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It's the sun
Climate's changed before
There is no consensus
It's cooling
Models are unreliable
Surface temp is unreliable
Ice age predicted in the 70s
We're heading into an ice age
It hasn't warmed since 1998
Al Gore got it wrong
View All Arguments...


Latest Posts


Models are unreliable

The skeptic argument...

"Models solve the equations of fluid dynamics and do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields, farms and forests. They do not begin to describe the real world that we live in. They are full of fudge factors that are fitted to the existing climate, so the models more or less agree with the observed data. But there is no reason to believe that the same fudge factors would give the right behaviour in a world with different chemistry, for example in a world with increased CO2 in the atmosphere," he states. (Source: Freeman Dyson)

What the science says...

There are two major questions in climate modelling - can they accurately reproduce the past and can they successfully predict the future?

Reproducing the past

A way to test the accuracy of models is through hindcasting - see whether they successfully predict what has been observed over the past century. Here is the IPCC model of surface temperature from the 1800's - both with and without anthropogenic forcings.

The key point is that all the models fail to predict recent warming without taking rising CO2 levels into account. Noone has created a general circulation model that can explain climate's behaviour over the past century without CO2 warming.

Another way to look at it is multiple studies (both using models and independently) calculate a climate sensitivity of around 3°C (Hegerl 2006, Annan 2006, Tung 2007). In other words, global temperatures would warm 3°C if CO2 was doubled. To deny anthopogenic warming, you need to not only explain what's causing global warming but also explain why increasing CO2 isn't causing the expected and observed warming. More on climate sensitivity...

Predicting/projecting the future

A common argument heard is "scientists can't even predict the weather next week, how can they predict the climate years from now". This betrays a misunderstanding of the difference between weather, which is chaotic and unpredictable and climate which is weather averaged out over time. While you can't predict with certainty whether a coin will land heads or tails, you can predict the statistical results of a large number of coin tosses. Or expressing that in weather terms, you can't predict the exact route a storm will take but the average temperature and precipitation will result the same for the region over a period of time.

Climate projection is a difficult and ever refining art. There's the problem that future behaviour of the sun is very difficult to predict. Similarly, short term perturbations like El Nino or volcanic eruptions are difficult to model. Nevertheless, climate scientists have a handle on the major drivers of climate. Way back in 1988, James Hansen projected future temperature trends (Hansen 1988). Those initial projections show remarkable agreement with observation right to present day (Hansen 2006). Hansen even speculated on a volcanic eruption in 1995 but missed the date by a few years (we'll cut him some slack there).

The image “http://www.realclimate.org/images/Hansen06_fig2.jpg” cannot be displayed, because it contains errors.

Hansen's Scenario B (described as the most likely option and in hindsight, the one that most closely matched the level of CO2 emissions) shows close correlation with observed temperatures. In fact, Hansen overestimated future CO2 levels by 5 to 10% so if his model was given the correct forcing levels, the match would be even closer. There are deviations from year to year but this is to be expected. The chaotic nature of weather will add noise to the signal but the overall trend is predictable. More on predicting the future...

Other results successfully predicted and reconstructed by models

  • Cooling of the stratosphere
  • Warming of the lower, mid, and upper troposphere
  • Warming of ocean surface waters (Cane 1997)
  • Trends in ocean heat content (Hansen 2005)
  • An energy imbalance between incoming sunlight and outgoing infrared radiation (Hansen 2005)
  • Amplification of warming trends in the Arctic region (NASA observations)

Uncertainties in future projections

The other misconception is that climate models are biased towards exagerating CO2 effects. Uncertainty could go either way - catastrophic climate surprises are as likely to occur as smaller-than-expected changes. Many current models don't take into account positive feedback systems such as melting permafrost releasing additional greenhouse gases or warming oceans releasing more CO2. For example:

  • IPCC projections fail to take into account non-linear feedback effects like melting ice causing a loss of albedo which further accelerates warming. Analysis of past sea levels shows instances of 'albedo flips' that spark rapid climate change (Hansen 2007)
  • IPCC sea level projections may have "substantially underestimated the contribution of small glaciers and ice caps" to rising sea levels (Meier 2007)
  • Actual CO2 emissions from 2000 to 2004 are higher than any rate used in IPCC emissions scenarios (Global Carbon Project)

Do we know enough to act?

There is a notion that we should wait till models are 100% sure and get it perfectly right before we act on reducing CO2 emissions. If we waited for that, we would never act. Models are in a constant state of improvement as they include more processes, rely on fewer approximations and increase their resolution as computer power develops. The complex and non-linear nature of climate means there will always be refinements and subtleties to be included.

The main point is we know enough to act. Models have evolved to the point where they successfully predict long term trends and are always improving on predicting the more chaotic, short term changes. Multiple lines of evidence tell us global temperatures will change 3°C with a doubling of CO2. The uncertainty is ±1°C degree but this uncertainty is decreasing (and the climate sensitivity of 3°C reaffirmed) as new studies refine our understanding.

Models don't need to be exact in every respect to give us an accurate overall trend and its major effects - and we have that now. If you knew there was a 10% chance you'd be in a car crash, you'd wear a seatbelt. In fact, if there was any possibility, you'd still do it. The IPCC consider it at least 90% sure humans are causing global warming. Considering the negative impacts of global warming, to wait for 100% certainty before acting is recklessly irresponsible.

Further reading

  1. Look at plate 1 in Hansen's 88 paper, the model includes the oceans. Hansen's Scenario C is the one that most closely matches the "Land – Ocean" temperature.

    John Cook wrote:
    "A way to test the accuracy of models is through hindcasting - see whether they successfully predict what has been observed over the past century."

    Not true for any model. All that shows is they can fit the model to the history. That is beside the point as the IPCC does not claim that the models can predict anything.

    John Cook wrote:
    "The key point is that all the models fail to predict recent warming without taking rising CO2 levels into account."

    Given enough "tunable parameters" that should come as no surprise. The modelers also assume that there is some positive feedback, there is no proof that this is the case. Here is one for you straight from the IPCC, Chapter 8, page 596:

    "The number of degrees of freedom in the tuneable parameters is less than the number of degrees of freedom in the observational constraints used in model evaluation."

    IOW, the models are nothing more then sophisticated curve fits.

    Calling the models "predictions" does not instill confidence that you have done your homework.

    Kevin E. Trenberth
    http://blogs.nature.com/climatefeedback/2007/06/predictions_of_climate.html
    "In fact there are no predictions by IPCC at all. And there never have been. The IPCC instead proffers “what if” projections of future climate that correspond to certain emissions scenarios."

    And from the same letter:
    "Even if there were, the projections are based on model results that provide differences of the future climate relative to that today. None of the models used by IPCC are initialized to the observed state and none of the climate states in the models correspond even remotely to the current observed climate. In particular, the state of the oceans, sea ice, and soil moisture has no relationship to the observed state at any recent time in any of the IPCC models."

    John Cook wrote:
    "Satellite measurements show that the troposphere is warming"

    The models predict that the troposphere should warm faster then the surface, it isn't.
    [ Response: Re tropospheric warming, I recommend reading Satellite show little to no warming in the troposphere. The argument over "prediction" vs "projection" is semantics. Kevin Trenberth is merely saying we don't know with certainty what future emissions will be so we make predictions based on various emission scenarios. However, lest it be a stumbling block, I'll update the text. Thanks for the feedback! ]
  2. Models are the biggest gun in the arsenal for AGW. What people like Dyson are telling us is that the models use assumptions that are not validated by observation and that cannot account for many known effects. The models might be right but they haven't got a good track record except in hind sight. (After they've been fudged to fit the past) Someday they will probably be good they are better than 20 years ago.
  3. I recommend this paper and it references for this section as well

    http://members.iinet.net.au/~glrmc/2007%2005-03%20AusIMM%20corrected.pdf
  4. Will Nitschke (www.capitaloffice.com.au) at 21:50 PM on 20 December, 2007
    Leaving aside the silly notion that you can 'prove' a model's accuracy by checking it's fitting to the historical record--I mean honestly, you are aware that these models are tweaked *until* they fit the historical record, aren't you? The past is not the problem.

    The Hansen forecast sounded impressive, so I looked over the paper and did some googling. There is definitely a different spin on the accuracy of the forecast. Discussed here:

    http://www.climateaudit.org/?p=796

    which demonstrates that scenario B is nowhere near the perfect fit implied by your article or Hansen. Hansen could be right, but he doesn't seem to explain where he is getting his data from. I can only find vague references to 'Station Data' and 'Land-Ocean'. What data is it he is using? How has it been adjusted? At least the sceptical article above is up front on where the data is coming from. This doesn't prove that Hansen is wrong. But it doesn't leave one with a high degree of confidence either.
  5. Well, here is NASA telling us there is no meaningful comparison of models to observed global temp change
    "The analysis by Hansen et al. (2005), as well as other
    recent studies (see, e.g., the reviews by Ramaswamy
    et al. 2001; Kopp et al. 2005b; Lean et al. 2005; Loeb
    and Manalo-Smith 2005; Lohmann and Feichter
    2005; Pilewskie et al. 2005; Bates et al. 2006; Penner
    et al. 2006), indicates that the current uncertainties
    in the TSI and aerosol forcings are so large that they
    preclude meaningful climate model evaluation by
    comparison with observed global temperature change.
    These uncertainties must be reduced significantly for
    uncertainty in climate sensitivity to be adequately con-
    strained (Schwartz 2004). Helping to address this chal-
    lenging objective is the main purpose of the National
    Aeronautics and Space Administration (NASA) Glory
    mission, a remote sensing Earth-orbiting observatory"

    http://ams.allenpress.com/archive/1520-0477/88/5/pdf/i1520-0477-88-5-677.pdf
  6. Will Nitschke (www.capitaloffice.com.au) at 12:13 PM on 9 January, 2008
    Here is an interesting quote from IPPC's AR4 found in chapter 1:

    "The strong emphasis placed on the realism of the simulated base state provided a rationale for introducing ‘flux adjustments’ or ‘flux corrections’ (Manabe and Stouffer, 1988; Sausen et al., 1988) in early simulations. These were essentially empirical corrections that could not be justified on physical principles, and that consisted of arbitrary additions of surface fluxes of heat and salinity in order to prevent the drift of the simulated climate away from a realistic state. The National Center for Atmospheric Research model may have been the first to realise non-flux-corrected coupled simulations systematically, and it was able to achieve simulations of climate change into the 21st century, in spite of a persistent drift that still affected many of its early simulations. Both the FAR and the SAR pointed out the apparent need for flux adjustments as a problematic feature of climate modelling (Cubasch et al., 1990; Gates et al., 1996).

    By the time of the TAR, however, the situation had evolved, and about half the coupled GCMs assessed in the TAR did not employ flux adjustments. That report noted that ‘some non-flux adjusted models are now able to maintain stable climatologies of comparable quality to flux-adjusted models’ (McAvaney et al., 2001). Since that time, evolution away from flux correction (or flux adjustment) has continued at some modelling centres, although a number of state-of-the-art models continue to rely on it."

    A 'flux adjustment' is where you discover that the model's predictions start to vary so much from the historical record that you have to go in and change the values inside the software to re-fit the model to what's actually happening. Very confidence inspiring. And what does 'a number of' mean? 50%? 20%? 80%? How many of these models are manually fiddled with to get them to continue to work...?
  7. Will Nitschke (www.capitaloffice.com.au) at 08:32 AM on 18 January, 2008
    Here is another posting assessing Hansen's model work in a not very favourable way:

    Whether these alternate assessments of Hansen's work stand up is a separate issue. I would point out we should not accept them blindly any more than we should blindly accept Hansen's paper on how brilliant Hansen's previous work was, as this naive article does...
  8. "The models might be right but they haven't got a good track record except in hind sight. (After they've been fudged to fit the past)"

    "Leaving aside the silly notion that you can 'prove' a model's accuracy by checking it's fitting to the historical record--I mean honestly, you are aware that these models are tweaked *until* they fit the historical record, aren't you?"

    Nonsense. Are you saying that Hansen, way back in 1988, was able to travel in a time machine to 2006 and back, so that he could make the adjustments to his 1988 models to make them agree all the way to the present?

    The denialists have nothing but nonsense.
  9. Oh, and ClimateAudit is a barrel of laughs:

    http://scienceblogs.com/deltoid/2008/01/climate_audit_comedy_of_errors.php
  10. And besides, if models can be "fudged" to fit anything -- as our `skeptics' claim -- why are the _same_ `skeptics' saying that they can't get Hansen's model to fit the data?

    Can it be because our `skeptics' are simply full of junk?
  11. Wondering Aloud at 10:25 AM on 8 February, 2008
    No, we are saying that Hanson's model from 1988 does not fit the present, even his conservative projections are significantly high of actual observation at this point. (High relative to the ground based measurements and wildly high compared to satellite and balloon measurements to be more specific)

    If a model can't take past conditions and produce results that fit current reality it would be obviously useless.

    However since modelers are not simpletons that isn't the problem that was being discussed! The problem is just because current models have been changed so they can somewhat be used to fit past observations that doesn't mean those changes were the correct changes, therefore it doesn't mean that they are making correct predictions. The models still contain assumptions for various parameters that have not or perhaps can not presently be varified.

    Freeman Dyson is correct here, Models are improving but they have a long way to go before they are better than educated guesses.

    You should read Dyson's entire statement this is a bit out of context.
  12. Wondering Aloud:

    "because current models have been changed"

    You're clearly off spouting rubbish you don't know a thing about.

    Look at the temperature predictions in Hansen et al. (2006) and Hansen et al. (1998). They are _exactly_ _the_ _same_. The 1998 model has _not_ been changed at all, and it still agrees all the way to 2006. All your talk about "fudge factors" can't explain that.
  13. And you say I'm the one who clearly doesn't know what he's talking about!
  14. Models are as reliable as the data put into them.
  15. I thought this comment was interesting and relevant.

    It is taken from the US Senate Committee on the Environment and Public Works - http://epw.senate.gov/public/index.cfm?FuseAction=Minority.SenateReport#report

    Physicist Dr. Freeman Dyson, Professor Emeritus of Physics at the Institute for Advanced Study, in Princeton, is a fellow of the American Physical Society, a member of the US National Academy of Sciences, and a fellow of the Royal Society of London. Dyson called himself a "heretic" on global warming.

    "Concerning the climate models, I know enough of the details to be sure that they are unreliable. They are full of fudge factors that are fitted to the existing climate, so the models more or less agree with the observed data. But there is no reason to believe that the same fudge factors would give the right behavior in a world with different chemistry, for example in a world with increased CO2 in the atmosphere.," Dyson said in an April 10, 2007 interview. Dyson is also a fellow of the American Physical Society, a member of the US National Academy of Sciences, and a fellow of the Royal Society of London.
  16. I'll also raise the question whether anyone really believes this extract (from above) which appears to be a basic premise for the page:

    "This betrays a misunderstanding of the difference between weather, which is chaotic and unpredictable and climate which is weather averaged out over time. While you can't predict with certainty whether a coin will land heads or tails, you can predict the statistical results of a large number of coin tosses. Or expressing that in weather terms, you can't predict the exact route a storm will take but the average temperature and precipitation will result the same for the region over a period of time."

    It's a false analogy. Random *independent" events provide statistical certainty over a period of time. The climate does not fit this description.

    Can anyone provide some evidence -peer reviewed citations - that long range climate forecasting is more accurate than weather forecasting? I know the IPCC claimed it in their report but they didn't backup the claim.
    [ Response: That's the problem with using analogies - the comparison always breaks down at some point when you compare it directly. The main point is the contrast between short term, random unpredictability and long term, statistical summations. While weather is chaotic and non-linear, long term climate trends are discernable and predictable. As is seen in these peer reviewed studies analysing the success of climate forecasts. ]
  17. A common comment regarding GCMs is that they do not account for clouds very well. This is a substantial weakness. There have been assertions that warming increases atmospheric water vapor which, through a feedback mechanism, increases warming. Certainly increased atmospheric water vapor would produce more, lower-level clouds. How do the GCMs account for this? A simple cloudy-planet point model where standard atmosphere tables are used to get average cloud temperature vs altitude shows that a change of average cloud altitude of 305 meters would result in an eventual average earth temperature change of 0.75C. Many other factors known to influence cloud formation are not accounted for in the GCMs.
  18. Frankbi said:
    "And besides, if models can be "fudged" to fit anything -- as our `skeptics' claim -- why are the _same_ `skeptics' saying that they can't get Hansen's model to fit the data?

    Can it be because our `skeptics' are simply full of junk?"

    I am surprised that John did not reply to this, but I assume he does not have the time to respond to every nonsensical claim that appears on his board.

    Frank, if you do not know that GCMs (and many other models) are "tweaked" to fit past data, then you have no place attacking others. It is common practice, and there is little that is nefarious about it, though it may appear as such. You probably know that there are many uncertainties and complexities in the climate system, and in attempting to model such a system, you must used what has already been observed to better your understanding and accuracy. If models were based purely upon theory for such a complex system, they would appear wildly inaccurate and worthy of no utilization.

    -Robert
  19. I'm repeating here what I've said in another place on your blog:

    The IPCC summary of computer simulations you link above only go back to 1850 and blurs out problems with individual models by replacing the spaghetti curve with a grayed out region. (Errors in the simulations are highly correlated from year to year, the figure makes it seem they are not, which is false and misleading.)

    Also did you notice the huge 0.3°C anomaly around 1940-1950 that the models, even with the fuzzing provided by IPCC, are unable to explain?

    Where did that warming come from? I would conclude from that, that we aren't at the place yet, even for a 150-year period with a lot of fudge factors thrown in, where we can accurately describe past climate, let alone accurately predict future climate.

    Secondly did you notice that there was very little anthropogenic forcing before 1970, according to the models? Have you ever considered how disingenuous it is, given this fact, to compare glaciers from e.g. 100 years ago to current, when the models say that almost all warming prior to 1970 was natural?
  20. Robert S:

    Yes, I do know that model parameters are usually adjusted according to some past data, _and_ the resulting model has to be validated with data that are _not_ used to configure the models in the first place. If I didn't make this clear enough, my apologies.

    From my understanding, this approach of tweaking and holdout validation is what climate scientists have been doing. And it's perfectly good science, of course.
  21. FACT: Only Computer Illiterates believe in "Man-Made" Global Warming.

    What people do not understand is that there is no proof of "Man-Made" Global Warming without using irrelevant computer models. Yes computer models have a place in engineering but are utterly useless at fortune telling, I mean "climate prediction". With engineering you can build and test in the real world to confirm the computer model's accuracy. You can do not such thing with the planet Earth and it's climate. You cannot build a planet and it's atmosphere to "test" your computer climate model.

    I am a computer analyst and can make a computer model do whatever I want by "tuning it" (adjusting variables by guessing until I get the answer I want or think is right). If you program a computer model so that X amount of CO2 increase "forces" X amount of temperature increase then it will happen, this does not make this true in the real world.

    GIGO: Garbage in = Garbage out

    Computers need exact information and the exact procedures to process that information to get accurate answers, without that you get useless results, period. There is no way around this. Computers cannot fill in the blanks for you like nature does when you do an experiment in the real world. With computers everything must be programmed into them from the begining and everything that is programmed into them must be 100% understood and 100% accurate. Even the most advanced and expensive computer climate models include various "aproximations", unproven theories, biased methods and data.

    Computing incomplete, biased or flat out wrong data (guesses and assumptions) based on poorly understood climate physics in a "model" will give you useless output. But since these models have been "tuned" (guesstimated or deliberately altered to get the results they want) they get results that "seem" likely or even convincing to the average computer illiterate, yet they are absolutely meaningless for prediction.

    Alarmist scientists presenting their predictions as fancy graphs or nicely colored renderings does nothing for the accuracy of the prediction. They like to color small variances in temperatures using yellow, orange and red to exaggerate them. This is to have an obvious emotional effect for a relatively meaningless change.

    Nothing is emotional about computers they are pure logical machines, 1 + 1 must = 2. Imagine trying to use random numbers to get a right answer on a calculator but you do not know if you are to add or multiply those numbers and you have no way to confirm that "right answer" except to wait 50-100 years. Sound crazy? Welcome to Global Climate Modeling.

    What the modelers do is they keep playing with the numbers until they think they guess right, a useless exercise. Technically they are mathematically adjusting various climate related equations based on theoretical assumptions. These same climate model computers are used to predict your weather and you know how accurate they are. But damn! Al Gore and Gavin Schmidt can certainly tell your what the climate will be 50-100 years from now! Give me a break. Don't be fooled that modeling climate is different than the weather or one is more accurate than the other long term. The difference is simply a matter of resolution and scale.

    Testing a model against past climate is an advanced exercise in curve fitting, nothing more and proves absolutely nothing. What this means is you are attempting to have your model's output match the existing historical output that has been recorded. For example matching the global mean temperature curve over 100 years. Even if you match this temperature curve with your model it is meaningless. Your model could be using some irrelevant calculation that simply matches the curve but does not relate to the real world. With a computer model there are an infinite number of ways to match the temperature curve but only one way that represents the real world. It is impossible for computer models to prove which combination of climate physics correctly matches the real world. Do not be fooled this logic is irrefutable by anyone who understands computer science and computer modeling.

    Question: Why is 100% of the computer code for every computer climate model not made publicly available?

    To make matters worse it is not computer scientists creating these models but natural scientists coding them using Fortran. These natural scientists do not even begin to have the basic understanding of computer science or proper coding practices. Their code is not 100% available publicly and you do not have independent auditing or code validation. Sloppy and buggy code is very likely littered inside these climate model programs yet there is next to no accountability for any of this. How do you separate a programming error from a temperature anomaly? How can you replace observational data with a complex mathematical equation? You can't.

    FØRTRAN: "Write all your code in FORTRAN. If your boss ask why, you can reply that there are lots of very useful libraries that you can use thus saving time. However the chances of writing maintainable code in FORTRAN are zero, and therefore following the unmaintainable coding guidelines is a lot easier."

    "If your boss thinks that his or her 20 year old FORTRAN experience is an excellent guide to contemporary programming, rigidly follow all his or her recommendations. As a result, the boss will trust you. That may help you in your career. You will learn many new methods to obfuscate program code."

    How many of the models used by the IPCC have had ANY bug fixes or code changes since the most recent IPCC report? If they have had ANY - all previous model run results become null and void based on simple logic thus easily invalidating the ridiculous conclusions of the IPCC report.

    All the computer illiterates are convinced that because something is done on a "super computer" that costs "millions of dollars" it is infallible. The more complex the model, the more "mysterious" it seems to the average person. The public gives computer climate models this mystical aura because they are largely computer illiterate about how they actually work and when they hear the term "computer" they do not want to sound or feel stupid, so they nod their heads and go along with it.

    Why are we not turning to models to predict the future for everything? Because they can't, not even remotely. Some of them work "sort of" for the weather in very, very short term results (1-3 days) until all the data they are processing that is wrong combined with all the data they are missing and the millions of variables they are not accounting for start to kick in and grow exponentially the farther out the model runs and wham - the model is wrong. No kidding, there are simply way too many variables that they cannot account for and the computer power necessary to even start to take these variables into account does not exist.

    You are expected to believe that they can "model" the climate 50-100 years in the future when they cannot even give you accurate weather 3 days out? Don't be fools, I do this for a living, Computer Models cannot predict the future with anything as complex as the Earth's climate.
  22. Poptech
    When I was in college we were taguht Fortan IV, even though it had already been supplanted by Fortan 77. I did not realize that anyone was still using it. My own last experience was in SAS and that was in the 90s. Are you saying that these climate models are being coded in Fortran?
  23. Wow Poptech, what a rousing, impassioned, statesman-like speech.

    Unfortunately, it contains no verifiable concrete facts.
  24. Poptech, nice job of trying to help people understand what computer modeling is and what it can do.

    Folks, if a climate model doesn't predict past data 100% perfectly then it's useless. You can create an infinite number of different mathematical models that will predict any data series 100% perfectly. To deserve any respect these climate models must predict the previous data perfectly as a start, none should even be thought about unless it does that, and then it has to predict the future better than a simple polynomial fit that also perfectly predicts past data.

    Frankbi, all the facts in Poptech's post are verifiable. I learned them in school. His analysis is spot on.
  25. "all the facts in Poptech's post are verifiable. I learned them in school."

    I don't think that's what "verifiable" means.

    As always, the "criticisms" of climate models are devoid of any concrete, testable facts.

    -- bi, International Journal of Inactivism, http://frankbi.wordpress.com/
  26. Will Nitschke (www.capitaloffice.com.au) at 19:23 PM on 15 May, 2008
    Here is a new study that evaluates the accuracy of climate models:

    D.Kutsoyiannis,N.Mamassis,A.Christofides,A.Efstratiadis,􀈱S.M.􀈱Papalexiou
    Department of Water Resources and Environmental Engineering National Technical University of Athens
    (www.itia.ntua.gr)

    http://www.itia.ntua.gr/getfile/850/3/documents/2008EGU_ClimatePredictionPrSm.pdf

    Or to sum up the study:

    "Climatic models generally fail to reproduce the long term changes on temperature and precipitation."
  27. http://www.realclimate.org/index.php/archives/2008/05/what-the-ipcc-models-really-say/#comment-87205
    on the Skeptic article, by the other author on the same issue.

    Koutsoyiannis mentioned here:

    "Cohn and Koutsoyiannis, one of them the author of the very paper that I had criticized, sat down next to me. We nevertheless had a very civilized and friendly chat, deciding to disagree on the matter of natural trends.

    But Dr. Koutsoyiannis commended us for being respectful in our reply to his comments. I think this is a very important issue – we have to be respectful, sincere, and show courtesy in our criticism, even when we argue why we think that a paper has flaws. ..."
    http://www.realclimate.org/index.php/archives/2008/04/egu-2008/

    Use the Search box at the top of the RC page, paste in:
    Koutsoyiannis
    Dr. Koutsoyiannis posts there in two of the discussions.
  28. "on the Skeptic article, by the other author on the same issue."

    I didn't think Koutsoyiannis was writing up a "skeptic article", but rather an assessment of climate models.

    "'Cohn and Koutsoyiannis, one of them the author of the very paper that I had criticized, sat down next to me. We nevertheless had a very civilized and friendly chat, deciding to disagree on the matter of natural trends.

    But Dr. Koutsoyiannis commended us for being respectful in our reply to his comments. I think this is a very important issue – we have to be respectful, sincere, and show courtesy in our criticism, even when we argue why we think that a paper has flaws. ...'"

    I don't see how this is relevant-- the paper that Rasmus criticized was a paper titled "Nature's style: Naturally trendy" by Timothy Cohn and
    Harry Lins. The "But Dr. Koutsoyiannis commended us for being respectful in our reply to his comments" part of it involved comments made by Koutsoyiannis on a 2006 realclimate thread.

    So hank, I am not exactly sure where you are getting at with your comment here. Just a little background information on Koutsoyiannis?
  29. Fundamental Computer Science, if a Computer Model includes merely one approximation for what latter dependant calculations or data are derived from then the output of the model is useless. This is Computer Science 101.

    Hansen's 1988 "Predictions" have been proven wrong thus further evidence that the models cannot predict the future:

    Evaluating Jim Hansen’s 1988 Climate Forecast
    http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000836evaluating_jim_hanse.html

    "...all of our models have errors which mean that they will inevitably fail to track reality within a few days irrespective of how well they are initialised." - James Annan, William Connolley, RealClimate.org

    "These codes are what they are - the result of 30 years and more effort by dozens of different scientists (note, not professional software engineers), around a dozen different software platforms and a transition from punch-cards of Fortran 66, to fortran 95 on massively parallel systems. [...] No complex code can ever be proven 'true' (let alone demonstrated to be bug free). Thus publications reporting GCM results can only be suggestive." - Gavin Schmidt, RealClimate.org

    This site is a cruel joke for Computer Illiterates. Yes the models have to be exact to give any sort of relevant results. That is like saying a calculator does not have to be based on accurate Arithmetic to be a useful tool in mathematics. Utter Propaganda.
  30. Just saw this article referenced on another climate blog:

    http://www.atypon-link.com/IAHS/doi/abs/10.1623/hysj.53.4.671

    It studies the accuracy of climate models. Basically compares the model's predictions vs what happened. The conclusion was that climate models don't predict forward very well. I don't have the background to judge whether this article is credible but it did go through a peer reveiw process.
  31. Oh - and in my research on this subject I found the chart you had above 'Average Mean Global Temperature Change' had been updated over on ClimateAudit:

    http://www.climateaudit.org/?p=3354#more-3354

    Can I trust the updated charts posted there? They seem to show actual temperature date significantly diverging from Hansen C (ie: lower). Again - I'm not the expert so I'm here asking questions of those who are :-). Thanks.
  32. To put the Global Warming issue in context, consider:
    1. That average global temperature has decreased since 1998. The anomalies from NOAA data are:
    1998 0.5763
    1999 0.3947
    2000 0.3629
    2001 0.4934
    2002 0.5573
    2003 0.5565
    2004 0.5336
    2005 0.6044
    2006 0.5428
    2007 0.5458
    Jan to June 2008 average 0.44
    2. That GCMs (Global Climate Models) do not yet adequately account for the absorbed infrared radiation energy that is transported up by atmospheric convection currents.
    3. That GCMs are not yet capable of dealing objectively with clouds so they are accounted for with subjective parameterization.
    4. That currently used GCMs invoke water vapor positive feedback that climate history shows to be not valid.
    5. That the GCM users/creators won’t divulge to competent evaluators some of the details of their computer programs.
    6. That the only indicators that human activity causes global warming are these GCMs.
    7. That the multi-billion dollar government grants for ‘climate research’ depend on ominous prediction of looming catastrophe.
    8. That over 30,000 qualified scientists and engineers have signed a document stating that human activity has had no significant influence on climate.
  33. 1. probability and possibility are two different things.
    You may show statistically that something is probable and therefore, sooner or later will happen. This is only true mathematically and not necessarily works in the real world. Any computer model that includes assumptions, 'tweaked' data, or excludes any factors relevent to the model will give a rubbish result.

    2. Remember the Chaos Effect. Small things through iterative action can have BIG consequencies, so the apparently small and irrelevent must be accounted for.
    Worse yet, we don't even know if we know ALL the factors influencing the climate....so any model will be suspect.
  34. Poptech
    Re: comment 29
    Please correct me if I am wrong but was not Fortran 66 (1966) not machine dependent as well as structure dependent? I am not familiar with Fortran 95 as I stopped using Fortran 77 around 1983 and switched to Pascal so my code would be transportable.
  35. Just read an interesting abstract on the effect of the moon on the monthly GMT.
    "Over the past fifty years, the Diurnal Temp Range has decreased by about half a degree.Conventional wisdom blames this on the greenhouse effect. But this decrease is just a trend observed in data that vary over shorter
    timescales. Cerveny and Balling show that for the period between 1950 and 1995, the DTR fluctuates with the phases of the Moon. It tends to increase towards Full Moon, and tends to be lowest at New Moon. Simple
    monthly differences in DTR between New Moon and Full Moon may be as much as 0.309 ºC -- in other words, 60% of the entire 50-year decrease. The message should be clear: all possible sources of variation should be
    investigated before blaming human activity alone for observed changes in climatic parameters."

    There is a correlation between full moon and monthly DTR variations most of which is ascribed to the changing earth/moon barycentre. This has prompted a look at the effects of a shifting sun/earth/moon barycentre on earth climate.
    Another piece in the puzzle?
  36. Mizimi

    I would imagine that the difference between full and new is reflected sunlight and whatever radiation it may contain. This would have an effect on GHGs (I am thinking water vapor and methane which a recent article at LiveScience talks about.

    Re: "This has prompted a look at the effects of a shifting sun/earth/moon barycentre on earth climate."

    Have you ever read The Solar Jerk by Dr. Rhodes Fairbridge?
  37. QM: Yes, just recently, which prompted me to look for further info on how a shifting barycentre could affect climate.
    One thought which I am currently pursuing is adiabatic cooling of the upper atmoshere caused by the tidal effect of sun/moon. As the barycentre moves it causes the shape of the atmospheric envelope to alter, effectively expanding the volume, which should cause a cooling effect.
  38. The models did a pretty good job stating where hurricane Gustav would end up. Should the people of New Orleans have ignored them as well - because they couldn't be 100% certain of their accuracy?
  39. Sandy Winder:
    Gustav was weather, not climate. Gustav was the end product of the climate process.
    Weather can be predicted over VERY short periods with a reasonable level of accuracy; at present, climate cannot. This is a good chunk of what the argument is all about. The uncertainty with Gustav was not that it would hit, but exactly where and at what level ( eventually I think downgraded to Cat2) so it would have been foolish to ignore it.
    A side benefit of the dispute is that we are learning a lot more about climate,history,the biosphere etc.
  40. QM:
    The earth-moon barycentre is around 1700km BENEATH our crust..so the tidal effect of the moon/sun would 'stir up' the lower mantle...presumably a very low frequency effect....and increase surface volcanic activity??
  41. Apparently climatologists do not have much grounding in how feedback works. Unaware of their ignorance, they invoke net positive feedback in their GCMs. This mistake causes the GCMs to predict significant ‘enhanced global warming’. Anyone who has the ability and interest to look at the NOAA data from Vostok Ice Cores for the last glaciation (and prior glaciations) will discover that, repeatedly, a temperature increasing trend changed to a decreasing trend with the carbon dioxide level higher than it had been when the temperature was increasing. Graphs of NOAA and other credible data, all fully sourced so they can be verified, can be seen at http://www.middlebury.net/op-ed/pangburn.html. (The web site is controlled by Middlebury, not me.) Those who understand how feedback works will know that this temperature trend reversal is not possible with significant net positive feedback. Thus, as far as global climate is concerned and contrary to the assumption in the GCMs, significant net positive feedback does not exist. Other assessments from entirely different perspectives also determine that there is no significant net positive feedback. They can be seen at http://www.climate-skeptic.com/2008/01/index.html and http://www.weatherquestions.com/Roy-Spencer-on-global-warming.htm
  42. "In addition phytoplankton emit Dimethyl Sulphide (DMS), which reacts with oxygen in the atmosphere to produce sulphur dioxide. This acidic gas forms tiny droplets which help to seed clouds over the ocean, and these reflect sunlight thus cooling the planet. Measurements of methane sulphonic acid (MSA, which is derived from DMS) in ice core bubbles indicate that there were more phytoplankton in the polar oceans during the ice ages, as expected from the theory above. Therefore as the climate gets warmer there will be less seeding of clouds over the ocean - clearly a positive feedback."

    http://www.chooseclimate.org/climatetrain/scipolcc.html
  43. Atmospheric water vapor is also clearly a positive feedback. There are also negative feedbacks. Dr. Richard Lindzen has identified one, his iris effect. Response of the climate system depends on the combined effect of all feedbacks, known or not. When all are combined, the NET feedback can not be significantly positive. This is mandated by the temperature trend reversals of the last and previous glaciations.
  44. Dan:
    Depends what you take as significant. The time span is important,as well as the net feedback quantity.
    A very small change over a very long period ( like glacial periods) can eventually have a profound effect, This is the basis of Chaos Theory.
    One of our major problems is that we do not have enough hard data to quantify these matters to sufficient degree to allow a reasonable model to be constructed.
    We have a lot of information, knowledge and some data, but mostly we have guesstimates derived by various means ( some quite dubious), and that isn't good enough for a system of this complexity.
  45. There is only one complete and exact computer of global climate and that is the planet itself. By definition it complies with all laws of nature including physics and quantum mechanics. Einstein said “no number of tests can prove I’m right but only one is needed to prove I’m wrong”. That one test that proves to be wrong the theory that added atmospheric carbon dioxide causes global warming was run on the planet computer and the results are archived in the Vostok ice cores. They show that, repeatedly, a temperature increasing trend changed to a decreasing trend with the carbon dioxide level higher than it had been when the temperature was increasing. Those who understand how feedback works will know that this temperature trend reversal is not possible with significant net positive feedback. Thus, as far as global climate is concerned and contrary to the assumption in the GCMs, significant net positive feedback does not exist.
  46. Re #41 & etc. Dan Pangburn

    Dan, you certainly do talk a lot of nonsense, and you seem to have gone to extraordinary lengths on your webpage to put together a deliciously incorrect view of the science!

    Let's look at just a couple of things:

    (1) ["The planet plunged in to the Andean-Saharan ice age 440 million years ago10 when the carbon dioxide level was over ten times higher than now."]

    No.....there certainly does seem to have been significant glaciation dated to around 445.6 mya - 443.7 mya, but the atmospheric CO2 levels for this period are simply not known. You seem to have fallen for the trick of some dubious character who has drawn straight lines across vast ranges (10’s to 100's of millions of years) of geological time based on some unspecified temperature estimates (your posts on this thread are displaying that odd habit of denigrating pukka science by misrepresentation while at the same time embracing stuff that is very obviously ludicrous rubbish!).

    I would expect everyone can understand the problem that if there are one or two paleo proxies (temp or CO2, for example) known for some periods in the past, that one can only say that that's what the temperatures/CO2 levels were AT THOSE PARTICULAR TIMES. One can't draw a line between the points and consider that the temperature/CO2 levels over vast intervening periods is thus established. Imagine an equally dumb geologist from the far future dating atmospheric CO2 level estimates from 430,000 years ago and 1000 years ago. "Goodness", he might say, extrapolating massively between limited data points in gay Scotese style, "highish CO2 levels right through this period. And yet there is evidence for multiple ice cap incursions right down to the South of England and deep into North America. Clearly there can't be any relationship between atmospheric CO2 and temperature"

    Doh!

    You need to go back and look at the relevant science, rather than trawling for dodgy “information” on websites[***]! The science has been compiled, for example, in a recent review by Royer:

    D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675.

    Or see:

    R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202

    Or:

    W. M. Kurschner et al (2008) “The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of the terrestrial ecosystem” Proc. Natl. Acad. Sci. USA 105, 499-453.

    And so on….

    Sadly there isn't a proxy CO2 measure for the late Ordovician glacial period. So we don't know if there is a mismatch between atmospheric CO2 levels and evidence for a cold spell then. It's rather clear (see Royer review, for example, and the masses of cited data therein, or the other articles cited just above) that where paleoproxies for atmospheric greenhouse gas levels and cold/warm spells are dated contemporaneously, that there is a rather good match (high CO2 associated with warm periods/low atmospheric CO2 with cold periods).

    (ii) Surely by now everyone can understand the rather simple contributions to ice age cycles and the fundamental differences between solar driven effects (with CO2/water vapour/albedo feedbacks) and greenhouse gas driven effects of the sort that we are now seeing. I find it hard to believe that you consider that you’ve found something worth making such a fuss over, as if there’s something about the lag between temperature and CO2 levels in the Vostock core that is not obvious, rather well-understood and pretty consistent with what we know about greenhouse gases and their effects.

    Let’s look at what happens during the ice age cycles driven by the small, painfully slow variations in the Earth’s orbital properties (Milankovitch cycles). As the pattern of insolation changes through these cycles the Earth warms (in a glacial to interglacial transition), ice sheets recede, albedo effects amplify the warming, the warming oceans release CO2 into the atmosphere resulting in further warming, atmospheric water vapour levels rise, and so on. Obviously, since the primary inducer of the warming is increased solar radiation, and the atmospheric CO2 rise is a result largely of the release of CO2 from the oceans, the temperature rises in advance of the atmospheric CO2 levels. That’s pretty obvious and uncontroversial (part of the lag is apparently also due to interhemispherical effects).

    Going the other way (your example of events 112,000 years ago), it’s not surprising that decreased polar insolation resulted in cooling in advance of the lowering of atmospheric CO2 levels. It takes rather a long time for atmospheric CO2 to be absorbed from the atmosphere, and there’s nothing surprising about the fact that as one “lowers the heater” that the Earth cools while CO2 levels remain relatively high, as CO2 is very slowly reabsorbed by the oceans and terrestrial environment..

    And of course the CO2 level changes are small and the rates of change are tiny compared to present day, where the warming we are seeing is the result of enhanced greenhouse effects with a relatively constant solar insolation. So whereas during the last glacial to interglacial period, for example, atmospheric CO2 rose by around 80 ppm over 5000 years (1.6 ppm per 100 years averaged over the transition), now atmospheric CO2 levels are rising at well over 100 times faster (2-2.5 ppm per year).

    Everyone that takes the smallest effort to inform themselves is aware of the essential differences between ice age transitions (Milankovitch cycles drive extremely slow variations in atmospheric CO2 with very slow feedbacks) and present day warming (extremely rapid increases in atmospheric greenhouse gas concentrations resulting in rapid temperature increases). During ice age transitions the processes were sufficiently slow that the Earth’s temperature likely was near-equilibrium with the forcings (varying insolation, greenhouse gas levels and associated feedbacks). Now atmospheric greenhouse gas levels are rising far more quickly than the Earth’s temperature is able to keep pace with (the inertia from the massive ocean) and so we still have rather a lot of warming “in the pipeline” from current levels of atmospheric CO2, not to mention the amount of warming yet to be unmasked, as a result of man-made aerosolic countering of enhanced greenhouse-induced warming:

    e.g. V. Ramanathan and Y. Feng (2008) “On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead.” Proc. Natl. Acad. Sci. USA in press.

    http://www.pnas.org/content/early/2008/09/16/0803838105.abstract

    (iii) Your data on temperature/CO2 relationships are laughable. Just to choose one jaw-dropping example, there is one single data point in the Vostock core (1999 data set) that shows an anomalous temperature, and from this you conclude that “the average global temperature 400 years ago was significantly higher than now”! One data point from one location does not an “average global temperature” give. The pukka science carefully collects a range of proxy data from multiple sources using many different methodologies, taken from as many places on Earth as possible to assess careful paleoproxy temperature data that is truly globally (or at least hemispherically) averaged. You (having other fish to fry one suspects than assessing the best possible understanding from the available data) base your entire analysis on one data point, from one data set from one location on Earth. Oh dear!

    And so on. Happily the individuals and organizations that address these issues maturely and seriously don't fall for that sort of nonsense....


    [***] In fairness to Christopher Scotese, his site is quite good. He does need to update his paleotemperature graph though!
  47. Chris:
    Your assertion “…talk a lot of nonsense…” may reveal that you simply do not understand how feedback works. The graphs in the Middlebury link are plots of data from NOAA and other credible sources. They speak for themselves and are as correct as the data sources.

    Apparently you accept Scotese’s temperatures. The carbon dioxide level at that time is from GEOCARB III as published in the American Journal of Science. The graph at http://www.globalwarmingart.com/wiki/Image:Phanerozoic_Carbon_Dioxide_png shows a lot of illogical scatter in Royer’s compilation but fair agreement between 30Myr filtered Royer, Copse and GEOCARB III. I have found no rational argument as to why the atmospheric carbon dioxide level should dramatically change prior to the temperature dropping into that ice age. The assertion remains that the temperature dropped while the carbon dioxide level was several times higher than now.

    The graph of CO2 and average global temperature during the Phanerozoic (all of the time that there have been complex life forms, the last 550 million or so years) at http://mysite.verizon.net/mhieb/WVFossils/Carboniferous_climate.html is as good as any. A lot of imagination is needed to see any correlation there between atmospheric carbon dioxide and average global temperature.

    You say “the warming oceans release CO2 into the atmosphere resulting in further warming”. That would be a ramp up in temperature. But then the ramp up changed direction and became a ramp down. And this direction change in temperature trend happened repeatedly during the last and previous glaciations. That could not happen if there was significant net positive feedback.

    For those who understand how feedback works, this temperature trend direction change proves that there is no significant net positive feedback. All that is needed to determine if there is net positive feedback is a temperature trace for a long enough time to average out cyclic variation from random noise and other factors. The temperature trace does not even need to be correct in absolute terms just reasonably accurate in relative terms time-wise. Without significant net positive feedback added atmospheric carbon dioxide does not produce significant increase in average global temperature. Even the flawed GCMs give that result. Those who think they “…know about greenhouse gases and their effects…” apparently do not recognize the significance of this observation.

    While determination of the magnitude and even the sign of net feedback in climate may be difficult using climatology (Spencer at a link in 41 above and also Monckton at http://www.aps.org/units/fps/newsletters/200807/monckton.cfm have done it), it is trivial, as described above, for someone who understands feedback, to deduce from the temperature record that net positive feedback does not exist. Many climatologists apparently don't know how feedback works so they don't realize this. Unaware of their ignorance, they impose significant net positive feedback in their GCMs which causes them to predict substantial warming from carbon dioxide increase. Without significant net positive feedback, the GCMs do not predict significant Global Warming. From Monckton’s paper “The IPCC overstates temperature feedbacks to such an extent that the sum of the high-end values that it has now, for the first time, quantified would cross the instability threshold in the Bode feedback equation and induce a runaway greenhouse effect that has not occurred even in geological times despite CO2 concentrations almost 20 times today’s, and temperatures up to 7 ºC higher than today’s.”
    Do you realize how many times you said in 46 that the sun started it? These were extracted from your text: “…insolation changes…”, “…primary inducer of the warming is increased solar radiation…”, “…decreased [s]olar insolation resulted in cooling…”, “…one “lowers the heater” that the Earth cools…” Solar variation is certainly a major part of it. Of the list of other possible contributors to climate change, some ignored, some subjectively parameterized; solar wind, clouds, vertical convection, cosmic rays, Milankovitch cycles, etc. and factors not yet discovered, only significant net positive feedback is readily ruled out. Influencing any of the others doesn’t look promising. Humanity needs to adapt to climate change. Warming is not a problem. If it gets too hot or wet or dry where you are at, move. There are currently places that lack permanent occupancy because they are too hot, too cold, too wet or too dry. Half of humanity may starve in the coming glaciation, however, because rice does not grow on ice.

    The high rate of change of the level of atmospheric carbon dioxide today is not relevant to climate change since the level of atmospheric carbon dioxide has no significant influence on climate. Eventually, excess atmospheric carbon dioxide will dissolve in the ocean which already holds over 50 times as much as the atmosphere. Interestingly, I have read that the rate of increase of carbon dioxide in the atmosphere is about half of what is calculated based on the amount added by humanity.

    In your lawyer-like advocacy and nitpicking of the scarcity of paleo data you appear to have completely missed the point of temperature trend reversals ruling out net positive feedback. I suggest that you break out of the box that you are in, adopt engineer/scientist-like objectivity and learn about feedback.

    There are legitimate reasons to constrain the use of fossil fuels. As the level of atmospheric carbon dioxide continues to increase, and it will, humans may find enclosed places becoming ‘stuffy’ sooner than previously. The consumer price rise of liquid fuels as a result of ‘peak oil’ will curtail their use and stimulate alternate fuels such as algae produced biodiesel. I have been antagonistic to coal for decades and am suspicious of claims that mercury, soot and acid can be effectively removed from the exhaust. When humanity gets past their unjustified paranoia regarding nuclear power and start building breeder reactors they will have all of the energy needed for millions of years. Enough to recharge their hybrids and even synthesize liquid fuel to go beyond battery range.
  48. Re #47

    No Scotese's temperatures are horribly incorrect (that's obvious surely). It's not clear where they came from (can you enlighten us?), and they clearly bear little relation to reality or to the paleotemperature data that is compiled extensively in the recent scientific literature (see citations at bottom of post for example).

    Try using Google Scholar or visit .edu sites (or your local University library - there are a number of relevant papers at the bottom of this post). In addressing scientific issues, one should address the science.


    ["The graph of CO2 and average global temperature during the Phanerozoic (all of the time that there have been complex life forms, the last 550 million or so years) at http://mysite.verizon.net/mhieb/WVFossils/Carboniferous_climate.html is as good as any."]

    No it isn't. Sadly it's a laughable parody of the data that has been complied in a large number of studies, and it's surprising that someone with an apparent interest in this subject would consider it to be so in the light of the abundant scientific data on this subject (see citations at bottom of this post). Obviously if one puts together a completely false representation of the scientific data on paleoCO2 and paleotemperature one shouldn't be surprised if one is led to fallacious interpretations.

    And suggesting that pointing out gross misrepresentation of the science based on ludicrously inadequate graphs using unspecified data on dubious websites with contrived misinterpretation, is "Lawyerlike advocacy and nit-picking", is a delightful lu-lu!

    As for feedbacks, I suspect you've managed to be misinformed through poor analysis or the perusal of dodgy sources (Christopher Monckton? isn't this supposed to be about science?). There's no question that raising atmospheric CO2 levels results in a re-equilbration of the Earth's temperature such that internal variations fluctuate around a higher equilibrium temperature (assuming volcanic/solar contributions are flattish), and that this involves feedbacks (e.g. a warmer atmosphere caused by enhanced atmospheric CO2 results in a higher concentration of water vapour.....enhanced warming results in enhanced ice melt and reduced albedo and so on)... The science indicates that the Earth responds to raised CO2 with a raised equilibrium surface temperature near 3 oC (+/- a bit).

    I'm not sure why you have a problem with this and feedbacks in general. Clearly during ice age cycles the dominant driver is cyclic variations in insolation due to slow variations in the Earth's orbital properties. It only requires that the insolation cycles dominate over the effects of CO2 (feedbacks included) to observe the relationships between temperature and CO2 levels in the Vostock core that you are so exercised over. If CO2 levels rise from 180-280 ppm over thousands of years(due to very slow solar induced warming) resulting in enhanced direct CO2 (greenhouse) warming with fast positive water vapour feedbacks and slower albedo feedbacks, and then the solar contribution diminishes, much of the atmospheric CO2 will still be there (for hundreds of years) as the temperature cools in the early stages of the next Milankovitch cooling cycle. And as the temperature cools due to decreased insolation, so the water vapour levels drop, even as CO2 levels remain high. That's not difficult to understand at all..

    You make some other very odd comments. Yes, high levels of atmospheric CO2 will eventually be drawn out of the atmosphere. This is a very slow process (your own Vostock data show this). And of course "the rate of increase of carbon dioxide in the atmosphere is about half of what is calculated based on the amount added by humanity." Half of the CO2 we've released into the atmosphere has been absorbed by the oceans with a very measurable drop in pH (increased acidity).....already the absorption of our emissions by the oceans is decreasing due to the saturation of the upper oceanic waters. Each of these is problematic.

    All in all, you've chosen to use ludicrous data from some website to pursue the unsupported notion that there isn't a relationship between atmospheric CO2 lelvels and the earth's global temperature. And yet the science clearly shows otherwise (e.g. papers cited below). No one disputes the fact that CO2 is a greenhouse gas, and greenhouse gases cause the Earth to warm above its black body temperature (by around 30 oC worth of warming on Earth). Or do you consider that CO2 stops being a greenhouse gas above some concentration or other?

    Anyway, here's some of the science that one would hope you might access in place of dodgy websites:



    D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675.
    (this is a review compiles much of the published data)

    Even more recent studies supplement the information in Royers compilation and cover additional periods with new data sets right through the past several hundreds of millions of years:

    R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202

    W. M. Kurschner et al (2008) “The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of the terrestrial ecosystem” Proc. Natl. Acad. Sci. USA 105, 499-453.

    D. L. Royer (2008) “Linkages between CO2, climate, and evolution in deep time” Proc. Natl Acad. Sci. USA 105, 407-408

    Zachos JC (2008) “An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics” Nature 451, 279-283.

    Doney SC et al (2007) “Carbon and climate system coupling on timescales from the Precambrian to the Anthropocene” Ann. Rev. Environ. Resources 32, 31-66.

    Horton DE et al (2007) “Orbital and CO2 forcing of late Paleozoic continental ice sheets” Geophys. Res. Lett. L19708 (Oct. 11 2007).

    B. J. Fletcher et al. (2008) “Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change” Nature Geoscience 1, 43-48.
  49. The Andean-Saharan issue is simple. The ice age happened and the carbon dioxide level was much higher than now when it started. The chart uses data compiled by Christopher R. Scotese, Ph.D., University of Chicago, 1985, currently an Associate Professor geologist at the University of Texas at Arlington. Research interests include plate tectonics, paleogeography, and paleoclimatology and R. A. Berner, Department of Geology and Geophysics, Yale University. Contrary to your implication, they are university scientists.

    My understanding of feedback in a complex system comes from having an advanced degree in Mechanical Engineering and many years of engineering practice including rocketry, nuclear power, and meteorological satellites. Many engineers understand and successfully apply feedback in complex systems and have for many decades. Although climatologists use a somewhat different formulation, the end result is the same.

    Your discussion of feedback verifies that you don’t understand feedback very well. That explains why you don’t recognize that the temperature trend reversals during the previous glaciation (not talking about 100,000 year ice age cycles here) prove that significant net positive feedback does not exist in climate.

    If you use the same argument regarding the temperature trend reversals as you use for changes from glacial to interglacial then all temperature trends would be reversed by unpredictable solar changes which would make GCMs useless as climate predictors.

    I am puzzled as to why you call some of my comments “very odd” and then proceed to agree with them.

    The data that you disparagingly refer to as ludicrous is well referenced and came from NOAA as you could have easily discovered.

    I say that there is no significant net positive feedback and you claim that I said “there isn't a relationship between atmospheric CO2 lelvels and the earth's global temperature”. Some scientists express their interpretations and you say “science says”. More scientists and engineers are on record declaring that atmospheric carbon dioxide level has no significant influence on climate than there are saying that it does (Not that it matters).
  50. Oh dear...


    You don't seem to get it:

    (1) There is unfortuantely no paleoCO2 proxy that coincides in time with the late Ordovician paleoevidence for glaciation. Therefore we don't know the relationship between paleoCO2 and paleotemperature for that particular event. There's no point in pretending otherwise.

    (ii) Pretty much every case where we do have contemporaneous paleoCO2 and paleotemperature temperature proxies, the relationship between atmospheric CO2 and temperature is rather clear. See the list of scientific papers in my post #48.

    (iii) If one want's to assess scientific issues, one goes to the published science, not to dodgy outdated, and unattributed pictures on websites.


    (iv) Christopher Scotese seems a perfectly excellent chap. However his website was last updated around 2002, and his site is principally to illustrate tectonic effects on continental movement. Sadly his site happens to contain a completely incorrect graph of paleotemperature data. It's more of a child-like crude sketch. I've no idea where it comes from...(can you enlighten us?)

    (v) I've shown you a long list of papers, including a recent review that compiles all of the data up to around 2005/6. Unfortunately, rather than taking the effort to explore the science on this subject, you prefer to argue over a crude unattributed graph that is clearly incorrect....go figure!

    (vi) You have an advanced degree on Mechanical Engineering and so on...and yet you have spent an apparently significant eforrt in putting together a web page full of the most blatant misrepresentations. While real scientists assess multipile paleotemperature data sets obtained with many different methods from as many places on the earth as possible to obtain truly global (or at least hemispheric) paleotemperature estimates, you choose ONE data point, in ONE data set, from ONE place on Earth and presume to aseet that 400 years ago the globally averaged temperature was higher than now...

    (vii) Even though that's a dismal piece of misrepresentation, and Scotese's temperature data is clearly incorrect, and your arguments about feedbacks have no basis in science......

    ..you are still asserting that you are right on these matters whereas all the climate, meterological, ocean, paleoenvironmental scientisits and so on are all incorrect....

    I don't think so Dan.....why not make an effort to access the science on these issues. I've given you a wealth of sources that bear exactly on the subjuect of issue that containis the most up to date data.
  51. Oh dear is right . . .

    Graphs of source referenced NOAA data are presented and you see “blatant misrepresentation”.

    The proof that significant net positive feedback and therefore AGW does not exist does not use Holocene data but you persist in worrying about a specific data point.

    You point out that other scientist’s have different interpretations of the Andean-Saharan ice age and you have decided which ones you agree with. Perhaps you do not realize that A/S is also not a necessary consideration to prove that significant net positive feedback does not exist in climate. The Scotese-Berner assessment of A/S defrays concern for planet-wide runaway temperature rise but the logarithmic decline in infrared radiation intensity with distance from the radiating surface with what is called the ‘saturation’ effect of atmospheric carbon dioxide refutes the ‘tipping point’ nonsense without any other consideration.

    Apparently you still don’t understand how feedback works. Perhaps we are not communicating. Let’s try a specific example. Look at the temperature trend from 55,000 ybp to 50,000 ybp. (This is from NOAA Vostok data as graphed in the second graph on the Middlebury website but the EPICA core shows about the same only shifted slightly in time.) See that this uptrend changes to a down trend at 50,000 ybp. This downtrend continues until about 45,000 ybp. This direction change from an up trend to a down trend could not take place if there were significant net positive feedback. Now look at the rest of the graph and see that there are many similar examples.

    Only the few who still believe that the rising atmospheric carbon dioxide level will have a significant effect on average global temperature are incorrect.

    Learn about feedback and then read 45 again.
  52. Don't be silly Dan,

    It's you that is "worrying about a specific data point"

    or actually two specific data points.

    NUMBER ONE:

    I am basing my understanding of the strong relationship between paleoCO2 measures and paleotemperature measures right back through the last 500 million years, BASED ON HUNDREDS OF CONTEMPORANEOUS CO2 and TEMP MEASURES (see data in my references cited in the posts above)

    You are taking one specific part of the paleodat where there is evidence for glaciation (i.e a coolish/cold Earth) and assuming that there is no relationship with atmospheric CO2. However THERE IS NO CONTEMPORANEOUS PALEO-CO2 MEASURE THAT OVERLAPS THIS PERIOD...and therefore your focus on a specific data point is spurious.

    NUMBER 2:

    I am basing my understanding of the paleotemperature data of the last 2000 years which indicates that late 20th century and contemporary warming is well above anything experienced during this time period. THIS DATA IS BAED ON NUMEROUS DATA SETS USING NUMEROUS METHODS OBTAINED FROM MANY DIFERENT PLACES ON EARTH.

    You are making a blatant misrepresentation of the data by basing your interpretation on ONE data point, from, ONE location, using ONE method.

    For some reason you're trying to construct a whole edifice of misrepresentation based on single data points.


    And for some reason, despite your assertions of scientific credentials you can't seem to grasp that primary effects (raised CO2 levels) supplemented with feedbacks can be overpowered by other effects (reduced insolation during waning Milankovitch cycles)...

    ..your blatant fallacious misinterpretations of paleodata don't actually give us very much confidence in your misassertions aboutfeedbacks...
  53. We seem to have drifted off point (as presented at 41 and 45). The Middlebury website is offered as a source for graphs of government and other credible data. Your disagreement with that data is with the government and the other sources, not me.

    The issue confronting humanity today is whether human produced carbon dioxide is causing global warming. The only indicator that it is comes from GCMs and then only when their users impose significant net positive feedback. Without significant net positive feedback, the GCMs do not predict significant Global Warming from increased atmospheric carbon dioxide.

    The proof that significant net positive feedback and therefore AGW does not exist DOES NOT USE anything from A/S.

    The proof that significant net positive feedback and therefore AGW does not exist DOES NOT USE anything from the Holocene. (For those interested, http://www.ncasi.org/publications/Detail.aspx?id=3025 , which uses data from many different proxies but excludes tree ring proxy data, is an assessment of the average global temperature for the last 2000 years.) This may be the source that Chris alludes to. It shows that the Medieval Warm Period, which was before the industrial revolution, probably reached higher average global temperatures than now and the steepest recent (around 1990) rate-of-change trend is about the same as it was at 4 other times in the last 800 years.

    A temperature trend direction change proves that there is no significant net positive feedback. Temperature data have been extracted from ice cores and are reported by NOAA and ORNL. All that is needed to determine if there is net positive feedback is a temperature trace for a long enough time to average out cyclic variation from random noise and other factors. The temperature trace does not even need to be correct in absolute terms just reasonably accurate in relative terms time-wise. This is obvious, even trivial, to me. Apparently the importance of the change in direction of temperature trend is not recognized by those who do not understand how feedback works.

    The trends used in the example in 51 are each about 5000 yr long and other trends have various lengths. The shortest Milankovich cycle is about 23000 yr. Milankovich can have no significant influence on the direction changes of the trends. Besides, the direction changes go both ways. You state “primary effects (raised CO2 levels) supplemented with feedbacks can be overpowered by other effects (reduced insolation during waning Milankovitch cycles)”. If feedbacks can be overpowered by other effects then ‘other effects’ determine which direction future temperature trends will go and predictions of GCMs are meaningless.

    Either way, the GCMs are invalidated as temperature predictors. That is pretty much the point.
  54. re #54

    Dan Pangurn is wrong again, and compounds his errors with another piece of gross misrepresentation of the science.

    Since Dan is pursuing these misrepresentations of the science in support of fallacious interpretations, it isn’t really “off-topic” to address them! Dan Pangburn’s nebulous point about “feedbacks” isn’t well-defined (he hasn’t really explained his problem)…we can look at that in a seperate post.

    Dan makes a weasel defence in his post #53 that my “disagreement is with the data” and not with him. That’s nonsense, of course. The data is fine. Dan has just cherry-picked and misrepresented it horribly. Let’s have a look again:

    (i) There is a vast wealth of data on millennial scale paleotemperature proxy data (see links/citations at bottom of post). To assess globally averaged paleotemperatures, competent and honest scientists use as many validated paleotemperature records as possible, using as many data points as possible, using a range of different paleotemperature proxies, from as many places on Earth as possible.

    Dan selected ONE data point from ONE record, from ONE location on Earth, and attempted to pursue the deceit that this indicates that the global temperature was warmer than now 400 years ago. There’s nothing wrong with the dataset. Dan has just grossly misused it by an extraordinary piece of cherry-picking.

    (ii) There is a wealth of data on the relationship between paleoCO2 and palaeotemperature in the deep past (see citations in my posts #46 and #48 above). These cover vast periods of the entire Phanerozoic and indicate a strong temperature/CO2 coupling throughout the last 500 million years.

    Dan selected ONE time period in which there is evidence of a cold Earth, and attempted to sell the notion that there is a disconnect between paleotemperature and paleoCO2. Unfortunately, there isn’t a paleotemperature proxy for this period (late Ordovician), and so Dan Pangburn’s interpretation is fallacious.

    (iii) Dan Pangburn has added to his set of fallacious interpretations with another piece of cherrypicking. There are many studies on paleotemperature variation throughout the last 1000-2000 years (see citations/links at bottom of the post), and these uniformly indicate that current temperatures are well above those of the past 1000 (and up to 2000) years. Dan has selected one study published in a non-science magazine whose editor openly admits to publishing non-science in pursuit of dubious agendas. Let’s look at Loehle’s paper that Dan Pangburn linked to in his post #53:

    According to Dan “It shows that the Medieval Warm Period, which was before the industrial revolution, probably reached higher average global temperatures than now and the steepest recent (around 1990) rate-of-change trend is about the same as it was at 4 other times in the last 800 years”. Neither of these is true; let’s see why:

    (a) If anyone has bothered to follow Dan’s link to the Loehle paper in “Energy and Environment”, you can see that the paper comes with a CORRECTION. There are several things that Loehle has had to correct, one of the more blatant ones being a shift in the entire data series back by around 50 years. Loehle’s original data set extended to around 2000; in the correction the data sets extend to around 1950. What’s going on there??

    The answer is a bit of incompetence. Since scientists are compiling paleodata all the time, it makes sense to reference these to a common year. So when a paleodata point is dated as 1000 BP, with BP meaning “Before Present”, “Present” does not mean 2008 (or 2009 or 2010 or 2015 and so on), unless specifically indicated. In fact the convention is to use 1950 as the “Present”, so that all data sets are referenced to a common year and can thus be compared by simple juxtaposition. Loehle apparently didn’t realize this!

    What does this mean for Dan Pangburn’s assertion that Loehle’s “data” shows that the Medieval Warm Period (MWP) was probably globally warmer than now? It means that it’s another fallacious misinterpretation. Since Loehle suggests that the MWP might have been 0.3 oC warmer than 1950, and the globally averaged temperatures are now 0.5-0.6 oC above 1950 temperatures (e.g. NASA GISS temperature data), it’s clearly warmer now than during the MWP, even using Loehle’s decidedly dodgy analysis [see (b) and (c)].

    How could Loehle publish such a nonsense? The answer is that Energy and Environment isn’t a science journal. It only pretends to be one. It’s a repository for stuff that supports the weird agenda of its Editor. The papers aren’t peer-reviewed, and so ludicrous errors aren’t picked up. In their defense they have issued a correction to Loehle’s paper. Unfortunately, as in many instances where agenda-led nonsense is subsequently corrected or debunked, the corrections may go un-noticed, and unscrupulous individuals seem happy to ignore them anyway…..

    Two other quick points:

    (b) Dan Pangburn talks about rates of temperature change, and suggests that Loehle’s data indicates that current/recent rates of temperature change are not anomalous. He says: “…. and the steepest recent (around 1990) rate-of-change trend is about the same as it was at 4 other times in the last 800 years”. Sadly, Dan has messed up yet again. Remember that Loehle made a silly boo-boo with his timescale. His data only goes up to the year 1950. The “steepest recent (around 1990) rate of change trend..” that Dan refers to is now “around 1940” in Loehle’s corrected data. In fact even using Loehle’s dubious data it’s clear that the rate of temperature increase we’ve seen during the last 30-odd years is very much faster than any time in the last 800 years (see Wikipedia link just below, for example). If one examines the science as opposed to nonsense, the paleotemperature data demonstrate that the late 20th century temperature rise is much faster than anything in the past 1000 years:

    http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png

    (or look at the papers cited below). Since Loehle completely omits the last around 60 years of temperature rise from his analysis/presentations, the scale of the large post-1950’s temperature rise that rather dominates the record is completely lost!

    (c) It’s worth pointing out that apart from Loehle’s rather ludicrous error highlighted above, his data analysis is extremely dodgy. Two things are worth highlighting. For example, much of Loehle’s very limited data sets are extremely sparse in both time and location. A large chunk of the data involves data points averaged over huge time periods (e.g. a time point every 100 years). Clearly while one can “join up the points”, it’s impossible to say anything about rates of temperature change with grossly averaged data. Where spatially widespread data are used (e.g. Viau et al’s N. America composite from pollen analysis) the data actually show rather small temperature variation before the 20th century, not just for the past 1000 years, but during the 7-8000 years before the 20th century (e.g. Viau et al state “Our results show millennial-scale climate variability on the order of +/- 0.2 oC during the entire Holocene at the North American scale”; we’ve had approaching 1 oC of warming over the same region just in the last 30-odd years).

    One could highlight more of the dreary errors in Loehle’s analysis and Dan’s interpretations. But what’s the point? Surely if we are interested in what the science shows, we address the science published in the scientific literature. We don’t ignore the science and hunt around for dodgy nonsense from dubious sources.

    --------------------------------------------------Here’s some of the abundant paleotemperature data covering the last 1-2000 years:

    The published data from multiple sources of published scientific research is compiled by the NOAA and can be found here:

    http://www.ncdc.noaa.gov/paleo/recons.html

    Wikipedia has a reasonably good account of this data, and an overlay of many of the paleotemperature proxy data can be found here:

    http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png

    recent papers with datasets/analyses that may not be in the Wikipedia compilation are:

    M. E. Mann et al (2008) “Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia” Proceedings of the Natl. Acad. Sci. USA 105:13252-13257;

    D'Arrigo RD, Wilson R, Jacoby G (2006) “On the long-term context for 20th century warming.” J Geophys Res 111:D03103.

    Hegerl GC et al (2007) “Detection of human influence on a new, validated 1500 year temperature reconstruction.” J Clim 20:650–666.

    Lee TCK, Zwiers FW, Tsao M (2008) “Evaluation of proxy-based millennial reconstruction methods.” Clim Dyn 31:263–281.

    Viau, AE et al (2006) “Millennial-scale temperature variations in North America during the Holocene” J. Geophys. Res. 111, D09102.
  55. Re #53 Dan Pangburn

    You are pursuing a very vague point about warming feedbacks, which you assert, in contradiction to the scientific data, don't exist. You haven't explained your argument for this other than to state the likes of (paraphrasing) "look at this ice core data - clearly feedbacks don't exist - it seems obvious, even trivial, to me."

    But what seems obvious, even trivial, to you, may simply be another example of misunderstanding of the science. It's simply not possible to maintain the deceit that CO2-induced atmospheric warming (or atmospheric warming from any source) doesn't result in a positive feedback from enhanced water vapour concentrations. That's really beyond dispute.

    So you need to try to explain rather more explicitly why you don't believe in feedbacks. I have a feeling that your particular Engineering background may have confused you over the meaning of "feedback" as applied in Engineering compared to that used in Ocean and Atmospheric Physics. But we won't know that unless you are rather more specific about your problem.

    Notice, by the way, that GCM's are certainly not "the only indicator that...human produced carbon dioxide is causing global warming". That's a very odd thing to say. The reason that CO2-induced warming is included in GCM's is because the physics of the greenhouse effect is rather well understood. You've rather put the cart before the horse!
  56. New Study Increases Concerns About Climate Model Reliability
    ScienceDaily (Dec. 12, 2007) — A new study comparing the composite output of 22 leading global climate models with actual climate data finds that the models do an unsatisfactory job of mimicking climate change in key portions of the atmosphere.
  57. A list of all legitimate indicators that human produced carbon dioxide is a substantial contributor to global warming is welcome. The record of approximately 30-year long up and down temperature trends during the steady progressive rise in atmospheric carbon dioxide level of the 20th century certainly is not one since it corroborates that there is no significant correlation between rising atmospheric carbon dioxide and global average temperature.

    All of my sources are cited so that they can be checked. None are misrepresented. Quoting a maximum or minimum in a data set hardly qualifies as ‘cherry picked’. The Middlebury link (post 41) includes links to all of the source data that is graphed there.

    The corrections to Dr. Loehle’s paper are included with the original in the link at http://www.ncasi.org/publications/Detail.aspx?id=3025 . Select ‘Download File’ to get both the original and the corrections. Contrary to assertions by Chris, review of this paper reveals that the ‘corrections’ made little change to the results. Loehle used a 29 year smoothing which allowed comparison only through 1992 at the time of the paper. The smoothed average global temperature in 1992 reached about the same as was reached during the Medieval Warm Period. Loehle describes all of the data sources and methods that were used and solicits feedback by also giving his email address.

    Regarding the Medieval Warm Period, this is what Dr. Loehle actually said (in the correction): “The peak value of the MWP is 0.526 Deg C above the mean over the period (again as a 29 year mean, not annual, value). This is 0.412 Deg C above the last reported value at 1935 (which includes data through 1949) of 0.114 Deg C. The standard error of the difference is 0.224 Deg C, so that the difference is significantly non-zero at the 10% level (t = 1.84). While instrumental data are not strictly comparable, the rise in 29 year-smoothed global data from NASA GISS (http://data.giss.nasa.gov/gistemp) from 1935 to 1992 (with data from 1978 to 2006) is 0.34 Deg C. Even adding this rise to the 1935 reconstructed value, the MWP peak remains 0.07 Deg C above the end of the 20th Century values, though the difference is not significant.”

    Utilizing information from several publications as well as the web helps to compensate for the bias, agenda, group-think and de facto censoring that can exist with a particular publication. There are undoubtedly many publications that supposedly show that added atmospheric carbon dioxide is a significant cause of Global Warming. That can happen when you start out with a conclusion and then set out to justify it. I started out with the relation of carbon dioxide and Global Warming as a question. Although I try to listen very carefully to what others say, I withhold judgment as to validity until vastly corroborated and even then remain alert to contradiction.

    The above and, except for mentioning feedback, the lengthy comments by Chris are not particularly relevant to the issue of reliability of GCMs. Although reliability as used here is ambiguous, I assume, as probably most do, that it means that it pertains to whether GCMs can reliably predict future climate. Maybe some day some of them will be able to but not yet. Three major issues are apparent: 1) Vertical convection is subjectively parameterized. 2) Clouds are also subjectively parameterized, and rather poorly (see post 17). 3) The users arbitrarily impose substantial positive feedback which, climate history proves is a mistake. There are other issues as listed at post 32 (Average temperature anomaly from NOAA for Jan thru Sept 2008 is 0.445). There is one exact computer of earth’s climate as I described at post 45 above. Of course any credible temperature proxy can be used as an archive of results.

    It appears that Chris either did not read or did not understand my earlier post (43) on feedback. Referring to feedback as “vague” and “nebulous” further verifies a lack of understanding of feedback. Failure to see the difference between the paraphrase of my words “clearly feedbacks don't exist” and my actual assertion that NET positive feedback does not exist also indicates a lack of understanding of feedback. Failing to understand feedback explains why temperature TREND reversals during the previous glaciation are not recognized as proving that significant NET positive feedback does not exist in climate.

    Actual temperature response is influenced by NET feedback. NET feedback is the combined effect of positive feedbacks such as water vapor, negative feedbacks such as Lindzen’s iris effect, and all other feedbacks whether recognized or not.

    Although the numerical values and formulation are different between engineering feedback and Ocean and Atmospheric Physics feedback, positive feedback means the same thing in both. The response is greater with positive feedback than it would be if there were no feedback. NET means the combined effects of all active feedbacks whether known or not.

    A temperature TREND direction change proves that there is no significant NET positive feedback. Any credible source of temperature can be used. All that is needed to determine that there is no net positive feedback is a temperature trace for a long enough time to average out cyclic variation from random noise and other factors such as ENSO. Of course it must also be substantially longer than any smoothing period that was employed. The temperature trace does not even need to be correct in absolute terms just reasonably accurate in relative terms time-wise. Apparently the importance of the change in direction of temperature trend is not recognized by those who do not understand how feedback works. Without significant net positive feedback, the GCMs do not predict significant Global Warming.
  58. Re #57

    There are some extraordinary misconceptions and lovely examples of deliberate misinterpretation in Dan’s post. Let’s have a look (a response to Dan’s “feedback” stuff in a separate post):

    We can examine the wealth of paleoproxy data published in the scientific literature (these can be found in the NOAA site urled in the list below, and some of these are compiled in a graph on the Wikipedia page...…more recent data sets that aren’t in the Wikipedia composite are cited below too). All of this data from a very large number of analyses indicate that we are a good bit warmer now (by 0.4-0.6 oC or more) in the Northern hemisphere now than during the so-called “Medieval Warm Period” (MWP).

    Dan has chosen to ignore all of the published data, and to refer us to an article in a non-science magazine who’s editor is quite open about her inclusion of (non-peer reviewed) stuff that supports her rather odd political considerations. Dan's article is scuppered by a ludicrous howler in which the author (Loehle) misunderstood the dating of paleodata and thought that his data sets progressed to the present, when in fact they extend at the very most to 1949. In other words Loehle misses out completely the very marked global scale warming of the last nearly 60 years. Loehle corrected his analysis.....now taking Loehle’s own CORRECTED data at face value his analysis demonstrates that it is a good bit warmer now that during the MWP.

    So Dan got it wrong. Note that although Loehle was honest enough to print a correction of his paper, Dan chose to base his original “analysis” (post #53) on the incorrect presentation even ‘though the correction is joined into the same document as the original incorrect article...that’s a dull piece of contrived misrepresentation and cherrypicking……sadly, that seems to Dan’s modus operandi (see posts #46, 48, 50, 52, 54).

    It’s worth noting Dan’s attempt to “rescue” the “situation”. Dan points out that Loehle still considers that the MWP might have been (in the Northern hemisphere) as warm as now. However Loehle makes another fundamental error here. Note that Loehle’s paleodata set is extremely sparse (18 records) and some of these records themselves are extremely sparse (e.g. a paleotemperature point every 100 years). This might be contrasted with the recent paleoanalysis of Mann et al (2008), for example, which also addressed the paleodata without using tree ring proxies, and who's analysis uses around 170 paleotemperature data sets with the stipulation that the data has at least decadal temporal resolution. Examination of Loehle’s original sparse records shows considerable variability, and (as is quite normal) in order to make the paleotemperature variations accessible and to incoproprate disparate sets into a common record, the data are smoothed by averaging in the time domain. Loehle used a 30 year running mean (changed to a 29 year running mean in his correction). The problem is that Loehle then chose to compare his most recent paleoproxy temperature point (the year 1935), with the instrumental temperature record (from NASA GISS: http://data.giss.nasa.gov/gistemp/) smoothed as a 29 year running average. Of course that doesn’t make any sense. We know what the earth’s land/sea surface temperature has done since 1935. It’s risen by around 0.6 oC. If one arbitrarily averages the real measured temperature with a 29 year running average, one arithmetically “magic’s” away a good bit of the warming.

    O.K. so Loehle’s analysis is pants on a number of levels. But for all its ludicrous faults, taken at face value it still indicates that we are a good bit warmer now (in the N. hemisphere) than during the MWP. I would suggest that if anyone is interested in looking at what the science indicates on this subject, they look at the paleodata on the NOAA NCDC database or download the very recent extensive analysis of Mann et al (2008) published as an Open Access article in the Proceeds of the National Academy of Sciences (http://www.pnas.org/content/105/36/13252.full)

    M. E. Mann et al (2008) “Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia” Proceedings of the Natl. Acad. Sci. USA 105:13252-13257


    -------------------------------------------------------

    The extensive published paleoproxy temperature data is compiled here:

    http://www.ncdc.noaa.gov/paleo/recons.html

    Wikipedia has a reasonably good account of this data, and an overlay of many of the paleotemperature proxy data can be found here:

    http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png

    recent papers with datasets/analyses that may not be in the Wikipedia compilation are:

    M. E. Mann et al (2008) “Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia” Proceedings of the Natl. Acad. Sci. USA 105:13252-13257.

    (http://www.pnas.org/content/105/36/13252.full)

    D'Arrigo RD, Wilson R, Jacoby G (2006) “On the long-term context for 20th century warming.” J Geophys Res 111:D03103.

    Hegerl GC et al (2007) “Detection of human influence on a new, validated 1500 year temperature reconstruction.” J Clim 20:650–666.

    Lee TCK, Zwiers FW, Tsao M (2008) “Evaluation of proxy-based millennial reconstruction methods.” Clim Dyn 31:263–281.

    Viau, AE et al (2006) “Millennial-scale temperature variations in North America during the Holocene” J. Geophys. Res. 111, D09102.
  59. Re #57, on CO2 and feedbacks.

    There is a large amount of paleodata on the relationship between Earth’s paleotemperature data and paleoCO2 measures, and these indicate that the Earth in the deep past was warm when atmospheric CO2 levels were high, and cool/cold when atmospheric CO2 levels were low. Some of these data are listed at the bottom of the post (data set #2)..

    Dan makes an odd statement about the record of “30 year long up and down temperature trends during the steady progressive rise in atmospheric carbon dioxide level of the 20th century”. But one only needs to look at the temperature record (e.g. http://data.giss.nasa.gov/gistemp/), to see that the trend is a positive one. The earth’s surface temperature is undergoing a rapid increase in temperature that is following the extraordinarily rapid rise in atmospheric CO2.

    But one needs to be careful of course. The temperature rise that results from enhanced atmospheric CO2 levels relates to the temperature AT EQUILIBRIUM. There are two problems with Dan’s simple misrepresentation. Internal variations in the climate system (ocean currents, El Nino’s, La Nino’s) that temporarily redistribute heat, the effects of volcanic eruptions that transiently cool the atmosphere (or man made aerosols), the solar cycle, and so on, result in fluctuations around the equilibrium temperature that is effectively “set” by the solar output and the greenhouse effect. So we obviously don’t expect to see a perfectly steady increase in temperature as CO2 levels rise. The earth’s temperature has been rising by around 0.2 oC per decade during the last 30-odd years. However internal variation can be as large as 0.1-0.2 oC per year. So the temperature rise is overlaid with “noise” from these fluctuations. That’s pretty obvious. Likewise right now we’re smack at the bottom of the solar cycle. So for the last couple of years and for perhaps another couple the Earth’s temperature rise is being opposed by a slightly cooler sun. In a couple of years the rise in solar output will add to the greenhouse warming..

    ..and so on. The fact is that when we assess the trends over longish periods, the Earth is on a warming trend…we’re around 0.5 oC warmer globally than 30 years ago. The temperature may have gone “up and down” a bit during this period...but overall it’s gone up!

    A large number of analyses indicate that the Earth’s EQUILIBRIUM temperature rises by around 3 oC (+/- a bit) per doubling of atmospheric CO2. A significant part of this temperature rise results from feedbacks, the most important one being the water vapour feedback. As the atmosphere warms under the influence of raised CO2 levels, so the atmospheric concentration of water vapour rises. Does this feedback actually exist? Yes. We can measure the enhanced atmospheric water vapour directly in the real world [see Soden et al (2005); Brogniez H and Pierrehumbert RT (2007); Santer BD et al. (2007); Buehler et al. (2008); Gettelman and Fu (2008)…and so on (citations below].

    So the major feedback to enhanced CO2 level exists. As atmospheric CO2 levels rise so atmospheric water vapour levels rise, pretty much in expectations with predictions based on straightforward atmospheric physics (not to mention models which also predict the observed tropospheric moistening).

    It’s difficult to know exactly where Dan is confused with respect to “feedbacks” since he is very vague. Notice that Dan is being a tad dishonest in his comments in post #57, since I don’t refer to feedbacks as “vague” and “nebulous” at all, but to Dan’s “discussion” of these as vague (this dishonesty is similar to Dan’s pretence that my criticism of Dan’s appalling cherrypicking of paleotemperature data equates to a disagreement on my part with the data). The problem is that Dan makes very vague comments about feedbacks. He talks about “feedbacks, known or not”. He alludes to negative feedbacks without really addressing what these might be, other than alluding to a negative feedback “identified” by Dr. Richard Lindzen and “his iris effect”. But of course Lindzen didn’t “identify” an “iris effect”. Lindzen hypothesised such a possibility…however real world analysis hasn’t really provided any evidence for such a thing (see below). Lindzen earlier postulated that increased CO2-induced warming would cause a drying of the troposphere, but in the face of real world data world [see Soden et al (2005); Brogniez H and Pierrehumbert RT (2007); Santer BD et al. (2007); Buehler et al. (2008); Gettelman and Fu (2008)…and so on (citations below], Lindzen had to dump that notion too. Unverified or disproven hypothesis don't constitute evidence of anything.

    The problem with vague assertions about hypothetical negative feedbacks is not just that these are ill-defined, and that the evidence indicates that these hypothetical feedbacks don’t exist or are small. Real world observations support the conclusions that (i) that the climate sensitivity to raised CO2 is rather significant (around 3 oC per doubling of atmospheric CO2), and (ii) that putative, hypothetical negative feedbacks are not very significant. Thus many of the determinations of climate sensitivity are empirical analyses that relate warming to variations in forcings and accommodate all feedbacks whether negative or positive. Thus determination of a climate sensitivity to CO2 by analysis of glacial-interglacial transitions, by analysis of paleotemp/paleoCO2 data [Royer et al (2007)]; by analysis of the Earth’s temperature response to the solar cycle [Tung and Camp (2008)], and so on, implicitly incorporate all of the forcings whether negative or positive. These give values near 3 oC of warming per doubling of atmospheric CO2. Likewise we’ve had a very marked warming during the last 30 years (around 0.5-0.6 oC) in response to an increase in atmospheric CO2 from 330 ppm to 385 ppm. If we’ve had 0.5-0.6 oC of temperature rise from a “small” (!) CO2 rise of 55 ppm on the course of a potential doubling of 330-660 ppm, then that seems highly inconsistent with a low climate sensitivity; the same conclusion arises from the extent of warming we’ve had in response to a relatively small proportion of doubling of atmospheric CO2 during the 20th century. In fact the temperature increase of the 20th century, modelled using the full set of known contributions, is entirely compatible with the effects of feedbacks (Hansen et al, 2005) and predictive simulations set up in the 1980’s have done a rather good job of predicting the subsequent global temperature increase (Hansen et al, 2006) and so on.

    Thus it’s perverse to suggest that what exists (since we can measure it in the real world) doesn’t exist…or to assert that what doesn’t seem to exist (since there seems precious little evidence for it!), does. Dan also needs to be far less vague about his comments concerning temporal relationships between temperature and greenhouse gas levels during glacial cycles. He’s confused over something and thinks that everyone else might be wrong…but unless he is explict about his problem we’re unlikely to be able to help him…


    Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data. J. Geophys. Res. 113, art #D14110

    Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912

    Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback . J. Climate 21, 3282-3289

    Hansen, J. et al (2005) Earth's energy imbalance: Confirmation and implications. Science, 308, 1431-1435.

    http://pubs.giss.nasa.gov/docs/2005/2005_Hansen_etal_1.pdf

    Hansen, J. et al. (2006) Global temperature change. Proc. Natl. Acad. Sci., 103, 14288-14293.

    http://pubs.giss.nasa.gov/docs/2006/2006_Hansen_etal_1.pdf

    Royer DL et al. (2007) Climate sensitivity constrained by CO2 concentrations over the past 420 million years Nature 446, 530-532

    Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253

    Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening
    Science 310, 841-844.

    Tung and Camp (2008) Solar Cycle warming at the Earth’s surface and an observational determination of climate sensitivity

    http://www.amath.washington.edu/research/articles/Tung/journals/solar-jgr.pdf
    -------------------------------------------------
    Data set #2:

    A wealth of paleoproxy data support the conclusion of a strong relationship between atmospheric CO2 and earth’s surface temperature during the deep past. These data support a high climate sensitivity to CO2 and indeed analysis of the relationships between paleotemperature and paleoCO2 indicate that the earth’s temperature sensitivity to enhanced CO2 has been high for 500 million years. Explicitly a value for the climate sensitivity of 2.8 oC per doubling of atmospheric CO2 has been determined (see Royer et al (2007) in the citayions listed above.

    D.L. Royer (2006) "CO2-forced climate thresholds during the Phanerozoic" Geochim. Cosmochim. Acta 70, 5665-5675.
    (this is a review compiles much of the published data)

    Even more recent studies supplement the information in Royers compilation and cover additional periods with new data sets right through the past several hundreds of millions of years:

    R.E. Carne, J.M. Eiler, J. Veizer et al (2007) "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" Nature 449, 198-202

    W. M. Kurschner et al (2008) “The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of the terrestrial ecosystem” Proc. Natl. Acad. Sci. USA 105, 499-453.

    D. L. Royer (2008) “Linkages between CO2, climate, and evolution in deep time” Proc. Natl Acad. Sci. USA 105, 407-408

    Zachos JC (2008) “An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics” Nature 451, 279-283.

    Doney SC et al (2007) “Carbon and climate system coupling on timescales from the Precambrian to the Anthropocene” Ann. Rev. Environ. Resources 32, 31-66.

    Horton DE et al (2007) “Orbital and CO2 forcing of late Paleozoic continental ice sheets” Geophys. Res. Lett. L19708 (Oct. 11 2007).

    B. J. Fletcher et al. (2008) “Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change” Nature Geoscience 1, 43-48.
  60. Re #56

    Quietman, the posting of your link to a paper purporting to identify an incompatibility between tropospheric temperatures in the tropics and modelled tropospheric temperature is fascinating. Here’s a very recent paper by a large group of 17 climate scientists. It (abstract at bottom of post) completely contradicts the paper that you linked towards:

    B. D. Santer et al. (2008) Consistency of modelled and observed temperature trends in the tropical troposphere. International Journal of Climatology 28, 1703 – 1722.

    You can download and read it from here: https://publicaffairs.llnl.gov/news/news_releases/2008/NR-08-10-05-article.pdf


    What can be going on?

    The answer is the guys whose paper you linked towards (Drs Douglass, Christy, Pearson and Singer; DCPS) messed up somewhat (incidentally you should always be a little suspicious of papers containing the rather dubious S. Fred Singer).

    Here’s the story:

    1. Simple atmospheric physics indicates that as the atmosphere warms under the influence of raised [CO2], a water feedback (raised water vapour in a warming atmosphere) should kick in resulting in additionally raised atmospheric temperature. This is observed in models (both the raised water vapour and atmospheric temperature), and is generally consistent with real world measurements.

    2. But not fully. There has been an apparent mismatch between predicted tropospherical warming and measured warming in the tropics. Radiosonde data (crude temperature measures in weather balloons) especially, don’t seem to show the predicted temperature increase. Something is wrong.

    3. But what? In this case it looks like it might be the measurements that are wrong. In fact the paper you linked towards (DCPS) was not so much about demonstrating that there is a mismatch between the models and tropical tropospheric temperature measures (there quite likely isn’t), but in asserting that the tropospherical tropical temperature measurements are sufficiently free from error that such a comparison can be reliably made. In fact it seems that they aren’t.

    4. What does the evidence indicate? It’s been known for some time that there is a very significant problem with the radiosonde tropospheric data, and this is particularly severe in the tropics. If these errors are taken into account, then the model and tropical tropospheric temperature can be be reconciled. However this requires a recognition of the substantial errors in the measured raiosonde data and a proper evaluation of these errors when assessing any real or potential disparity with the models.

    S. C. Sherwood et al. (2005) Radiosonde Daytime Biases and Late-20th Century Warming Science 309, 1556 – 1559.

    Abstract: “The temperature difference between adjacent 0000 and 1200 UTC weather balloon (radiosonde) reports shows a pervasive tendency toward cooler daytime compared to nighttime observations since the 1970s, especially at tropical stations. Several characteristics of this trend indicate that it is an artifact of systematic reductions over time in the uncorrected error due to daytime solar heating of the instrument and should be absent from accurate climate records. Although other problems may exist, this effect alone is of sufficient magnitude to reconcile radiosonde tropospheric temperature trends and surface trends during the late 20th century.”

    L. Haimberger et al (2008) Toward Elimination of the Warm Bias in Historic Radiosonde Temperature Records—Some New Results from a Comprehensive Intercomparison of Upper-Air Data. J. Climate 21, 4587-4606.

    M. P. McCarthy et al. (2008) “Assessing Bias and Uncertainty in the HadAT-Adjusted Radiosonde Climate Record”. J. Climate 21, 817-832.

    P. W. Thorne et al. (2007) Tropical vertical temperature trends: A real discrepancy? Geophys. Res. Lett. 34, L16702.

    And so on…


    5. And in fact, if tropical tropospheric temperatures are assessed using other measured correlates of temperature, there is increasing evidence that in fact the tropical troposphere is warming as predicted:

    Allen RJ and Sherwood SC (2008) Warming maximum in the tropical upper troposphere deduced from thermal winds. Nature Geoscience 1, 399-403.

    Abstract: "Climate models and theoretical expectations have predicted that the upper troposphere should be warming faster than the surface. Surprisingly, direct temperature observations from radiosonde and satellite data have often not shown this expected trend. However, non-climatic biases have been found in such measurements. Here we apply the thermal-wind equation to wind measurements from radiosonde data, which seem to be more stable than the temperature data. We derive estimates of temperature trends for the upper troposphere to the lower stratosphere since 1970. Over the period of observations, we find a maximum warming trend of 0.65 +/- 0.47 K per decade near the 200 hPa pressure level, below the tropical tropopause. Warming patterns are consistent with model predictions except for small discrepancies close to the tropopause. Our findings are inconsistent with the trends derived from radiosonde temperature datasets and from NCEP reanalyses of temperature and wind fields. The agreement with models increases confidence in current model-based predictions of future climate change."

    6. What are the conclusions? The first is that one should be carefully not to be fooled by dubious papers that are circulated around the blogosphere to fool the unwary. There are usually a number of papers that are relevant to assess particular issues, and one should try to address all of the evidence. Secondly, one can only assess the relationship between predicted/modeled analyses and real world data if the real world data is sufficiently accurately defined to make a valid comparison. Although this is often the case, in the particular instance of measured tropical tropospheric temperatures, the evidence indicates that the real world measurement errors are still too large. However as Santer et al indicate, they are improving, and there is now no substantial disagreement between modelled and measured data.
    -----------------------------------------------------

    B. D. Santer et al. (2008) Consistency of modelled and observed temperature trends in the tropical troposphere. International Journal of Climatology 28, 1703 – 1722.

    Abstract
    "A recent report of the U.S. Climate Change Science Program (CCSP) identified a potentially serious inconsistency between modelled and observed trends in tropical lapse rates (Karl et al., 2006). Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in well-mixed greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of surface and tropospheric temperature changes. We find that there is no longer a serious discrepancy between modelled and observed trends in tropical lapse rates.
    This emerging reconciliation of models and observations has two primary explanations. First, because of changes in the treatment of buoy and satellite information, new surface temperature datasets yield slightly reduced tropical warming relative to earlier versions. Second, recently developed satellite and radiosonde datasets show larger warming of the tropical lower troposphere. In the case of a new satellite dataset from Remote Sensing Systems (RSS), enhanced warming is due to an improved procedure of adjusting for inter-satellite biases. When the RSS-derived tropospheric temperature trend is compared with four different observed estimates of surface temperature change, the surface warming is invariably amplified in the tropical troposphere, consistent with model results. Even if we use data from a second satellite dataset with smaller tropospheric warming than in RSS, observed tropical lapse rate trends are not significantly different from those in all other model simulations.
    Our results contradict a recent claim that all simulated temperature trends in the tropical troposphere and in tropical lapse rates are inconsistent with observations. This claim was based on use of older radiosonde and satellite datasets, and on two methodological errors: the neglect of observational trend uncertainties introduced by interannual climate variability, and application of an inappropriate statistical consistency test."
  61. It was somewhat surprising to discover that the study of climate science does not require any exposure to the ‘theory’ (it is widely and successfully applied practice in some engineering disciplines, especially electrical, mechanical and aeronautical) of dynamic systems with feedback control. Their ignorance has resulted in climatologists coming up with their own expression for feedback and the perception that feedback in climate is somehow different from feedback in other systems. In effect it isn’t (for more, see 49 above). Earth’s climate is a dynamic system that is controlled by NET feedback. A lack of understanding of dynamic systems with feedback and how they work has resulted in many articles being published that a reviewer who was knowledgeable in dynamic systems with feedback would quickly recognize as patently false. Climate publications are staffed by climate scientists. Articles for publication in climate publications are peer reviewed by climate scientists. None of them appear to be knowledgeable in dynamic systems with feedback and thus they are unable to recognize information that is readily shown to be false and should never have been published.

    Feedback means that the output (results, response) influences the input. Feedback can be positive or negative. Positive feedback means that the output is greater than it would be without feedback. Negative feedback means that the output is reduced from what it would be without feedback. Net feedback is the effective feedback when there are both positive and negative feedbacks. If net feedback is positive the trend must continue up at a progressive rate. The effect on a savings account balance with compound interest is a familiar example of net positive feedback. Complexity does not alter how net feedback works.

    Now look at any credible historic temperature data. To be credible, a temperature trace must be for a long enough time to average out cyclic variation from random noise and other factors such as ENSO. The temperature trace does not even need to be correct in absolute terms just reasonably valid in relative terms time-wise. It should also be substantially longer than any smoothing period that was employed in generating the data set. A temperature trend can not change direction from up to down if net positive feedback exists. If there is at least one change of average global temperature trend from up to down (a down trend of average global temperature can not exist with net positive feedback) without an overpowering external influence, it proves that net positive feedback does not exist. There are many and there are downtrends. Therefore net positive feedback does not exist. Without net positive feedback the climate computer models (GCMs) do not predict significant global warming from increased atmospheric carbon dioxide. There are other issues with GCMs and their use as described at 32 above.

    Climate scientists and climate scientist wannabes who claim that ‘the science says’ are simply ignorant of an important part of science that is relevant to the issue. Climate scientists, in their ignorance, impose net positive feedback on their GCMs which causes them to falsely predict that added atmospheric carbon dioxide causes significant global warming.
  62. Re #61

    Dan’s pursuing another error that results from not bothering to find out what the term "feedback" means in an unfamiliar field.

    The mistake is easy to see in Dan’s definition of "feedback". Here it is: [Dan: "Feedback means that the output (results, response) influences the input."]

    But that definition doesn't really apply to the climate system and its temperature inputs/outputs in relation to the energy balance that defines an equilibrium temperature.

    Here's a simple example. The solar output increases a tad (perhaps during the solar cycle). As a result the atmosphere warms a bit. What might also happen? Since the relative humidity of the atmosphere tends to remain constant, and a warmer atmosphere has a higher saturation point for water vapour, the atmospheric water concentration rises (we can measure this in the real world). This is considered a positive feedback in atmospheric physics.

    Does this accord with Dan’s definition of "feedback" as used in engineering? Not really. I think we’d all agree that the enhanced water vapour concentration doesn't alter the solar output.

    Of course there is an element of "engineering"-style "feedback" in the water vapour feedback. The solar warming results in raised water vapour concentration which warms the atmosphere further resulting in further enhanced water vapour concentration. If the solar change results in a 1 oC change, and the resulting water vapour feedback adds an additional x of additional warming then the total warming from the solar enhancement + water vapour feedback is something like 1 + x + x^2 + x^3 + x^4 ...

    which is 1/(1-x).

    We can make the same argument for the enhancement of atmospheric CO2 concentrations. If the atmospheric CO2 concentrations rise by an amount giving a 1 oC of warming then the water vapour feedback will result in a total warming of 1/(1-x), where x is the temperature rise at equilibrium resulting from the enhanced water vapour concentration that is induced by a CO2-driven rise in temperature of 1 oC. Again note that in this case (enhanced CO2 forcing a temperature rise that generates a positive water vapour feedback), Dan’s “engineering-style feedback” barely applies (it might a tad). In other words, the water vapour feedback doesn’t recruit further rises in atmospheric CO2.

    Note that this is a little different from the CO2 feedback warming from enhanced insolation, for example during glacial-interglacial transitions driven by Milankovitch cycles. Here the enhanced insolation results in atmospheric warming which recruits a small amount of CO2 from the ocean and terrestrial environment, which results in a small amount of enhancement of the water vapour concentration with a tiny additional enhancement of the atmospheric CO2. But we know that the temperature-dependent recruitment of CO2 into the atmosphere is quite small. So, for example, the last glacial-interglacial transition from around 15000-10000 years ago resulted in a global temperature increase near 6 oC, and a warming-induced increase in atmospheric CO2 of around 90-100 ppm. So it takes a 1 oC of temperature rise to raise atmospheric CO2 levels by around 15-16 ppm. Interestingly this takes around 1000 years (averaging over the transition), whereas we’re getting this amount of enhanced CO2 in around 7 years now.

    Dan suggests that: “If net feedback is positive the trend must continue up at a progressive rate. The effect on a savings account balance with compound interest is a familiar example of net positive feedback. Complexity does not alter how net feedback works.”

    But each of those statements is untrue in the context of atmospheric physics and the Earth’s energy balance. Even though the net feedback is positive, the “trend” DOESN’T “continue up at a progressive rate “. This is because the feedback doesn’t affect the input in the manner that Dan suggests, (and also because the “strengths” of the feedbacks are not sufficiently large as to cause the system to “continue up at a progressive rate “ - see the pnt about the atmospheric CO2 feedback to Milankovitch warming in the last but one paragraph).

    What happens is that the Earth’s energy balance progresses towards a new equilibrium with a temperature that is somewhat higher than it would be without feedbacks. It’s not like Dan’s idea of “compound interest” in “a savings account balance”, at all.

    We can add other feedbacks. Some of these, of course, might well be negative. But we know for example that there is at least one more additional positive feedback. The warming from raised CO2 results in melting of mountain glacial and polar sea and land ice. Since this doesn’t result in very much in the way of recruiting of additional CO2, again this is a feedback that doesn’t influence the input (enhanced atmospheric CO2) to any great extent. So we can treat it much as we did above. It will cause additional atmospheric warming as more solar shortwave infrared is absorbed by the earth and converted into thermal energy. This will warm the atmosphere a bit more, and more water vapour will be “recruited”…

    ..again the Earth’s “temperature” will settle towards a new equilibrium temperature that is a bit warmer than that resulting only from the enhanced atmospheric CO2 with its water vapour feedback. In effect this will be the Earth’s equilibrium temperature that applies to this particular insolation, with this particular atmospheric CO2 concentration and this particular atmospheric water vapour concentration and this particular albedo. Note that the albedo effect is inherently self-limiting, and this is another example of where Dan’s mis-application of “engineering-style” “theory” to an inappropriate example breaks down. We could discuss this too…

    Overall, we can examine the paleoclimate record, analyze the warming resulting from Milankovitch-forced glacial-interglacial transitions, analyze the 20th century warming record, determine the atmospheric response to volcanic eruptions, study the theoretical response in computer models and so on….all of these indicate that the Earth’s climate responds to enhanced atmospheric Co2 concentrations with positive feedbacks of the sort described in the preceding paragraphs, such that the Earth’s “energy balance” shifts to a new equilibrium that gives us a higher surface temperature that would result solely from the enhanced CO2 without feedbacks. This new equilibrium temperature is around 3 oC of warming per doubling of atmospheric [CO2].
  63. Chris apparently has no knowledge of dynamic system theory. That helps explain the overt hostility (under the false assumption that I am just making stuff up) and why he/she mistakenly declares that some of my assertions are erroneous.

    Dynamic systems with feedback are phenomena of the natural world, like thermodynamics, genetics, cosmology, etc. etc., which can be studied and understood. The subject is studied by some engineers; usually as part of a post graduate course. They study the phenomenon and learn concepts and applicable mathematic tools and usually apply them to things like the guidance system of an antimissile missile, cruise control device for a vehicle, etc. Learning about dynamic systems is not required for climate scientists. They appear to be totally unaware that knowledge of dynamic systems would drastically alter their perception of world climate.

    Knowledge of dynamic systems allows recognition that world climate, as summarized by average global temperature, can be viewed as a dynamic system and that the mathematics and concepts of dynamic systems apply. Some things are immediately obvious to anyone familiar with dynamic systems with feedback. For example, the existence of temperature downtrends proves that significant NET positive feedback does not exist. Failure of climate scientists to recognize this stems from a lack of knowledge of that part of science pertaining to dynamic systems. Incidentally, a lack of knowledge of dynamic systems resulted in misinterpreting the meaning of ‘input’. Input to a dynamic system refers to the input to the transfer function. This input is not merely the output of the source of energy (as Chris erroneously guessed), which in the case of climate is the sun, but also includes any and all feedbacks (the combined effect of which is NET feedback). Also, lacking an understanding of dynamic systems can result in the delusion that world climate is somehow special and does not follow the same (dynamic system theory) rules as other dynamic systems. The output of this dynamic system model is average world temperature. The transfer function is by definition a function that accounts for all factors that influence average world temperature.

    Lack of understanding of dynamic systems with feedback has resulted in a repeat of stuff that no one that is knowledgeable on the subject disputes and a failure to realize that temperature downtrends prove that substantial negative feedback must exist because the NET feedback can not be significantly positive. Temperature observations are widely available. They show temperature downtrends when there is no significant influence from Milankovitch. This could not take place (without change to influence from outside the planet) if there were any net positive feedback. Without the imposition of net positive feedback by the GCM users, the GCMs do not show significant global warming. Other shortcomings of GCMs and their use are described at 32 above.

    Any good reference on dynamic system theory and application would serve to learn how dynamic systems work. As a start, one might review the applicable chapters in Phelan, R 1967, Dynamics of Machinery McGraw Hill Book Co. NY. Although the subject is presented in the context of control systems it is readily generalized to apply to global climate and global average temperature.
  64. O.K. Dan, I think we're making some progress. It seems your "disagreement" with the science relates to a misunderstanding of the nature of "feedback" in relation to the earth's energy budget combined with a reliance on inappropriate analogies ("anti-missile missiles"; "cruise control devices"), a misunderstanding of insolation effects resulting from the cyclical elements of the earth's orbital properties that modulates the pattern of insolation on the 10's of 1000's of years timescale, and (judging by your previous posts and your dismal web page) a desire to impose a false view of this entire subject through a propagation of contrived misrepresentation.

    Is that "hostile"? Possibly...but I'd prefer "trenchant", since I think one should address contrived misrepresentation with a bit of vigour!


    Feedbacks. The evidence indicates that there is a NET positive feedback to enhanced atmospheric CO2 concentrations. You’ve said in another post somewhere that positive feedbacks occur with carbon dioxide and water. That’s exactly right. The warming effect of enhanced atmospheric CO2, for example, is amplified by a water vapour feedback, and certainly an albedo feedback. It seems that we agree about that. Overall the evidence indicates that the NET feedback results in a warming resulting from doubling of atmospheric CO2 of around 3 oC (+/- a bit). You seem to have a residual problem with this…I wonder whether it relates to your reliance on analogies and a textbook (Phelan, 1967) based on the analysis of control systems. Unfortunately feedbacks in relation to “control systems” are not really appropriate (see following):


    Dynamic systems/control systems. The climate is a dynamic system with elements involving forcings and feedbacks that "act" on many different timescales, as well as stochastic and non-stochastic elements that provide “noise” in various accessible parameters (such as the surface temperature anomaly). It differs from your notion of a “control system” in that the feedbacks are neither “designed” nor constrained to maintain an equilibrium, even if parameters (like the earth’s surface temperature anomaly) might well be in equilibrium for long periods as a result of a relatively steady state in relation to forcings (e.g. the sum of solar and greenhouse contributions). If there is a change in these forcings (a change in solar output or a change in greenhouse gas concentrations) the earth doesn’t respond so as to maintain an equilibrium surface temperature. The earth’s climate system evolves dynamically under the influence of the new forcings until a new (dynamic) equilibrium is reached. In the case of enhanced greenhouse forcing at constant insolation, the new equilibrium is around 3 oC of raised surface temperature per doubling of atmospheric [CO2]. There’s a NET positive feedback.


    Does the climate system have elements of your “control systems”. It does a bit. For example the vast oceans provides a heat reservoir that regulates surface temperature somewhat, both directly and through the evaporation/precipitation cycles. The vast ice sheets also provide a bit of a thermal “buffer” due to the large heat capacity associated with the ice/water phase transition. Over very long periods greenhouse-induced warming is countered by increased weathering that draws CO2 out of the atmosphere. But overall the earth isn’t really under the influence of “control systems” and certainly doesn’t respond in that manner. It responds to a change in forcings via dynamic transitions to new (dynamic) thermal equilibria.

    Milankovitch/feedbacks. I suspect you’re still confused by these. Variations in the earth’s orbital climatic precession, obliquity and eccentricity result in a rather complex, but well-defined variation in insolation that matches rather well the progression of temperature anomalies in the ice cores. I suggest that you look at some of the papers linked by John Cook here:

    http://www.skepticalscience.com/co2-lags-temperature.htm

    especially Petit et al, 1999 and Shackleton, 2000. If you have access to last week’s Nature magazine (6th November) read the paper on page 85 (Lisiecki et al (2008) “Atlantic overturning responses to Late Pleistocene climate forcings” Nature 456, 85-88.), or the accompanying commentary by Michael Crucifix “Climate’s astronomical sensors” on page 47. I know that you don’t like reading scientific papers and prefer weird websites and non-science magazines. However, one may as well obtain one’s information from the source that mature and well-informed policymakers source theirs!

    The significant NET positive feedback that amplifies CO2-induced warming relates to a relatively constant insolation. So in our present situation with a rather constant solar output and no significant Milankovitch contributions for many thousands of years to come, the enhanced greenhouse forcing is giving us (and will give us further) warming resulting from the earth’s climate sensitivity to enhanced [CO2] which the best evidence indicates is near 3 oC (+/- a bit) of warming for a doubled [CO2]. Obviously if the solar contribution diminishes either in relation to total solar output, or due to altered insolation patterns during Milankovitch cycles, the earth will still undergo cooling even ‘though there there is (a) a NET positive climate warming feedback to enhanced [CO2] under conditions of constant insolation, and (b) a residual highish concentration of atmospheric CO2 (since CO2 is drawn only very slowly out of the atmosphere).
  65. Chris is not only unaware of a well established part of science but apparently refuses to consider it. Dynamic Systems Theory is readily applied to global average temperature history and easily proves that there is no significant NET positive feedback. Instead we get parochial rationalizations and erroneous estimates of future temperature as calculated by flawed computer programs that mistakenly invoke significant net positive feedback.

    The current UAH satellite numerical temperature anomaly data (these data consist of the differences of lower atmospheric temperature from the 1979 thru 1998 average) are at http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt . According to these data, the AVERAGE GLOBAL TEMPERATURE for the first 10 months of 2008 is LOWER than the average from 2000 thru 2007 by an amount equal to 40.3% of the total linearized increase (NOAA temperature anomaly data from ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/annual.land_and_ocean.90S.90N.df_1901-2000mean.dat) during the 20th century. Since 2000, the CARBON DIOXIDE LEVEL HAS INCREASED by 14.4% of the total increase since the start of the Industrial Revolution (from several sources which are given on the fourth graph in the Middlebury link at 41 above).

    None of the GCMs predicted anything remotely close to this decline of average global temperature with rising atmospheric carbon dioxide level. The GCMs are little more than glorified curve fitting to historical data and apparently have negligible predictive capability. It will probably need to get much colder for some people to realize that they may be missing something. As the carbon dioxide level continues to increase and the average global temperature doesn’t, many people are looking more and more foolish.
  66. I see...a gear switch into tropospherical temperature measures now?

    Fair enough...however your problems on this issue are similar to those in relation to your cherrypicking of paleotemperature data (see posts #46, 48, 50, 52), your contrived misrepresentation of paleoCO2 data that is completely contradicted by the pukka scientific data (see posts #46, 48, 50, 52, 54), your dull cherrypicking of an incompetent paleotemperature "analysis" in a non-science magazine in which you pretended that the authors own rather fatal correction didn't exist (see posts #54, 58), your confusion over feedbacks…..and Milankovitch contributions (see posts #59, 62, 64)......and so on

    ..We've pretty much sorted out each of these (see posts #46, 48, 50, 52, 54, 58, 59, 62, 64)....so what about that tropospheric temperature data?


    There's a pretty serious problem with it I think we would agree. There's no question that the Earth's surface temperature is rising, and has done so rather dramatically since the mid 1970's. We can see this in the surface temperature record..or we can dispense with direct temperature records and construct a temperature record from the record of mountain glacier retreat…it’s pretty uncontroversial that it’s been getting significantly warmer, and rather quickly during the past 30-odd years. Basic atmospheric physics and associated climate models predict a significant tropospheric warming (it should be a bit larger than the surface temperature increase in response to enhanced greenhouse warming). However, the tropospheric temperature record from satellites (Microwave Sounding Units; MSU) and radiosondes (weather balloons) are giving some rather ambiguous data. What’s going on…?

    Your choice of the UAH record is interesting. The characters that compile this data have pursued a path of studied incompetence during the last 15 or more years, during which their early attempt to sell the notion that the troposphere was actually undergoing a cooling trend, was revised after it was pointed out that (a) their analysis was not sufficiently constrained to distinguish cooling from a warming consistent with physical expectations [ONE], (b) the method of averaging different satellite records introduce a spurious cooling trend [TWO], and (c) their incompetent disregard of orbital decay introduced another spurious cooling trend [THREE]. A little later it was shown (d) that MSU-2 showed a spurious cooling trend due to spillover of stratospheric cooling into the tropospheric temperature signal [FOUR], and later still it was pointed out that (e) the diurnal correction applied by Christy and Spencer (a sad litany of incompetence) was of the wrong sign and gave yet another spurious cooling trend [FIVE].

    SO UAH is a rather dodgy source of data unfortunately. It’s a pretty scandalous record in fact. The RSS tropospheric data is likely to be more robust.

    But, unfortunately, however you look at it, the tropospheric temperature record from satellite measures [the radiosonde record has been shown to be highly contaminated by artefactual biases (see post #60 above)], is still poorly constrained. Despite Christy and Spencers’ assertions of “precision” in these analyses, they seem sadly inaccurate (and more so with Spencer and Christy’s litany of spurious adjustments towards cooling trends which has bedeviled the UAH analyses). Finally even Christy agrees that the tropospheric data worldwide is consistent with expectations from models, although he considers there is still a problem with the tropospherical temperature in the tropics. However that has been resolved recently, and there doesn't seem to be any substantive disagreement between the tropical tropospheric temperature trend as measured by satellites and predicted by models [SIX].

    But it’s probably true to say that tropospheric temperature measures cannot really be used to make conclusive conclusions about either the agreement of satellite (or radiosonde) tropospheric temperatures with models or their disagreement. We need better tropospheric temperature measures I suspect.

    So if we’re really interested in knowing what the Earth’s surface temperature is doing in response to enhanced greenhouse forcing, we can look at the long term surface temperature record (around 100 years longer than the very short satellite tropospheric temperature record), and monitor the effects of warming (enhanced rate of sea level rise; large scale retreat of mountain glaciers; hugely increased rate of attenuation of Arctic sea ice…and so on). We can also note with respect to the troposphere, that the water vapour levels in the troposphere are increasing much as predicted by models [SEVEN], and alternative measures of tropospheric temperature that are not so affected by artifacts (not to mention incompetent mis-analysis; see above) give rather large warming trends (e.g. tropsopheric thermal wind measurements give maximum tropospheric temperature trends of 0.65 +/- 0.47 K per decade [EIGHT]).

    [ONE] B.J. Gary and S. J. Keihm (1991) Microwave Sounding Units and Global Warming Science 251, 316 (1991)

    [TWO] J. W. Hurrell & .K E. Trenberth (1997) Spurious trends in satellite MSU temperatures from merging different satellite record. Nature 386, 164 – 167.

    [THREE] F. J. Wentz and M. Schabel (1998) Effects of orbital decay on satellite-derived lower-tropospheric temperature trends. Nature 394, 661-664

    [FOUR] Q. Fu et al. (2004) Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends Nature 429, 55-58.

    [FIVE] C. A. Mears and F. J. Wentz (2005) The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature, Science 1548-1551.

    [SIX] B. D. Santer et al. (2008) Consistency of modelled and observed temperature trends in the tropical troposphere. International Journal of Climatology 28, 1703 – 1722.

    [SEVEN] Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening Science 310, 841-844;
    Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253;
    Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912; Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data. J. Geophys. Res. 113, art #D14110;
    Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback . J. Climate 21, 3282-3289

    [EIGHT] R. J. Allen & S. C. Sherwood (2008) Warming maximum in the tropical upper troposphere deduced from thermal winds. Nature Geoscience 1, 399 – 403.
  67. The discovery that the Climate Science Community is uninformed on Dynamic System Theory and the ramifications thereof were presented at post 61. Their lack of understanding of Dynamic System Theory prevents them from recognizing that some important aspects of earth’s climate are easily determined; specifically that the imposition of significant net positive feedback in their GCMs is a mistake (other deficiencies regarding GCM use are listed at post 32). All of Chris’ comments and references should be considered in the context that they are uninformed in a relevant part of science and that they are unaware that they are uninformed.

    Chris presented an extensive diatribe (including several references) denigrating the UAH reporting of lower atmospheric temperature anomalies that were based on measurements made by satellite. The diatribe includes comments such as “incompetent disregard”, “UAH is a dodgy source” and “scandalous record”. Then Chris writes “The RSS tropospheric data is likely to be more robust.” The reader is invited to look at the RSS data set. It can be seen at http://www.ncdc.noaa.gov/oa/climate/research/rss_monthly_msu_amsu_channel_tlt_anomalies_land_and_ocean.txt . Doing the same analysis on the RSS data as was done on the UAH data shows that the AVERAGE GLOBAL TEMPERATURE for the first 9 months of 2008 is LOWER than the average from 2000 thru 2007 by an amount equal to 39.8% of the total linearized increase (NOAA temperature anomaly data) during the 20th century. Thus the RSS data corroborate the UAH data. It will be interesting to see what fault Chris now finds with the RSS data.

    Both the UAH and RSS data sets use satellite information which measures lower atmospheric temperature. The atmosphere has low thermal capacitance (ability to store heat) so it changes temperature comparatively quickly. The other sources: Hadley, http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt, GISS, http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt and NOAA, ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/monthly.land_and_ocean.90S.90N.df_1901-2000mean.dat , report land, ocean and combined land-ocean measurements. The land-ocean measurements are weighted to account for the fact that there is much more ocean area than land area (and other factors) and are presented as average global temperature. Applying the same method to the global average surface temperatures (latest available) as was done for the atmospheric temperature results in (there is less decline because of the influence of higher thermal capacitance) 21.8% (9 mo), 20.0% (10 mo) and 14.4% (9 mo) for Hadley, GISS and NOAA respectively. Thus all agencies are consistent in reporting the recent temperature decline. But understanding global climate does not come from examining a period so brief as the last decade, or even the last century. Any assessment of climate change that limits itself to a period that is a recovery from the LIA (Little Ice Age) while ignoring the decline in temperature that occurred during the change from the Medieval Warm Period (aka Medieval Climate Optimum) to the LIA is at best incomplete.

    Be aware that the ONLY predictors of significant Anthropogenic Global Warming are Global Climate Models (aka General Circulation Models) or GCMs. The only existing exact, correct computer of global climate is the planet itself. One of the outputs of this computer is recorded as temperature history. Temperature history, to those with even a minimum understanding of Dynamic System Theory, proves that net positive feedback does not occur in global climate. Without significant net positive feedback the GCMs do not predict significant global warming.

    Chris talks about glacier shortening but ignores that the glaciers started shortening about a century BEFORE the beginning of increase of substantial fossil fuel use and continued to shorten at the same rate with absolutely no indication of any influence from increased atmospheric carbon dioxide. This contributes to the growing realization that the GCM based predictions are faulty. Incidentally, imagine what was happening to glacier length during the period from the Medieval Climate Optimum (that Mann tried to claim never happened) until the lowest temperatures of the Little Ice Age.

    No one can be sure where the average global temperature will go from here. According to Vostok ice core and other data it has been warmer than now at other times during the Holocene (the last 11,000 or so years) and other interglacial periods so eventual temporary further rise is not out of the question. However, the change in pattern since 2001, the recent downtrend, and continued quiet sun are all indicating that the planet is in for a continuation of the cooling trend. The huge thermal capacitance of the oceans will cause the cooling to be gradual, as was the warming.

    The real issue is not the climate. There is no objective evidence that human activity has ever had or ever will have any significant effect on it. The real issue is the damage to human freedom and prosperity that can happen because of a few government financed alarmists and their followers who are unaware of a relevant part of science. Record low temperatures and newsworthy rare or early snow falls are starting to get attention. Unfortunately, it may require a drastic decline of temperature with accompanying crop failure and wide spread starvation for many to begin to realize that they may be missing something.
  68. Oh dear. You're attempting to sell the unsubstantiated deceit that climate scientists don't understand feedbacks in relation to the earth's energy budget, and thus you can make a blanket dismissal of everything I present or every reference I cite.

    That's an excellent wheeze..you're entranced by the conceit that you are right and everyone else is wrong! Sadly, so far it's been easy to show that it is you that has glaring misconceptions on the science. Let's look at the essential errors in your post #67:

    1. I pointed out that the UAH satellite data is rather dodgy, bedevilled as it is by a slew of errors yielding artefactual cooling trends (see references cited in post #66). The RSS data set is likely to be rather more accurate. Not very controversial I think.

    2. I also pointed out that the tropospheric temperature measures are not particularly robust (they are broadly consistent with the land-sea surface record, but are not particularly well-constrained), and that while efforts are made to improve these, particularly in relation to calibrations, and taking account the relatively short time series (satellite measurements of tropospheric temperatures are available only from 1979), it makes more sense to consider the land-sea surface temperature measures if one wants to establish how our world is responding to enhanced greenhouse gas forcing (see references cited in post #66). Not very controversial either.

    3. These (NASA GISS, Hadcrut, NOAA) show long warming trends from the mid 1970's through to the present.

    4. You are choosing to make an analysis in which part of the land-sea surface 2008 data (the first 9 months) is compared to the 2000-2007 mean. But it doesn't make any sense in the context of greenhouse-forced warming trends, to compare single years (or parts of year) with anything.

    This should be obvious. Here’s why:

    5. The land-sea surface records show a warming trend somewhere near 0.18-0.2 oC per decade over the last 30-ish years. Obviously, since year on year variations can result in short term drops or rises in the surface temperature by 0.1 oC (or even 0.2 oC if one considers the effects of the extraordinary El Nino year, 1998), one needs to consider trends over longish periods - looking at parts of single years is highly misleading, since there is rather a lot of “noise” on the temperature record.

    6. Let's look for example at your cherrypicked early-mid 2008. The first 5-6 months of 2008 were strongly influenced by a La Nina episode that suppressed the surface temperature measurably. In addition the sun has reached the very bottom in its 11 year solar cycle and will only start to significantly supplement greenhouse warming in a couple of years. So we've had a short period when "cooling" phenomena have coincided. That's measured in the surface (and tropospheric) temperature records. Not a big surprise.

    7. But of course if we're interested in how the Earth's surface temperature responds to enhanced greenhouse warming, we don't play at contrived wonderment that the surface temperature has cooled a bit due to fluctuations that happen to be in a cooling direction for several months. In another years or two the rise in the solar cycle will be supplementing the greenhouse enhanced forcing rather than opposing it as in the last few years. No doubt we’ll get the next record year at the next significant El Nino or two…

    Here's the other problems in your post:

    1. Oddly, while you attempt to make an "argument" on the basis of a short 9 month period, you then proceed to attempt a completely contrary “argument” around the notion; [Dan Pangbourn: "But understanding global climate does not come from examining a period so brief as the last decade, or even the last century"]. A lovely cherrypicking of 9 months of data is fine though!

    The other problem with the "argument" that you attempt to develop from that, is that no-one has ignored the temperature changes during the past 1000 years. There's a reasonably good understanding of those (hint - it's the sun and volcanic activity that has resulted in small and slow changes in the earth's surface temperature during those periods). Note that the Earth's surface temperature "recovered" from the Little Ice Age by around the middle of the 19th century. I wonder whether you are trying to pretend that 20th century and contemporary warming is "recovery" from the LIA!

    2. Be aware that the only predictors of significant Anthropogenic Global Warming are certainly NOT Global Climate Models or GCMs. What an odd notion to try to insinuate; what evidence lends to you consider such an ill-informed idea? The major predictor of Anthropogenic Global Warming is our understanding of the Earth's greenhouse effect and the physics/thermodynamics of the response of the earth's energy budget to enhanced greenhouse forcing.

    That's why (to give one of dozens of examples going pack to the mid 19th century), Wallace Broecker was able to predict in 1975 that the Earth’s global temperature would likely be warmer by the early 2000’s than at any period in the previous 1000 years. The evidence indicates he was right.

    [[b][/i]Broecker, WS (1975) “Climate Change: Are we on the brink of a pronounced global warming ? Science 189, 460-463[/i][/b]]

    Broecker didn’t have a GCM at hand (and nether did John Tyndall in the mid 19th century nor Arrhenius in the late 19th century and so on, each of whom understood that atmospheric CO2 contributed to the Earth’s enhanced temperature above its “black body” temperature and the effects of enhancing greenhouse gas forcings). You seem to have a severe misconception of the scope of GCM’s and their use in relation to understanding the evolution of the climate in a warming world, its spatial distribution and consequent effects (rainfall patterns, heat transfer by air and ocean currents and so on).

    So let’s not pretend that anthropogenic global warming arises magically from climate models. We’ve known about global warming in response to anthropogenic enhancement of the earth’s greenhouse effect for over 100 years.

    3. There isn’t any data from the Vostok core that indicates “its been warmer than now at other times during the Holocene”. Unless by “it” you mean Vostok. One location does not a global temperature make.

    4. It does seem to have been a tad warmer during the last interglacial period particularly around 130,000 to 125,000-ish years ago. Unfortunately sea levels were around 4 metres higher then than now as a result. That’s one of the many reasons we don’t want to push temperatures up much further.

    5. What “quiet sun”? The present minimum which is opposing enhanced greenhouse-induced warming will in a year or two begin to “supplement” this. Getting excited about the low point in the rather regular 11 year sinusoidal variation in the solar output is nonsense.

    And your repeated misconception about feedbacks:

    6. Despite agreeing that enhanced CO2 results in enhanced greenhouse forcing with resultant atmospheric warming that yields a water vapour feedback, and the abundant evidence that the Earth responds to enhanced atmospheric CO2 concentrations with a warming encompassing a net positive feedback that yields a surface temperature near 3 oC, you still assert with zero substantiation that net positive feedbacks don’t exist.

    I wonder when you’re going to provide any evidence in support of that assertion other than “I know I’m right and everyone else is wong”!

    I explained some of the essential features of feedbacks in post #64. Your response was to parrot your mantra (paraphrasing) “I’m right and everyone else is wrong”. Some argument!.....
  69. Radiated energy (from all surfaces, including earths) varies as the fourth power of absolute temperature so a temperature down trend is insufficient to prove that net positive feedback does not exist. My bad to have overlooked this before. However, review of temperature during the last and previous glacial periods reveals that the temperature changed from an uptrend to a down trend with the atmospheric carbon dioxide level higher during the down trend than it had been during the uptrend. That could not happen if atmospheric carbon dioxide level increase was a significant driver of average global temperature increase.

    The present atmospheric carbon dioxide level is somewhat higher than it was during the glacial periods. As Carbon dioxide level increases, each additional increment has less influence than the previous increment. This effect is appropriately called saturation. Thus increased atmospheric carbon dioxide now is even less able to influence temperature than it was during the last glacial period when temperature increasing trend changed to a decreasing trend. The conclusion from all this is that the current rising atmospheric carbon dioxide did not have a significant influence on any temperature rise including the temperature rise from the mid 1970s until about a decade ago and will never be a significant factor in temperature increase.

    Contrary to Chris’ assertion which was “The major predictor of Anthropogenic Global Warming is our understanding of the greenhouse effect …” the discovery long ago that carbon dioxide and water vapor absorb certain wavelengths of infrared radiation does not mandate that human activity has caused the planet to get significantly warmer. It is pretty widely known that the infrared absorption, mainly by water vapor, helps make the planet have the nominal temperature that it does. It is less widely known that the absorption takes place close to the emitting surface (half within 24 meters as calculated from Barrett’s paper at http://www.warwickhughes.com/papers/barrett_ee05.pdf , others calculate even closer).

    Adding carbon dioxide to the atmosphere results in the infrared radiation being absorbed a bit closer to the emitting surface. The atoms that absorb the infrared radiation energy nearly all immediately share it by thermal conduction with the much more abundant adjacent atoms that are transparent to infrared radiation. That, for the most part, is what warms the air. The shared energy is then carried up by convection currents. Existing GCMs are unable to objectively account for this natural convection so the process is imposed on the models with a contrived parameterization.

    Contrary to one of many of Chris’ erroneous assertions, that I have stated that “I am right and everyone else is wrong”, I share the perception with over 31,000 other scientists and engineers at http://www.petitionproject.org/ that human release of carbon dioxide will not cause catastrophic global warming. These scientists and engineers gain nothing for this declaration while the 2500 or so alarmist climatologists must make dire predictions for the government grants to continue.
  70. Just another modelling error:
    Global Warming Predictions Are Overestimated, Suggests Study On Black Carbon ScienceDaily (Nov. 19, 2008) — A detailed analysis of black carbon -- the residue of burned organic matter -- in computer climate models suggests that those models may be overestimating global warming predictions.
  71. chris
    Just a small point re: "3. These (NASA GISS, Hadcrut, NOAA) show long warming trends from the mid 1970's through to the present."
    In reality only GISS actually shows a slight increase, the others are actually slightly negetive.
  72. chris
    disregard that - I misread your statement. I was referring to the last 10 years while you referred to the entire length of the last PDO.
  73. Re #69 Dan

    O.K., so you've finally come round to the truism that a downtrend in temperature is not proof that a net positive feedback doesn't exist, after all. So everyone else but you wasn't wrong! Your bad indeed.

    But we got there in the end...


    Your second paragraph is illogical. We all know that the Earth's equilibrium temperature response has a logarithmic relationship to the atmospheric CO2 concentration. Arrhenius had worked that out already over 100 years ago.


    Your third and fourth paragraphs are nonsense too. Why go to a non-science magazine created with the intention (as the Editor admits) of misrepresenting the science on power industry-related matters? We've already seen (see posts #54 and #58) that "articles" in that magazine on climate-related matters are dodgy.

    Not surprisingly, the author of that article has got it wrong. There are lots of errors:

    (i) absorption of EM radiation doesn't "take place close to the surface". Photons can travel vast distances before being "absorbed". It depends on the absorbtivity/transmisivity of the medium through which the photons pass.

    (ii) If one considers longwave IR emitted from the Earth's surface, the wavelength/energy of the emitted wavelength has to be considered, since the absorption coefficient (k) is inversely related to the wavelength of the absorption band. The transmisivity, t, (absorbtivity = 1-transmisivity) of a column of air =

    t = e^(-k*p*l)

    where k is the absorption coefficient, p is the partial pressure and l is the path length.

    since the absorption coefficients for the absorption bands of the greenhouse gases are known[1], we can calculate the pathlength required to effectively absorb all of the radiation (at that energy/wavelength).

    For 99% absorption, the pathlength of the 4-5 micron absorption band of CO2 is 625 metres at current atmospheric CO2 concentrations

    and for the ~14-20 micron absorption band, CO2 at 385 ppm is still unsaturated at 7,800 metres of altitude.

    likewise for the 12-20 micron infrared absorption band of water at 0.4%, water vapour is still absorbing at 1,700 metres.

    (iii) in other words at current atmospheric greenhouse gas concentrations, the absorption bands aren't saturated, and enhancement of the concentration of greenhouse gases, particularly at higher altitudes [see (iv)], is effective in trapping more of the longwave IR emitted from the Earth's surface.

    (iv) In any case, the altitude of absorption of IR emitted from the Earth’s surface isn’t that important. A key element of the greenhouse effect is the altitude of emission of longwave IR into space. This has to happen for radiative balance between incoming radiation and outward radiation. You’ve actually given a clue to an important consideration unwittingly in the very first statement of your post:

    [Dan “bad boy” Pangbourn: “Radiated energy (from all surfaces, including earths) varies as the fourth power of absolute temperature”]

    Exactly so. As greenhouse gases are added to the Earth’s atmosphere, the radiation of IR into space is suppressed at any altitude (especially altitudes far from the Earth’s surface). So the radiation emitted to space from (say) 5 km is suppressed by enhanced CO2 concentrations, and so the altitude of mean radiation to space is increased. Since an increased altitude in the troposphere is at a lower temperature, the efficiency of radiation to space is decreased (as you said yourself). What’s the effect of this? The troposphere must warm in order to restore radiative balance. Since the surface and troposphere are strongly coupled, the warming of the troposphere is transmitted to the earth’s surface (and vice versa) [2].

    (v) The article in the anti-science journal that you linked to makes three more errors that relate to ignoring real world measurements. These are:

    (i) on page 1044 your ill-informed author states:

    “It would be expected that more CO2 would have a greater effect on atmospheric warming at higher altitudes, but that seems not to be occurring in spite of the predictions of most GCMs”.

    But as we’ve seen already on this thread, the tropsopheric warming is quite consistent with GCMs (see my posts #60 and #66, where this exact issue is addressed).

    (ii) on page 1045 your ill-informed author states:

    “The GCMs take feedbacks into account, such as the supposed positive feedback from extra warming caused by the radiation by extra water vapour”.

    Yes, exactly. In line with the enhanced tropsopheric warming caused by enhanced [CO2], the troposphere is accumulating extra water vapour rather in line with predictions [3-7]. According to your ill-informed author this shouldn’t be happening since adding extra greenhouse gases isn’t (according to him) supposed to make the troposphere warmer!

    (iii) and overall your ill-informed author neglects to state that we can measure in the real world, not only the longwave radiation transmitted down to the Earth’s surface from the troposphere (which shouldn't be happening according to your ill-informed author), but the enhancement of this radiation due to the enhanced greenhouse gas concentrations of the last 30 years (which also shouldn't be happening according to yuor ill-informed author), or the reduction in this radiation outwards to space [8-12]

    ----------------------------------------
    [1] this has been known for decades. See e.g RM Goody and GD Robinson (1951) Quart. J. Roy. Meteor. Soc. 77, 153

    [2] Shine, KP (1995) Spectrochimica Acta A 51, 1393-4.

    [3] Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253

    [4] Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening. Science 310, 841-844.

    [5] Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data. J. Geophys. Res. 113, art #D14110

    [6] Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912

    [7] Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback. J. Climate 21, 3282-3289

    [8] Harries JE et al (2001) Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997. Nature 410, 335-337.

    [9] Worden HM et al. (2008) Satellite measurements of the clear-sky greenhouse effect from tropospheric ozone. Nature Geoscience 1, 305-8.

    [10] Philipona R et al (2004) Radiative forcing - measured at Earth's surface corroborate the increasing greenhouse effect. Geophys. Res. Lett. 31, art # L03202.

    [11] Wild M et al. (2008) Decadal changes in surface radiative fluxes and their role in global climate change Adv. Global Change Res. 33 , 155-167.

    [12] Philipona R et al (2005) Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe Geophys. Res. Lett. 32, art # L19809.

    etc. etc. etc. etc……
  74. Re #70
    I wouldn't really say that's a modelling error Quietman. Have a read of the original article in Nature Geosciences. A very small amount of carbon from inefficient burning of fossil fuels (that isn't captured in catalytic converters!), or from forest fires under oxygen-deficiency, or from people that use inefficient wood-burning stoves in the less-developed world, may be retained in the soil for long periods, and thus the amount released into the atmosphere may be reduced somewhat.

    Remember that no one expects the GCM models to be perfect. We know that they're not. That's not really the point of modelling. We know already from basic atmospheric physics and from numerous studies of the real world that the Earth responds to enhanced greenhouse gases with a warming somewhere of the order of 3 oC per doubling of atmospheric CO2. That's completely independent of models.

    The models help us to predict the spatial distribution of this warming, its effects under different emission scenarios and such like. As new information is obtained about contributions and their paramaterization, so the models are iteratively improved.

    So the work just published in Nature Geoscience will be explored further no doubt, and when it's sufficiently characterized/parameterized will be incorporated into the models...

    ..that's how science works!
  75. During the last and previous glacial periods the temperature changed from an uptrend to a down trend with the atmospheric carbon dioxide level higher during the down trend than it had been during the uptrend. That could not happen if there was significant net positive feedback and proves that significant net positive feedback does not exist. Without the imposition of substantial net positive feedback the GCMs do not predict significant global warming.
  76. Come on Dan. You provided your own answer to that illogical mantra in your first paragraph of your post #69:

    [Dan ".....a temperature down trend is insufficient to prove that net positive feedback does not exist. My bad to have overlooked this before."]

    You were right in your post #69. Why change your mind again??
  77. Post #75 was a repeat of the statement in #69 that followed the statement quoted in #76. It is unclear why you did not appear to notice this before and now do not seem to be able to see the difference between the two statements.
  78. Don't be silly Dan. You don't need to point out that you're parotting phrases from post to post..we can see that ourselves!

    The point is that your parroted phrases are illogical. The fact that insolation effects drive downtrends in temperature while CO2 levels remain high doesn't necessarily say anything about the net feedbacks to raised CO2 levels at constant insolation.


    This is explained in my post #64. You could look at the papers cited in that post which will enlighten you considerably about the rather straightforward phenomenon of Milankovitch-forced warming/cooling transitions. Look at the papers John Cook links to here, for example:

    http://www.skepticalscience.com/co2-lags-temperature.htm

    (Petit et al, 1999 and Shackleton, 2000 are two helpful papers.) You would also benefit from reading:

    Kawamura et al (2007) Northern Hemisphere forcing of climate cycles in Antarctica over the past 360,000 years. Nature 448, 912-918.

    Although your conundrum has been resolved by explanation several times already, here's another explanation:

    (i) raised CO2 levels stay raised for long periods, since CO2 is drawn out of the atmosphere rather slowly, for example in response to temperature downtrends.

    (ii) therefore if insolation effects (due to Milankovitch cycles) reduce critical insolation, the Earth's temperature will drop even 'though CO2 levels remain high.

    (iii) therefore during the ice age cycles, insolation changes that drive temperature changes will precede the CO2 responses.

    (iv) this doesn't mean that variation of atmospheric CO2 at constant insolation doesn't have associated positive feedbacks. All of the evidence (that we can measure in the real world, including an increase in tropospheric humidity as a feedback response to raised tropospheric warming, and reduced albedo due to surface ice recession and so on) indicates that the effects of CO2 variations are amplified by net positive feedbacks.

    (v) one can point out a simple analogy of the day/night cycle. Although atmospheric CO2 levels don't change overnight and remain very very high, as the sun goes down, the temperature measured at the Earth's surface drops.

    (vi) In other words a temperature downtrend at high/highish atmospheric CO2 levels only means that the particular driver of the temperature trend at that paticular time is variation in insolation.

    (vii) which we all know very well since it's rather obvious and well characterized!
  79. In post #68 Chris says “What quiet sun?” There are several agencies that report on solar activity that Chris could have accessed to find out. NOAA has revised several times their predictions of the magnitude and delay of the start of cycle 24. An animated display of the revisions can be viewed at http://wattsupwiththat.com/2008/10/05/nasa-moves-the-goalposts-on-solar-cycle-24-again/ . A day-by-day report of solar activity is available at http://www.dxlc.com/solar/ and http://www.swpc.noaa.gov/forecast.html. Numerical monthly sunspot averages since 1749 are at ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/MONTHLY. As can be observed, the sun remains quiet, even for a solar minimum.

    The assertion that all temperature trend direction changes are brought about by Milankovitch cycles is rejected by history and logic. The longest Milankovitch cycle is about 100,000 years and has been associated with the glacial/interglacial cycle. Most have determined that it accounts for about half of the glacial/interglacial climate change. The shortest and much weaker 23,000 year Milankovitch cycle explains only about 10% of the variance (http://www.physics.ohio-state.edu/~wilkins/energy/Companion/E16.7.pdf.xpdf) . There is no mechanism by which any Milankovitch cycle could cause the observed temperature trend changes that last only a few millenniums or so.

    Chris has finally (albeit inadvertently) conceded that average global temperature uptrends and downtrends take place irrespective of the atmospheric carbon dioxide level with the statement in post #78 “a temperature downtrend at high/highish atmospheric CO2 levels only means that the particular driver of the temperature trend at that particular time is variation in insolation”. Think about it. A temperature downtrend continuing for a millennium or so with the carbon dioxide level higher at any given temperature than it was during a prior uptrend.

    The Vostok data show repeatedly a temperature uptrend changing to a downtrend with the carbon dioxide level during the downtrend higher than it had been during the uptrend. The NOAA data are graphed at the Middlebury web site given at post #41 or at http://www.roperld.com/science/CO2_Temp.pdf . No amount of spin or deception can alter that this proves that significant net positive feedback does not exist. Without the imposition of significant net positive feedback by the GCM users, the GCMs do not predict significant global warming.

    The many references that Chris likes to list are evidence of the group-think mentality that permeates the climate scientist community who benefit from dire predictions.
  80. Come off it Dan..

    1) re "quiet sun".

    We're smack at the bottom of the solar cycle. Nothing surprising, or out of the ordinary, about that. For the last couple of years the very small reduction in solar irradiation has been opposing greenhouse-induced warming a tad...in a couple of years it will be supplementing greenhouse-induced warming.

    Not sure what point you're attempting to make about the fact that the sun is at the bottom of its solar cycle!

    2) re Milankovitch cycles.

    No one says that "all temperature trend direction changes are brought about by Milankovitch cycles", so let's not make stuff up!

    Otherwise, I suspect that you haven't read the papers I cited. You need to come to some decision about whether you want to understand this stuff or not.

    Remember that the 100,000 year, the 41,000 year and the 23,000 year cycle are out of phase. So it's quite straightforward to understand how the net insolation effect can produce a pattern of cyclical temperature variation as observed in the record.

    So, for example, if the delta T or delta 18O records from the Dome Fuji or Vostok cores are Fourier transformed to extract their power spectra, the three dominant Milankovitch cycles stand out rather clearly (111 kyr; 41 kyr; 23 kyr).

    see, for example, Figure 2 of:

    Kawamura et al (2007) "Northern hemisphere forcing of climate cycles in Antarctica ove rthe past 360,000 years" Nature 448, 912-919.

    It really is difficult to see your problem....insolation changes due to Milankovitch cylces seem to have dominated temperature (and atmospheric CO2 concentration) variations during the ice age cycles.

    I suggest you have a more careful read of the article whose url you cited. It gives a pretty good account: http://www.physics.ohio-state.edu/~wilkins/energy/Companion/E16.7.pdf.xpdf

    Sadly, I suspect you're never going to get the simple and obvious truth that significant insolation changes due to the slow cyclical orbital properties of the Earth, can result in temperature changes that result in slow drops in temperature in advance of changes in atmospheric CO2 concentrations. Happily, competent scientists and policymakers don't seem to share your mental blockage!

    One of the things that you haven't commented on with respect to the temperature and CO2 changes due to Milankovitch effects, is the really very, very small changes in atmospheric CO2 concentrations [see for example: http://www.skepticalscience.com/co2-lags-temperature.htm]. So some of the changes over which you are very confused involve extremely small changes in atmospheric CO2; e.g. reductions of 10 or 20 ppm of atmospheric CO2 during several thousands of years.

    These changes are very likely a consequence of the very slow temperature drop that results from insolation changes. The amplify the cooling as expected from the basic physics of the greenhouse effect. But these changes are pretty small (i.e. changes within the major glacial-interglacial transitions). There the sorts of changes occurring over thousands of years that we are now seeing in 4-5 (10 ppm) or 8-10 (20 ppm) years at the current rate of expelling massive amounts of greenhouse gases into the atmosphere.

    So the Earth is warming at a rate that massively exceeds the very slow temperature changes due to the very, very slow Milankovitch cycles. During ice age cycles insolation changes dominated temperature changes with warming effects resulting in water vapour, CO2 and albedo feedbacks. Now during an extraordinarily miniscule time period in relation to the vast millenia of the ice age transitions, a rapid increase in temperature is occurring during a period of relatively constant insolation as a result of a massive hiking upwards of the atmospheric greenhouse gas concentration (with water vapour and albedo feedbacks as we can measure in the real world).

    It ain't rocket science Dan!

    And I'm afraid that blanket dismissal of scientific research that doesn't accord with your agenda, is taking conspiracy theorising too far!
  81. Contrary to the statement in post #80 “No one says that "all temperature trend direction changes are brought about by Milankovitch cycles", so let's not make stuff up”, the statement “So it's quite straightforward to understand how the net insolation effect can produce a pattern of cyclical temperature variation as observed in the record” and several similar statements in post # 80 indicate that Chris seems to realize that temperature up trends and downtrends were not driven by atmospheric carbon dioxide level in the past. In post #73 with the statement “We all know that the Earth's equilibrium temperature response has a logarithmic relationship to the atmospheric CO2 concentration” Chris appears to also understand that added increments of carbon dioxide have diminishing influence on temperature. But then Chris and apparently the rest of the alarmists fail to put the two observations together which would prove to them that temperature trends now are also not driven by atmospheric carbon dioxide level.
  82. Do you really expect that logical fallacies are going to fool anyone on a skeptics board Dan?

    The ice age cycles were/are dominated by Milankovitch cycles (insolation pattern variations resulting from achingly slow cyclical variations in the Earth's orbital properties).

    Carbon dioxide is a greenhouse gas. The Earth has a warming response to raised atmospheric CO2 of the order of 3 oC per doubling of atmospheric CO2.

    Each of those phenomena apply to the Earth's temperature response and both of the statements are true. They're not mutually exclusive as you attempt to insinuate. It's logically fallacious to attempt to pursue the deceit that only one thing can influence a particular parameter (like the earth's temperature).. the fallacy of the single cause.


    Here's what the evidence idicates rather clearly:

    (i) there is a clear relationship between atmopheric CO2 levels and earth's temperature throughout the last 500 million years (see citations in my post #48).

    (ii) this is entirely consistent with the well-established fact that CO2 is a greenhouse gas, enhanced levels of which contribute to a warming response (amplified by feedbacks like raised water vapour and albedo response that we can observe and measure in the real world).

    (iii) During the slow, slow ice age cycles insolation effects result in a second-order cyclical temperature variation...

    it ain't rocket science Dan!
  83. Not forgetting that WV is also a GG, and has considerably greater warming effect than CO2.
    And that during glacial cycles the amount of WV would decrease thus adding to a more rapid/longer cooling cycle. In order to reverse WV driven cooling you need to get more WV into the atmosphere...through volcanic action or increased evapo/transpiration. If you don't increase the WV content significantly CO2 levels would have to rise dramatically to get you out of the glacial cycle. But we don't see such patterns in the CO2 record, so the primary forcing has to be increasing WV.
  84. re #83

    Remember that water vapour is a feedback. Its atmospheric concentration is a consequence of the atmospheric temperature (and pressure), and so the levels of water vapour respond largely to variations in the atmospheric temperature. These respond rather quickly (days-months), and so the atmospheric water vapour levels are near equilibrium with respect to the atmospheric temperature.

    So you can't add water vapour to the atmosphere in the manner that you suggest. Thus volcanic eruptions don't add water vapour (nor does evapo/transpiration)....in general they reduce water vapour. For example, after the 1991 Pinatubo eruption the atmospheric water vapour levels fell in response to reduced atmospheric temperature as a result of the cooling effect from the blasting of particulates high into the atmosphere and the reduction of solar irradiance at the surface [***].

    So water vapour can never be a “primary forcing”.

    It’s quite well understood that the primary driver of the ice age cycles is the slow, slow sinusoidal variations in the earth’s orbital parameters (Milankovitch cycles). As the Milankovitch insolation takes the earth through a glacial to interglacial transition, the awesomely slow primary atmospheric warming is amplified essentially immediately by the water vapour positive feedback that occurs as a spontaneous response to atmospheric warming. This is further amplified by a slower responding CO2 feedback (which recruits its own enhanced water vapour as a positive feedback). The reverse happens during the waning phases of the Milankovitch cycles.

    Of course water vapour responds essentially passively to ANY forcing that results in a change in atmospheric temperature. Following volcanic eruptions the atmosphere cools and water vapour levels drop as observed [***]. And as the atmosphere warms under the forcing of massively enhanced greenhouse gas concentrations, so the atmospheric water vapour concentration response passively as a positive feedback. We can observe this in the real world too [*****].




    [***] e.g. B. J. Soden et al. (2002) Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor. Science 296, 727-730.


    Abstract: The sensitivity of Earth's climate to an external radiative forcing depends critically on the response of water vapor. We use the global cooling and drying of the atmosphere that was observed after the eruption of Mount Pinatubo to test model predictions of the climate feedback from water vapor. Here, we first highlight the success of the model in reproducing the observed drying after the volcanic eruption. Then, by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling. These results provide quantitative evidence of the reliability of water vapor feedback in current climate models, which is crucial to their use for global warming projections.

    [*****] e.g.

    Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253

    Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening
    Science 310, 841-844.

    Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback . J. Climate 21, 3282-3289

    Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data. J. Geophys. Res. 113, art #D14110

    Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912
  85. Actually a valid assessment of GCM predictions is fairly simple. But clear thinking might be prevented by the preconceived notion that increased atmospheric carbon dioxide is a significant cause of global warming. It might help to realize that the climate scientists who promote this notion did not need to learn about Dynamic System Analysis yet they impose substantial net positive feedback (feedback is a factor in Dynamic System Analysis) in their Global Climate Models which causes the models to predict significant global warming. Without the imposition of substantial net positive feedback the GCMs do not predict significant global warming.

    You can avoid being hoodwinked by the group-think bias of others by looking at the ‘raw’ data. First observe closely the temperature trends and carbon dioxide levels during the last glacial period (e.g. from 110,000 ybp to 20,000 ybp) as available on the web from NOAA. The data was extracted from proxies archived in the Vostok Antarctica ice cores. This is the same data that, in an unfocused view, was used in An Inconvenient Truth the substantially fictional movie that misled so many. A close look at this data exposes the mistake. The digital temperature data is available at http://cdiac.ornl.gov/ftp/trends/temp/vostok/vostok.1999.temp.dat and digital data for the Carbon dioxide levels from http://cdiac.ornl.gov/trends/co2/vostok.html . To facilitate the examination, this data is graphed as the second graph at the Middlebury web site given in post #41. If atmospheric carbon dioxide was a significant driver of average global temperature the temperature could not be in a declining trend when the atmospheric carbon dioxide level was higher that it had been when the temperature was in a rising trend. It is astounding that some supposedly cognitively competent people cannot seem to grasp this.

    Lacking any other knowledge one might think that if the atmospheric carbon dioxide level increases enough it may then significantly drive temperature. But when the carbon dioxide level is higher, increased increments of carbon dioxide have less influence than the same size increments had when the atmospheric carbon dioxide level was lower. Thus average global temperature was not significantly driven by atmospheric carbon dioxide level during the previous glacial period and atmospheric carbon dioxide level has even less influence on climate now.
  86. You keep repeating the same fallacious non-sequiters Dan without addressing straightforward critique.


    1. Real world observations strongly support positive feedbacks to CO2-induced warming. We can measure the major feedback (enhanced water vapour) in the real world (see papers cited in my post #84), and recent work has reinforced the identification of the water vapour feedback and its quantitation:


    e.g. Dessler et al (2008), Water-vapor climate feedback inferred from climate fluctuations, 2003–2008, Geophys. Res. Lett., 35, L20704

    for a layman's description see:

    http://www.nasa.gov/topics/earth/features/vapor_warming.html

    the identification and effects of the albedo feedback can be seen very clearly in the Arctic, and so on..So there’s no value in pretending that what exists doesn’t exist.


    2. It’s rather well understood that the ice age cycles are driven by slow sinusoidal cycles in the earth’s orbital properties that alter the pattern of insolation. Sinc atmospheric CO2 levels respond very slowly to drops in global temperature (driven by Milankovitch cycles, for example), it’s not surprising that there is a significant lag between Milankovitch cooling and reduced CO2. Note that these CO2 changes in response to temperature during glacial cycles are rather small and extremely slow. They occur more than 100 times more slowly than the present rate of change in atmospheric CO2 resulting from massive burning of fossil fuels.

    It’s a logical fallacy to attempt the deceit that because CO2 variations weren’t the primary driver of temperature changes during ice age cycles (it amplified the changes of course), that massively increased atmospheric CO2 levels won’t increase the earth’s temperature under conditions of relatively stable insolation.

    3. …and yes, we all know that the earth’s temperature varies as the logarithm of the atmospheric greenhouse gas concentrations. Welcome to the 19th century! This really has been known for more than 100 years. As we also all know, the earth’s temperature responds to enhanced atmospheric CO2 with somewhere near 3 oC of warming per doubling of atmospheric CO2. So yes, if we ramp up the atmospheric CO2 concentrations we expext that the world will warm. That’s also pretty consistent with real world observations. It's the greenhouse effect Dan!
  87. Here again you use a time period that includes the murky transitions from interglacial to glacial and glacial to interglacial instead of sticking to a period that excludes the transitions and the interglacials. Stick to the time period from about 110,000 ybp to about 20,000 ybp. Then the Milankovitch effect is very small but along with other factors still drives the temperature. The effect of the atmospheric carbon dioxide at that time must have been even smaller since it does not drive the temperature. We know that because the record shows that temperature trended down when the carbon dioxide level was higher than when the temperature was trending up. If you have a rational explanation that proves otherwise than give it. Your endlessly quoting fellow victims of group-think proves nothing.

    Oh, and in the world that I am in, there is 6% more arctic ice than last year, average global temperature in 2008 is the lowest this century and the atmospheric carbon dioxide level has increased since 2000 by about 14% of the total rise since the start of the industrial revolution. What world are you in?
  88. You're not paying attention Dan. This was all explained to you in posts #78 and #80 above.

    Remember that the earth's orbital parameters are characterized by three major cycles having periods near 100,000 years, 41,000 years and 23,000 years. Since these cycles are out of phase a rather complex insolation pattern accrues from the "summation" of the cycles which matches the ice core data quite well.

    You'd benefit from reading this paper which describes some of the data in a manner that you could probably understand. Figure 2 is interesting; it illustrates the extraction of the earth's orbital cycles by Fourier transformation of ice core data on proxy temperature and 18O variations. The power spectrum shows clear strong peaks at 111,000, 41,000 and 23,000 years, which matches the orbital cycle frequencies rather well:

    Kawamura et al (2007) "Northern hemisphere forcing of climate cycles in Antarctica over the past 360,000 years" Nature 448, 912-919.

    You would also benefit from reading some of the papers John Cook discusses in his article on top of this thread.

    You shouldn't be frightened of the science Dan. Averting your eyes from scientific papers with schoolboy insults will only leave you woefully misinformed.
  89. In post #80 Chris said “…the simple and obvious truth that significant insolation changes due to the slow cyclical orbital properties of the Earth, can result in temperature changes that result in slow drops in temperature in advance of changes in atmospheric CO2 concentrations…”. That is a fairly clear statement that Chris correctly perceives that atmospheric carbon dioxide level change did not cause average global temperature change during the last glacial period but in fact carbon dioxide level change lagged temperature change (the Middlebury site at post #41 gives links to the NOAA data that show this). In post #73 with the statement “We all know that the Earth's equilibrium temperature response has a logarithmic relationship to the atmospheric CO2 concentration” Chris appears to also correctly understand that added increments of carbon dioxide now have less influence on temperature compared to the influence on temperature that previous increments of the same size had when the atmospheric carbon dioxide level was lower and atmospheric carbon dioxide level did not drive temperature. But then Chris appears to ignore these correct perceptions and instead switches to the alarmist mantra that added atmospheric carbon dioxide now will cause a devastating increase in average global temperature.

    Perhaps Chris has abandoned logic and/or common sense as a result of becoming immersed in some of the products of group-think that he/she thinks passes for science. Or maybe he/she has simply become confused by the plethora of insignificant and/or irrelevant minutia. It will be interesting to find out just how cold the planet will need to get before the alarmists begin to realize that maybe they missed something. The rapidly growing number of scientists who recognize that it is a mistake to think that the planet will significantly warm because of increased atmospheric carbon dioxide may be an indication that this has already started to occur. It will probably take longer for the technologically incompetent politicians to relinquish their prosperity-diminishing control.

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