The case of the vanishing post

Posted by William M. Connolley on December 18, 2007
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According to google reader, RP Sr posted the below today to his “blog” (only its not really a blog cos it doesn’t allow comments), in a post entitled Question The Weblog Real Climate. And indeed he did; the comment is here. This is something RP has been harping on about for a while. Gavin gave him the obvious answer: I fail to see how you are parsing this to find an inconsistency. The footnote is clear that the term ‘radiative forcing’ in the IPCC report refers to the change in forcing from a 1750 baseline. More precisely, it is defined as the change in radiation at the tropopause after stratospheric temperature adjustment but with all other factors kept fixed when going from 1750 conditions to a new value. The caption to the figure discusses the radiative forcing (which remember is defined relative to 1750) in 2005. i.e. the forcing calculated in going from 1750 conditions to 2005. What is the problem? Oddly, though, RP *hasn’t* posted Gavins response but seems to have deleted the entire misconceived post. Anyway, here is RP’s question:

Climate Science has asked the questions below in a comment on the weblog Real Climate. Their answer will be posted here also.

Climate Science has a question for Real Climate (the answer of which will also be posted on that website). The 2007 IPCC Statement for Policymakers [Figure SPM.2] has the following caption

“Global average radiative forcing (RF) estimates and ranges in 2005 for anthropogenic carbon dioxide (CO2 ), methane (CH4 ), nitrous oxide (N2O) and other important agents and mechanisms, together with the typical geographical extent (spatial scale) of the forcing and the assessed level of scientific understanding (LOSU).”

but also the footnote on page 2 that

“Radiative forcing is a measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. Positive forcing tends to warm the surface while negative forcing tends to cool it. In this report, radiative forcing values are for 2005 relative to pre-industrial conditions defined at 1750 and are expressed in watts per square metre (W m-2)…..”

Which of the two are correct?

Assuming that you agree that the footnote is correct, and the figure caption is in error, what is the Real Climate estimate in Watts per meter squared in 2005 (or in 2007) of the radiative forcing components and range for a figure analogous to Figure SPM.2 in the Statement for Policymakers?

[Update: the post is back, with no explanation. RP repeats his question. The answer is that the figure and the footnote are both correct, but "what is the current radiative forcing (i.e radiative imbalance)" is wrong]

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Comments

  1. #1 Eli Rabett
    2007/12/18

    RP Sr thinks he has found a way to harumph without being interrupted by reality or noisy bloggers. RPS has always been fond of harumphing. While we appreciate the service you are providing (see for example the blog Moon of Alabama), a place to sit down, break bread and discuss what the old guy is up to, perhaps he should be left in peace to mutter in the corner?

  2. #2 Roger A. Pielke Sr.
    2007/12/18

    William – Thank you for posting on your weblog. Gavin did not adequately answer the question before, so I am trying again.

    The important question to Real Climate is

    “[W]hat is the Real Climate estimate in Watts per meter squared in 2005 (or in 2007) of the radiative forcing components and range for a figure analogous to Figure SPM.2 in the Statement for Policymakers?”

    Gavin can seek to “spin” the figure caption, but it is clearly an error which is misleading to policymakers.

  3. #3 James Annan
    2007/12/18

    I think RP is really asking about the current radiative imbalance: while I do not think it is wrong or misleading to talk about total forcing (with a 1750 baseline) as the IPCC do, the other question is also interesting as it relates directly to warming “in the pipeline”. Of course the answer is we do not know for sure, since it directly depends on the climate sensitivity (and even the effective climate sensitivity of the current climate state, which may be slightly different again). But a rough ballpark estimate would be that a little more than half of the total forcing (IPCC terminology) remains as a current imbalance (the “commitment” runs in the AR4 show the future warming due to this imbalance). Of course splitting this up further into the contribution of each component would then become rather arbitrary.

    [Now I'm confused. The current radiative imbalance is measureable, and indeed Hansen claims to have measured it; isn't that the basis of his 0.5 W/m2 or whatever the value is? -W]

  4. #4 CapitalistImperialistPig
    2007/12/19

    About that “old guy . . . mutter[ing] in the corner” talk. Watch that nasty ageist rhetoric, would you Eli. Insofar as I can tell, Roger is a few years younger than I, though I have a bit more of my hair left.

  5. #5 Luboš Motl
    2007/12/19

    Gavin’s answer contradicts James’s answer.

    Climate sensitivity is a typical example of these definitions. In the proper definition, we must instantly double CO2 from 280 ppm to 560 ppm, wait for a few years until the new quasi-equilibrium is reached, and the change of temperature at a reference point – or the change of the total radiation power per square meter emitted (and absorbed) by Earth – is referred to as climate sensitivity.

    In the paragraph above, I wrote that we must wait for a few years and we only reach a quasi-equilibrium at the end. This is a fuzzy definition and can’t be really improved. Gavin’s answer that only the stratosphere is allowed to be adjusted is internally inconsistent because in reality, processes that drive the system to equilibrium always occur simultaneously and can’t be separated by name. A physical separation of the stratosphere from the rest would completely change the behavior of Earth, too. These things must simply be considered at the same moment. They can only be separated by timescales.

    So when you define climate sensitivity, do you wait for oceans to adjust themselves and provide the rest of Earth with their feedback? Gavin’s answer would probably be No – that’s what he means by keeping other things fixed. James’s answer would probably be Yes – that’s what he means by “total forcing” including the energy “waiting in the pipeline”. Could you please try to reach a consensus about this elementary point about a definition, dear consensus scientists?

    Moreover, I had to carefully write the timescale “waiting for a couple of years” because if we wait for a few centuries, the CO2 is reabsorbed by the oceans and gradually drops from 560 ppm back to 280 ppm. Climate is always changing and various definitions of oversimplified quantities implicitly assume that certain things remain in equilibrium even though their constancy would contradict laws of Nature.

    Instead of increasing fog, could someone please write a meaningful exposition of these basic things? It is not hard to find contradictions in the IPCC report – it was incoherently written by hundreds of not-so-smart people, if you want me to be extremely polite. But one coherent scientist above a certain level should know what he is doing. I am afraid that RP is the only one in the thread above who has both the capacity and will to eliminate obvious contradictions and inconsistencies and replace fog by clarity.

    [I'm not aware of any contradictions in the IPCC report, and RP's question simply makes no sense. There is no condtradiction; the figure and footnote are both correct. "what is the current radiative forcing (i.e radiative imbalance)" is wrong: RF relative to 1750 is not the same thing as the imbalance.

    If you are aware of any contradictions, please reply with the most obvious *one* -W]

  6. #6 Ian
    2007/12/19

    Since when does the definition of “blog” = “web pages that allow comments”?

    [Can you point to any real blogs that don't? RPs used to -W]

  7. #7 Eli Rabett
    2007/12/19

    Yeah, whiskey bar (which has since been taken down by the author, Billmon) did not. It was quite popular and another blog, which continues, moon of alabama started up to allow comments and continues. Billmon was trying to follow the old tradition of pamphleteering which sought to arouse discussion without needing feedback.

    BTW the names of the blogs are from a song in the Weill-Brecht opera Mahagony. . . Oh show me the way to the next whiskey bar, for if i don’t find the next whiskey bar, surely I must die. Surly I must die. and the chorus, Oh moon of Alabama please don’t ask me why. . .

    And we return you to our previously announced sho

  8. #8 Adam
    2007/12/19

    To briefly continue OT, the originator of the word weblog was Jorn Barger, and his blog doesn’t have comments – it’s a list of links with minimal description, which is what he was meaning when he coined the term – “logging the web”.

  9. #9 James Annan
    2007/12/19

    Hansen is definitely based on model results:

    http://pubs.giss.nasa.gov/abstracts/1997/Hansen_etal_5.html

    OTOH one might hope that satellite observations could address the question directly. I don’t recall seeing anything on that. Maybe the obs aren’t precise enough.

  10. #10 Roger A. Pielke Sr.
    2007/12/19

    William – regarding your comemnt

    “[Now I'm confused. The current radiative imbalance is measureable, and indeed Hansen claims to have measured it; isn't that the basis of his 0.5 W/m2 or whatever the value is? -W]”

    The radiative imbalance that Hansen (and others) have calculated in the sum of the current radiative forcings and feedbacks! This is of why I am raising this issue. James’s comment succinctly adds to this issue in his first comment, however, he is in error with respect to Jim Hansen’s study. In addition to model results, he also obtains an estimate from ocean heat content changes, as he discussed on Climate Science; see

    http://climatesci.colorado.edu/2005/08/08/comment-from-jim-hansen-on-the-august-2-climate-science-posting/

    and

    http://climatesci.colorado.edu/2005/08/02/pielke-and-christy-comment-on-hansen-et-al-science-paper-entitled-earth%e2%80%99s-energy-imbalance-confirmation-and-implications/

  11. #11 Hank Roberts
    2007/12/20

    I asked in that thread if what’s missing is an instrument to measure that instantaneous number

    http://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory

    in a consistent stable position (Lagrange 1) far enough from Earth to allow measuring the whole planet, as can be done for more distant planets from our vantage point; RP answered:

    “… the radiative imbalance can and has been diagnosed for relatively short time periods using the accumulation of Joules in the climate system over a this period.”

    I dunno. Seems rather vague.

    [He is pushing his ocean metric again. But it has large errors, so isn't much use -W]

  12. #12 Eli Rabett
    2007/12/20

    Right now the only way to measure the (change in) energy/enthalpy content of the system is to measure three dimensional temperature fields, and RPS donna like that. Any figure he produces has to have huge error bars.

  13. #13 Hank Roberts
    2007/12/20

    Is it correct that we can do this for other planets because we’re far enough away to point a thermometer at them, so to speak, and we know the solar constant, and that’s how we tell that, say, Jupiter emits more heat than it receives, and Mars varies as it changes albedo with dust storm cycles, and so on?