Radical New Hypothesis on the Effect of Greenhouse Gases
Posted by Michael Hammer, March 3rd, 2009 - under Opinion.
Tags: Climate & Climate Change
CLIMATE is complex but in an attempt to understand the effects of increasing levels of atmospheric carbon dioxide on global temperatures simplified General Circulation Models (GCMs) have been developed and are used by the United Nation’s Intergovernmental Panel on Climate Change (IPCC). Al Gore, in his famous movie ‘An Inconvenient Truth’, explained that as the concentration of carbon dioxide increases in the atmosphere, more energy is trapped, warming the planet. This assumption is central to the GCMs and the current consensus on climate change.
Some sceptics complain that the GCMs do not realistically simulate climate because there are many processes that can’t be adequately modelled including cloud formation. Michael Hammer, an engineer who specializes in spectroscopy, is also sceptical of the GCM but his criticism is more fundamental. In the following paper, using the basic laws of spectroscopy, he shows that a significant portion of energy loss from the Earth’s surface is by direction radiation to space at wavelengths not absorbed by carbon dioxide and other greenhouse gases. This is in direct contrast to the IPCC explanation that there is low radiation from the Earth’s surface to space and potentially high radiation from the atmosphere to space.
Science is a process of getting it wrong and hopefully learning – on this single issue Michael Hammer and the IPCC can’t both be right.
AN ANALYSIS OF THE EFFECT OF GREENHOUSE GASES IN THE ATMOSPHERE
By Michael Hammer
1. SUMMARY
Kiehl and Trenberth in 1997 published a global mean energy budget for Earth. This budget has significant implications for the proposed greenhouse mechanism and indirectly leads to the concept of an equivalent radiation altitude for Earth which changes with greenhouse gas concentrations. The K&T and similar models form a basis for the global circulation models used in climate science.
This analysis derives a partial global energy budget based on an analysis of the observed atmospheric lapse rate, and basic laws of spectroscopy, which is at considerable variance with the K&T findings. The differences have significant implications for the greenhouse mechanism and suggest that the concept of an equivalent radiation altitude has no meaning.
It also suggests that the amount of positive feedback attributed to water vapour by these global circulation models is impossible and thus that the temperature rise postulated from the predicted increase in carbon dioxide concentration is greatly exaggerated.
2. INTRODUCTION
Greenhouse gases in the atmosphere act entirely through radiative processes. Earth’s net energy balance is also entirely due to radiative processes since a planet in space can only gain or lose energy by this means. For these reasons, this paper is primarily concerned with an analysis based on radiative effects.
While this paper specifically mentions the Kiehl & Trenberth model in some detail (since it is the model used by the IPCC), it is recognised that there are other models also used in modelling, for example, the one quoted in “An introduction to Three-Dimensional Climate Modelling” by Warren Washington and Claire Parkinson ISBN 0-935702-52-0 University Science Books. While they show some differences compared to the K&T model they seem to share the same basic structure of low radiation from the surface to space and high radiation from the atmosphere to space. This is the dominant issue being questioned and the K&T model is used here as a convenient example.
3. THE ROLE OF CONVECTION AND LATENT HEAT
This paper is primarily concerned with radiative processes. This should not be taken as denying the role played by convection and latent heat. Clearly these processes have enormous effect within the troposphere and indeed are a dominant cause of our weather. They are also extremely significant in distributing heat around the planet and especially in energy transport from the equator to the poles.
Convection and latent heat effects impact on energy loss to space by changing the temperature versus altitude and latitude profiles within the atmosphere. The variation in height and temperature of the tropopause with latitude is an example of this. These represent perturbations superimposed on radiative processes. While their effects are reduced by averaging over the planet, it is acknowledged that the impact does not entirely cancel out because of the non linear relationship between temperature and energy radiated. Ignoring these effects thus introduces approximations which reduce the precision of the results obtained.
None the less, it is claimed that the mechanisms discussed in this paper are the dominant mechanisms controlling heat loss from this planet and the conclusions following from the analysis are extremely relevant in assessing the impact of green house gases in the atmosphere.
4. SOME BASIC SPECTROSCOPY
If a material absorbs light, one might intuitively expect the amount of light absorbed to be proportional to the concentration of the material, so that doubling the concentration doubles the amount of light absorbed. This is not the case as can be seen by a simple thought experiment. Imagine we have a piece of material which absorbs 50% of the light incident on it transmitting the other 50%. Doubling the concentration of material is exactly equivalent to adding a second identical piece of the material behind the first piece. The first piece absorbs 50% of the light incident on it transmitting the remaining 50%. The second piece being identical does exactly the same, absorbing 50% of the light that passed through the first piece and transmitting 50%. Thus the net light passing through the two pieces is not 0 but 25%. If we have n identical pieces the transmission will be 0.5n.
The relationship between concentration and light absorbed is not linear. Spectroscopists use the term absorbance to define the degree to which a sample absorbs a particular wavelength of light. Absorbance is defined by the equations;
Fraction of energy transmitted = 10 –absorbance
Fraction of energy absorbed = 1 – 10 –absorbance
If a sample has an absorbance of 1, it means that it absorbs 90% of the light incident on it, transmitting the remaining 10%. The absorbance of a sample is directly and linearly proportional to the amount of absorbing material in the light path (Beers law). Thus if a particular sample has an absorbance of 1 then doubling the concentration of the absorbing species for the same path length or doubling the path length with the same concentration will change the absorbance to 2.
5. THE SIGNIFICANCE OF EMISSIVITY
All material substances both absorb radiant energy incident on them, and emit radiant energy at a rate dependent on their temperature. The degree to which they absorb incident energy is often called the absorptivity and the degree to which they emit energy is often called the emissivity. However from Kirchoff’s law of thermal radiation the emissivity and absorptivity must be equal to each other.
The absorptivity/emissivity is a property of the substance and its form. A highly polished surface absorbs and emits less energy than a dull surface and a white surface absorbs and emits less energy than a black surface. What Kirchoff’s law is stating is that absorption of radiant energy and emission of radiant energy are reciprocal processes, a material that does not absorb will also not emit and vice versa. The same factor governs both to an equal extent.
Most of the atmosphere is made up of nitrogen and oxygen which do not significantly absorb infrared energy because their emissivity in this portion of the electromagnetic spectrum is exceptionally low. This means they also do not emit significant infrared – they are not greenhouse gases. Other gases however have a very strong ability to absorb energy at some wavelengths between 4 and 50 microns (the approximate range of emission wavelengths from earth’s surface). They are the greenhouse gases and the most significant is water vapour followed by carbon dioxide and then methane and ozone. Because their emissivity is high at the absorption wavelengths and low at other wavelengths they also selectively radiate energy at these same absorption wavelengths.
5. AN ANALYSIS OF THE KIEHL AND TRENBERTH MODEL
This model is documented at;
www.cgd.ucar.edu/cas/abstracts/files/kevin1997_1.html
(from Bull Amer. Meteor Soc, 78, 197-208 1997).
There is an update dated 2008 at;
chrisclose.wordpress.com/2008/12/10/an-update-to-Kiehl-and-trenberth-1997/
both documents specify very similar numbers. The K&T model (2008 update) specifies the following energy flows all with the units watts/m2.
Incoming solar radiation 341
Reflected solar radiation 102
Energy radiated from earth’s surface 396
Surface radiation absorbed by the atmosphere 356
Energy radiated from surface directly to space 40
Energy emitted by atmosphere to space 169
Energy emitted from clouds to space 30
Energy transported to atmosphere via
Convection and latent heat of water vapour 97
Solar radiation directly absorbed by atmosphere 78
This data shows that energy input to the atmosphere via radiative processes = 356 + 78 = 434 watts/m2. Energy input via convective processes = 97 watts/m2. Thus energy input to the atmosphere is dominated by radiative processes (82% radiative and 18% convective).
It should also be noted that the global circulation models GCM’s use a concept called the equivalent radiation altitude. This is a hypothetical altitude from which it is assumed long wave radiation back out to space emanates. Changes in greenhouse gas concentrations are assumed to change the equivalent radiation altitude. Changes to this equivalent radiation altitude together with the known lapse rate through the atmosphere are used to calculate changes in surface temperatures.
There is a well known and documented temperature versus altitude data (lapse rate) for Earth’s atmosphere. This temperature profile is established and maintained by the need for energy balance at every altitude.
The lapse rate consists of an almost linear decrease in temperature with altitude from the surface (+14C) to the top of the troposphere – the tropopause (at between 10 – 14 km altitude) where the temperature is between about -60 and -80 C depending on latitude. Above the tropopause (in the stratosphere) the temperature rises, again almost linearly, to a maximum of about -20C at an altitude of about 50 km.
The tropopause is thus a cold region sandwiched between warmer regions above and below. For this situation to be stable (and it is stable), the tropopause must have a way of losing energy to a colder sink – otherwise it would warm up due to energy input from the adjacent regions. The only colder region available is space itself and the only energy transfer mechanism available is radiative loss.
Thermal emissions from the tropopause will all be in the 5 micron to 50 micron wavelength range (governed by the temperature of the emitter) and can only occur at the characteristic absorption/emission lines of the green house gases. There is however a problem with this scenario. Ten percent of Earth’s atmosphere is above the tropopause in the stratosphere and the greenhouse gases in this region would normally absorb the emissions from the tropopause.
Further, since the air in the stratosphere is warmer, the downwards radiation onto the tropopause would exceed the upwards radiation from it leading to net energy gain not loss. Yet the tropopause is colder than the stratosphere so it must have a mechanism for losing energy.
A solution to this apparent paradox is that there is an abrupt change in the greenhouse gas composition at the tropopause such that the tropopause can radiate at wavelengths which the stratosphere is not capable of absorbing. The tropopause represents a temperature inversion which greatly inhibits convection and when that is coupled with the fact that water vapour is carried up from Earth’s surface principally by convection, one would immediately suspect water vapour as the variable component – high concentration in the troposphere and low concentration in the stratosphere. This suspicion is confirmed by the two quotes taken from the following link;
http://www.metoffice.gov.uk/education/secondary/teachers/atmosphere.html
“The atmosphere is well mixed below 100 km, and apart from its highly variable water vapour and ozone contents, its composition is as shown below”
“As well as a noticeable change in temperature, the move from the troposphere into the stratosphere is also marked by an abrupt change in the concentrations of the variable trace constituents. Water vapour decreases sharply, whilst ozone concentrations increase. These strong contrasts in concentrations are a reflection of little mixing between the moist, ozone-poor troposphere and the dry, ozone-rich stratosphere.”
This information explains how the tropopause can remain colder than the air above and below. It also explains why temperature rises in the stratosphere. Ozone is a strong absorber of ultraviolet energy from the sun and such absorption will warm the stratosphere. The energy gained will be re-emitted as thermal infrared energy at the absorption/emission lines of the greenhouse gases present, mainly CO2 and methane. The energy absorption by ozone is greatest at around 50 km altitude which is why the temperature peaks at this point and the temperature profile down to the tropopause is essentially an upside down version of what happens in the troposphere.
It should be noted that the tropopause radiates at all wavelengths corresponding to greenhouse gas absorption/emission lines but those greenhouse gases present in the stratosphere also radiate back down onto the tropopause and since they are warmer, the downward radiation exceeds the upwards radiation. Thus the only net energy loss from the tropopause occurs at the wavelengths corresponding the water vapour absorption/emission lines.
Since the tropopause can radiate relatively strongly at the water vapour absorption/emission lines (strongly enough to keep itself cold) it follows that the emissivity at these lines must be relatively high which also means that the absorptivity is also high for the reasons discussed in the earlier section titled “the significance of emissivity”. Couple that with the fact that water vapour concentration is higher at lower altitudes and it follows that the tropopause (possibly together with a small region immediately below it) will be opaque to radiation at the water vapour absorption/emission lines. That means that emission from lower in the atmosphere directly to space becomes impossible at the water vapour absorption/emission lines because the energy is re-absorbed by the region at or immediately below the tropopause.
The implication is that thermal energy from the surface can escape to space in only two ways. First, by surface emission escaping directly to space at wavelengths which the greenhouse gases do not absorb. Second, by emission from the tropopause at wavelengths corresponding to the water vapour absorption/emission lines.
It is possible to gain at least some idea of the relative magnitude of these two emission mechanisms.
Ozone absorbs essentially all radiation below 290 nanometers (UVC radiation) . It further absorbs approximately 90% of radiation between 290 and 320 nanometers (UVB radiation) plus a decreasing amount of UVA radiation up to about 350 nm. The amount incoming solar radiation in these wavelength ranges can be determined by solving Planck’s equation for a 5800K emitter (scaled to 341 watts/m2 total) at wavelength increments of, say, 5 nanometers and then numerically integrating over each wavelength range. The result is 8.3 watts/m2 for UVC, 6.3 watts/m2 for UVB and 8.3 watts/m2 for UVA up to 350 nm. The total absorbed by ozone is 8.3 + 0.9*6.3 + 0.5*8.3 = 18.1 watts/m2 . It should be noted that ozone absorption peaks at around 50 km altitude which should be above most of the albedo effects.
The ultraviolet energy absorbed by ozone is not capable of being re-emitted at the same wavelengths because the gas is too cold. Instead it will be re-emitted as long wave radiation at the CO2 and methane absorption/emission lines. For a maximum stratosphere temperature of about -20C the black body radiation between 14 and 15.5 microns is 17.5 watts/m2 which is in reasonable agreement with the calculated energy absorption by ozone.
The remaining incoming solar energy is either reflected back out to space (due to Earth’s albedo) or is absorbed lower in the atmosphere or at the surface.
The overall albedo of Earth is 0.3 so 341 * 0.3 = 102 watts/m2 is reflected back to space leaving 341 – 102 – 18.1 = 221 watts/m2 to be absorbed at or below the tropopause. All of this must be radiated back out to space as long wavelength radiation if thermal balance is to be maintained.
There are many water vapour absorption lines below 8 microns. Between 14 microns and 15.5 microns carbon dioxide absorbs strongly and above 15.5 microns water vapour again has many absorption lines. Between 8 and 14 microns there is a window where the atmosphere offers little if any impediment to direct radiation to space from the surface.
Retrieved from http://en.wikipedia.org/wiki/Atmospheric_windows
“The atmospheric window refers to those parts of the electromagnetic spectrum that are, with the earth’s atmosphere in its natural state, not absorbed at all. One atmospheric window lies approximately at wavelengths of infrared radiation between 8 and 13 or 14 micrometres[1].”
[1] ISBN 0521339561 Houghton, J.T. The Physics of Atmospheres
And;
Retrieved from “http://en.wikipedia.org/wiki/Water_absorption”
Cotton, William (2006). Human Impacts on Weather and Climate. Cambridge: Cambridge University Press. ISBN 0521840864. “Little absorption is evident in the region called the atmospheric window between 8 and 14 μm”
Solving Planck’s equation on a spreadsheet for a 288 K source at wavelength increments of 0.2 microns and then numerically integrating yields energies as follows;
Below 8 microns 45 watts/m2
8 microns to 14 microns 143 watts/m2
14 microns to 15.5 microns 28 watts/m2
Above 15.5 microns 174 watts/m2
Interestingly, the energy radiated by Earth’s surface over the strong carbon dioxide absorption band between 14 and 15.5 microns is 28 watts/m2 which is in good agreement with the value typically claimed for the energy retained by carbon dioxide.
It is also important to note that the regions below 8 microns and above 15.5 microns are not totally opaque. There are multiple absorption lines but there are gaps between these lines where substantial energy can escape to space, especially in the wavelength region above 15.5 microns. If this were not the case, line broadening through increasing concentrations of green house gases would have little if any impact on incremental energy retention (discussed in more detail later). This substantially adds to the 143 watts/m2 calculated above.
6. THE IMPACT OF CLOUDS
The above numbers do not allow for the impact of clouds. Clouds are droplets of liquid water and in the thermal infrared, water has an emissivity very close to 1 (hence the high emissivity of earth’s surface at these wavelengths). It is therefore reasonable to expect clouds to act as grey or black body absorbers with an emissivity approaching 1 as the clouds get thicker. This would mean that thick clouds would absorb all the thermal infrared energy incident on them and in turn emit energy as a black body from the cloud top. Since the cloud top is colder than the surface, the energy emitted over the atmospheric window will be lower. How much lower is easy to calculate by integration of Planck’s law given the known atmospheric lapse rate of 6.5C per kilometer and the height of the cloud.
Thin clouds with an emissivity less than 1 would have a smaller impact.
Only a portion of the Earth’s surface at any given time is cloud covered and much of the dense cloud is low altitude cloud, thus a reasonable estimate for the Earth as a whole would be that clouds reduce the energy escaping to space in the atmospheric window by no more than about 15% to 20%.
The radiation from the cloud tops is admittedly no longer radiation directly from earth’s surface but it is still black body radiation and the fraction in the atmospheric window (and in the gaps between the lines at other wavelengths) can still escape directly to space without impediment from green house gas effects. Thus, while clouds do cause some attenuation, their action does not negate the basis of the hypothesis being presented in this paper.
7. ENERGY RADIATION FROM THE TROPOPAUSE
Earlier discussion suggested that the tropopause can only generate net radiation to space at the water vapour wavelengths which means below 8 microns and above 15.5 microns.
Again solving and numerically integrating Planck’s equation over these wavelengths for a temperature of 213K (-60C) yields a total energy of 82 watts/m 2. Surface/cloud plus tropopause radiation must equal 221 watts/m2 implying the net energy radiated from the surface and cloud tops would have to be about 139 watts/m2. However the presence of gaps between emission lines suggests the tropopause radiation will be somewhat lower and the surface/cloud top radiation higher. When this is taken into account the numbers are entirely consistent with earlier calculations. Purely as a hypothetical example, if we assume cloud cover causes 15% attenuation and 17% of the energy in the below 8 micron and above 15.5 micron ranges is not absorbed we get;
Surface/cloud emission = 0.85 * ( 143+0.17*(45+174)) = 153 watts/m2
Tropopause emission = 0.83 * 82 = 68 watts/m2
Total emission = 221 watts/m2
Water vapour also has very strong absorption bands in the NIR centred at 1.45 microns, 1.95 microns 2.5 microns plus other weaker lines. There is a significant amount of incident solar energy at these wavelengths and that energy will be rapidly absorbed once water vapour concentration becomes appreciable, which means at or close to the tropopause. As a consequence, much of the energy emitted from the tropopause is not energy that has percolated up from the surface but rather energy absorbed directly from incoming solar radiation at or near the tropopause.
8. IMPLICATIONS OF THIS ANALYSIS FOR THE KIEHL TRENBERTH MODEL
The global mean energy budget claimed by K&T suggests the vast majority of the energy radiation to space comes from the atmosphere. It paints a picture of an atmosphere which absorbs almost all surface emissions and then re-radiates a variable amount of this to space. This implies that slight changes in concentration can vary the fraction emitted thus changing temperatures. Hence the concept of an equivalent emission altitude and the prediction of a high sensitivity to changes in greenhouse gas concentrations.
The picture emerging from this analysis suggests the opposite, with most of the energy reaching the ground being radiated directly back to space from the surface or cloud tops in the windows between the atmospheric absorption lines. It implies an atmosphere which blocks almost all the energy radiation from the surface to space at the GHG wavelengths while barely impeding energy radiation to space at other wavelengths. In this scenario, changing GHG concentrations can only affect warming via line broadening.
The concept of an equivalent emission altitude is not needed and indeed has no meaning in this scenario. Energy loss to space from Earth’s surface can only occur directly from the surface/cloud tops or from the tropopause although the relative magnitude of each could change with changing greenhouse gas concentrations.
The very large difference in surface versus atmospheric emission levels predicted from this analysis compared to the Kiehl Trenberth model calls into question the basis of global circulation models based on K&T or other similar data. It also calls into question the reliability of the output from such models and in the predictions flowing from those models.
It is possible to reinforce this finding by a completely different analysis which is shown below.
9. A SPECTRSCOPIC ANALYSIS OF GREEN HOUSE GAS ABSORPTION
Imagine a single greenhouse gas which absorbs energy at only one specific wavelength. As the greenhouse gas absorbs energy it heats up until the energy it emits equals the energy it absorbs. Because it only has significant emissivity at the absorption wavelength the energy will be re-emitted at this wavelength. However, the emitted energy will be emitted in all directions. Since the atmosphere is a thin continuous shell covering the entire earth it has only two surfaces, an inner surface adjacent the planet itself and an outer surface adjacent to space. Radiation leaves the atmosphere through one of these two surfaces. Thus, radiating in all directions in effect means 50% will be emitted towards space and 50% returned to the planetary surface.
A very simplistic first approximation would be to say if the absorbance of the gas column is N then the gas absorbs 1- 10-N per unit of the incident energy and 50% of this is returned to the earth’s surface giving an effective energy retention of
Energy retained = 0.5*(1-10-N). (1)
That may be correct when N is very small (<<1) but is grossly in error for higher absorbances because it ignores repeated re-absorption and re-emission of energy within the gas column.
As the absorbance of the gas column rises, repeated absorption and re-emission becomes very significant. In this context we must again remember that the same emissivity covers both absorption and emission so that emitted energy will be predominantly at the absorption wavelengths thus facilitating repeated absorption and re-emission. By the time the atmospheric absorbance has reached 1, 90% of the energy at the absorption wavelengths is being absorbed which also means that much of the energy emitted by the atmosphere will be re-absorbed within the atmosphere, possibly going through several absorption re-emission cycles within the atmosphere.
To analyse this situation, imagine we treat the entire gas column as stack of 1 absorbance layers. As a first order approximation, assume that each layer absorbs all the energy it receives from above or below and maintains itself in thermal equilibrium by emitting an equal amount of energy, half towards the surface and half away from the surface. The result is shown diagrammatically for an N absorbance atmosphere.
Where
E1 is the total energy absorbed by layer 1
E2 is the total energy absorbed by layer
En is the total energy absorbed by layer n
EN is the total energy absorbed by layer N
Equations (2) to (5) are obtained by summing energy into each layer.
Substituting (2) into (3) gives E2 = 2 * E3 / 3 (6)
Rewriting (4) with n=3 and then
Substituting (6) into it gives E3 = 3 * E4 / 4 (7)
In general for the nth layer En = n/(n+1) * En+1 (8)
Replacing n by n-1 in (8) gives En-1 = (n-1)/n * En (9)
Since equn (9) holds for any n we can replace n by N to get
From (9) EN-1 = N-1/N * EN
Substituting into (5) gives EN = (N-1)/2N * EN +1
And rearranging EN = 2N/(N+1) (10)
If we expand (8) as a series we get;
En = n/n+1 * En+1
= n/n+1 * n+1/n+2 * En+2
= (n/n+1) * (n+1/n+2) * (n+2/n+3) *…* (N-1/N) * EN
Cancelling common terms gives En = n/N * EN (11)
Substituting for EN from equn (10) gives
En = 2n/(N+1)
The energy radiated away to space is 0.5 * E1 = 1/(N+1) (12)
The energy returned to the earths surface is 0.5* EN = N/(N+1) (13)
Equations 1 and 13 are plotted below. Interestingly, even below 1 absorbance equation 13 gives essentially the same result as equation 1 and can thus be treated as a reasonable approximation over the entire absorbance range.
10. INTERPRETATION OF THESE RESULTS
Heinz Hug (http://www.john-daly.com/artifact.htm) has measured the absorbance of the atmospheric column of CO2 at 280 ppm and reports a total absorbance in excess of 2000. The above calculation suggests that the fraction of energy at the absorbing wavelength which is radiated to space is only 1/2001 or 0.05%. This is in agreement with the analysis derived from the temperature versus altitude profile.
In the case of water vapour, it is only necessary to note that Fourier transform infrared spectrometers with an optical path length of well under 1 meter need to be either purged with dry gas or packed with desiccant and sealed in order to avoid unacceptably high energy loss from water vapour absorption and that the troposphere is 10,000 meters thick (more than 10,000 times the path length) to realise that a similar situation exists for water vapour.
11. THE IMPACT OF LINE BROADENING
Both of the above analyses suggest that greenhouse gases almost totally block energy loss to space at their absorption/emission wavelengths. This implies that significant energy loss from the surface or cloud tops is by direct radiation to space at wavelengths where the greenhouse gases do not absorb. Given that, one might be tempted to conclude that since the greenhouse gases already absorb everything they can, further increases in concentration should have no impact. This is not the case because of an effect known as line broadening.
The absorption versus wavelength profile for a green house gas line does not have infinitely steep sides. As concentration rises the line centre will saturate but absorption out in the wings of the line are not yet saturated. Further increases in concentration have no impact on the behaviour at the line centre but do slightly increase absorption out in the wings. In effect the line slowly broadens as the concentration increases. It is this effect that gives rise to the well known logarithmic relationship between concentration and energy absorbed.
In fact, the unsaturated lines of greenhouse gases are so narrow and therefore absorb so little energy, that the overall impact of a greenhouse gas does not become significant until the line centres saturate and the line start to broaden. This means that all greenhouse gases of significance are likely to display the logarithmic relationship between concentration and energy absorbed.
As the lines broaden they further constrict the wavelengths at which radiation can escape from Earth’s surface to space. For the same energy to be emitted from a narrower window implies higher energy density at the remaining wavelengths which implies a higher surface temperature.
In the case of carbon dioxide, the IPCC in their fourth assessment report stated that the increase from 280ppm to 390 ppm increased energy retained by 1.77 watts/m2. Applying the logarithmic relationship;
1.77 = n * log (390/280)
from which it follows that n = 12.3.
The increase from 390 ppm to 560 ppm (2070 projection from IPCC 4th assessment report) would increase retained energy by 12.3 * log (560/390) = 1.93 watts/m2 . Applying Stefan’s law at 288 kelvin (+14C) we find that each degree rise in temperature takes 5.4 watts/m2 . Thus the direct effect of the rise in carbon dioxide is 1.93/5.4 = 0.36C.
IPCC inflates this to about 3C by assuming massive positive feedback from water vapour. A 3C rise implies an additional 16.2 watts/m2 of which 16.2 – 1.93 or 14.3 watts/m2 must be coming from water vapour. The CRC handbook of chemistry and physics shows that water vapour content at constant humidity rises exponentially with temperature roughly doubling for each 10 K rise in temperature. This can be expressed as
water vapour concentration is proportional to 10 (temperature/33.2)
A 3C rise in temperature increases water vapour concentration by 10 (3/33.2) = 1.23 (23%). Applying the same calculations as for carbon dioxide
14.3 = m * log (1.23) from which m = 159 and each doubling of water vapour changes energy retained by 159 * log(2) = 48 watts/m2 .
The earlier Planck’s law calculations suggested water vapour at +14C retains at most 219 watts/m2 (in fact less when one allows for gaps between absorption lines). Coupling that with the CRC handbook data that water vapour doubles or halves for each 10C change in temperature, a sensitivity of 48 watts/m2 per doubling implies the following;
14C energy absorbed/emitted <219 watts/m2
+4C energy absorbed/emitted < 171 watts/m2
-6C energy absorbed/emitted < 123 watts/m2
-16C energy absorbed/emitted < 75 watts/m2
-26C energy absorbed/emitted < 27 watts/m2
-36C energy absorbed/emitted 0 watts/m2
This is completely incompatible with water vapour radiating substantial amounts of energy at -60C which is necessary to explain a cold tropopause.
12. CONCLUSIONS
Both the analysis from basic spectroscopy and the analysis based on atmospheric lapse rates give similar results and imply that greenhouse gases almost totally block energy loss to space at their absorption/emission wavelengths. That in turn suggests that a very significant portion of the energy loss from Earth’s surface is by direct radiation to space at wavelengths where the greenhouse gases do not absorb.
This is in conflict with the Kiehl & Trenberth model and other similar models which suggest that most of the energy loss to space is from the atmosphere. If the atmosphere emits little energy, and then largely from the tropopause and stratopause, the concept of an equivalent radiation altitude has no meaning. Further, the analysis suggests that most of the radiative energy loss from the atmosphere to space is re-radiation of solar energy absorbed high up in the atmosphere.
Surface temperature will increase with increasing greenhouse gas concentrations due to line broadening. The direct effect of carbon dioxide (in the absence of any feedbacks) using the IPCC quoted sensitivity and their postulated rise in carbon dioxide from 390 ppm to 560 ppm will contribute 0.4 degrees by 2070. The IPCC claim that positive feedback from water vapour will increase that to about 3C would imply a sensitivity of 48 watts/m2 per doubling in water vapour concentration. Such a high sensitivity is not compatible with the observed atmospheric temperature versus altitude profile.
It should be noted that this analysis does not predict no radiation to space at the greenhouse gas absorption lines. There is still energy at these absorption lines emitted to space. For the well mixed greenhouse gases such as CO2 and CH4 this energy largely emanates from the stratosphere and is powered significantly by UV absorption of incoming solar radiation by ozone plus some absorption of surface radiation at 9.6 micron . In the case of water vapour, the energy emanates from near the tropopause and is powered significantly by near infrared absorption of incoming solar radiation by water vapour.
**************
Michael Hammer graduated with a Bachelor of Engineering Science and Master of Engineering Science from Melbourne University. Since 1976 he has been working in the field of spectroscopy with the last 25 years devoted to full time research for a large multinational spectroscopy company.
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283 Responses to “Radical New Hypothesis on the Effect of Greenhouse Gases”
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“Al Gore, in his famous movie ‘An Inconvenient Truth’, explained that as the concentration of carbon dioxide increases in the atmosphere, more energy is trapped, warming the planet. This assumption is central to the GCMs and the current consensus on climate change. ”
It’s not an assumption. It’s an observation.
“Assumption…..observation.” Only if your eyes are closed and the lobotomy has kicked in.
A masterful effort by MH; it follows on from an earlier piece by him;
http://www.lavoisier.com.au/articles/greenhouse-science/climate-change/Hammer2007.pdf
Cripes another clown with a pencil. At least the last one knew how to do these calculations.
“It’s not an assumption. It’s an observation.”
I am constantly amazed about how much climate science we don’t know and how much is assumed. And yes, the IPCC uses many assumptions to get the predicted warming. If they used observations, they would have packed it up long ago.
Come on, Eli, you are not adding anything, again….
“…Planck’s law calculations suggested water vapour at +14C retains at most 219 watts/m2…water vapour doubles or halves for each 10C change in temperature, a sensitivity of 48 watts/m2 per doubling implies the following…-36C energy absorbed/emitted 0 watts/m2
…This is completely incompatible with water vapour radiating substantial amounts of energy at -60C which is necessary to explain a cold tropopause.”
And they promised us no worries, the basic science is settled, then took an ax to our economy. And we all lived happily ever after. The End.
Excellent post it confirms much of what I have read over the years and provides a lot of much needed detail to fill in some gaps.
A couple of observations I note that a constant adiabatic lapse rate has been assumed throughout, as a pilot of close to 40 years experience the lapse rate through clouds is assumed to be much less than the adiabatic rate possibly due to latent heat being given off during condensation, not sure if that is significant. From climate4you the global cloud cover varies from about 63% to 69% so I am not sure where the 15 to 20% factor comes from.
Another point is that when applying Beer’s law since the density decreases with altitude the mean path upwards is longer than the mean path downwards so it not quite 50/50.
Regarding the positive water feedback with increasing temperature Dr. Lindzen postulated as far back as 1990 that increasing temperatures caused accelerated water evaporation which then caused an increase in lower rain clouds which in effect stripped the water out of the atmosphere at a lower altitude thus leaving less water in the upper troposphere which becomes a negative forcing effect. This has been confirmed from the satellite data by Dr. Spencer and others independantly. Again climate4you shows decreasing upper troposphere water content with increasing surface temperatures and a lower upper troposphere temperature which is the reverse of the IPCC computer models. They have also added TOA radiation data recently which is very interesting as it has a very close inverse corellation with surface temperature.
“Only a portion of the Earth’s surface at any given time is cloud covered and much of the dense cloud is low altitude cloud, thus a reasonable estimate for the Earth as a whole would be that clouds reduce the energy escaping to space in the atmospheric window by no more than about 15% to 20%.”
This is the key part of the calculation, and you’re just plucking figures out of the air. I’m surprised that a spectroscopist would do all these sums without reference to the actual spectra observed from space, especially the ERBE experiments. You’ll need to do this before you can claim to have overthrown K&T.
That said, the precise proportion of outgoing LW that is declared to be direct from the Earth’s surface is hard to pin down, and not particularly important. Here’s what K&T 97 say:
“ The estimate of the amount leaving via the atmospheric window is somewhat ad hoc. In the clear sky case, the radiation in the −2
window amounts to 99 W m-2 , while in the cloudy climate change, the dominant contribution of water case the amount decreases to 80 W m−2, showing that there is considerable absorption and re-emission at wavelengths in the so-called window by clouds. The value assigned in Fig. 7 of 40 W m−2 is simply 38% of the clear sky case, corresponding to the observed cloudiness of about 62%. This emphasizes that very little radiation is actually transmitted directly to space as though the atmosphere were transparent.“
I just can’t resist the temptation to ask, who is John Galt?
This looks like a very large stake in the heart of climate frankinscience. Or is it just the natural consequence of the shedding of daylight on the denizens of the shadows?
Such a grand bull$hit edifice completely shattered by the addition of a single variable, the full spectrum of radiative wave lengths.
And nothing but moronic bleating from Brer Rabett.
Now lets see, Luke will probably respond with a 30 page cut and paste job to bury the material and the usual rent-a-crowd will hive in with the ad homs to distract the readers.
All it takes is faith……..
jae “Come on, Eli, you are not adding anything, again….”
I’m sure there is an excellent reason for that but what I’m not sure.
Nick “You’ll need to do this before you can claim to have overthrown K&T.”
All we need for that is to show there is no vacuum (or other perfect insulator) between the surface and the atmosphere to create the infinite temperature gradient at the surface.
The 15-20% for clouds seems about right if you average the cloud cover at different levels;
http://mclean.ch/climate/Cloud_global.htm
Barry; just one question; if density decreases with height, as it does, wouldn’t the mean path be shorter upwards than downwards?
Cohenite
No, you shouldn’t average, it’s more like the total that is needed. Look at the bottom plot. K&T use 62%. It’s this figure that makes the main difference.
Well, let’s look at this Nick; the lower cloud coverage is about 27%; the mid, 20% and the upper about 13%; if all cloud levels are occupying different parts of the atmosphere a cumulative cover is about what K&T say; but is that likely? If the cloud cover at the different heights is roughly vertically parallel then the average cover is about 15-20% as MH estimates.
For the ozone calculations, in an extreme case, if there was only one ozone particle it could not produce a significant effect. That is, the effect of ozone is concentration dependent. I did not see a calculation (though I might have missed it) showing that there is indeed adequate ozone to give the derived numbers.
Ex-spectroscopist.
Geoff.
Cohenite , If you look at beer’s law in terms of absorbance it is a lot clearer.
The Beer-Lambert law (also called the Beer-Lambert-Bouguer law or simply Beer’s law) is the linear relationship between absorbance and concentration of an absorber of electromagnetic radiation. The general Beer-Lambert law is usually written as:
A = a x b x c
where A is the measured absorbance, a is a wavelength-dependent absorptivity coefficient, b is the path length, and c is the analyte concentration.
so as c decreases b increases.
I must admit I still do not get the 15 – 20%. I agree with the 27-20-13 distribution although it is a little low but whether we are talking water aerosols or ice crystals they all still absorb the entire spectrum as opposed to wavelength specific absorbtion as in the case of molecules.
Even if the clouds are stacked the radiation from the lower cloud would be absorbed by the higher cloud. Perhaps a measure of cloudless sky would be more useful.
Firstly thanks to all of you who have taken the time to read and comment on my article whether critical or supportive.
To answer some of your comments; many of you have commented on the 15% to 20% figure with regard to clouds. I clearly did not explain myself well enough so I will try to clarify.
Several of you suggest clouds cover about 60 to 70 percent of Earth’s surface which agrees with the data I have. Now not all of this cloud is thick enough to have an absorptivity of 1 but admittedly most probably will. As a reasonable assumption we could assume 60% of Earth’s surface is covered by cloud all of which it thick enough to have an absorptivity of 1. Then 40% of the energy radiated from Earth’s surface in the 8-14 micron atmospheric window will escape to space, the remaining 60% will be absorbed by clouds. But these same clouds also emit 8-14 micron energy and the amount depends on their altitude as calculated in the table I gave. Kiehl and Trenberth claim that full cloud cover reduces the energy from 99 watts/sqM to 80 watts/sqM suggesting that they are assuming an average cloud altitude of about 2 km. I assumed a somewhat higher average altitude of about 3 km. From the table this means they will emit about 71% of the 8-14 micron energy they absorb or about 60%*0.71 = 43%. Thus the total radiation to space in the atmospheric window is 40+43% = 83% which is about 17% less than the clear sky case. This last number is the 15% to 20% I was referring to in the text. As I said, I clearly did not explain myself well enough.
In the last paragraph of that section I mentioned that this radiation is not all from Earth’s surface some is from cloud tops (in fact about 50:50) but that this does not negate my thesis. The reason for that claim is that all of this is black body radiation escaping directly to space without any impediment or being affected in any way by green house gas effects.
Barry Moore you comment that the emission up and down will not be 50:50 because of the density gradient. I think I understand what you mean by this but I do not quite agree. The emission from a surface depends only on its emissivity and temperature. If each layer is thick enough to have an emissivity of 1 then the emission up and down should be the same (clearly that thickness in meters increases as one goes higher in the atmosphere). Of course the amount of energy received from above and below will be different so the nett emission up and down will be different but that comes out of my calculations.
Nick Stokes you comment that I should have compared my analysis with the experimental measurement taken from space. In fact I did but I made the mistake of not including the comparison in the paper. Again let me correct it now. The websites Miskolczi.webs.com and http://ceos.cnes.fr:8100/cdrom-98/ceos1/science/dg/dg20.htm both give plots of measured emission versus wavelength as measured by the Nimbus satellite with the black body curves corresponding to various temperatures overlayed on this measured data. The data from the second web site show emission between 10 and 14 microns corresponding to that from a 320K source (+47C) and between 8 and 9.5 microns as corresponding to a 300K source (+27C). Now unless the satellite was over a desert at noon on a cloudless day I suspect the +47C could incorporate a bit of calibration error however the point is that the only area at these temperatures is the Earth’s surface. This means the satellite is seeing black body radiation directly from Earth’s surface in the atmospheric window which is exactly what I predict. The dip at 10 microns due to stratospheric ozone and the much larger dip between 14 and 15.5 microns due to CO2 are also clearly visible. The attenuation above 15.5 microns is less than my calculations predict but I suspect this is due to the limited resolution of the interferometer. It is not able to resolve individual lines and some of the energy being received in this spectral region is due to energy from the surface escaping directly to space in the gaps between the lines.
The data from the Miskolczi source (on page 8) shows a very similar result. The energy in the atmospheric window now corresponds to a black body at about 280C which would be very consistent with a surface plus partial cloud cover or of course a cold region say at night. Again however energy levels corresponding to a black body at 280K implies radiation directly from the surface – the atmosphere would not be warm enough. Certainly it is not compatible with an equivalent radiation altitude which would have to be at about 255K.
I hope this answers the main queries to date.
On another subject, I have just found out that I will be travelling on business for 2 weeks. I will try to get to an internet site as often as I can but that could be infrequent. Please do not take this as a sign that I am not willing to answer questions or engage in debate.
Regards
Geoff Sherrington, apologies I missed your comment on ozone levels. The ozone is continuously formed by incomng solar radiation at wavelengths shorter than 190 nanometers. Such radiation has sufficient energy to split the oxygen-oxygen bond forming atomic oxygen which very readily reacts with an O2 molecules to form O3 so it will always be present.
I note in reading over my previous post that the page reference on the Miskolczi paper is incomplete – it should read page 8.
An excellent paper for discussion.
Eli Rabett helpfully says “Cripes another clown with a pencil. At least the last one knew how to do these calculations.” Is that the best scientific critique you can come up with Eli? Or is it that you just like insulting people for no apparent reason?
Nick Stokes quotes K&T as: “The estimate of the amount leaving via the atmospheric window is somewhat ad hoc.” Can we place any reliance on an ad hoc estimate? A calculation of the amount of radiation leaving via the atmospheric window has got to be better than an ad hoc estimate. Seems like the science is not settled.
I won’t pretend to have anything beyond a rudimentary understanding of the technicalities of this article. But I do understand this much… The actual behaviour and changes in climate are not well explained by the theories used by IPCC and brethren, and people like Michael Hammer are working hard to contribute to a more complete and accurate understanding. I therefore extend my very sincere thanks to Michael, and also my congratulations on his willingness to share this information so fully and so well presented.
A good effort trying to ascertain why and how the consensus view of climate is failing to keep up with or anticipate real world developments.
There seems to be more scientific thought to be found in blogs like this than within the climate establishment.
Cohenite: “Barry; just one question…”
Whenever Cohenite asks the dreaded question you just know that someone is about to stitch himself up right good, as they say. Brings to mind Detective Colombo in his beige raincoat. I thought I would add that since we already have this thread dedicated to Mike Hammer.
Yes, well, Jimmock, I am short, stocky, beady-eyed, irritable and irritating; actually I have a lot of time for Barry, he’s always worth listening to.
Who would have thought the answer was water; well, Lindzen, Spencer, Braswell, Miskolczi, just about everyone except the modellers. Can someone please go and bury K&T? And does anyone want to buy a t-shirt saying;
C.R.A.P. [carbon really ain't pollution]?
I see cohenite “A masterful effort by MH; it follows on from an earlier piece by him” still views the world through the same tiny keyhole. IMO Michael Hammer doesn’t seem to get a berth outside the Lavoisier club and associated blogsphere.
I had the privalige to hear some highlights from Aynsley Kellow’s “The Wrong Stuff” Perth address Oct 08 on ABC radio tonight and recognised much of the rhetoric trotted out here as arguments for damming the IPCC, warmers, greenies and so on. See -
http://www.ipa.org.au/people/aynsley-kellow
Although I enjoyed the broadcast including the debate following Aynsley I could not help thinking again his points were hollow if indeed there is climate change caused by the increasing production of man made GHGs. Note; IMO Aynsley gave us no real evidence to the contary all through. That’s the cop out!
But we can each look for evidence, one way or the other on AGW and climate change matters without waiting for governments funding for “alternative” science. Before leaving for NZ friends kindly loaned us a book “The Beauty of New Zealand” 1975 with lots of pictures. On return we noticed a current brochure on the Fox glacier had a more recent photo taken from the same place as the one in the book. Comparing notes; we found the glacier was 16 km long then compared with only 13 km now. However walking up the muddy moraine had convinced me the thing was reeling backwards at an easily obsevable rate. BTW our motel host had a call from the Tasman side. It too suddenly lost another 200 m that week
I read elsewhere tonight about a new effort to make raw climate data more “independent”
NASA-Cisco climate project to flash ‘Planetary Skin’
http://www.nytimes.com/gwire/2009/03/03/03greenwire-nasacisco-project-to-flash-planetary-skin-9959.html
While Aynslie and others like me have commented here in the past on the lack of agreed standards for climate science measurements, we are fast approaching a point when opinions re “alternatives” drop out of backwards thinking.
Gavin:
Does what you say have any relevance to the paper by Michael Hammer? Or do you just like writing long, random and irrelevant essays about odds and ends and personal experiences?
Mike,
I’m now unclear as to what flux you are considering to be flux through the atmospheric window (AW). To most people, it is the flux that goes through with no absorption, and corresponds to the K&T figure of 40 W/m2. If you count IR that was in the AW when it was blocked by a cloud, well, then, indeed the energy is re-radiated (but half up and half down), but as you say, with a BB spectrum. In other words, even the energy that continues to be radiated is mostly no longer in the AW band. And much of that is then absorbed by GHGs.
The spectrum you point to is the right kind of thing to be looking at. Actually, a hot land surface of 47C is not so unreasonable. My bare feet encounter that quite often. Here I discussed a clear-sky spectrum (Fig 8.2a), over ice, which simplifies the interpretation. It shows the direct AW transmission very clearly.
But I’ve lost track of exactly what it is in K&T that you now claim to have disproved. After all, they knew about these spectra too.
One assumes that the next step is for this to be peer reviewed and published in a reputable scientific journal… and Hammer will be a Nobel Laureate with all the trimmings.
Hmm or it could all be a bulldust smokescreen un-peer-reviewed piece of denialist clap-trap…
I guess time will tell – I’m not holding my breath…
M. Lapin making his usual useless contribution by adding nothing but insults to the paper.
Eli, if you are the climate expert you claim to be why don’t you contribute in the manner of a REAL scientist.
Explain why you KNOW the paper fails and where it fails and what evidence there is that you can derived from the paper that proves that it fails. That’s how real scientist work, isn’t it?
MattB:
Your comment is nothing but ad hominem. Point to a single error in fact in MHs calculations or analysis and perhaps you’d get a hearing. If perchance you have not the expertise to do so, then you ought just lurk and keep your ad hominems on AGW alarmist blogs where they seem to thrive.
Gavin:
While a retreating glacier may be an indicator of warming, it says nothing about the cause of the warming. That is the fundamental dispute.
Mike:
I’d ditch the references to Wikipedia. Find another source, preferably a primary source. Otherwise my first read left me with the impression of a well-thought out analysis. I also liked that you did not get defensive in your reply to thoughtful criticisms, but strove to clarify.
Of course that is the true scientific process that so many, including those who should know better, have forgotten.
Back to lurking.
I have a question for Michael Hammer.
I have been persuaded by work such as Svenmark’s, “The Chilling Stars” that the recent warming we have seen (as described by here by Gavin’s essay) correlates much better with solar activity than with CO2. Total solar irradiance is quite constant. Svenmark’s theory is that a secondary effect, changes in the magnetic field and solar wind cause changes in high energy cosmic rays that are significant in forming low level clouds that reflect sunlight.
Could another secondary effect by important? The high energy uv and solar wind from the sun is highly variable with the solar cycle. As an example there were stories of satellites coming down early due to enhanced drag form an expanded atmosphere from when the sun was more active. Could the additional absorbers, more ozone, more atomic oxygen, etc.; that are created by the variable uv have a significant effect on radiation transport at the top of the atmosphere? By significant, I mean ~1 watt/m^2. So far what I have found says no, the effect is much less. But the article only talked about atomic oxygen at a particular wavelength and I haven’t found a good reference for the total integrated effect.
Thanks for the article.
Nick:
OK, he plucks some numbers out of the air, and he says so. But his basic mechanisms look pretty sound, no? I’ve never seen such a detailed description of all the relationships between wavelengths, the lapse rate, tropopause temperatures, etc. A lot of what is observed can be explained by this paper; whereas, Kiehl and Trenberth’s stuff is much more abstract.
Where are the flaws in his basic reasoning?
Thanks for the clarification MH. I was thinking of just the initial surface radiation not the overall effect, I have used the 50 up 50 down argument many times myself so I was just hitting a blank spot. Must be getting old.
Since the mean path at 1 atmos 385 ppm of the resonant frequencies is in the region of 2 to 3 m ( ref John Nicol ) I agree it is pretty academic but it may be more significant at the higher altitudes where the mean paths are much longer.
MattB great idea to hold your breath why not try it for 30 minutes and give us all a break and while you are at it since you are so fanatical about peer reviews try teaching the IPCC to incorporate all their peer reviews not just the politically acceptable ones. Read some of Dr. Vincent Grey’s comments on the peer reviews he submitted on all 4 IPCC reports.
Hello Nick; What I am considering flux through the atmospheric window is energy that is radiation without any interaction from green house gas effects, so to compare, that would be the 70 watts/sqM in the Keihl Trenberth model.
To take up your comment of the difference between what I suggest and the Keihl Trenberth model. K&T are claiming 169 w/sqM out of a toal of 239 W/sqM energy loss to space is radiation from the atmosphere or about 71% of total emission. This would have to be generated by emissions from green house gases since the other components of the atmosphere (mainly oxygen and niitrgen) have essentially zero emissivity. A black body emitting 169 w/sqM would have surface temperature of about 255K which would put it well inside the troposphere. That means that most of the emission from space emanages from within the troposphere probably spread in varying degrees across all altitudes. In fact, since the green house gases cannot radiate between 8 and 14 microns (since if they don’t absord they also don’t emit) the equivalent temperature would have to be significantly higher, closer to 262K or an equivalent radiation altituide of about 4 km. The point here is that their model implies most of the energy loss from Earth is via green house gas emissions and changes in concentration lead to changes in the equivalent radiation altitude.
Also, since the green house gases cannot emit in the atmospheric window the only energy in this wavelength range would be the 70 watts/sqM from the surface and clouds. That would correspond to an equivalent black body temperature of about 250K.
Most importantly, all this suggests what I would call an analogue picture where green house effects modulate (attenuate? forgive my electrical engineering background) most of the emission.
What my calculatuions suggest is a very different picture where most of the emissions from earth are in the atmospheric window and radiate without impediment from any green house effects. According to these calculations there is very little net radiation loss to space from green house gases within the troposphere only from the tropopause and a significant portion of that is re-radiation of energy absorbed from incoming solar energy in the NIR absorption bands from water vapour.
I think of this as much closer to a digital model where at each wavelength energy is either free to radiate to space without green house gas impediment or is almost totally blocked by green house gases. Very little is partly blocked or attenuated. I see this as a significant difference especially when evaluating the effect of incremental increase in a green house gas component.
If we look at the Nimbus spectra, the K&T model would lead one to predict that the energy received in the atmospheric window was less than the energy at other wavelengths (250K equ black body temperature versus 262K elsewhere) so the spectrum in that area should show a dip. According to my calculations the energy received in the atmospheric window should be substantially higher than elsewhere showing a peak at those wavelengths and attenuation elsewhere. The Nimbus plots I have seen seem to distinctly favour my view.
Gary P; The impact of ozone formation and then UV absorption by ozone are all controlled by the UV energy from the sun. This UV energy is readily determined from Planck’s law since the sun behaves as a black body emitter. Now my calculations show about 17 watts/sqM of UV below 350 nm. A 1 watt/sqM change represents a change of nearly 6%. If that were to happen the changes in the visible would be of similar magnitude which I think is very unlikely. Maybe there is some other mechanism I don’t know about but if you force me to guess I would have to say i think it unlikely.
On the subject of modulation of cosmic rays, I also have read about Svensmark’s theory and I think it quite plausible. The question of whether comsic rays influence cloud formation is to my thinking beyond dispute. For many years the priniciple tool used by physicists to make cosmic ray tracks visible was the Wilson cloud chamber. This works by creating a super saturated volume of gas. Cosmic rays travelling through this region ionise gas molecules which then act as condensation nuclei leading to vapour trails ie: cloud precursors. To me that essentially proves that cosmic rays do help to initiate cloud formation. We then need to see whether the cosmic ray flux does indeed vary with solar activity. I have seen some very brief reports which suggest that this effect has been measured succesfully although the data I saw was sketchy. however as I say, right now the theory sounds plausible to me. There does seem to be correlation between solar magnetic activity and temperature on Earth.
Good old peer review always pops up whenever there is threat to the cosy and thoroughly inadequate arrangement for deciding whether the huge amounts of public money has been been wisely spent.
Its a pity these so called rational thinkers who have their collective siphons so deep into the public coffers couldnt spend at least few spare neurones to come up with a more reliable and ethical process for deciding whats kosher.
Peer review as currently prescribed is unreliable, biased and tantamount to fraud.
Michael Hammer,
Can you clarify the point that the oxygen and nitrogen don’t radiate? Surely they are not at absolute zero and hence must radiate? Isn’t the oxygen microwave radiation used to infer atmospheric temperatures from satellite measurements?
Thanks. Great article, much food for thought.
OK, so MH shows the window is bigger than AGW allows for; he also looks at the logarithmic decline in the effect of the absorbance and emission of the GHGs; several issues with that; if incoming solar [reaching the surface, although atmospheric reradiation is a factor] is known then so to must be the surface emissions; a fixed amount of CO2 is sufficient to mop up that surface emission with any extra CO2 surplus to requirements; that is a crucial issue which means that extra CO2 has no heating effect; Hug puts an upper limit on this of 357ppm;
http://www.john-daly.com/artifact.htm
Secondly, Miskolczi’s theory says that an optical density will be maintained by equilibriating factors [such as the decline in atmospheric SH] such that the greenhouse effect is, without gross variation in incoming energy, always operating at maximum; variations in GHGs cannot disturb that maximum equilibruim; the crucial factor here is water; Dessler and Soden and the AGW posse generally maintain there is an increase in water, which, with an increase in CO2, would disturb both Miskolczi’s and MH’s observations; NOAA, of course shows water consistent with Miskolczi and MH; so which is right?
Michael,
If we look at the Nimbus spectra, the K&T model would lead one to predict that the energy received in the atmospheric window was less than the energy at other wavelengths (250K equ black body temperature versus 262K elsewhere) so the spectrum in that area should show a dip.
I’m getting more confused about what your quantitative disagreement with K&T actually is. Could you quote one of their figures that you think is wrong, and say what you think it should be?
Re the Nimbus spectra, do you mean total energy, or energy flux per wavelength band (radiance), which is what the plot shows. Total energy is what K&T would predict, and to get that you have to integrate over the whole spectrum. The result is not obvious just from looking at the plot, especially as part of the range is missing. K&T’s statements about flux across all wavelengths in no way suggest that there should be a dip in the spectrum at AW frequencies. Like everyone, they would say that the radiance should correspond to the temperature of the source.
I’m still very puzzled about your notion of AW(8-14 μ) transmission. When energy from this band is blocked by a cloud, and subsequently radiated, then OK, it was not at that point radiated by GHG. But it will be radiated as BB, and most of that will subsequently be absorbed and re-radiated by GHG’s. So from space it will be seen as GHG radiation.
Michael Hammer: “A black body emitting 169 w/sqM would have surface temperature of about 255K which would put it well inside the troposphere.”
Surely you mean 239 W/m^2 has a BB temperature of ~255K?
I’m trying to clarify some things here.
“Also, since the green house gases cannot emit in the atmospheric window the only energy in this wavelength range would be the 70 watts/sqM from the surface and clouds. That would correspond to an equivalent black body temperature of about 250K.”
So 70 W/m^2 would be the portion Planck radiation for a BB at 250K within the spectral range of the atmospheric IR window?
Nick; 2 things; you seem to be saying that saturation is not a factor, but surely GHG concentration above a certain threshold will not continue to absorb the same amount of relevant wavelength radiation; which means that above that threshold GHG wavelength radiation must escape; also, you seem to be saying that GHG aborbs across the spectrum; surely that is erroneous and one of K&T’s mistakes; why would you intergrate across the whole spectrum?
Cohenite,
No, I’m not saying anything about saturation or varying GHG concentration. All I’m saying is that the GHG’s currently there will absorb the fraction of BB radiation from clouds that falls within their absorption region. That isn’t all of it, but it is a lot.
Neither I nor K&T say that GHGs absorb across the whole spectrum. What I am saying is that if you want to relate radiance measurements, as in the Nimbus spectra, to energy fluxes in W/m2, you have to integrate across the wavelength range.
Nick
I think you are discounting the fact that energy absorbed by GHGs from the BB radiation eminating from the clouds and other aerosols is transferred by collision i.e. kinetic energy transfer to the large majority of the atmosphere, oxygen and nitrogen. The wavelengths of the GHGs are therefore removed from the spectrum and not replaced except by other BBs. Exactly the same thing happens at the surface, all the originating resonant frequencies from the surface, i.e. water and CO2 wavelengths virtually dissapear in the first 50 m. Everything else is just energy transfer from one component to another which has a net energy balance of zero when considering the total energy in the atmosphere. ( TOA excepted)
However it is not quite true that increased CO2 has absolutely no effect because of the wavelength broadening which is used to justify the logrithmic formula, but I believe the effect of an increase in CO2 has a minimal effect on temperature which is completely overshadowed by all the other drivers of our climate and there is no amplification by positive water forcing since this has been proven by observation to be a negative forcing effect.
Yes, Barry, this part of MH’s excellent thesis is giving me pause; GHGs, when excited by absorption, divest energy through collision, mainly with the dominant atmosphere gases, N2 and O2, and by emission; the collision will thermalise the packet of air to a LTE condition but the emission would be at a lower wavelength because the GHG has lost energy through collision; this effect would, you would think, mean less atmospherically sourced radiation for further GHG absorption and increase the window amount.
Nick; I still don’t understand why you have to integrate across the whole spectrum; this is an issue raised by Pielke Snr;
http://www.climatesci.org/publications/pdf/R-321.pdf
As Pielke says, “The spatial distribution matters’; both horizontally and vertically; by integrating these “spatial differences” are ignored or masked; without wishing to revisit the Tafe/Teff issue from Arthur Smith’s paper, “Proof of the Atmospheric Greenhouse Effect”, suffice to say that apparent temperature increases may not be mirrored by energy retention due to the regional/spatial distribution effect of Stefan-Boltzmann based energy emission and consequent aborption; a temperature increase in one region may be compensated for by a temperature decrease in another with overall energy balance at TOA being maintained because the temperature increase may be from a lower SB energy base. Complementing MH’s thesis, if upper atmosphere, below the tropopause, concentration of water is dropping, as NOAA data suggests, then it doesn’t matter that there is a slight effect from increased line broadening because the decreased water means less interception and more window facility for outgoing radiation.
“And does anyone want to buy a t-shirt saying;
C.R.A.P. [carbon really ain't pollution]?”
Sign me up!
I am a bit confused as to whether the absorption/radiation by H2O changes when it is present as visible cloud or invisible water vapour. It seems to me that its presence as water vapour is being ignored in the calculations, unless I have missed something in my old age. Obviously, it will be different in the visible part of the spectrum, but elsewhere is my concern.
The assumption of a constant lapse rate in the atmosphere might also need some revision.
Barry,
No, the role of O2 and N2 is irrelevant. They act as a thermal reservoir. IR is absorbed and emitted by the GHGs, and by Kirchhoff’s Law, is emitted preferentially in the same frequency bands as it is absorbed. MH explains all this correctly. My point is that once the energy which was originally emitted from the surface in an AW band, absorbed by a cloud, and is then reemitted, it has lost all connection with the AW, and is indistinguishable from all the other IR that got there by other means. And from space, you can’t distinguish its history.
Cohenite, I couldn’t make any sense of your first para. Nor of your reference to Pielke, who is talking about spatial issues. The issue here is absolutely elementary. You have a spectrum of radiance, in Watts/m2/cm, or a more antique equivalent. The cm refers to wavelength. If you want to use it to talk about a flux in W/m2, you have to integrate over wavelength.
Comment from: gavin March 4th, 2009 at 8:37 pm
Was that OT nonsense from the famous gavin of RC fame?
Unless I’ve missed it somewhere, nobody has yet shown any major flaws in Hammer’s analysis. Only nit-picks. Did I, indeed, miss something?
Jae,
No you haven’t missed anything. You may have forgotten, but you said it yourself. “OK, he plucks some numbers out of the air”. It’s a major flaw in a scientific analysis, especially when those numbers are vital.
However, if you’re in triumphalist mode, you might like to explain what he’s actually proved.
Ahh Jan Pompe you are correct at 255K the black body emission is 239 W/sqM not 169 W/sqM. Proves one should never write things in a rush and i was hurrying to try and get last details organised for my trip tomorrow.
To correct, according to K&T the atmosphere emits 169 W/sqM. Since the atmosphere has extremely low emissivity in the 8-14 micron region it cannot significantly emit in that range – the emssion is all below 8 or above 14 microns. If one integrates Planck’s law for the range below 8 microns and above 14 microns a black body which emits 169 W/sqM has a surface temperature of about 255K. In fact the equivalent temperature would have to be somewhat hgher than that because there are wavelengths above 14 microns (and below 8) where the atmosphere also does not emit (the gaps between the lines).
The temperature of a black body which emits 70 w/sqM between 8 and 14 microns can be obtained by integrating planck’s law over this wavelength range and it turns out that is around 250K.
Thus looking down from space the energy over the wavelength range below 8 and above 14 microns wouold be roughly the same as from a black body at 255K and the energy between 8 and 14 microns would be the same as a 250K black body. Both regions look like about the same black body temperature, Thus what the Nimbus satellite should see is a complete spectrum equivalent to a 250K source.
However when one looks at the spectrum from the Nimbus satellite (either of the two sources I gave in an eralier post) one sees very substantially more energy between 8-14 microns than for the regions below 8 and above 14. The region between 8-14 corresponds to a source of about 280K or 310K depending on which of the two references you look at and there is marked reduction in energy below 8 and above 14. That means there is substantially more energy in the atmospheric window and less elsewhere which does not fit with the K&T prediction but is exactly in line with what my calculations suggest.
Nick in your 8:06 post you mention that the energy radiated by the cloud tops will be subsequently absorbed bu GHG. There is a slight misunderstanding here. In my quotes of the emission from the cloud tops what I am quoting is NOT the total emission, it is only the emission between 8 and 14 microns ie: that fraction of the emission which is within the atmospheric window. And yes to determine this value one needs to integrate Planck’s law which is exactly what I did. I am claiming that emission in that wavelength range is not impacted on significantly by GHG.
I noticed a question as to whether oxygen and nitrogen have emissions – suggestion of microwave emissions. There may well be weak emissions in the microwave frequency range but my understanding is that the amount of energy involved is neglegible compared to the levels we are discussing here. If that were not the case then nitrogen and oxygen would (by Kirchoffs law) also have to absorb significant energy whcih would make them GHG as well.