Water Vapor Rules the Greenhouse System - Humans cause 0.28% of the "Greenhouse Effect"

geocraft.com ^ | 2003 | Monte Hieb

[AaronInCarolina]

From 10% to 25% depending on who you talk to. Small but not miniscule.

I've never heard anyone cite percentages that high, except the boobs (congressmen) in the congressional hearings over global warming who were all trying to do math in their head all based upon the the parts-per-million changes in CO2 concentration.

Look, there is one way to look at how small CO2 is in the atmosphere just by looking at the almost-universally accepted concentration level. It is widely accepted that the current concentration is around 380 ppmv (parts per million by volume). Now, this in an increase over pre-industrial levels, which were around 280 ppmv, for a change of about 100 ppmv. So based upon these numbers, one can without controversy calculate that CO2 makes up only about 38/1000ths of 1% of the earths atmosphere (simple math). And the increase over the past 150 years has been about 1/100th of 1% of the atmosphere. Why do AGW alarmists believe that a change in atmosphere content this trivial (1/100th of %1)could cause such a catastrophic increase in tropospheric temperature? Well, they say there is an amplifying effect, where such a small change (1/100th of 1%) causes water vapor to become an even more effective greenhouse gas, so that ultimately these small changes in CO2 "ultimately" causes the warm-up. I don't buy it. I think the only place they see this amplifying effect is in their GCM's (General Circulation Models) which are computer models that have this amplification embedded in their models. And in order to justify this amplifier in their model, they basically have to null-out most natural causes such as solar irradiance variability and albedo effects of GCR's (Galactic Cosmic Rays).

So, no matter what percentage of total greenhouse gases that the current levels of CO2 represents, one can't deny that is extremely minute, and probably cannot explain the apparent increase in temperature over the past few decades.

A lot of the reason people began to worry about CO2 on this planet was because of the true greenhouse effect that exists on the planet Venus. But Venus is dramatically different from Earth. Where CO2 in the Earth's atmosphere amounts to 0.038%, it comprises 97% of Venus' atmosphere. And even at those concentrations and with Venus' orbit much closer to the sun, scientists calculate that such a greenhouse effect would only amount to about 25C. Venus is much hotter than that, of course, but it is because of other gases.

With CO2 concentrations of 380ppm (granted its likely to increase steadily until we move away from fossil fuels, which will inevitably occur) I feel pretty safe that we won't be cooked alive anytime soon.

[palmer]

As Lindzen points out here http://www.heartland.org/Article.cfm?artId=19485 the increase from 280 to 380 should have produced more than the observed 1F increase over the last century. CO2 is a minor GH gas and even a large increase would cause a minor increase in temperature, but not "trivial". The water vapor feedback is real and probably also nontrivial although I am very skeptical of water vapor models that don't model weather properly (even leaving out precipitation altogether) As for solar variability, that is steadily increasing, but very slowly (http://www.ucar.edu/news/releases/2006/brightness.shtml) and only explains about 0.2C over 2000 years.

The cosmic ray flux is generally decreasing, but that decrease is dwarfed by the solar cycle. As the Svensmark charts show, the slight decrease in cosmic rays (and correlating decreases in low clouds) is very small compared to the 22 year solar cycle. If the climate effect was profound enough to be behind a nontrivial part of the recent warming, we would also see a profound 22 year climate cycle. We don't, so the effect is interesting but trivial for climate (unlike CO2).

[AaronInCarolina]

Hi Palmer,

Thanks for your reply. I think your quote of Lindzen slightly mis-characterizes the point he was making in that article. What he was trying to say was that "IF you accept the fact that the 0.7C rise in temperature WAS due to the increased CO2, then BASED UPON THEIR MODELS it should have actually been more. He is not a believer that the CO2 increase led to the 0.7 degree temperature increase. If he accepted that, then he would presumably have to accept the alarmists projections of continued increases as future CO2 increases occur.

Regarding the water vapor feedback... just how proven is this? Is it proven beyond the fact that it is modeled in the GCM's to produce matches with past temperature records?

Regarding solar variability, I hear a lot of different opinions on just how much the sun has been increasing through various measurements. I think the jury is still out on just how the sun's variations affect the earth and our climate. I am very much aware of how little the IPCC attributes recent changes to solar variability. The following graph comes from the IPCC-friendly RealClimate.org's own website:



This graph clearly shows a dramatic increase in sunspot numbers and solar modulation. Notice the steady increase from 1900 to the present. The IPCC bases, as I understand it, their conclusion that the sun can not be responsible for the most recent temperature increase based upon the roll-off at the end of the graph, suggesting therefore that it could not be a forcing. As I understand it, they attribute some of the 1910-1940 steep temperature rise (a rise as steep as in recent decades) on increased solar irradiance. But they say that since the sun's irradiance in the last decade of the 20th century dropped off, that it could not be the cause. They don't want to consider a water vapor feedback from solar warming that could amplify the suns's increases, but they are eager to explain an increase of 1/100th of 1% increase in CO2 make-up of the atmosphere causing a large amplifying water vapor feedback.

Regarding GCR flux, I think the jury is still way out on just how much of an impact it may cause. There has been an orchestrated effort to discredit Svenmark, Calder and Shaviv in their efforts to uncover the link between GCR's and cloud formation. But they are going to continue their research anyway, and efforts to impede their research should be condemned by all scientists.

Often, sunspot numbers are considered a significant metric, but the paper by Jason Kirkby in 1998 at CERN, in Switzerland. Page 8 of this pdf document:

CLOUD Chamber (Cosmics Leaving OUtdoor Droplets Chamber)

Contains a very interesting correlation between average sunspot cycle length rather than sunspot number. Whether this really amounts to anything, I don't know, but I do believe we have a LOT more to find out about how the sun affects our climate than we currently know.

[palmer]

Hi Aaron,
As RealClimate is fond of pointing out, water vapor essentially *is* feedback. I think that's true as the water cycle dwarfs any water vapor forcing from volcanoes by many orders of magnitude. It is also mostly a positive feedback although at higher concentrations it can become negative (e.g. certain types of clouds). It also happens to fit their agenda that CO2 is mostly a forcing and mostly not feedback from warming although they would admit to some slow feedback.

The RealClimate approach to solar irradiance, cosmic rays and anything else that's not part of the agenda is strictly divide and conquer. If there's a solar component then it's small and slow (I tend to agree). Cosmic rays are unknown and small, Milankovitch is large but slow, etc, etc. Then they improperly use ancient ice cores to show that CO2 was always slow or bounded in the past which is ridiculous considering there are 1000's of years between measurements in the oldest cores so any fast rise (and fall) that occured would be invisible.

You correctly point out that once they have divided and conquered the non-CO2 forcings they rule out (and usually don't bother to model) any water vapor feedback from them.

In the end there are many factors involved and the twin approaches here at FR (discredit CO2 and toss around new forcings out of context) is not particularly convincing to me.

[palmer]

The problem with the statement "water vapor is 95% of greenhouse effect" is that the primary greenhouse forcing is CO2 and the water vapor is a feedback from that warming. The 95% statement comes from here: http://www.eia.doe.gov/cneaf/alternate/page/environment/appd_d.html but that's for the troposphere. For the whole atmosphere, if removing water vapor still traps 64% of heat and water vapor results from the heat trapping of CO2, then it's obvious that "95%" is meaningless.

[aruanan]

I knew that Organic Chemistry would come in handy!!! bwahahahahaha

Yes, but there's nothing organic about nitrous oxide since it lacks carbon.

[Starrgaizr]

It is interesting to ponder what the political situation would look like in the hypothetical case of global cooling from entirely natural causes, say, solar variation. Imagine that the ice caps were growing and glaciers beginning to advance, with reduced growing seasons and some northern cities becoming uninhabitable.

Can anyone imagine the environmental lobby arguing that we should embark on a massive effort to pump more CO2 into the atmosphere to stabilize the earth's temperature? No way.

So, all of the human effects which supposedly justify a massive reorganization of advanced economies are just a smoke screen. The environmentalist position on global warming has absolutely nothing to do with saving Venice or Pacific islands. Those are just ways to enlist the masses to support anti-capitalist and anti-industrialist policies and reduce the competitive advantage of the United States in the world.

That said, whatever their motives, it is theoretically possible that the activists have accidentally reached the correct cost-benefit result. But knowledge of the political calculus cannot but cast doubt on the reliability of the catastrophic scenarios which are predicted.

[AlexW]

"water vapor results from the heat trapping of CO2"

You have bought into the big Goreon scam...See the film:

http://video.google.com/videoplay?docid=9005566792811497638&q=The+Great+Global+Warming+Swindle&hl=en

[palmer]

The main swindle in that movie was the use of myths like volcanoes emitting more CO2 than humans, and harping on the solar link without specifics. The solar luminosity increase over 2000 years is small leading to about 0.2 degrees of warming. The cosmic ray flux may be more significant but that wasn't mentioned in the movie.

I haven't "bought into" anything, I am a skeptic.

[tcrlaf]

"The house of cards is starting to crumble. The credibility of the global scientific community is going to take a big hit over this."

Ya think???
I don't....

Any breathy explanation is NOT as readily digested by the sheeple, as is an easily shouted "WE'RE ALL GOING TO DIE!!!", delivered in the 30 second news brief before "Idol", or "XFactor"....

The religion of Global Warming is a PROPOGANDA EXCERCISE, and has little to do with actual science.

[ancient_geezer]

The problem with the statement "water vapor is 95% of greenhouse effect" is that the primary greenhouse forcing is CO2 and the water vapor is a feedback from that warming.

You are reading too much hype from the IPCC. As regards CO2 the so-called water vapor feedback is a minimal effect due to the overall hydrological cycle and spectral overlap.

Water vapor acts as a field response to any thermal input including solar irradiance as well as ionizing cosmic ray interactions that are modulated by solar magnetic fields. A feedback it may be but of negligible effect where CO2 is concerned due to CO2'a very limited spectral response.

The reality is that CO2 acts more as a feedback to solar input than it does a driver in its own right as solar energy tends to stimulate both biological as well as geological sources of CO2 into the atmosphere.

Any direct warming from CO2 is only ~0.2^oC for a doubling of CO2 concentration. The change in temperature CO2 can actually induce at the surface is ~0.3^oC figuring an increment in water vapor using standard humidity calculations (assuming no change in preciptation and cloud cover i.e. the hydrological cycle) into account that tend to operate to remove water vapor from the atmosphere.

In point of fact, water vapor interferes with CO2 capacity to aborb IR as water vapor absorption spectrum overlaps CO2's spectral response:

 

IR absorption overlap between Water Vapor and Carbon dioxide
http://earthobservatory.nasa.gov/Study/ArbitersOfEnergy/

 

interfering with CO2. The more water vapor in the atmosphere, CO2 actually becomes even less effective than the nominal logrithmic relationship it would otherwise exhibit.

DF = 5.35 ln(C/C₀) wm^-2 [Myhre et al. 1998, Geophys.Res.Lett., 25:2715-2718]

CO2, because of the prevalance of water vapor in the atmosphere, is limited to only 1/3 of the value it would otherwise have, at the top of the atmosphere, roughy ~1.2w/m² at surface concentrations as opposed to 3.6-4w/m², hence actually cooling the upper atmosphere by reradiation to space faster than it can absorb IR at the earth's surface.

 

"-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)."

 

Add ontop of this the fact that additional water vapor put into the atmsphere tends to increase low level cloud cover which actually acts to cool the surface by absorbing high altitude IR and reemitting upward as broadband blackbody radiation (as opposed to the narrow bands where CO2 can absorb IR) and reflecting solar visible light back to space, the net response is actually a negative feedback to CO2 as opposed to a positive one.

 

"The surface of the earth does not cool primarily by infrared radiation. It cools mainly through evaporation.⁷ Most of the evaporated moisture ends up in convective clouds (clouds with strong vertical currents carrying the air and its contents upward, as opposed to layered clouds, which form and stay at a particular level) where the moisture condenses into rain. Just as evaporation cools, the condensation of watervapor heats, and the atmosphere realizes most of this heat at altitudes >5km. It is at these heights that the atmosphere must balance the heat deposited by convection from the surface through cooling by thermal radiation. It is worth noting that, in the absence of convection, pure geenhouse warming would lead to a globally averaged surface temperature of 72^oC given current conditions (Moller and Manabe 1961). Our current average temperature, 15^oC, is actually much closer to the black body temperature temperature (-18^oC), than to the pure greenhouse result.⁸ The relative ineffectiveness of the greenhouse effect is due to convection which carries heat past the bulk of watervapor (which has a characteristic scale height of about 2km), and to large-scale meridional heat transport which carries heat from the moist tropics to the less moist higher latitudes. Because of this transport, it is primarily the distribution of infared absorbers above 5km (rather than below 5km) that is important for containing the heat carried away from the earth's surface (Lindzen et al. 1982)."

*** SNIP ***

"In the meantime greenhouse effect is not nearly as straight forward as is commonly stated."
--- Richard Lindzen (1990) Some coolness concerning global warming. Bull. Amer. Met. Soc., 71, 288-299.

"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;

 

OTOH, Water Vapor responds across a very broad spectrum, much greater than that of CO2 reponding into the near infrared and down through microwave regions of the spectrum and is a factor for all thermal input regardless of source.

In the end there are many factors involved.

Indeed there are as described above.

and the twin approaches here at FR (discredit CO2 and toss around new forcings out of context) is not particularly convincing to me.

I doubt anything is particularly convincing to you. You have crystalized your views so I hardly figure you to change your mind with information running contrary to the stance you have convinced yourself to take.

OTOH, other people need to recognize there is more to the science than what is coming out of the UN/IPCC political machine's bait and switch routine driving the current charge over the lemming's cliff.

 

An Economist's Perspective on Climate Change and the Kyoto Protocol,
by Ross McKitrick. November 2003
http://www.lavoisier.com.au/papers/articles/McKitrick.pdf

The 1992 UN Framework Convention on Climate Change (UNFCCC) defined "climate change" as follows:

"Climate change" means a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.
( http://unfccc.int/index.html )

The recent Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) defined it differently ( http://www.ipcc.ch/ ):

Climate change in IPCC usage refers to any change over time, whether due to natural variability or as a result of human activity.

This is a very important difference: The IPCC is looking for signs of any change, whereas the policy instruments prescribed by the UNFCCC are not triggered unless it is a particular kind of change: that attributable to human activity. When IPCC officials declare that "climate change" is for real, this is about as informative as announcing that the passage of time is for real. Of course the climate changes: if it didn't Winnipeg would still be under a glacier. But the fact that the last ice age ended doesn't imply that the policy mechanisms of the UNFCCC should kick in. That's the problem with the ambiguity over the term "climate change"-and it seems to trip up a lot of people-accepting the reality of "climate change" does not mean accepting the need for policy interventions. And denying that global warming is a problem requiring costly policy measures is not the same as denying "climate change."

http://www.pacificresearch.org/pub/cap/2003/cap_03-02-20.html

"The Economist, which provides the best environmental reporting of any major news source, carried a small story last week about a simple methodological error in the latest U.N. global warming report that has huge implications. The article, "Hot Potato: The Intergovernmental Panel on Climate Change (IPCC) Had Better Check Its Calculations" (February 15 print edition), reviews the work of two Australian statisticians who note an anomaly in the way the IPCC estimated world carbon dioxide emissions for the 21st century."

......

"The IPCC's method has the effect of vastly overestimating future economic growth (and, therefore, CO2 emissions) by developing nations. The fine print of the IPCC's projections, for example, calls for the real per-capita incomes of Argentina, South Africa, Algeria, Turkey, and even North Korea to surpass real per-capita income in the United States by the end of the century. Algeria? North Korea? The IPCC must be inhaling its own emissions to believe this."

[ancient_geezer]

For the whole atmosphere, if removing water vapor still traps 64% of heat and water vapor results from the heat trapping of CO2, then it's obvious that "95%" is meaningless.

Ahhm, we happen to live at the bottom of the troposphere my friend. It is hardly meaningless.

In fact it is very much to the point as the downward re-reradiation from CO2 is where the limited watervapor feed back derives from the downward longwave flux at the surface, as opposed to the upward longwave flux as measured at the top of the troposphere as tropopause cooling the troposphere by radiating to space.

 

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). DF_T^N 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

[ancient_geezer]

The religion of Global Warming is a PROPOGANDA EXCERCISE, and has little to do with actual science.

Indeed!!

"The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary."
-- H. L. Mencken

"On the one hand, as scientists we are ethically bound to the scientific method, in effect promising to tell the truth, the whole truth, and nothing but - which means that we must include all the doubts, the caveats, the ifs, ands, and buts. On the other hand, we are not just scientists but human beings as well. And like most people we'd like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need to get some broadbased support, to capture the public's imagination. That, of course, entails getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. This 'double ethical bind' we frequently find ourselves in cannot be solved by any formula. Each of us has to decide what the right balance is between being effective and being honest. I hope that means being both."
--- Steven Schneider, Quoted in Discover, pp. 45-48, Oct. 1989; see also American Physical Society, APS News August/September 1996.

"Scientists who want to attract attention to themselves, who want to attract great funding to themselves, have to (find a) way to scare the public . . . and this you can achieve only by making things bigger and more dangerous than they really are."
-- Petr Chylek, Professor of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, commenting on reports that Greenland's glaciers are melting. Halifax Chronicle-Herald, August 22, 2001

"The data don't matter. We're not basing our recommendations [for reductions in carbon dioxide emissions] upon the data. We're basing them upon the climate models"
-- Chris Folland, UK Meteorological Office

"The trouble with this idea is that planting trees will not lead to the societal changes we want to achieve"
-- Kyoto Delegate, 05 December 1997

[ancient_geezer]

For the whole atmosphere, if removing water vapor still traps 64% of heat and water vapor results from the heat trapping of CO2, then it's obvious that "95%" is meaningless.

What is obvious is the fact your hypothetical is in meaningless. The problem being two fold,

1) without water vapor in there is no water vapor feedback to enhance CO2 as a GHG and the earth would be an ice ball for lack of watervapor acting as the dominant greenhouse gas, and

2) you can't remove watervapor from the atmosphere without turning off the sun as the amount of water vapor in the atmosphere is overwhelmingly due to near infrared and visible wavelengths of solar irradiation of ocean surfaces not back radiation of CO2 concentrations.

CO2 acting on its own limits the surface temperatures of the earth far below the deepest ice age tempertures, in the deepest glacial periods some 9oC global anomoly below the current interglacial period, CO2 was at approximately 185ppm, a doubling bring it to 370ppm and ~3.7 w/m² forcing amounting to ~0.6^oC increment at the surface in the absense of water vapor.

Fortunately for mankind and life on earth, the sun and water vapor are the controlling factors not CO2.

[palmer]

As you point out, without CO2 the water vapor condenses and freezes and earth is an ice ball. The GH component of water vapor and CO2 are seen by removing them from the model. The model is fairly easy to agree on since it does not involve changes like doubling CO2. That's where there's merit in your material from Lindzen. But not the 98% comment, nor the 95% that the authors use.

The number from the models for water vapor, clouds and ozone is 88% http://www-ramanathan.ucsd.edu/publications/Ramanathan%20and%20Coakley%20RevGSP%201978.pdf and CO2 is the other 12%. Without water vapor CO2 traps a lot more heat, but because of the overlap and the low altitude of water vapor, the CO2 heat trapping is cut in a third. The model is tuned with parameters that match observed values for clouds, lapse rate, and surface albedo. The results match the global average temperature so the model is verified for static equilibrium.

Adding CO2 is a whole nother ballgame and I disagree with the authors that their model has any useful predictive value. That's because the weather patterns will change significantly in a warmer world altering the clouds, lapse rate, and water vapor distribution and making their parameterizations useless.

But suffice to say that the increase in GH effect from man is going to be a fraction of the 12% (not the whole 30% rise in CO2 since 1850, but perhaps 10%). Bottom line the 0.28% in the headline above should be 1.2% or more. Does that matter? Perhaps not, but it should be corrected.

[ancient_geezer]

But not the 98% comment, nor the 95% that the authors use.

I can gurantee it is at least 92% for water vapor alone, not counting the effect of clouds and the hydrologic cycle that 98% encompasses.

 

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.

 

 

The number from the models for water vapor, clouds and ozone is 88% http://www-ramanathan.ucsd.edu/publications/Ramanathan%20and%20Coakley%20RevGSP%201978.pdf and CO2 is the other 12%

Actually looking in the Ramanathan paper, Ramanathan states the CO2 contribution as being 9%. refer:

7. Role of H2O, CO2, O3 and Clouds starting page 17 of the PDF ( page 481 of the paper) Table 6.
Ramanathan, V. and J. A. Coakley, Jr., 1978: Climate Modeling through Radiative-Convective Models. Rev. Geophys. and Space Physics, 16: 465-490.

My calculation using the flux numbers provided by Ram. in the referenced table makes it 8.88%, which leaves more than 90% for the remainder. You really should read the papers you refer to.

Without water vapor CO2 traps a lot more heat.

I suggest we actually quantify that, the actual number for forcing is 3.7 w/m² forcing lacking the presense of water vapor as opposed to 1.2w/m² in the presense of water vapor.

DF = 5.35 ln(C/C₀) wm^-2 [Myhre et al. 1998, Geophys.Res.Lett., 25:2715-2718] as used in the NOAA annual greenhouse gas index calculations.

Without water vapor change CO₂ forcing for a doubling from 185ppm of deep ice age conditions to current levels of CO₂ is quite limited, using the in fact we can calculate just how much temperature change it is capable of effecting:

Given 288K current global surface temperature less 9^oC for global surface temperature (279K) under the deep glacial periods the following blackbody calculations hold true:

Starting with 279K initial surface temperature of ice age conditions:

One may apply the Stefan-Boltzman relation to determine the maximum change in temperature due to the CO2 component:

F=sT⁴

where:

F = total amount of radiation emitted by an object per square meter (Watts m^-2)
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 279^oK surface temperature of the earth.

Flux (F₂₇₉) at the Earth's surface with atmosphere               = 5.67*10^-8(279K)⁴ = 343.56 w/m²

To which we add the increment of 2XCO2 direct radiative forcing at the surface DF = 3.70w/m².

F = 343.56 + 3.70 = 347.26 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 = (347.26/5.67*10^-8)^0.25 = 279.74K

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 due (2xCO²) direct radiative forcing alone.

DT = 279.74-279 = 0.74K

Against the aproximate 9K increment in temperature since the deep glacial ice age predominately due to solar interaction with the hydrologic cycle, not CO2.

Bottom line, CO2 contribution to current surface conditions and for any reasonable projection of future CO2 emissions in the presense of water vapor is negligible, being well less than 10% of total effect arising from direct and indirect effects of changes in solar activity and changes in insolation due to orbital parameters.

[Lancey Howard]

You obviously never did Whippets when they were popular back in the early '70s.
N2O is correct. It's laughing gas.

[ancient_geezer]

But suffice to say that the increase in GH effect from man is going to be a fraction of the 12% (not the whole 30% rise in CO2 since 1850, but perhaps 10%). Bottom line the 0.28% in the headline above should be 1.2% or more. Does that matter? Perhaps not, but it should be corrected.

Actually looking at the numbers, knowing that direct forcing for CO2 doubling is 1.2w/m² & ~0.2K increment per doubling in the presence of water vapor overlap as opposed to the hypothetical 3.7 w/m² (0.74^oK per doubling) obtained without water vapor overlap.

One must of necessity figure the contribution of CO2 to be very marginal and clearly on the order of 3-5% inferred from the calculations above taking water vapor overlap into account. Looking at the potential increment in global surface temperature due to direct effects of CO2 from current atmospheric conditions projecting forward the climate sensitivity to CO2 is indeed clearly limited as compared to the full ramifications of say changes in solar activity that have take place just across the 20th century:

http://www.copernicus.org/EGU/annales/22/4/1395.htm

Annales Geophysicae (2004) 22: 1395 - 1405

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

M. Lockwood, R. B. Forsyth, A. Balogh, D. J. McComas

Results from all phases of the orbits of the Ulysses spacecraft have shown that the magnitude of the radial component of the heliospheric field is approximately independent of heliographic latitude. This result allows the use of near-Earth observations to compute the total open flux of the Sun. For example, using satellite observations of the interplanetary magnetic field, the average open solar flux was shown to have risen by 29% between 1963 and 1987 and using the aa geomagnetic index it was found to have doubled during the 20th century. It is therefore important to assess fully the accuracy of the result and to check that it applies to all phases of the solar cycle.

[ancient_geezer]

The model is tuned with parameters that match observed values for clouds, lapse rate, and surface albedo. The results match the global average temperature so the model is verified for static equilibrium.

A singular data point match does not imply an accurate rendition by any means, in order to say a model is verified even for static equilibrium it must be tested across perturbations sufficient to show its sensitivity to change from nil to current condition and whether or not it can provide a functional simulation of how a real atmosphere acts.

In fact the model Ramanathan evaluates misses by a lot according to his own assessment when tested for climate sensitivity. Indeed, the only verification done by Ramanathan in regard the model is a comparative one with other models, and not a real world empirical study at all.

Quoting from Rathmanathan's concluding remarks concerning the central model he evaluates in his paper:

"The important limitation of the model is that the model results are mostly of academic interest, since the model does not give any information about regional and latitudinal temperature ranges. Furthermore, many of the model parameters (cloud amounts, surface albedo, relative humidity, and critical lapse rate, to name a few) are prescribed on the basis of present day conditions which may not apply for large departures from present conditions. For example, the study by Wetherald and Manabe [1978] indicates that for a 2% increase in solar constant the radiative-convective model results for DT_s, are within 20% of the GCM results, while for a 4% decrease in solar constant the two models differ by a factor of 2 in the estimated value of DT_s. Clearly, radiative-convective models cannot be applied for large perturbations from present conditions."

 

I can guarantee a change from current current condition to nil in any factor is one very large perturbation and thus not to be relied upon for any sense of precision.

Here we are not talking mere 2 or 4% changes in a factor, we are talking total elimination of components in the mix thus can only get a sense of direction of change but magnitude of effect can be off by tremendous factors even for the relatively small perturbations mentioned by Ramanathan.

[uglybiker]

Someone needs to tell Algore.

Judging from the pics I've seen of him lately, I'd say he's retaining dihydrogen monoxide.

It might explain why he acts so weird.