Posted on 10/16/2003 10:31:58 AM PDT by dirtboy
I will grant that the opinions of informed individuals on subjects that lie outside of their area of expertise can be valuable, if those individuals are truly well-informed. However, the ability to be "truly" well-informed on a particular topic becomes more difficult as the complexity of the topic increases. An uninformed opinion, or an opinion based only a skewed awareness of the information that is relevant to the topic, is not very valuable. If uninformed or skewed opinions are presented as being equivalent to well-informed opinions, then the validity of any conclusions that can be drawn about the topic from a compilation of such opinions is marginal.
Let's break this down to a very simple example (which happened to me recently). You're driving through an unfamiliar town trying to find the local post office. You can ask anybody you see how to get there. You happen to spot a mail carrier delivering mail to the businesses along a central street in the town.
Would you prefer to ask the mail carrier for directions to the post office, or just anyone who is walking on the street? (You can assume that most people walking on the street are local and might know how to get to the post office.) Explain your answer.
Extend this a bit. Just imagine that you can survey two groups in the town to get directions to the post office from a given location. One group is made up exclusively of the town's mail carriers; the other is a random group of town citizens. When you examine the two sets of responses, would you expect the quality of the responses from the mail carriers to be generally better than the quality of responses from the random group of citizens?
Now let's go one step further. Imagine that instead of mail carriers, you have one group made of citizens of the town, and another group composed of citizens from the state that the town is located in. The only criterion for inclusion in the latter group is that the citizens can locate the town on a map of the state.
Which of these groups will likely provide the better set of directions to the post office?
Who do you think might have a better understanding of global warming -- a meteorologist or a microbiologist? Now, the meteorologist could be a dunce and the microbiologist a brilliant person who knows a lot about a lot of things (including global warming): but without knowing anything other than their profession, who would you choose?
In the meantime, can you expand on what you meant by this?
One should note that temperature leads CO2 concentration in the most recent ice core data the most: If that's in the cited paper, please confirm. And tell me what your comment pertains to in particular.
Sorry, the chart image URL that was meant to go with the comment, was bad in prior reply.
As can be clearly seen in the above graphic, the Temperature transitions clearly lead the CO2 concentrations. An effect that is more pronounced as the ice is closer to present day.
Would you prefer to ask the mail carrier for directions to the post office, or just anyone who is walking on the street? (You can assume that most people walking on the street are local and might know how to get to the post office.) Explain your answer.
I would trust a postman because I have no reason to think he would lie and I don't think the post office is all that corrupt and incompetent. But there are other organizations.
Who would be more likely to know about how planets affect an individual's future. Someone who studies the subject -- an astrologer, or a man on the street? More likely the man on the street. I don't believe in astrology.
You say you don't like being compared to an astrologer? Okay, how about an "expert" -- a public school teacher? Who would you trust to educate a child? A New York Public school teacher or the average man on the street? Well, it turns out home-schoolers do better than public school students on standardized tests so I would trust the man on the street.
Professions can become corrupt. It happens quite frequently and the average man needs to know who he can trust because corrupt professions can become corrupt rule. Honesty is much more important than competence. If an honest scientist makes a mistake eventually he will see it or someone will point it out to him. But a dishonest scientist will be more inclined to obfuscate because is not interested in the truth, only in presenting facts in a way that will advance himself.
BINGO! --- the NAS (for whatever reason) simply decided to caution people that this was not an official publication of theirs.
So what? Who ever thought it was?
There simply is not sufficient evidence to support the viewpoint that significant danger is posed to the planet by mankind's meager contribution to "greenhouse gasses" and supporting a radical change in our economy.
All I can find, that holds up under close scrutiny, seems to support that view.
For purposes of clarity and a reality check against the UN/IPCC model outputs, the following is a summary of my position concerning the relationship between CO2 concentration and global surface temperatures.
I would appreaciate any evaluation or correction you may care to provide.
Note that the doubling of CO2 used here as a measurement basis is merely for convience of discussion consistent with terms used by the IPCC. It does not represent what I believe to be a reasonable projection of changes in the CO2 concentration for the future century.
From observed data:
0.27oC change in Earth's surface temperature for CO2 doubling is depicted in the following graphic:
Which appears to merely be a confirmation of what can determined from first principles:
Given:
The temperature of the Earth's surface with an atmosphere is 288oK (+15oC).
and the blackbody temperature of the Earth without atmosphere at 255oK (-18oC)
One may apply the Stefan-Boltzman relation:
E=sT4
where:
E = 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 GHG radiative forcing necessary to maintain the atmosphere/surface greenhouse temperature at the current 288oK surface temperature of the earth.
Under constant albedo conditions (CO2 does not contribute to earth's albedo) The total flux at the Earth's troposphere/surface system due to greenhouse factors is:
Flux (E288) at the Earth's surface with atmosphere = 5.67*10-8(288oK)4 = 390.08 w/m2
Blackbody flux (E255) without atmosphere = 5.67*10-8(255oK)4 = 279.74 w/m2
==================================================================
difference = 110.34 w/m2
The (natural + anthropogenic) CO2 contribution is 3.6% of atmospheric greenhouse warming. When expressed in terms of overall radiative forcing acting on both atmosphere and surface all radiative flux associated with CO2 must, of necessity, be:
0.036*110.34 w/m2 = 3.97 w/m2
However, CO2 IR flux at surface temperature from CO2 concentrations in the atmosphere is less than half that total CO2 contribution of 3.97w/m2 to the system, (at least half of the CO2 IR flux is radiated and/or scattered by clouds & dust upward to be lost to space and atmospheric heating rather than contributing towards surface warming.)
Re-cycling of Infra-Red Energy
According to Dr Hugh Ellsaesser's IPCC submission, "The direct increase in radiative heating of the lower atmosphere (tropopause level) due to doubling CO2 is 4 wm-2. At the surface it is 0.5 - 1.5 wm-2". Schlesinger & Mitchell (1985), estimated this surface flux at 2 wm-2. Thus, depending on the model, or modeler, the estimates for increased surface flux following a CO2 doubling, varies between +0.5 and +2 wm-2. An above-averaged figure of +1.5 wm-2 will be assumed here for purposes of analysis and comparison.
Doubling the atmospheric CO2 concentration can only add 1.5w/m2 at the surface for a total surface radiative forcing of
390.08+3.97 = 391.58w/m2
Giving us
(391.58/5.67*10-8)0.25-288oK = 0.277oK (C)increase in surface temperature for doubling of atmospheric CO2 concentration.
A result well within any reasonable expectation of our rough graphic estimate of 0.27oC associated with CO2 doubling derived from the paleo CO2-temperature record in my prior replies.
Number 1: is the derivation of average global temperature something that you did as an analysis, or is it taken from an accessible publication? I.e., is there any justification other than your own ideas for your running a trendline through peak global temperatures to show the correspondence of CO2 and temperature? The main reason that I'm asking this is that I will contrast it with the CO2 + sun forcing plot that is provided in the aforementioned Crowley and Berner paper. Radiative forcing varies from a minimum value of -13.5 W m-2 to a maximum of 10+ W m-2 over the Phanerozoic. On the same plot they provide a scaled del oxygen 18 temperature data from deep-sea sediments over the past 100 million years, which shows a temperature decrease from the Cretaceous of about 4.5 C. (The decrease into the Holocene is right on the edge of the graph.) The latter data agrees with what we see on the right side of your graph.
Sooo... while Crowley and Berner show major variations in net forcing due to CO2 variability, your analysis does not. I do not know how to reconcile this discrepancy. In essence, the radiative forcing during glacial periods is shown as roughly 20 W/m -2 compared to non-glacial periods.
Your analysis indicates that for a 20 W m-2 forcing difference, which corresponds to a 10 deg C change in global temperature over the same time period, only 1 deg C of that change is due to CO2? That's the BIG discrepancy of which I speak. Feel free to explain; please concentrate on this point.
Two short points. Crowley and Berner say this directly about the Ordovician glaciation:
"In the case of the relatively short-lived Ordovician glaciation (about 440 Ma) which occurred at a time of high net radiative forcing, climate models suggest that the unusual continental configuration of Gondwanaland (essentially a large landmass tangent to the South Pole) could result in conditions where high CO2 and glaciation can co-exist. A brief negative excursion of CO2 at this time may also have contributed to this glaciation. *" (Latter text also refers to other processes that could have affected ocean heat transport.)
* not very large, according to the graph
Last point, regarding the temperature and CO2 variability over the past 420,000 years. It is indeed true that temperature increase preceded CO2 rise each time. This is fairly obvious, and likely primarily due to release of CO2 from a warmer ocean. The current situation, however, is without precedent, as the CO2 concentration has exceeded the boundary conditions for atmospheric CO2 concentrations over that interval by about 80 ppmv. This is why predictions of what will happen are difficult to compare to the paleoclimate record.
Next week I want to re-examine the relationship between radiative forcing and climate sensitivity, and determine if what I mean by "climate sensitivity" is the same or different than what you mean by it.
Sorry for the necessary brevity of this response; we will continue next week.
is the derivation of average global temperature something that you did as an analysis,
http://www.doc.mmu.ac.uk/aric/eae/Climate/Older/Global_Climate.html
"Today, the global average surface temperature is about 15°C. This is 33°C warmer than the average surface temperature of the moon, which is about the same distance from the Sun as the Earth. The moon, of course, does not have an atmosphere, and therefore no greenhouse gases to trap extra heat."
Though any value in the range from 13.38 through 14.4oC for yr 2000 might be more precise refer to chart: http://carto.eu.org/article2480.html would provide a more precise calculation.
Just do a google search on [ earth average surface temperature ], and pick an article to your liking.
I.e., is there any justification other than your own ideas for your running a trendline through peak global temperatures to show the correspondence of CO2 and temperature?
Yes, the clear limitations set by the Stefan-Boltman relation laid out in reply #90, the HITRAN analysis of IR absorption in CO2 watervapor system done by Hug, the joint paper with additional additional investigation done by Hug & Barret presented to the the DECHEMA colloquium, 2001,
Sooo... while Crowley and Berner show major variations in net forcing due to CO2 variability, your analysis does not.
Crowley and Berner show major variation in net forcing due to many factors of which CO2 is only one offered possibility. You are leaving out the other obvious and primary factors claimed for the initiation of deep iceages such as Plate Tectonics, Gamma Ray Bursts, meteoric and volcanic events, etc. All of which initiate atmospheric cooling incident to the creation of high altitude cloud cover & icefields altering the albedo of the earth.
I do not know how to reconcile this discrepancy.
Albedo effects from changing cloud cover & especially the creation of glacier ice, lower overall absorbed irradiation of the earths surface and hence cools the surface into ice age conditions. Under such conditions the major multi-million year iceages are induced.
Remove those effects from the overall record. What is left behind is a residual that can be perceived as the 1oC change across a 500 million year record. A 1oC change for more than 4 doublings of CO2 concetration consistant with:
and many more.
Last point, regarding the temperature and CO2 variability over the past 420,000 years. It is indeed true that temperature increase preceded CO2 rise each time. This is fairly obvious, and likely primarily due to release of CO2 from a warmer ocean. The current situation, however, is without precedent, as the CO2 concentration has exceeded the boundary conditions for atmospheric CO2 concentrations over that interval by about 80 ppmv. This is why predictions of what will happen are difficult to compare to the paleoclimate record.
Not difficult at all, at least for estimating the effects of CO2 on climate. 0.277oC per doubling of CO2 regurdless of the source of that CO2.
Now any other changes in global temperature can be due to many factors GHG's being only a portion of the issue, but CO2's contribution is so low in comparison with Water Vapor and the effects of Ice and Clouds on albedo, that CO2 can be essentially neglected as a substantive contributor to Earth's climate.
Anthropogenic (man-made) Contribution to the "Greenhouse
Effect," expressed as % of Total (water vapor INCLUDED)
| Based on concentrations (ppb) adjusted for heat retention characteristics | % of All Greenhouse Gases |
% Natural |
% Man-made |
| Water vapor | 95.000% |
94.999% |
0.001% |
| Carbon Dioxide (CO2) | 3.618% |
3.502% |
0.117% |
| Methane (CH4) | 0.360% |
0.294% |
0.066% |
| Nitrous Oxide (N2O) | 0.950% |
0.903% |
0.047% |
| Misc. gases ( CFC's, etc.) | 0.072% |
0.025% |
0.047% |
| Total | 100.00% |
99.72 |
0.28% |
Next week I want to re-examine the relationship between radiative forcing and climate sensitivity, and determine if what I mean by "climate sensitivity" is the same or different than what you mean by it.
No problem:
JGR Authors Set the Record Straight
Science Magazine, Volume 295, Number 5554, Issue of 18 Jan 2002, pp. 441-442
"[C]limate sensitivity is the change in average global near-surface temperature (DT, ºC) for a prescribed radiative forcing (F, in units of watts per square meter), expressed as DT or l = DT/F."
see also:
Any Climate factor, solar irradiance, cloud cover, glacial ice extent, GHG concentrations, etc which can be resolved into units of watts per square meter through the stefan-boltzman relation, may expressed as a radiative forcing ( F ) for which a ( DT ) can be determined.
The relationship between ( F ) & ( T ) is the stefan-boltzman law E=sT4 equating radiant flux ( E )and temperature ( T ).
Based on what we've discussed so far, you've created an analysis of peak global temperatures in the Phanerozoic that purports to show a maximum 1 deg C influence from variable atmospheric CO2 concentration. This analysis is based on the Hug and Barrett spectroscopic results that indicate the maximum amount of heat/energy (?) that can be generated by the radiative forcing of atmospheric CO2. This is what I have gathered so far, and I will note that we have previously discussed this. I will return to Hug and Barrett further down.
In the course of this discussion, the first aspect of the discussion was addressing the paleoclimate temperature curve, where CO2 concentrations are superimposed; the CO2 concentrations are from Berner's modeling work, which is why I had the idea to bring him and his work into the discussion. It was fortuitous that the publication of Veizer et al.'s work prompted both the publication of Crowley and Berner's Science paper and commentary from Dr. Lee Kump.
The 'conventional' view of Crowley and Berner, and Kump, is that atmospheric CO2 concentrations are a driving factor in Phanerozoic climate. The radiative forcing due to CO2 is only modified by variable solar luminosity. Peak radiative forcing periods correspond with warm epochs, and minimum radiative forcing periods correspond to glacial epochs. The primary exception to this is the short Late Ordovician glaciation, which is explained as due to a unique continental arrangement where the Gondwanaland continent was very close to the South Pole.
Berner's modeling work incorporates plate tectonics and erosional weathering as a major aspect generating and controlling atmospheric CO2 concentrations over Phanerozoic time; therefore, plate tectonics are not an "alternative" explanation for the variation in radiative forcing, as you suggested. It strains credibility that gamma-ray bursts would influence climate over the multi-million year range covered by the Phanerozoic model to such an extent as determining Earth's major glacial epochs. Crowley and Berner due allow that the complexities of climate modeling may possibly provide an explanation of Veizer et al.'s results, which indicated that CO2 was not a strong influence on long-term climate patterns. This explanation is only deemed necessary IF Veizer et al.'s results are confirmed by "further scrutiny", which has not yet taken place.
Many researchers on climate and paleoclimate have called what humans are doing, i.e., increasing the CO2 concentration of the atmosphere due to fossil fuel burning and land-use changes, a "great global experiment", the results of which are difficult to predict. That is quite true; the fact that the CO2 concentration range shown in the Vostok ice core (which I have found according to one reference is accurate to +/- 5 ppmv) has now been exceeded by 80+ ppmv in a span of less than 200 years makes the outcome of such a perturbation difficult to determine, particularly if the radiative forcing due to CO2 and climate sensitivity are in alignment with conventional, rather than unconventional, climate research results.
New to this discussion is the published paper indicating that the Paleocene- Eocene Thermal Maximum, likely caused by a major methane hydrate release and subsequent CO2 production, was due to the radiative forcing of atmospheric methane and CO2. This event fulfills many of the requirements that would be desirable in a natural analogue to modern-day conditions, i.e., the natural release of greenhouse gases and an indication that the temperature response of the climate is in accord with theoretical prediction. An alternate theory based on unconventional science would have to provide a plausible explanation for the observed data (much as conventional science must provide a plausible explanation for the Late Ordovician glaciation occurring during a period of high atmospheric CO2 concentrations and high radiative forcing).
We can then bring up the subject of climate sensitivity. In essence, the position that CO2 has a minimum effect on climate is due to two factors: a posited low radiative forcing due to CO2, and a posited low climate sensitivity to variable radiative forcing factors. Below is a discussion, gleaned from other sources, that provides some indications of why the low radiative forcing indicated by Hug and Barrett may be erroneous. However, prior to that, a short explanation of the 'conventional' view of modern-day climate sensitivity.
As a note, this Web site has a large number of publications relevant to climate sensitivity studies:
Climate Sensitivity Research Lounge
The following text was excerpted from this Web page:
The Lessons of History
"When the temperature, CO2 and CH4 curves are carefully compared, it is found that temperature changes usually precede CO2 and CH4 changes by 500-1000 years on average. This indicates that climate change causes CO2 and CH4 changes. However, these greenhouse gas changes are a positive feedback that contributes to the large magnitude of the climate swings."
"Climatologists are still developing a quantitative understanding of the mechanisms by which the ocean and land release CO2 and CH4 as the Earth warms, but the paleoclimate data are already a goldmine of information. The most critical insight provided by the ice age climate swings is an empirical measure of climate sensitivity."
"The composition of the ice age atmosphere is known precisely from air bubbles trapped as the Antarctic and Greenland ice sheets and numerous mountain glaciers built up from annual snowfall. The geographical distributions of the ice sheets, vegetation cover, and coastlines during the ice age are well mapped. From these data, we know that the change in climate forcing between the ice age and today was about 6 1/2 W/m2 (Figure 3). This forcing maintains a global temperature difference of 5 °C, implying a climate sensitivity of 3/4 ± 1/4 °C per W/m2. Although climate models yield a similar climate sensitivity, the empirical result is more precise and reliable because it includes all the processes operating in the real world, even those we have not yet been smart enough to include in the models." (all emphases are my own additions, above and below)
I apologize for the overly dramatic nature of the art accompanying this figure, but it was the only representation of it that I could find on the Web. It reproduces a figure that I viewed in a previous online presentation.
The following text was excerpted from this Web page:
Global warming
"As summarized in Box 4, most of the energy imbalance has been heat going into the ocean. Sydney Levitus (Reference 4) has analyzed ocean temperature changes of the past 50 years, finding that the world ocean heat content increased about 10 watt-years, consistent with the time integral of the planetary energy imbalance. Levitus also found that the rate of ocean heat storage in recent years is consistent with our estimate that the energy balance of the Earth is now out by 0.5 to 1 W/m2. Note that the amount of heat required to melt enough ice to raise sea level 1 m is about 12 watt-years (averaged over the planet), energy that could be accumulated in 12 years if the planet is out of balance by 1 W/m2."
So that is the conventional view of current radiative forcing, paleoclimate radiative forcing, and climate sensitivity. Note also that a direct query to Dr. Hansen elicited that the major climate positive feedbacks are relative humidity increase (thus the primary radiative forcing contribution of water vapor is not ignored, as some would suggest), and ice sheet/glacier albedo effects. NASA research results that were prominent in the media last week indicated that the Arctic perennial sea ice cover is in a state of decline. This is a positive feedback factor for two reasons; one, the albedo of the large ice area is reduced, and two, the heat absorption capability of dark ocean (compared to reflective ice) is increased.
Below is some discussion of Hug and Barrett's research work, excerpted from a newsgroup thread on that topic. I am not qualified to judge the accuracy of the comments, but I feel that they are relevant as criticism to those who understand this area far better than I do.
"As Barrett, Braterman and Courtney have all correctly noted, the principal infrared absorption bands of carbon dioxide are optically thick under atmospheric conditions. How, then can an increase in atmospheric CO2 result in increased absorption of infrared energy by the atmosphere? This is an argument that goes back to the early years of the 20th century. While the global warming potential (GWP) of CO2 is indeed smaller than that of other greenhouse gases, such as methane, nitrous oxide, CFCs and CFC replacement compounds, it is nevertheless not zero. It was already recognized in the 1950s that hot bands, high rotational levels and most importantly wing absorption of pressure broadened lines all contribute to a net radiative forcing by incremental CO2. Furthermore, this effect is not uniform throughout the atmosphere---the variation of pressure, composition, temperature and radiative flux with altitude must be explicitly taken into account when evaluating the overall GWP. These effects are all included in the radiative transport codes incorporated into the General Circulation Models from which a net radiative forcing of ~4W/m2 is estimated for doubled CO2 content in the atmosphere (which is one possible scenario for the mid-21st century)"
"Returning to Barrett and the other comments, they all omit (although I believe that it is well known to Shine and Houghton) that although the forcing directly due to increases in the CO2 mixing ratio is less than linear, any additional forcing will increase the vapor pressure of water vapor, amplifying the net effect. I believe this is included in the 4W/m2 figure quoted above."
"Perhaps the simplest way of looking at this is that at 300 K there will be a steady state population of CO2 in the lowest excited mode of about 7% assuming local thermodynamic equilibrium. For a mixing ration of 300 ppm this corresponds to a density of vibrationally excited CO2 of 4 x 10^14 molecules/cc. Why won't they emit IR radiation?? Remember, that for local thermodynamic equilibrium, for every one of these that de-excites via collision (and it takes many collisions to loose vibrational energy in a gas where the density of states in the collision partners is small) another is excited by collision. The situation looks a lot like the Hinschelwood mechanism
CO2 + M -----> CO2* + M k1 rate
CO2* + M -----> CO2 + M k(-1)
CO2* -----> CO2 + hv kr = ln2/tau
where tau is the radiative half life. the ratio of k1/k(-1) = [CO2*]/[CO2] so the rate of radiation is kr k1/k(-1) [CO2] and you can calculate the ratio of [CO2*]/[CO2] from the Boltzmann equation.
The following is from a different newsgroup thread; in previous FR correspondence I provided the first part of this quote.
"Comment on "The roles of carbon dioxide and water vapour in warming and cooling the Earth's troposphere" "
John Houghton
Spectrochimica Acta v.51A, p.1391-1392 ( 1995 )
"Sir John very politely, and carefully points out the problems, and goes on to explain that as the concentration of CO2 in the atmosphere increases, so too does the average height (about 6km) from which CO2 emits radiation in space. Since atmospheric temperature in the lower atmosphere falls with altitude, if nothing changes other than the amount of CO2, the amount of radiation to space is reduced. For atmospheric CO2, this reduction is about 4Wm^-2. To restore the Earth's energy balance the temperature thoughout the lower atmosphere has to increase - hence the enhanced greenhouse effect."
"There is also a response from K.P.Shine, whose "constructive criticism of a previous version of this paper" is acknowledged in Barrett's paper. He notes that the previous paper had been submitted to another journal, and he "firmly recommended rejection of that paper and continue to profoundly disagree with the conclusions he reaches" in his review. He then goes on to repeat the points of Sir John, with another couple added for good measure. All in good, clear English that is too often missing from such journals. ( Spectrochim.Acta Part A 51 p.1393-4 (1995) )"
-------------------
That should be sufficient 'fodder' for additional discussion on many aspects of this topic. I look forward to it. Already this discussion and related information acquisition has provided me with knowledge of a remarkable era in paleohistory, the Paleocene-Eocene Thermal Maximum, about which I had been previously unaware.
Based on what we've discussed so far, you've created an analysis of peak global temperatures in the Phanerozoic that purports to show a maximum 1 deg C influence from variable atmospheric CO2 concentration.
True, at least across that data that depicts most nearly constant factors other than CO2 and is of the magnitude of direct radiative forcing. One should remove data representing ice ages which can be attributible to many factors such as continental drift, catastrophic Volcanic & metoric events (e.g. K-T extinction) and Gamma Ray Burst events as the earth moves through the galactic arms ...
This analysis is based on the Hug and Barrett spectroscopic results that indicate the maximum amount of heat/energy (?) that can be generated by the radiative forcing of atmospheric CO2.
No it is based on the the Stefan-Boltzmann relation:
E=sT4
equating direct radiative forcing E(w/m2) with temperature T(oK) at blackbody radiative equilibrium through the Stefan-Boltzmann constant.
Ramanthan (JGR, vol. 84, pp. 4949-4958) states:
"the direct radiative effects of doubled CO2 can cause a maximum surface warming [at the equator] of about 0.2 K, and hence roughly 90% of the 2.0-2.5 K surface warming obtained by the GCM is caused by atmospheric feedback processes described above."
From my rough Stephan-Boltzmann estimate
(391.58/5.67*10-8)0.25-288oK = 0.277oK (C)increase in surface temperature for doubling of atmospheric CO2 concentration.
And from the Phanerozoic CO2 vs T chart above:
0.27oC change in Earth's surface temperature for CO2 doubling is depicted in the following graphic:
Please note the phrase "is depicted". and merely showing while confirming the first principles of the Stefan-Boltzmann relation as it regards 4.45 doublings of CO2 concentration going backward 540 million years to 7000 ppmv CO2.
The addition of the red lines merely illustrates the magnitude of Stefan-Boltzmann. And the statements of Ramanthan as to the direct radiative forcing of a doubling of CO2 concentration.
Hug Barrett and others merely attempt to quantify the effects that a nitrogen and water vapor atmosphere have on CO2 radiative absorption/emission so that the amount of forcing attributable to changes CO2.concentration can be isolated and measured.
Equating change in radiative forcing expressed as watt/m2 with temperature change is a separate issue altogether.
The amount of direct radiative forcing (w/m2) must have the same effect on temperature oK regardless of source of that radiative forcing and that relationship is expressed by Stefan-Boltzmann.
. Crowley and Berner due allow that the complexities of climate modeling may possibly provide an explanation of Veizer et al.'s results, which indicated that CO2 was not a strong influence on long-term climate patterns. This explanation is only deemed necessary IF Veizer et al.'s results are confirmed by "further scrutiny", which has not yet taken place.
To the contrary, the direct radiative forcing of CO2 is very much limited by Stefan-Boltzmann as previously shown ~0.2-0.3oC per doubling and this alone would invalidates a reliance on changing CO2 concentrations as a major causative factor of iceages whether inducing one or ending such.
Changes in aldebo from melting ice today can no more be placed at the doorstep of anthropogenic CO2 change than temperature across time due to other factors.
As can be clearly seen in the above graphic, the Temperature transitions clearly lead the CO2 concentrations. That along with the mininmal direct radiative forcing of CO2 in comparison with other factors, ( water vapor concentration 95% of greenhouse effect, ice pack extent, clouds, etc.)
see also: Origin of the 100 kyr Glacial Cycle
by Richard A. Muller
Whenever ice is heated above 0oC (even from constant solar irradiation and no other factor) it's going to melt, as it melts the extent of the icepack decreases with albedo decreasing as a consequence providing more heating. CO2 is not even a sufficient much less a necessary factor to the event of warming, as historically the surface Temperature leads CO2 concentration as you have noted yourself. Changes in water vapor add even more significantly as one advances out of colder climes of an ice age.
What must be determined is the initator of such warming & cooling events, and changes in CO2 concentration simply does not qualify for lagging in time as well as lack as an IR active substance in comparison with even very small concentrations of water vapor, coupled with the effect of high altitude ice clouds from Solar, interplanetary, and inter galactic events modifying albedo.
Below is some discussion of Hug and Barrett's research work, excerpted from a newsgroup thread on that topic. I am not qualified to judge the accuracy of the comments, but I feel that they are relevant as criticism to those who understand this area far better than I do.
Best to let Hug and Barrett defend their own work then :O)
http://www.vision.net.au/~daly/forcing/hug-barrett.htm
Abstract
At the DECHEMA colloquium, held in Frankfurt on 11th Oct, 2001, Hug and Barrett gave papers that expressed doubts about the details of the manner that spectroscopy has been applied by members of the IPCC in coming to their conclusions about future climate change. IPCC proponents Bakan, Birk and Hollmann opposed the views. This paper summarizes the main points of difference and attempts to put forward the Hug/ Barrett arguments in the clearest terms.
As well as the followup discussion that occurred with input from Courtney as will:
I haven't been disputing that the direct effect of CO2 is smaller than the effect that is magnified by positive feedback. So if Ramanathan is saying that a doubling of CO2 leads to a total temperature increase of 2.0-2.5 K in his GCM, that seems like a reasonable outcome. Perhaps lower than some estimates, higher than others.
Hansen estimates that the TOTAL increased radiative forcing due to all greenhouse gas emissions since 1850 is 2.3 W m-2, with 1.4 W m-2 due to CO2. (Note that this is not the NET radiative forcing change since 1850, it's just the radiative forcing change due to GHGs.) We've already seen that Hansen believes that climate sensitivity is about 3/4 C per 1 W m-2 forcing. So that means CO2 would be responsible for about a 1 C warming since 1850 (not for CO2 doubling).
What I cannot tell from Ramanathan (or you, for that matter) is what is the calculated radiative forcing change for a doubling of CO2 concentration. You say:
Equating change in radiative forcing expressed as watt/m2 with temperature change is a separate issue altogether.
That's the climate sensitivity issue. The concern, in a nutshell, is how much radiative forcing has changed/is changing/will change, and what this will mean in terms of change in global temperature. CO2 is a contributor to increased radiative forcing; if the overall trend in radiative forcing is positive (which is the ultimate problem), then increased radiative forcing will cause increasing global temperature.
So let me ask you a pretty straightforward question: do you think that 0.75 C per 1 W m-2 of radiative forcing is a reasonable value for climate sensitivity?
Now we're talking about two different things. A major glacial epoch is not the same as a glacial period (when the contrasting period is an interglacial). It would be helpful if you could see the Crowley and Berner figure, but I can explain it pretty easily. The whole Pleistocene period of glacial-interglacial oscillations counts to Berner as a glacial epoch, a period in which continental ice sheets were present. His Phanerozoic climate model doesn't have the time resolution capability of distinguishing glacial advance and retreat and the causes of them. I.e., the concentration of CO2 in the atmosphere, in concert with the global tectonic setting (meaning the continental arrangement, the presence, location, and height of mountain ranges) is the main determinant of global climate over periods of millions of years.
Other factors, particularly astronomical factors (though I did read a VERY recent paper by oceanographer Carl Wunsch that addresses Milankovitch forcing factors; he indicates that their influence should be much less than as has been promoted and understood, but the statistics are way, way beyond me) will determine climate change and global temperature over periods that are considerably less than "millions of years". It's obvious from the graph that we've shared that atmospheric CO2 concentration responds to these other factors. Did you notice that Hansen said, as I have said many times, that in this case CO2 acts as a "a positive feedback that contributes to the large magnitude of the climate swings"? Note that this means CO2 and other GHG concentrations act to magnify change in both directions, meaning increasing or decreasing global temperature, because of their radiative forcing effects! To whit, when global temperatures decrease, CO2 and other GHG concentrations decrease, which amplifies (perhaps even accelerates) the climate trend.
Changes in aldebo from melting ice today can no more be placed at the doorstep of anthropogenic CO2 change than temperature across time due to other factors.
That's disputable but not provable. Many of the scientists who have observed the loss of perennial Arctic sea ice have taken pains to make sure that they don't say that the melting ice is a direct consequence of global warming, i.e., GHG-induced climate change or global temperature increase. At the same time, they attribute the melting ice to the observed general warming over the Arctic, which has occurred in the same timeframe (obviously) as the global temperature trend. What I was trying to point out was that the radiative forcing due to ice loss is the same positive forcing factor that is found in Hansen's figure. So no matter what the cause of the melting Arctic ice, the result is a positive radiative forcing term.
What must be determined is the initiator of such warming & cooling events, and changes in CO2 concentration simply does not qualify for lagging in time as well as lack as an IR active substance in comparison with even very small concentrations of water vapor, coupled with the effect of high altitude ice clouds from Solar, interplanetary, and inter galactic events modifying albedo.
Here you state a vital point of convergence in our discussion. Yes, CO2 does not qualify as the initiator of warming and cooling events in the recent (420,000 year, or Pleistocene glacial period) paleoclimate record. I totally agree. Let me reemphasize: I totally agree. But what I have been pushing very strongly in our discussion is the fact that CO2 is a radiative forcing component of Earth's climate system. Increasing atmospheric CO2 concentrations (and the concentrations of other GHGs) should lead to increasing global temperature. The remarkable case of the Paleocene-Eocene Thermal Maximum seems to demonstrate an event in which most other climate components were stable (~unchanging), so that the only change was a rather dramatic increase in CH4 and then CO2 atmospheric concentrations, leading to an apparent large increase in global temperature. (Note also that this event was about 150,000 years long, not 200, leaving the question of how rapidly the climate would respond to this increase wide open -- and that's a very significant question.)
And then the bottom line is: since the mid-1800s, atmospheric CO2 concentrations have increased about 80 ppmv, and they will not stop increasing for decades. There are very few other radiative forcing changes happening in the Earth's climate system right now, though if the Sun launches a few more giant solar flares at us during what is supposedly the down phase of the solar cycle, I might have to change that statement. In the absence of other factors, the rapid increase in atmospheric CO2 concentrations, and the radiative forcing that results from that process, will have an effect on Earth's climate system. Since there is still considerable uncertainty about the magnitude of some negative forcings (particularly clouds), the net result of the GHG forcing is still quite uncertain. Hansen has stated that controlling black soot emissions would do much more than Kyoto x 10, and that technological advance can significantly slow the growth rate of CO2 in the atmosphere. Taken together, that would result in much less forcing than a "no change in current trends" scenario. I think he's right; I've said that before.
That's a lot to say. If there is any justification in calling "global warming" a "global warming hoax", it lies with the media that promote worst-case dire scenarios as if they were as plausible as the midrange, average, mean predictions. Obviously they aren't, but the headlines are more strident. Factually, atmospheric CO2 concentration is increasing, as are the concentrations of other GHGs, though I believe methane has hit a plateau for unexplained reasons. Increasing atmospheric CO2 concentrations are a positive radiative forcing factor. Increased radiative forcing is expected to have a noticeable effect on global climate.
The last three statements are straightforward, factual, and no hoax. Saying otherwise is not contributing to the effort to understand how Earth's climate responds to forcing factors, be they radiative or something else.
So let me ask you a pretty straightforward question: do you think that 0.75 C per 1 W m-2 of radiative forcing is a reasonable value for climate sensitivity?
Easily checked:
The solar flux normally exhibits a p-p variation of 0.1% over an 11 year sunspot cycle(see: graph 40yr solar irradiation). That is 1.4wm-2 (0.001*1366.5wm-2)p-p (i.e. 0.262 wm-2 (irradiance*albedo/4) *1.5 for back radiation from water vapor direct radiative forcing and other GHGs forcing manifested as a cyclic climate temperature variation).
Using this forcing and the GCM postulated feedbacks giving rise to climate sensitivity of 0.75oC/wm-2, we should expect to see a 0.20oC p-p variation in global tropospheric temperatures with an 11 year solar cycle period. Observations indicate that the temperature oscillation is less than 0.05 C and it is difficult to detect.
This implies
1) the "feedbacks" postulated in the GCMs are manifested in the real world at quarter that level or
2) there is a long time constant damping radiative forcing effects on surface temperature.
Looking at longterm secular change in solar irradiation since 1800-1996AD removes shorterm damping effect. Long term change in solar effects has been about 4 times the magnitude of the sunspot related cycles, about 4.3wm-2 overall change in Top Of Atmosphere(TOA) solar flux:
Hoyt, D. V. & Schatten, K. H.: The role of the sun in climate change. New York-Oxford, Oxford University Press, 1997, 61, 70, 86, 184,188,194, 214.
http://www.vision.net.au/~daly/solar/fig5.gifLong Term changes in Solar Irradiance,Solanki &Figge, Page 7 figure 6
http://www.astro.phys.ethz.ch/papers/fligge/solspa_2.pdf
That gives us a change 4.3*0.3/4 = 0.325 wm-2 available for surface heating with an additional 50% re-radiated back to the surface from atmospheric water vapor(95%) & other GHGs(5%) yielding a total 0.4875wm-2, the remainder radiated to space.
The actual peak change in global surface temperature since 1900-1995 has been about 0.65oC and has tracked with change in solar irradiation ±0.14oCrms.
Friis-Christensens E., Lassen K., 1994, Journal of Atmospheric and Terrestrial Physics 57(8), 835
http://web.dmi.dk/solar-terrestrial/space_weather/
http://www.astro.phys.ethz.ch/research/fligge/paleo_fig3_nf.html
http://solar-center.stanford.edu/sun-on-earth/glob-warm.html
Using the IPCC/GCM figure of 10 to 1 feedback, i.e. 0.75oC/w * 0.53 wm-2 = 0.4oCpeak
That leaves as much as 0.25oCpeak arising from other factors for that period in comparison to the ±0.14oCrms. (i.e. ±0.20oCp-p) curve fit error.
We must attribute 60% of the 20th century change to changes in solar irradiation with a remaining 40% to all other driving changes:
Friis-Christensens E., Lassen K., 1994, Journal of Atmospheric and Terrestrial Physics 57(8), 835
http://web.dmi.dk/solar-terrestrial/space_weather/
http://www.astro.phys.ethz.ch/research/fligge/paleo_fig3_nf.html
http://solar-center.stanford.edu/sun-on-earth/glob-warm.html
Or, we seem to have a case of some missing in action climate feedback in the real world when testing global temperatures against radiative forcing from solar activity.
60% solar to 40% solar unrelate forcings seems to be a reasonable division when using the IPCC/GCM 10 to 1 forcing multiplier.
As to whether or not that 10 to 1 multiplication bucketing multiple complex processes (volcanic action, dust & smoke airosols, etc) gives us any understanding of where that remainder 40% of forcing comes from is another issue altogether.
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