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This is a continuation of the thread TIME Special Article on Global Warming, which was getting too long to be manageable. I've optimistically entitled it "Science of global warming". Hopefully we can leave the political talk to a minimum.
Ignore this thread. Cogitator is just a flame-baiter. Don't give him the satisfaction.
Just out of curiousity, what was the % of C02 in the air 100 years ago and what is the % today? What % CO2 is expected in 100 years if there is no reduction of CO2?
Thanks for your assistance.
Whose model of the greenhouse theory are you quoting here? How old is the reference to the numbers you quote? Have the authors issued revisions? These are the latest consensus IPCC numbers.
OK. You're quoting very specific aspects of the models, which is not stuff that I find in the "Summary for Policymakers". According to the IPCC, they are just getting the numbers from models that have been published in the literature. So do you have a site that shows the actual numbers? (not that I'm disputing you; Spencer says that the models show more warming in the troposphere than is predicted).
Only an increase of continental cloud cover, possibly a consequence of anthropogenic aerosols, can damp the diurnal cycle by an amount comparable to observations. Yes, but subsequent studies have shown the diurnal temperature range is decreasing both in regions where clouds are increasing and clouds are decreasing, so greenhouse gases modifying cloud cover cannot explain the observations. There is no correlation between the diurnal cycle changes and cloud cover changes. Hansen's model is the only model that came close to explaining the diurnal cycle, but, now that it has failed and people no longer refer to it as a solution (e.g.,
Collatz, G.J., Bounoua, L., Los, S.O., Randall, D.A., Fung, I.Y. and Sellers, P.J. 2000), another cause for the diurnal cycle must be sought.
Got it. This paper is online at Inez Fung's Web site (PDF document alert):
A Mechanism for the Influence of Vegetation
on the Response of the Diurnal Temperature Range to a Changing Climate
Tropospheric aerosols can account for part of the continentally-located forcing, but alone they do not damp the diurnal cycle as observed. Hansen says aerosols won't explain the measurements either.
I read this Friday. Apparently (you can confirm this), the changing DTR was proposed as evidence for global warming, and now that's in question. The paper proposes that it's a response to increasing CO2 in the atmosphere. Well, we already knew that was happening. So what it amounts to is a CO2-related climate change that is not directly related to warming, right? Fine with me. There are likely to be other effects like that.
Why isn't this a concentration-based effect? I.e., the atmosphere is denser nearer to the surface (obviously). Why isn't more heat trapped as the atmosphere gets denser, with more molecules of GHGs available to absorb heat? These questions don't make sense to me, so I can't answer them. You seem to be confusing heat and temperature.
I tried not to. "Temperature" means that molecules of any phase "move" more, both internally (vibrational and rotational modes of the molecule) and externally (they move faster, bounce around faster). Heat means the actual radiation from these molecules. Is that accurate? My statement tried to say that if you add energy to the atmosphere, you have more heat capacity in the troposphere because you have more molecules in the denser atmosphere. I.e., more heat (energy) can be held in the troposphere. If I'm right, then that would mean that as the atmosphere gets less dense, the situation would become more dynamic.
The surface observer can never warm faster than the atmosphere, because, if it did, it would imply perpetual motion machines exist. "That's certainly correct, but I have a question."
Are you agreeing then that the temperatures increasing faster at the surface then in the atmosphere constitutes a perpetual motion machine? I suggest you do the following experiment. Open your oven door and put a thermometer in it. Put another thermometer facing the open oven about 10 feet away and turn the oven on. If the temperature of the thermometer outside the oven rises to a higher temperature than the thermometer inside the oven, then you will have an analogous situation to the atmosphere warming (the oven) causing the surface temperature (thermometer outside the oven) to increase by a greater amount and hence by a faster rate. I think you will find in both the oven case and the Earth-atmosphere case that it is impossible. The inescapable conclusion is that the surface thermometer readings are wrong or they are receiving heat from another source other than the greenhouse effect. The satellite observations put a very severe constraint on the values of the surface temperature trends.
According to this diagram, the ground absorbs 168 W/m^2 of the incoming 342 W/m^2 of solar radiation. The atmosphere absorbs 67 W/m^2. Greenhouse gases provide 324 W/m^2 of back radiation, while the surface provides 350 W to the atmosphere and 40 that escape to space. So if this diagram is correct, the surface heats up faster than the atmosphere, and the temperature nearer the surface should be warmer than higher in the atmosphere. So I probably didn't understand the point. Sorry.
Just out of curiousity, what was the % of C02 in the air 100 years ago and what is the % today? What % CO2 is expected in 100 years if there is no reduction of CO2?
Thanks for asking. The pre-industrial estimate of CO2 concentration in the atmosphere is about 280 ppm, based primarily on ice core data (see graph below, courtesy of a Princeton University site). Estimates of what CO2 could reach in the next century range up to 1000 ppm (which is outlandish). The estimates depend on a variety of emissions scenarios that I'm not qualified to discuss. The IPCC quotes the models with the various emissions scenarios, so they're the place to start.
One might wonder how much better the science is that links carbon dioxide emissions to global warming, than dioxin (aka Agent Orange) to human illness.
JasonC, I hope you'll bear with me on this. I thought about what you provided to me Friday, and what I want to do is try to break down the situation into simpler parts and see what I'm confused on. I think I'm most concerned about a factor of 4 discrepancy in what a different source says should happen with doubling CO2 and what you say should happen. But I want to make sure that I'm conceptualizing the system properly.
Here's the site that I'll refer to:
Solar and Earth Radiation
It's a simple frames site. I can say to click on a button on this site, and you can go to the link above and find the button (there are only six buttons). The "Earth's Balance" button is what provides the figure that the Earth's temperature would warm 1.2 C with doubled CO2, based solely on direct greenhouse gas (CO2) forcing.
The main topic that I want to be clear on is radiative balance (or imbalance). Below I'm going to describe three simple experiments. I'll rely on your expertise to explain to me if these do not apply to the Earth-Sun system, and why.
Experiment 1. We have two cups, one metal and one styrofoam, containing the same volume of water. We insert a heating element and run the same amount of energy through each element. My expectation of this experiment is that both volumes of water would reach about the same temperature, but the water in the metal cup would cool faster than the water in the styrofoam cup because the metal cup conducts heat better and radiates it more effectively. Is that correct?
Experiment 2. Now we have two metal cups containing two substantially different volumes of water. Again, we put in the heating elements and add the same amount of energy. My expectation is that the smaller volume of water would reach a higher temperature and also cool off faster than the larger volume of water. The larger volume would not reach as high a temperature, but it would "hold" more heat. Because the heat flux through the metal is constant, then the greater amount of heat content in the larger volume would take a longer time to dissipate. Is that correct.
Experiment 3. Again we have two metal cups with two equal volumes of water. We insert the heating elements and run power through both at the same rate. As this is being done, we begin to carefully wrap thin sheets of styrofoam packing material around one of the cups. My expectation of this experiment is that the temperature in the cup we are wrapping will begin to increase faster than the unwrapped cup. We are creating a radiative imbalance between the wrapped and unwrapped cup -- though the input is the same, energy is escaping faster from the unwrapped cup than the wrapped cup. Is that correct?
If so, if we then stop heating the water, the water in the unwrapped cup will be cooler than the wrapped cup, and it will also cool off faster.
This last experiment is the key (for me, at least). If the primary question with respect to GHGs is the retention of outgoing heat in the atmosphere, then we are strictly looking at the "escape rate" of the heat (the outgoing longwave radiation, if we want to be specific on terms). The experiment is an attempt to illustrate my concept of the system: if the outgoing heat flux is attenuated, then the system retains more heat and also loses it slower.
OK, so there are my examples. I've explained how I think the third relates to the Earth system: please correct my misconceptions. If I'm reasonably on target here, then I'll discuss experiments 1 and 2. But I do want to make sure that my conception of the outcomes is reasonable.
The reason that I'm doing this is that the concepts are important. I have no doubt that you're doing your calculations correctly, but unless I understand the concepts, your numbers won't have an impact.
One might wonder how much better the science is that links carbon dioxide emissions to global warming, than dioxin (aka Agent Orange) to human illness.
Right now I'm only interested in the former.
Roughly 275PPM; and 325PPM.
It seems to have leveled off in the past decade.
It is actually difficult to measure since it is never in complete flux.
The one thing you ignore is the cloud cover change likely to result from evaporative emissions and the resultant albedo effect which will reduce the total received radiation by backscatter.
"One might wonder how much better the science is that links carbon dioxide emissions to global warming, than dioxin (aka Agent Orange) to human illness."
No question, the science is incomplete and uncertain. The consensus is that global warming is real, but how much and how fast is still open to debate. It is precisely for that reason that we should proceed with caution, NOT continuing to spew gases into the atmosphere with no clear idea what havoc we might be wreaking.
So, let me get this straight: CO2 has increased by less than 1/100 %, and still is less than 1/10 % of the atmosphere. Yet this extremely small change in the atmosphere is responsible for recordable climate changes?
I remain skeptical about human actions effecting the global temperature. Thanks for your honest response.
Whoops. Meant to say that % of CO2 in the atmosphere had changed by less than 1/100%.
The globe may be warming, but credible evidence that CO2 is the cause of global warming is non-existent.
"The globe may be warming, but credible evidence that CO2 is the cause of global warming is non-existent."
And there's not likely to be any credible evidence until enough data has been collected to create an adequate baseline ...
Like about 100,000 years worth.
It seems to me the argument has come down to a chicken-or-the-egg question. Do temperatures go up because CO2 rises, or does the increase in temperature cause an upswing in CO2?
I saw in the January issue of "Science" an article "Atmospheric CO2 Concentrations over the Last Glacial Termination", which seems to indicate the latter. In other words, arguing CO2 levels is barking up the wrong tree.
So, let me get this straight: CO2 has increased by less than 1/100 %, and still is less than 1/10 % of the atmosphere. Yet this extremely small change in the atmosphere is responsible for recordable climate changes?
There may not be much CO2, but it's very important to the radiation budget. This is a good illustration:
"Compared to the 255 K blackbody [refers to the theoretical emission spectrum at 255 K, the smooth green line], the most obvious feature of the observed Earth spectrum is the much higher emission in the region of 800 - 1250 cm-1 (12.5 to 8 microns), where the blackbody temperature is closer to 290 degrees Kelvin. This spectral band is the "water vapor window" in which the cloud-free atmosphere is very transparent, so that the emission to space comes from regions very near the warm ocean surface. It is this window which allows the Earth to keep as cool as it does. The window is cut off on the lower wavenumber side by the strong CO2 absorption band centered around 650 cm-1, or about 15 microns, where the emission corresponds to temperatures well below 255. There is also significant absorption by ozone (O3) at around 1100 cm-1, or 9 microns. The many absorption bands on either end and throughout the measured spectrum are from water vapor, which is the primary absorber in the atmosphere. The primary reason that the surface temperature remains near 290, (or +15 C) rather than the 255 (-18 C) it would be if there were no atmosphere, is the absorption in the thermal infrared by atmospheric water vapor, as seen throughout this figure."
So, let me get this straight: CO2 has increased by less than 1/100 %, and still is less than 1/10 % of the atmosphere. Yet this extremely small change in the atmosphere is responsible for recordable climate changes?
There may not be much CO2, but it's very important to the radiation budget. This is a good illustration:
"Compared to the 255 K blackbody [refers to the theoretical emission spectrum at 255 K, the smooth green line], the most obvious feature of the observed Earth spectrum is the much higher emission in the region of 800 - 1250 cm-1 (12.5 to 8 microns), where the blackbody temperature is closer to 290 degrees Kelvin. This spectral band is the "water vapor window" in which the cloud-free atmosphere is very transparent, so that the emission to space comes from regions very near the warm ocean surface. It is this window which allows the Earth to keep as cool as it does. The window is cut off on the lower wavenumber side by the strong CO2 absorption band centered around 650 cm-1, or about 15 microns, where the emission corresponds to temperatures well below 255. There is also significant absorption by ozone (O3) at around 1100 cm-1, or 9 microns. The many absorption bands on either end and throughout the measured spectrum are from water vapor, which is the primary absorber in the atmosphere. The primary reason that the surface temperature remains near 290, (or +15 C) rather than the 255 (-18 C) it would be if there were no atmosphere, is the absorption in the thermal infrared by atmospheric water vapor, as seen throughout this figure."
The one thing you ignore is the cloud cover change likely to result from evaporative emissions and the resultant albedo effect which will reduce the total received radiation by backscatter.
I'm not ignoring it; I know that it's quite important. It just hasn't come up for discussion yet. And also cloud radiative feedbacks are very hard to quantify - they are the major unknown in all climate models.
"The consensus is that global warming is real, but how much and how fast is still open to debate. It is precisely for that reason that we should proceed with caution, NOT continuing to spew gases into the atmosphere with no clear idea what havoc we might be wreaking."
Quite so. But what country (or consumer) could afford that, and maintain their current manner of living?
And since we're having a cut and paste party, here's a few fun talking points, some of the quotes are a few years old, but the central points remain consistent:
Citizens For a Sound Economy (CSE) studied the list of 2,600 scientists allegedly signing onto the global warming statement. The list included many who never authorized the use of their names. In addition, the list included a hotel administrator, a linguist, a psychiatrist, seven sociologists, an acupuncturist, landscape architects, a philosopher, a dermatologist, a diplomat, a pair of anatomists, 73 zoologists, 2,325 from professions totally unrelated to climatologist... and of course, a gynecologist. (Washington Times 12/14/97 and other CSE Reports)
In addition, CSE found that only 182 of the 2,600 were in any related specialty that might have some bearing on climate. These included the fields of geology, oceanography, geography, and physics. Only 15 on the signatory clearly specialized in climate, weather, or atmospheric science. (Investor’s Business Daily 11/17/97)
Over 17,000 scientists have signed a petition saying, in part, "There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the near foreseeable future, cause catastrophic heating of the earth’s atmosphere and disruption of the earth’s climate. (Heartland Institute - Instant Expert Guide to Global Warming")
Two thirds of climatologist winning Nobel prizes do not agree with those who believe human activities are causing global warming. (Cal Thomas - Washington Times Weekly Edition 11/9/97)
A survey of state climatologist - scientists retained by state governments to monitor and research climate issues - conducted in 1997 found that 58% disagreed with the statement, "Global Warming is for real", while only 36% agreed. In addition, 89% believed that "Current science is unable to isolate and measure variations in global temperatures caused only by man-made factors." (As reported in the Heartland Institute "Instant Expert Guide to Global Warming" and quoting from American Viewpoint’s "Survey of State and Regional Climatologist - September-October 1997)
A Gallup Poll found that only 17% of the members in the Meteorological Society and the American Geophysical Society believe the slight warming in the 20th century has been the result of greenhouse emissions from the burning of fossil fuels. (Environmental News - August 1997)
Only 13% of the scientists responding to a Greenpeace survey believe catastrophic climate change will result from continuing current patterns of energy use. (Ecologic Magazine - July/August 1996 Edition)
According to Patrick Michaels, head Climatologist for the Commonwealth of Virginia, the Global climate Models (GCMs) have consistently projected higher increases in global and hemispheric temperature than those actually observed. (Global Warming: A Political. Economic, and Scientific Background - CSEF)
Jane Francis, a leading British scientist believes any so called warming trend is merely a blip in the long term trend towards another ice age. She stated: "What we are seeing really is just another interglacial phase within our big ice house climate." (Daily Herald 9/12/97)
According to Dr. Iben Browning, a renowned Climatologist, Physicist, Chemist, and Biologist, in 1991 there were 11,700 weather reporting stations in the United States. Of the total, 11,000 were located in cities, 430 in small towns, and the remaining 270 out in the country. While the 11,000 in the cities showed a temperature gain, the 430 in the small towns remained constant, but the 270 in the country showed a temperature drop. (Climate and the Affairs of Man: A 1991 Update)
Ground level measurements suggest a warming of 0.3 - 0.6 degrees Celsius since 1850. However satellite data over the last 18 years show no evidence of warming. (H. Sterling Burnett - Environmental Policy Analyst for the National Center For Policy Analysis)
The earth experienced greater warming between the 10th and 15th centuries than we have seen in the past century. (H. Sterling Burnett - Environmental Policy Analyst for the National Center For Policy Analysis)
Data from NASA satellites, confirmed by weather balloon records, show no significant trends for the past eighteen years. This has been reported in such respected journals as Nature, Science, and the Bulletin of the American Meteorological Society. (Joe Bast - President of the Heartland Institute)
Is it getting warmer or colder? According to climatologist Dr. S. Fred Singer, the answer is "Yes." "It all depends on the time scale you choose. The global climate has warmed over the last 100 years, but not appreciably over the last 50 years. And it is colder now than it was 1000 years ago." (Ten Things You Ought To Know About Global Warming by S. Fred Singer, Ph. D.)
Concerning CO2:
-The greatest temperature rise of the century (about 0.65° C) took place between 1910 and 1945 as atmospheric carbon dioxide rose only 3 percent.
-In the 33 year period of 1945 - 1978, the temperature fell by 0.2° C while atmospheric carbon dioxide actually rose by 9 percent.
-The temperature has been leveling off since 1990. (Climate Change 95: An Appraisal by Vincent Gray M.A., Ph. D.)
Here's a very cool statistic:
Because of their eating habits (cellulose products, wood, paper, etc.) and their digestive systems, termites are very gaseous critters and emit approximately 50 billion tons of CO2 per year. This make the 5 billion tons of CO2 created by the burning of fossil fuels pale by comparison. (Climate And The Affairs of Man: A 1991 Update)
More juicy tidbits can be found here.
What's missing from your analysis is a discussion of how a miniscule increase in CO2 (% wise) will cause large temperature rises. What I would like to see is a correlation between CO2 concentration and air temperature at a given point. If I were given the hypothesis that increased CO2 levels are responsible for global warming, the first thing I would do would be to correlate temperature and CO2. For some reason, I've never seen that particular analysis. ;^)
1 - 'Celestial Mechanics, Carbon & Climate - Solving the Puzzle of the Ice Ages', (especially the Chapters on the Milankovitch Cycle)...
www.sp.uconn.edu/~geo101vc/Lecture24/index.htm
2 - 'Astronomical Theory of Climate Change'...
www.ngdc.noaa.gov/paleo/milankovitch.html
3 - 'The Celestial Clock', book about polar axis shift & 120,000yr ice age cycle...
Two thirds of climatologist winning Nobel prizes do not agree with those who believe human activities are causing global warming. (Cal Thomas - Washington Times Weekly Edition 11/9/97)
Who did Cal Thomas consider climatologists who have won the Nobel Prize? There is no Nobel Prize in Climatology, so it would probably have to be in either Chemistry or Physics. Anybody know any winners of the Chemistry or Physics Nobels that would be considered climatologists?
I've seen the other quotes before. Some are more relevant than others.
What's missing from your analysis is a discussion of how a miniscule increase in CO2 (% wise) will cause large temperature rises. What I would like to see is a correlation between CO2 concentration and air temperature at a given point. If I were given the hypothesis that increased CO2 levels are responsible for global warming, the first thing I would do would be to correlate temperature and CO2. For some reason, I've never seen that particular analysis. ;^)
Well, I'm trying to work on that with my "colleagues" Number_Cruncher and JasonC. The basic theory says that CO2, methane, CFCs, and a few other gases absorb longwave radiation that would otherwise escape to space (the process keeping the Earth radiatively balanced). The gas molecules re-radiate the longwave radiation back down, and it adds to the continuous input of solar radiation. So since there's a radiative imbalance, the surface (primarily the ocean) and the atmosphere will get warmer -- until (as JasonC is trying to tell me, I think), a new radiative equilibrium gets established.
According to the link that I used to start this out, an instantaneous doubling of CO2 in the atmosphere would cause a 1.2 degree C directly-forced warming.
Because the main drivers of paleoclimate temperature changes are not atmospheric gases, paleotemperatures do not correlate with CO2 concentrations as cause-and-effect, i.e., CO2 rises do not commonly result in atmospheric temperature increases. In fact, because warming ocean waters release CO2 (simple dissolved gas chemistry), it's frequently the other way around. That is hypothesized to be part of Earth's thermostat: warming releases CO2, which maintains warm temperatures. Vice versa, cooling causes more desert soils to provide iron to the oceans, enhancing phytoplankton productivity which keeps CO2 concentrations down, keeping things cooler. (The latter is part of the iron fertilization theory first formulated by John Martin. The theory has been confirmed inasmuch as it's been shown that many parts of the ocean are iron-limited. The paleoclimatic aspects of the theory are still being researched.)
Thanks for the good links (I particularly like the first one). I've brought up Milankovitch a few times before in these discussions, particularly when discussing first-, second-, third, and fourth-order effects on climate. Milankovitch is generally considered second-order. That's not a popularity rating, it refers to the timescale of climatic changes.
I've seen the other quotes before. Some are more relevant than others.
Relevant in what ways? Can you dismiss them THAT easily?
For example: Jane Francis, a leading British scientist believes any so called warming trend is merely a blip in the long term trend towards another ice age. She stated: "What we are seeing really is just another interglacial phase within our big ice house climate." (Daily Herald 9/12/97)
In terms of relevance, sure, we could have a 300-year greenhouse gas warm period before things cool off again. This quote isn't exactly relevant to how uncomfortable things might get in those 300 years, is it?
The Younger Dryas was a 1000-year very cold period that occurred at the end of the last glacial period, due (probably) to a large input of glacial meltwater from the St. Lawrence channel into the North Atlantic. This 1000-year period was basically a "blip" in the warming trend out of the glacial period. It was pretty darned significant to the North American and European areas. (See what I mean?)
I don't want to argue about individual quotes. You provided them and they all have some bearing on the issue; and as I said, some are more relevant than others. If there is any particular quote to which you wish to draw my attention, please restate it and I'll take another look.
Oh! I'm sorry, I thought this was a thread discussing Global Warming.
Ok, on that diagram, you have 492 watts total at the surface, direct and back-radiation. With 342 given as top o' the atmosphere. One thing to notice right off, is the ratio of the two and the implied temperature effect from having an atmosphere at all. 492/342 ^ .25 = 1.0952. The current mean temperature is ~18C = 291K (not, incidentally, the 15C on your othe link), then that implies a temperature without atmosphere of 265.7K The well publicized figure for that is 255K. However, the picture is consistent with that, as it shows 30W reflection out of 198W incident sunlight at the surface, or about 15% reflection, and without an atmosphere that proportion would remain but apply to the higher 342 incoming sunlight. So you'd have 290W rather than 492, 1.7 times, check.
Now, on your link the fellow says 4 watts more will cause 1.2C warming. But that does *not* check. With total power 492W/m^2 from your diagream, maintaining the present temperature of 291K, an increase to 496 would only increase the temperature by (496/492) ^ .25 = 1.002026 times. Multiplying by the original 291K temperature, that means +0.59C, half of what the link stated. He evidently did not include the back radiation in the power maintaining the present temperature. It is of course only the proportional change in the total power the surface is receiving, that will cause (4th root) changes in the mean temperature.
Incidentally, the lower incoming sunlight power in your diagram compared to the figure I was using previously, is effectively a changeover of units, on the "area" side. But I believe it to be correct. It is a result of the geometry of the problem, essentially. The earth receives ~1380W/m^2 on a total area equal to the cross-section of a great circle perpendicular to the incoming sunlight. But it re-radiates from a total area equal to the surface of a sphere with the same diameter. In units of "per square meter of re-radiating surface", then, the average sunlight is 1380/4 = 345 W/m^2 - your diagram has 342 from a 1370W estimate of the total original sunlight term, but that is close enough. So this is a useful correction, and does imply slightly greater sensitivity to power changes.
But it still leaves the conclusion, +4 watts can't produce a 5C warming, it can barely produce a 0.6C warming. To warm up +5.3C (high end of UN projection) would require total power of [ (296.3/291) ^ 4 ] * 492W = 528.8 watts, or 36.8 Watts additional, not 4-8. They still need a huge amplifier, and they still haven't got one.
Then there is the related problem of just how believeable the UN wattage figures are. Because they have to include the same power budget assumptions. The old concentration was 280ppm, which means 0.28%, trace gas indeed. The past increase was 31%, to ~365ppm. That means the absolute portion of the atmosphere changing in composition, is .0868%. The existing back radiation from all greenhouse is 342W in your diagram. Naively, you'd only expect *on the order* of a 0.3W change from so small a change in composition. Why? Just a crude 1st approximation, % of atmosphere changing times watts from the whole atmosphere.
Actually, the UN estimates ~1.1 from CO2 alone, and throws in several other substances to arrive at the 2.4W figure, especially methane. And then they find numerous aerosol factors in the opposite direction.
Another way of looking at it, is to consider the well publicized statement that 98% of all existing greenhouse effect is known to be from water vapor. Which means the total of all greenhouse from everything in the atmosphere besides water vapor, is only 6.84 W/m^2 (342 x .02).
So you can not only double CO2, you can double every greenhouse effecting substance besides water vapor, and only pick up 6.84 W/m^2. 6.84 additional watts, on top of 492 currently operating, only raise equilibrium temperature by 1 degree C. That is what you'd expect from doubling every greenhouse substance but water, without any dampeners operating.
It is useful to get these numbers more accurate, and I thank you for the patience in going through it. I stand by my previous order of magnitude conclusions. 3-5C they do not have an adequate power source for that they can name, thus not a physical theory. Changes of less than a degree C from incremental greenhouse gases are possible, but that is all.
I don't disagree with any of your three thought experiments - in the second, you have left out volume to surface area effects on cooling, which are not the same as heat capacity effects; heat capacity refers simply to a denser body requiring more energy to increase by the same temperature - but those are quibbles - but I have to point out a somewhat different fact. In all three cases, you are going to end up at the same temperature, because you have not left a continually operating power source for any of the cases.
Incidentally, heat is not temperature. Usually you seem to have this right, but occasionally the usage seems slightly loose.
You have spoken of heating with energy added, and cooling after the input of additional energy is withdrawn, both correctly. But this obscures the more relevant point. You can leave the power source in any of them, and the cups will only warm up (temperature up) to a certain amount, and then they will stop warming further.
It requires a continually operating power source to maintain any body at a finite temperature. Insulated or not, some energy added to it before or not. The temperature falls until the cup and contents are in radiative equilibrium with the surrounding air etc.
Not only is the tendency back to equilibrium when a power source is removed, but it is also to equilibrium when the power source is left operating. Put the heating element in the cup and leave it there, and the cup will warm (increase in temperature) to a definite temperature and will then stop warming. At the higher temperature, the energy loss per unit time from the top and outer surfaces of the cup, will equal the energy input through your heating element. Once that relation is established, the contents cannot warm any further.
Oh! I'm sorry, I thought this was a thread discussing Global Warming.
There's one of those every day on FreeRepublic. This is a continuation of one where we attempted to get into some of the more contentions scientific issues behind the rhetoric and opinion polls. Not that public opinion isn't important, but this is a complex scientific issue, and the public doesn't always get it right. I consider myself reasonably informed, and I've had to clarify my language and my concept of the issue significantly in these discussions. And I bet a true climatologist would blanch at some of our more egregious misconceptions.
Ok, on that diagram, you have 492 watts total at the surface, direct and back-radiation. With 342 given as top o' the atmosphere. One thing to notice right off, is the ratio of the two and the implied temperature effect from having an atmosphere at all. 492/342 ^ .25 = 1.0952. The current mean temperature is ~18C = 291K (not, incidentally, the 15C on your othe link), then that implies a temperature without atmosphere of 265.7K The well publicized figure for that is 255K. However, the picture is consistent with that, as it shows 30W reflection out of 198W incident sunlight at the surface, or about 15% reflection, and without an atmosphere that proportion would remain but apply to the higher 342 incoming sunlight. So you'd have 290W rather than 492, 1.7 times, check.
That's fine (this is a good diagram of the whole system).
Now, on your link the fellow says 4 watts more will cause 1.2C warming. But that does *not* check. With total power 492W/m^2 from your diagream, maintaining the present temperature of 291K, an increase to 496 would only increase the temperature by (496/492) ^ .25 = 1.002026 times. Multiplying by the original 291K temperature, that means +0.59C, half of what the link stated. He evidently did not include the back radiation in the power maintaining the present temperature. It is of course only the proportional change in the total power the surface is receiving, that will cause (4th root) changes in the mean temperature.
Interesting. But are you considering the Earth as a theoretical blackbody to make this calculation? (Someone else asked you a similar question on a different thread and you seemed to concur with his analysis.)
Incidentally, the lower incoming sunlight power in your diagram compared to the figure I was using previously, is effectively a changeover of units, on the "area" side. But I believe it to be correct. It is a result of the geometry of the problem, essentially. The earth receives ~1380W/m^2 on a total area equal to the cross-section of a great circle perpendicular to the incoming sunlight. But it re-radiates from a total area equal to the surface of a sphere with the same diameter. In units of "per square meter of re-radiating surface", then, the average sunlight is 1380/4 = 345 W/m^2 - your diagram has 342 from a 1370W estimate of the total original sunlight term, but that is close enough. So this is a useful correction, and does imply slightly greater sensitivity to power changes.
OK.
But it still leaves the conclusion, +4 watts can't produce a 5C warming, it can barely produce a 0.6C warming. To warm up +5.3C (high end of UN projection) would require total power of [ (296.3/291) ^ 4 ] * 492W = 528.8 watts, or 36.8 Watts additional, not 4-8. They still need a huge amplifier, and they still haven't got one.
Well, one thing that I think is going on with the higher warming predictions is that they also result from high-end emissions scenarios. I.e., even tripling of CO2 concentration. That doesn't seem very likely, but because they are trying to get a range of predictions, even if some of the predictions are low probability. And the models disagree on mechanisms.
Then there is the related problem of just how believeable the UN wattage figures are. Because they have to include the same power budget assumptions. The old concentration was 280ppm, which means 0.28%, trace gas indeed. The past increase was 31%, to ~365ppm. That means the absolute portion of the atmosphere changing in composition, is .0868%. The existing back radiation from all greenhouse is 342W in your diagram. Naively, you'd only expect *on the order* of a 0.3W change from so small a change in composition. Why? Just a crude 1st approximation, % of atmosphere changing times watts from the whole atmosphere.
Right. As you note below, other greenhouse gases add a lot more forcing than CO2. (As an aside, that's why I advocate Hansen's "alternative scenario" over Kyoto.)
Actually, the UN estimates ~1.1 from CO2 alone, and throws in several other substances to arrive at the 2.4W figure, especially methane. And then they find numerous aerosol factors in the opposite direction.
Right, and you've seen Hansen's forcing figure before, too.
Another way of looking at it, is to consider the well publicized statement that 98% of all existing greenhouse effect is known to be from water vapor. Which means the total of all greenhouse from everything in the atmosphere besides water vapor, is only 6.84 W/m^2 (342 x .02).
So you can not only double CO2, you can double every greenhouse effecting substance besides water vapor, and only pick up 6.84 W/m^2. 6.84 additional watts, on top of 492 currently operating, only raise equilibrium temperature by 1 degree C. That is what you'd expect from doubling every greenhouse substance but water, without any dampeners operating.
So far so good. And here I'm going to make a comment that's an observation, and I don't want to offend you. The basic skeptic position seems parallel to what you've been saying. In essence, solely on basic principles, the warming estimates from the models seem excessive. The response from the climate modeling community is usually along the lines of "but basic principles are only part of the story." And then considerable disagreement ensues over how these other factors affect the climate. There's still an essentially unresolvable question in my mind over why your estimate for direct greenhouse forcing with doubled CO2 is 1/2 of the estimate on the page I cited. And I can't do the math to try and find a possible source of the difference. Do you want a homework assignment ;-) ?
It is useful to get these numbers more accurate, and I thank you for the patience in going through it. I stand by my previous order of magnitude conclusions. 3-5C they do not have an adequate power source for that they can name, thus not a physical theory. Changes of less than a degree C from incremental greenhouse gases are possible, but that is all.
Good, I think we're on the same page now. See the next reply.
I don't disagree with any of your three thought experiments - in the second, you have left out volume to surface area effects on cooling, which are not the same as heat capacity effects; heat capacity refers simply to a denser body requiring more energy to increase by the same temperature - but those are quibbles - but I have to point out a somewhat different fact. In all three cases, you are going to end up at the same temperature, because you have not left a continually operating power source for any of the cases.
Actually I realized that the volume/surface area effects would play a part, but didn't want to get into that level of detail. The essential part of #2 is that if you have two different volumes of water (or air) at the same temperature, the larger volume is storing more heat. #2 relates to the heat capacity of the oceans. What I believe Hansen has been saying, which the Levitus data may be demonstrating, is that since the establishment (or enhancement) of the radiative imbalance starting about 1850, the oceans have been warming up too. Hansen states this as "an additional 0.5 C of warming is already 'in the pipeline'." Leaving aside the question of how rapidly the heat content of the oceans could be transferred to the atmosphere, I interpret this to mean that the whole climate system has been storing some of the heat caused by the radiative imbalance. I.e., back in the mid-1800s, the forcing of the system was less than now, but even then heat was being stored, due to the large heat capacity of the oceans.
As for the continually operating power source, I could have phrased it that way, but I felt that it elucidated different aspects of the system better if I didn't. (#3 has a continuous power source, by the way.) The key about #1 is that a system that retards heat (longwave radiation) loss will rise to a higher temperature than a system that doesn't for the same energy input. If you had a continuous energy input, the more effective radiator would reach a lower equilibrium temperature than the less effective radiator. (Right?)
Incidentally, heat is not temperature. Usually you seem to have this right, but occasionally the usage seems slightly loose.
You and Number_Cruncher have forced me to tighten up my usage of the terms.
You have spoken of heating with energy added, and cooling after the input of additional energy is withdrawn, both correctly. But this obscures the more relevant point. You can leave the power source in any of them, and the cups will only warm up (temperature up) to a certain amount, and then they will stop warming further.
Sure. As I said above, under those circumstances, the more effective radiator will reach a lower equilibrium temperature than the less effective radiator.
It requires a continually operating power source to maintain any body at a finite temperature. Insulated or not, some energy added to it before or not. The temperature falls until the cup and contents are in radiative equilibrium with the surrounding air etc.
Not only is the tendency back to equilibrium when a power source is removed, but it is also to equilibrium when the power source is left operating. Put the heating element in the cup and leave it there, and the cup will warm (increase in temperature) to a definite temperature and will then stop warming. At the higher temperature, the energy loss per unit time from the top and outer surfaces of the cup, will equal the energy input through your heating element. Once that relation is established, the contents cannot warm any further.
True. Let me ask you a question for fun. In #3, it seems to me that if you added one layer of 1/16 inch styrofoam around the cup, that would cause the most significant difference between it and the "control" metal cup. Adding more and more layers of styrofoam would have less and less effect on the final equilibrium temperature that the insulated cup reaches. Is there a relationship that describes that? I'm relating this conceptually to increasing CO2 in the atmosphere. It seems to me that as you add more CO2, you're saturating the longwave absorption bands. Beyond a certain point, adding even more CO2 won't affect the system appreciably. But I don't know how you'd determine what that point is.
"There's still an essentially unresolvable question in my mind over why your estimate for direct greenhouse forcing with doubled CO2 is 1/2 of the estimate on the page I cited"
Because he did not use the full surface wattage in his calculation. Your diagram is not on his page. He did not include existing greenhouse effect in the power required to maintain the current temperature, only the sunlight portion.
And don't tell me you can't do the math, that is silly. Get a calculator. You can put in a number and take a square root twice, I hope. This isn't that hard, don't go "Barbie" on me.
For the 1.2C figure to make sense for 4 watts, the power maintaining the current temperature would have to be a mere 241 watts/m^2. You can check that easily. (292.2K/291K) is the postulated temperature change, so that ^4 is the postulated wattage change, as a proportion. You do the math, you get 1.0166 times as much power needed as there is now.
Now we can check to see what wattage he was assuming maintains the present temperature. He thought a 4 watt increase would cause that temperature change; let x equal the initial power consistent with that result. Then x+4 = 1.0166 x, 4 = 0.0166 x, x = 241 watts (or 240, close enough). He assumed the power maintaining the current temperature was only 241 watts (or 240), which was probably meant to be some sunlight-only figure, reduced for planetary albedo. But on your diagram, the power at the surface is 492 watts, not 241 watts.
His 241W is less power than the 291 watts the earth would get without any atmosphere at all, from your diagram (342 incoming, .15 reflected short from surface). And 291W would only maintain a temperature of 255K = -18K (the no atmosphere figure), so 241W (the figure he needs for his 1.2C to make sense) would only maintain a current temperature of (241W/291W)^.25 x 255K = 243.26K, or 47.74 degrees colder than it actually is.
It isn't minus 30C outside. So the power he used in his equation was wrong. There is no estimate of back-radiation, total greenhouse, in his page incidentally (as opposed to in your diagram), so this is not an altogether surprising mistake. He didn't include the existing greenhouse power to the surface, in the current power term (to maintain present temperature), so he overestimated the proportional effect 4W would have.
As for the statement that "there is disagreement about additional effects", well duh. The point is, the modelers haven't been able to name the power source they are relying on to make the 3-5C prediction. Yet they still make it. They wave their hands and say, "maybe there is some positive feedback", exactly the amplifier hunt I have been explaining to you.
But they arrive at the prediction somehow, *without* having testable, definited claims about what those supposed extra power sources are. Which means the predictions are not based on a physical model of the processes involved, only on data fitting, statistical correlations. This is backwards science, and bad statistics, and abuse of data.
When you can name a physical cause - enhanced greenhouse - it makes sense to estimate the scale of its effect and go look for that effect. And that effect is order of magnitude watts, so it explains temperature variations order of magnitude tenths of degrees.
Guess what? All the data variations are order of magnitude 10ths of degrees! There is no reason, nothing, nada, for their prediction of an effect an order of magnitude larger in the power (20-40 watts rather than watts).
And if such effects occurred, there would be no reason - in fact positive reason *not* - to link them to the CO2 changes. Because CO2 changes cannot cause effects of that scale. "Without help" - then get a theory of the "help", but the CO2 has nothing to do with it! They don't have a theory of the help, but they still make the larger predictions.
The only place in the record we see 3-5C variations is on ice-age timescales with another explanation able to account for the variation. The theory started as a means of explaining ice ages. Those are explained otherwise now. Also, they would be overexplained if both explanations supposedly operate, and the past change would be larger. You can't have two causes of the same scale variation operating at the same time without a larger variation.
And the modelers know this. When they first saw the innaccuracy of the power budget, they increased the estimated sunlight 6%. But that is the scale of the ice age change. They just popped it into their model.
Then they wave their hands about clouds. But data on clouds says #1 they cool and #2 they have increased in recent times, with higher levels of CO2 in the air. So they are damping, not driving. In addition, the scale is still wrong, with the estimate for no clouds ~13 watts, and no one even pretends a change of composition of a mere 0.1% of the earth's atmosphere is going to make all clouds disappear, so only a small fraction of that power is even potentially available, if the sign were right, which it isn't.
Then you say, "well maybe CO2 will triple instead of double". First off, it still won't come close. *All* greenhouse gases besides water vapor are only contributing on the order of 7W. CO2 is only a fraction of that. 3 times half of 7 is not going to get you 20-40. And they know this, so no, the high end projections are not merely based on higher forecasts of CO2.
I can tell you want they are based on. They are based on extrapolations from bad statistical fits to noisy near-flat-line data, with an "induced" giant amplifier supposed to just kick in somehow, they haven't a clue how, to make their messy coefficient-that-says-anything-I-tell-it-to and fudge-filled model, make the slightest bit of physical sense.
This is not how good science is done. You may notice an effect and hypothesize a cause. Then you go see if the cause is operating, *and how much*. And if that cause explains *half* of what you see in the data, you do not *assume* it is causing *all* of it because of sympathetic sun-output magic or hypothetical epicycle amplifiers you never dreamt of before the hypothesis. You just say, "my hypothesis can explain this much of the data. If there is additional signal, it must be coming from something else."
And that sort of explanation would give predictions of variations in future mean tempature of 1C or less. And incidentally, it is not in the least clear there *is* any more signal than that to start with. No change beyond that order of magnitude has been seen. If the 2.4 watt estimate of the UN for the past 250 years is correct, and the 492 watt power estimate from your diagram is correct, then you expect 0.35C warming over the past 250 years. Lo, the ocean says less, the surface says more. The data *bracket* the theory. What conceivable reason is there to assume a giant amplifier must be present anyway?
Can't you see how silly it is that they are continuing to predict temperature changes on the same order of magnitude as a discredited ice-age hypothesis from 1896 made without any knowledge to speak of, about radiative cooling? That it is silly for them to continue to predict 3-5C changes when their own power budgets say 1C or less? That it is silly for them to have two ice ages on top of each other, if they expect both the accepted orbit/sun theory and their CO2 theory to independently cause ice-age size temperature changes?
The prediction is "Plank's constant". The theory can change, the prediction cannot. Another epicycle hunt after hidden amplifiers can be launched, after a previous one is shot down, when there was never any reason to expect such amplifiers, certainly not of that scale (bigger than all clouds vs. none, several times bigger than all trace greenhouse gases vs. none?) in the first place.
Why is the prediction constant despite improving science that continues to drum away repeatedly that enhanced greenhouse is "real but 1C or less?" I'll tell you why, because the prediction is valued for reasons independent of its truth or lack thereof. It is a means to funding, it is a means to regulation. But the reputation of science is not done any favors by being misused in such a manner.
What is so frustrating about all this is that, despite the clear fraudulence of the claims of the green movement in this regard, they are still taken seriously. (I would say a political parallel would be the career of Jesse Jackson -- no amount of discrediting seems to be effective in eliciting his removal from public life.)
What I would love to see is this: Someone (preferably George W., though I'm not sure his style or presentation capability are right for it) stand up at an easel on national television with a pointer and explain what you have demonstrated so clearly on these threads. I envision a presentation on the order of Schwarzkopf explaining the Gulf War denouement. And end with a flourish, "And THAT is why I do not support these excessive regulations!"
"I'm not ignoring it; I know that it's quite important. It just hasn't come up for discussion yet. And also cloud radiative feedbacks are very hard to quantify - they are the major unknown in all climate models."
The impact of cloud cover/albedo is much better understood then the fringe theories about the impact of trace amounts of CO2 in the air. Are you implying that the impact of CO2 is a major _known_ in all climate models, compared to cloud cover?
Gradients drive everything, even stability. Albedo is a direct driver in the planetary energy balance, not fringe, and cloud cover is a significant driver of albedo. That is why Venus, with a 100% cloud cover and a much higher albedo then Earth ends up with a lower equilibrium skin temperature, even though it is closer to the Sun. (Yes, it has a much higher surface temperature, but that is due to the extremely thick atmosphere, which got that way because Venus never had water in all three states. If we boiled off all our pooled and frozen water into vapor, our atmosphere would be orders of magnitude thicker, denser, and hotter at the surface, too.)
What we _do_ know about Earth's cloud cover is that it is freakishly constant over time, as an average % of the total Earth disk. If it was not, Earth's albedo would vary wildly over time. Is this freakish stability an accident? Whatever the controlling feedback mechanism, it must be incredibly stiff and stable. If it was unstable, then perturbations would drive it to wildly different average %. So, what fortuitous set of facts keep this direct, primary driver of Earth's energy balance so constant over such long periods of time? I say, the same fortuitous facts which gave Earth a thin, not thick atmosphere; our neighborhood of surface temperature/pressure and the Triple point of water, creating a huge, natural buffer agent.
Hypothesize a sudden increase in atmospheric temperature. The atmosphere would suck up more water vapor, likely resulting in an increase in cloud cover. (If a decrease, then how?) But, this increase in cloud cover would net increase Earth's albedo, directly reducing the solar thermal load. Which would tend to lower the atmospheric heat loading, and temperature. One has to come up with mystifying, unspecified fringe effects counter to the above basic facts to put this in doubt, but more importantly, if the feedback were the other way, then perturbations would be unstable, and we would not experience this freakish, almost constant average % cloud cover over the Earth disk.
Hypothesize a massive increase not in temperature, but in particulates, which would increase not only cloud cover, but precipitation as well. Such as, a Pinatubo. If the atmosphere did not have a means of scrubbing itself, then sudden, high rate step purturbations such as a Pinatubo would certainly result in long term changes to albedo over time. Yet....it doesn't. Despite all the purterbations, the avg% of cloud cover over the Earth disk remains freakishly fixed. There is no doubt that our atmosphere does not have an infinite capapacity to accept infinite rate loading of heat or particulates, but there is also no doubt that Man is several orders of magnitude away from being able to boil off the oceans even if we wanted to try. The goofy arguments that Earth's atmosphere is in any way 'fragile' or is in a 'delicate' balance, such that the slightest perturbation from Man is going to send it wildly flying off to a Venus like fate just does not stand up to much scrutiny.
No, the same folks hawking manmade Ice Age 25 years ago, and who are now hawking manmade global warming, are doing it for precisely the same reason; demonization of business, industry, capitalism, etc., using any means necessary, before its successes render its detractors totally marginal. It is painfully transparent.
"What I would love to see is this: Someone (preferably George W., though I'm not sure his style or presentation capability are right for it) stand up at an easel on national television with a pointer and explain what you have demonstrated so clearly on these threads. I envision a presentation on the order of Schwarzkopf explaining the Gulf War denouement. And end with a flourish, 'And THAT is why I do not support these excessive regulations!'"
Bush had the perfect opportunity to do exactly that when he shot down Kyoto. That fact that he chose to frame it as a purely political decision, and not to question the science, speaks volumes. Even Bush realizes that the preponderance of scientific opinion is on the other side.
JasonC, thanks for the clarifications. I'm going to ask you a couple more questions, make a couple of statements, let you respond, and then we're probably near to closure on this (for now, at least). Sorry for any edits I made to keep this at a manageable length.
I said: "There's still an essentially unresolvable question in my mind over why your estimate for direct greenhouse forcing with doubled CO2 is 1/2 of the estimate on the page I cited"
You responded: Because he did not use the full surface wattage in his calculation. Your diagram is not on his page. He did not include existing greenhouse effect in the power required to maintain the current temperature, only the sunlight portion.
And don't tell me you can't do the math, that is silly. Get a calculator. You can put in a number and take a square root twice, I hope. (Yes, I can.) This isn't that hard, don't go "Barbie" on me.
For the 1.2C figure to make sense for 4 watts, the power maintaining the current temperature would have to be a mere 241 watts/m^2. You can check that easily. (292.2K/291K) is the postulated temperature change, so that ^4 is the postulated wattage change, as a proportion. You do the math, you get 1.0166 times as much power needed as there is now.
Now we can check to see what wattage he was assuming maintains the present temperature. He thought a 4 watt increase would cause that temperature change; let x equal the initial power consistent with that result. Then x+4 = 1.0166 x, 4 = 0.0166 x, x = 241 watts (or 240, close enough). He assumed the power maintaining the current temperature was only 241 watts (or 240), which was probably meant to be some sunlight-only figure, reduced for planetary albedo. But on your diagram, the power at the surface is 492 watts, not 241 watts.
His 241W is less power than the 291 watts the earth would get without any atmosphere at all, from your diagram (342 incoming, .15 reflected short from surface). And 291W would only maintain a temperature of 255K = -18K (the no atmosphere figure), so 241W (the figure he needs for his 1.2C to make sense) would only maintain a current temperature of (241W/291W)^.25 x 255K = 243.26K, or 47.74 degrees colder than it actually is.
It isn't minus 30C outside. So the power he used in his equation was wrong. There is no estimate of back-radiation, total greenhouse, in his page incidentally (as opposed to in your diagram), so this is not an altogether surprising mistake. He didn't include the existing greenhouse power to the surface, in the current power term (to maintain present temperature), so he overestimated the proportional effect 4W would have.
OK, let's take a break here. Your math looks good. However, I wanted to see if there was a simpler way that the 1.2 C figure was obtained. Happily for my simple-mindedness, I think I found it. You have to tell me why this is incorrect.
Chapter 12: Radiative Forcing and Feedback from the National Academy of Science online books, "Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base". The link above takes you to the beginning of the chapter. First of all, the chapter indicates that the total "greenhouse effect" is the difference between the TOA emission, which they say is 240 W/m^2 (the diagram says 235) and the surface emission, which they say is 390 W/m^2 (same as in the diagram). That just establishes that we're on the same page, radiation-wise.
Below is the key page and section, which I'll now try to reproduce imperfectly in ASCII/HTML:
"In order to demonstrate radiative feedback mechanisms, it is convenient to
assume initially that climate change is manifested solely by temperature changes
within the climatic system and that all other climate parameters remain fixed at
their unperturbed values. In this framework, there is no change in the climatic
system's 240 W/m^2 solar absorption." [That number confused me for a minute;
it's the incoming solar minus the reflected solar. From the diagram, it should be
235.] "Moreover, let G denote the 4.4 W/m^2 radiative forcing, and let deltaF
be the change in the TOA infrared flux following the imposition of the forcing.
Thus,
G = deltaF = df/df - deltaTs
where df/dT is the the black body rate of change of the surface radiative flux
per unit change of surface temperature, deltaTs. For the surface temperature of
this calculation (288 K), dF/dt is 3.3 W/m^2/deg C, and therefore
deltaTs = 4.4/3.3 =~ 1.3 C.
If it were not for the fact that this warming introduces numerous interactive feedback mechanisms, then deltaTs = 1.3 C (2.3 F) would be a robust estimate of the global mean quantity."
So that's an independent calculation of the doubling CO2 forcing yielding 1.3 C as the directly-forced temperature change. It essentially ignores everything but the W/m^2 of the radiative forcing. Are they leaving something key out of the calculation? (And why are so many people making this same mistake?)
As for the statement that "there is disagreement about additional effects", well duh. The point is, the modelers haven't been able to name the power source they are relying on to make the 3-5C prediction. Yet they still make it. They wave their hands and say, "maybe there is some positive feedback", exactly the amplifier hunt I have been explaining to you.
Here's another reference of interest:
The Global Warming Debate
Pay particular attention to the yellow sidebar entitled "Key Differences with
Skeptics", especially #2. What you've and other have been saying, and also which
was emphasized by Barnett in discussing the Levitus ocean temperature data, is that
climate sensitivity has been overestimated. And that's making an impression on me.
I think we may experience a "sea change" in the models in the next couple of years
due to an increased need to justify (or remove) the high and medium sensitivity
parameters if they continue to have little observational justification.
When you can name a physical cause - enhanced greenhouse - it makes sense to estimate the scale of its effect and go look for that effect. And that effect is order of magnitude watts, so it explains temperature variations order of magnitude tenths of degrees.
Guess what? All the data variations are order of magnitude 10ths of degrees! There is no reason, nothing, nada, for their prediction of an effect an order of magnitude larger in the power (20-40 watts rather than watts).
And if such effects occurred, there would be no reason - in fact positive reason *not* - to link them to the CO2 changes. Because CO2 changes cannot cause effects of that scale. "Without help" - then get a theory of the "help", but the CO2 has nothing to do with it! They don't have a theory of the help, but they still make the larger predictions.
The only place in the record we see 3-5C variations is on ice-age timescales with another explanation able to account for the variation. The theory started as a means of explaining ice ages. Those are explained otherwise now. Also, they would be overexplained if both explanations supposedly operate, and the past change would be larger. You can't have two causes of the same scale variation operating at the same time without a larger variation.
This paragraph made a big impression on me. If you'd like to, we can discuss it
further. I thought about two feedbacks that might cause much larger radiative forcing,
and two came to mind. One is the loss of summer arctic sea ice cover. Some data
(not all) indicates possible thinning of the ice pack and regression of the ice
boundary. If there's a significant loss of summer ice cover, the direct reflection
parameter is reduced (Earth albedo decreases). Two is methane. Increasing
temperatures might release methane from peat bogs, permafrost, and (of most concern
to me at least) from seafloor methane hydrates.
Update on Methane Hydrate Research and Development Act (5-8-00) contains this:
"Another concern about producing methane hydrate is the greenhouse effect of methane gas released into the atmosphere.
Methane is ten times more effective at insulating the planet than both water vapor and carbon dioxide, the two most abundant
greenhouse gases. Along that same vein, the destabilization of methane has been invoked as a means to explain some recent
(on a geological timescale) periods of climate warming since the Last Glacial Maximum, when changes in sea level move the
methane hydrates on the sea floor out of the pressure regime in which it is stable as a solid. Such changes would cause it to
become a gas, allowing escape to the atmosphere as a greenhouse gas."
These are provide as examples of possible positive feedbacks that aren't directly related to input/output via CO2. I don't know how much they figure into the highly sensitive models (there's probably some methane release from surface warming).
And the modelers know this. When they first saw the innaccuracy of the power budget, they increased the estimated sunlight 6%. But that is the scale of the ice age change. They just popped it into their model.
That's a pretty nasty fudge factor. Where is this alteration described?
Then they wave their hands about clouds. But data on clouds says #1 they cool and #2 they have increased in recent times, with higher levels of CO2 in the air. So they are damping, not driving. In addition, the scale is still wrong, with the estimate for no clouds ~13 watts, and no one even pretends a change of composition of a mere 0.1% of the earth's atmosphere is going to make all clouds disappear, so only a small fraction of that power is even potentially available, if the sign were right, which it isn't.
Obviously clouds are still a major uncertainty.
Then you say, "well maybe CO2 will triple instead of double". First off, it still won't come close. *All* greenhouse gases besides water vapor are only contributing on the order of 7W. CO2 is only a fraction of that. 3 times half of 7 is not going to get you 20-40. And they know this, so no, the high end projections are not merely based on higher forecasts of CO2.
I can tell you what they are based on. They are based on extrapolations from bad statistical fits to noisy near-flat-line data, with an "induced" giant amplifier supposed to just kick in somehow, they haven't a clue how, to make their messy coefficient-that-says-anything-I-tell-it-to and fudge-filled model, make the slightest bit of physical sense.
Now we're somewhat in the realm of opinion, so I'll just say that you'd have to take up these points with the modelers, not me.
This is not how good science is done. You may notice an effect and hypothesize a cause. Then you go see if the cause is operating, *and how much*. And if that cause explains *half* of what you see in the data, you do not *assume* it is causing *all* of it because of sympathetic sun-output magic or hypothetical epicycle amplifiers you never dreamt of before the hypothesis. You just say, "my hypothesis can explain this much of the data. If there is additional signal, it must be coming from something else."
And that sort of explanation would give predictions of variations in future mean tempature of 1C or less. And incidentally, it is not in the least clear there *is* any more signal than that to start with. No change beyond that order of magnitude has been seen. If the 2.4 watt estimate of the UN for the past 250 years is correct, and the 492 watt power estimate from your diagram is correct, then you expect 0.35C warming over the past 250 years. Lo, the ocean says less, the surface says more. The data *bracket* the theory. What conceivable reason is there to assume a giant amplifier must be present anyway?
Not sure I understand here. If there's a warming of ~0.5 C in the 0-900m surface ocean and a 0.6-0.8 C surface atmospheric warming, wouldn't you add them up to more than 0.35 C?
Can't you see how silly it is that they are continuing to predict temperature changes on the same order of magnitude as a discredited ice-age hypothesis from 1896 made without any knowledge to speak of, about radiative cooling? That it is silly for them to continue to predict 3-5C changes when their own power budgets say 1C or less? That it is silly for them to have two ice ages on top of each other, if they expect both the accepted orbit/sun theory and their CO2 theory to independently cause ice-age size temperature changes?
As I said, discussions here have caused me to reassess my opinion on climate sensitivity. I think the climate is less sensitive than most models are showing. I can't say how much less with any certainty -- so I'm tending to think that 1-3 C warming is about right for the next century.
I deleted the rest; any interested readers can look above for it.
Are you implying that the impact of CO2 is a major _known_ in all climate models, compared to cloud cover?
The direct radiative forcing due to CO2 is a basic parameter that must be accurate in all climate models. Cloud cover response is much harder to model and is therefore a major uncertainty, a point on which virtually all the modelers agree.
As for the rest of your post, there isn't a lot of belief in a runaway greenhouse. The factor that might have the most powerful effects that is currently under consideration is a marked reduction in deep water formation rates in the North Atlantic, which would have the effect of a strong cooling on the western Northern Hemisphere, particularly Europe. The cooling would be "temporary" geologically-speaking; could last 500 years.
Even Bush realizes that the preponderance of scientific opinion is on the other side.
Some of the best scientific opinion indicates that full implementation of the Kyoto Protocol would do very little about global warming. Unfortunately the Bush Administration has yet to emphasize this point very strongly!