure rotaional band, there is very strong "continuum" absorption by H2O in the 12-18 um region (Roberts et al., 1976). The few climate model studies which include the effect of this continuum (e.g., Wang et al., 1976) have not examined its rl in the increased CO2 radiative effects. In order to isolate the overlap effects of various H2O radiation processes in the 12-18mm region, we comput the radiative heating of the surface/troposphere system due to double CO2 with and without the H2O overlap effects.
*** SNIP ***
[p. 3] We consider three cases in which CO2 is doubled and the changes in longwave fluxes are computed for no overlap between water vapor and CO2. This is achieved by setting the transmissivity of H2O in the 12-18mm region to be equal to 1. In the second case, the H2O overlap due to the rotaional band is included. Finally we include the H2O continuum and calculate the flux changes using both continuum and line transmissivity (for the pure rotation band) described in the previous section. These cases illustrate the most important aspects of the water vapor overlap.
*** SNIP ***
Table 1. The effect of CO2 increase on the hemispherically
averaged net radiative heating (wm-2). DFTN is the change
in the net outgoing longwave flux (at the tropopause) due to
doubling of CO2; negative values of this quantity denote
heating of the joint surface/troposphere system. DF¯s is the
is the change in the downward longwave flux at the surface.
| Case |
Comments |
-DFTN |
DF¯s |
| 1 |
Without H2O absorption in
12-18 mm region |
4.69 |
3.65 |
| 2 |
H2O line absorption |
4.18 |
1.56 |
| 3 |
Line plus continuum absorption |
3.99 |
0.55 |
An effect that can readily be understood by comparing the absorption of the major active CO2 IR spectrum to the overlapping response of water vapor in the same region of the terresterial blackbody spectrum.
refer:
To continue with the basics:
According to the IPCC Third Assessment Report (TAR), The IPCC First Assessment Report: Scientific Assessment of Climate Change, Houghton et al. (1990) gives DF = 6.3 ln(C/C0) wm-2 for calculating changes in atmospheric concentration of CO2, for a radiative forcing at tropopause of 4.37 Wm-2 for a doubling of CO2 concentration in the atmosphere, approximately 9% larger than the mean value assumed by the main GCMs at that time [Cess et al. 1993]. The formula is said to derive from a paper by Wigley (1987), DF = 6.33 ln(C/C0) wm-2 with its genesis in the model of Kiehl and Dickinson (1987) and, over the range of 250-600ppmv, "is probably accurate to about ±10%".
NOAA, on the other hand uses, the more uptodate & considered to be a more accurate representation of CO2 forcing provided in DF = 5.35 ln(C/C0) wm-2 [Myhre et al. 1998, Geophys.Res.Lett., 25:2715-2718] to assess the relative contribution of IR active gases in the atmosphere in their empirical AGGI index @ http://www.cmdl.noaa.gov/aggi/. Which works out to be 3.71 wm-2 outwelling IR at tropopause as opposed to the 4.37 wm-2 forcing most often cited by the IPCC.
One should also understand that this relation for CO2 forcing represents outgoing IR at the troposphere not downwelling flux as it would be perceived at the surface.
An older but never the less helpful article in demonstrating the conventions used for citing CO2 forcing as it is practiced in the GW community.
Trace-Gas Greenhouse Effect and Global Warming
Underlying principles and outstanding issues
Ramanathan, Volvo Environmental Prize Lecture - 1997 :
page 4:
Magnitude of the Surface Warming:
The Case of CO2 Doubling
To illustrate the processes that determine the magnitude, we will perform a thought experimient of a doubling of the CO2 concentration, at say, time t = t0. The approach and results (Fig. 3) described below follow closely the study by Ramanathan (38). The system is initially in global energy balance before t0, such that Q(t<t0) = 0.0, where Q = S-F, S is the absorbed solar energy by the surface-troposphere system and F is the net (up minus down flux) longwave emission at the tropopause.
Principles of radiative convective adjustment are invoked to explain how feedbacks govern the magnitude of the warming. The global energy balance s reconciled with surface energy balance to illustrate the response of the hydrological cycle, which in turn feeds back on the warming through the so-called, water vapor feedback, cloud feedback (discussed in the last section) and snow/ice albedo feedback.
Radiative-Convective Adjustment
(i) Response at t = t0: The immediate response will be a reduction in the OLR at the tropopause by about 3.1w/m2 (Fig. 4) and an increase in the downward emission from the stratosphere by about 1.2w/m2 (Fig. 4). The sum of thetwo is the net forcing at the tropopause; in other words, the instantaneous forcing Q(t0)= 4.3w/m2.
Before proceeding further, we will discuss four aspects of the CO2 forcing to clarify certain misconceptions.
- Strong and Weak Bonds: Between the four important isotopes of CO2, there are several tens of strong fundamental and weaker isotopic and excited state absorption bands in the 13 to 18 mm region. The weak-band radiative forcing increases almost linearly with the CO2 concentration (39) and the often stated logarithmic dependance of the CO2 greenhouse effect (IPCC (1)) applies only to the strong bands (39). However, for present day CO2 levels, the strong bands contribute more than 80% of the forcing and hence the CO2 total greenhouse effect increases almost logarithmically with its concentration.
-Non-Uniform Forcing: CO2 radiative frocing is not uniform globally, even if the increase in CO2 concentration is globally uniform (40). The surface-troposphere radiative forcing (Fig. 4) is a factor of 2 to 3 larger in the tropics (~4.5w/m2) when compared with the polar forcing (1 to 3 w/m2) and, furthermore, it is larger in summer than in winter (40). The nonlinear increase of the Planck function with temperature, the nonlinear increase in hot bands' absorption coefficient, with temperature, and latitudinal variations in cloudiness contribute to the non-uniformity of th forcing.
- Stratospheric Contribution: The downward emission from the CO2 rich stratosphere contributes significantly to the tropopause radiative forcing as shown in Figure 4. In the tropics, this is about 25%, while at the polar regins the stratosphere cntributes more than 50%. The increase form tropics towards the poles is due to the factor of 2 increase in the mass of the stratosphere. The increased CO2 also cools the stratosphere and this decreases the downward emission only slightly (compare the "STRATOSPHERE T=0" curve in Figure 4, which does not account for statospheric cooling, with the STRATOSPHERE NFB: curve which does.).
"-Importance of Back Radiation at the Surface: It is commonly stated that CO2 absorbs upwelling radiation and then re-emits it to the surface as back radiation. The CO2 bands overlap with water vapor bands whose opacity is so large that most of the back radiation from CO2 is absorbed by the intervening layer of H2O. As a result, the CO2 back radiation at the surface increases by only 1.2w/m2 (Fig.3) as opposed to the 4.3w/m2 tropopause radiative forcing.
(ii) Response at t = t0+ few months: The stratosphere cools and comes into a new radiative equilibrium with the CO2 rich atmosphere, which reduces the increased downward emission at the tropopause by a few tenths of w/m2 (Fig. 3). The Q after the stratosphere has adjusted is:
Q(t=t0+ few months) ~ 4.2w/m2
This adjusted forcing is the number used in most assessments (including IPCC)."
One should note that nearly all IPCC measures of forcing are effective tropopause values.
This is a very subtle but very important convention to be aware of in interpreting any results published in AGW related papers. Such papers rarely specify the conventions used, as they are assumed to be known by the folks for who these papers are written, the trained person familiar with the conventions of climate analysis papers.
To continue from page 4 and going forward to page 5:
(iii) Response at T = T0 + decades: The surface-troposphere will warm until the entire system reaches a new equilibrium, i.e., Q =0 again. The magnitude of the warming is governed by the rate of heat loss per degree increase in Ts, l = -dQ/dTs. l is referred as the feedback factor since it is governed by feedback processes involving water vapor, clouds, ice and snow, ocean-atmosphere dynamics (to mention a few possibilities). l is positive, since Q decreases with an increase in Ts to restore energy balance. We now have for any time after t0, Q(t) = 4.2 - l[Ts(t)-Ts(t=t0)]. Ts will increase until, Q=0 again, such that from the above equation we have for the equilibrium warming DTs
DTs (2 CO2) = 4.2/l
For the simplest of all possible responses, S, the solar absorption does not change and F can be expressed as black-body emission, i.e. F=sT4, where Te, the effective emission temperature, is 255K; such that: l = -dQ/dTs. = 4 sTe = 3.8 m-2K-1. For this simple system, devoid of all feedbacks except black body emission, the magnitude of warming is 1.1K. If we next consider the realistic case of atmospheric emission happening in discrete spectral bands (Fig2), l reduces to about 3.3W m-2K-1 and surface warming is:
DTs (2 CO2) = 4.2/3.3 = 1.3K
You will note this is not calculating the results of radiative forcing due to 2XCO2 back radiation at 288K with atmosphere conditions at the surface.
It is calculating effective tropopause, (i.e. top of atmosphere nil atmosphere) referenced flux conditions and thus effective tropopause referenced temperatures, not temperature which one obtains from measurements at existing conditions at the surface. The conditions at surface are governed as explained at the beginning of the quoted sections regarding -Importance of Back Radiation at the Surface: above and as used in --- V. Ramanathan and M. S. Lian, J. Geophys. Res., Vol. 84, p. 4949, 1979.
In Ramanathan's 1997 lecture, the IPCC conventions mentioned on page 4 in section (ii) represent an effective change at tropopause and not the surface calculation at 288K with the specified 1.2w/m2 CO2 back radiation increment as heat flux from CO2 which would be the actual contribution of CO2 direct radiative forcing at the surface.
To determine the effects on temperature measurement at the surface from the back radiation of 2XCO2 (1.2w/m2), the calculation proceeds as follows:
Starting with 288K initial surface temperature @ current atmospheric conditions.
One applies the Stefan-Boltzman relation using an emissivity of 1 as we have the value of forcing taking the overlap atmospheric absorption of IR into account already:
F=esT4
where:
F = total amount of radiation emitted by an object per square meter (Watts m-2)
e is emissivity, the ratio of the radiation emitted by a surface to that emitted by a black body at the same temperature.
http://www.electro-optical.com/bb_rad/emissivity/emisivty.htm
s is a constant called the Stefan-Boltzman constant = 5.67 x 10-8 Watts m-2 K-4
T is the temperature of the object in K
to determine the total radiative forcing necessary to maintain the atmosphere/surface greenhouse temperature at the current 288oK surface temperature of the earth.
Flux (F288) at the Earth's surface with atmosphere = 1*5.67*10-8(288oK)4 = 390.08 w/m2
To which we add the increment of 2XCO2 direct radiative forcing at the surface DF = 1.2w/m2 (i.e downwelling flux at the surface where our interest is, as opposed to outgoing at tropopause at the topof atmosphere.)
F = 390.08 + 1.2 = 391.28 w/m2
And solve for the resultant equilibrium blackbody temperature at the surface for the doubling of CO2 concentration in the atmosphere.
T = (E/s)0.25 = (391.28/5.67*10-8)0.25 = 288.22K
Final step we determine our result in terms of change in temperature (DT) by subtracting our initial state temperature 288K for the resulting increment of temperature do (2 CO2) direct radiative forcing alone.
DT = 288.22-288 = 0.22K
Measurable at the surface, as opposed to 1.3K effective value at the tropopause reference convention of IPCC papers.
Note l as calcutlated by Ramanathan is not used in this calculation. l as such it is often used in climate related research papers, is a measure of a linear approximation of DT/DF (fixed increment of change for increment of radiative forcing applied) used to simplify calculation but accepting some error as the Stefan-Boltzman relation is a non-linear 4th power equation and does not have a straight line solution.
The integrated and precision amount of change in temperature for a blackbody solution is calculated as I have done above and clearly demonstrates Ramanathan's statement concerning the direct radiative effect of CO2.
"the direct radiative effects of doubled CO2 can cause a maximum surface warming [at the equator] of about 0.2 K, and hence roughly 90% of the 2.0-2.5 K surface warming obtained by the GCM is caused by atmospheric feedback processes described above.
--- "Increased Atmospheric CO2: Zonal and Seasonal Estimates of the Effect on the Radiation Energy Balance and Surface Temperature"
(V. Ramanathan and M. S. Lian), J. Journal of Geophysical Research, Vol. 84, p. 4949, 1979.
In regards
http://www.eia.doe.gov/cneaf/alternate/page/environment/chap2.html
Scientists used to believe that Venus fell victim to the greenhouse effect because 96 percent of its atmosphere is carbon dioxide, with nitrogen accounting for almost all the remainder [26]. It is now generally agreed within the planetary atmospheres community that carbon dioxide alone would lead to an average temperature of less than 25oC. The primary reason that Venus is warmer than this is the presence of sulfuric acid cloud cover over the entire planet, extending from about 50 kilometers to 70 kilometers from the surface.
Venus blackbody temperature is 231.7K [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html ]
By the Boltzman black body relation:
Blackbody flux (E231) without atmosphere & clouds effects = 5.67*10-8(231.7oK)4 = 163.41 w/m2
Venus: Surface pressure = 92 bars, @231.7K, CO2 concentration = 0.962;
Earth Surface pressure = 1 bar, @231.7K, @ CO2 concentration = 380ppmv, Tropopause IR flux = 139.79 w/m2
according to 1976 standard atmosphere MODTRAN Radiation Calc (with 0 GHGs other than CO2)
@ CO2 concentration = 380ppmv & 231K temperature condition, = 139.79 w/m2
@ CO2 concentration = 000ppmv & 231K temperature condition, = 152.23 w/m2
Yielding a total absorption of (152.23-139.79) = 12.44 w/m2 flux absorbed by 380 ppmv CO2 @ 231.7K temp.
The total concentration of CO2 on Venus with respect to 380ppmv level found on Earth is
92*0.962/(1*0.000380) = 230,373.68 times earth CO2.
Therefore Venus total CO2 IR flux absorption @ Venus 231K blackbody condition with 92 bar 0.962 CO2 is
(5.35*ln(230,376.68) + 12.44) = 78.5 w/m2.
The resulting Venus temperature due to CO2 absorption alone @ Venus blackbody conditions becomes:
[(163.41 + 78.5)/(5.67*10-8)]0.25 = 255.57K
Thus the maximum change in temperature on Venus for its current level of CO2 & pressure is
(255.57-231.7) = 23.87K (i.e. 23.9oC)
Which I would say demonstrates the EIA statement:
http://www.eia.doe.gov/cneaf/alternate/page/environment/chap2.html
Scientists used to believe that Venus fell victim to the greenhouse effect because 96 percent of its atmosphere is carbon dioxide, with nitrogen accounting for almost all the remainder [26]. It is now generally agreed within the planetary atmospheres community that carbon dioxide alone would lead to an average temperature of less than 25oC. The primary reason that Venus is warmer than this is the presence of sulfuric acid cloud cover over the entire planet, extending from about 50 kilometers to 70 kilometers from the surface.
Very well.
