Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
Keep me logged in
New? Register here
Forgot your password?

Latest Posts

Archives

Trenberth, Fasullo, and Abraham Respond to Spencer and Braswell

Posted on 20 September 2011 by dana1981

The journal Remote Sensing has published a Commentary by Kevin Trenberth, John Fasullo, and John Abraham, which mainly responds to Spencer & Braswell (2011) [SB11], whose publication led the journal's editor to resign.  The paper also comments on Lindzen and Choi (2009), as both of these papers attempted to constrain climate sensitivity with recent observational data.

Trenberth et al. note a similar conclusion as that determined by Santer et al. (2011), that short-term noise can disguise the long-term warming trend over periods on the order of a decade:

"deviations between trends in global mean surface temperature and TOA radiation on decadal timescales can be considerable, and associated uncertainty surrounds the observational record. The recent work suggests that 20 years or longer is needed to begin to resolve a significant global warming signal in the context of natural variations."

They also comment on some deficiencies in SB11:

"SB11 fail to provide any meaningful error analysis in their recent paper and fail to explore even rudimentary questions regarding the robustness of their derived ENSO-regression in the context of natural variability. Addressing these questions in even a cursory manner would have avoided some of the study’s major mistakes. Moreover, the description of their method was incomplete, making it impossible to fully reproduce their analysis. Such reproducibility and openness should be a benchmark of any serious study."

Some of these criticisms are very similar to those made in Dessler (2011).  Readers may recall from our discussion of Dessler's paper that SB11 performed a regression analysis on just 6 of the 14 models they examined – the 3 with highest and 3 with lowest equilibrium climate sensitivities.  Dessler noted that SB11 excluded some of the models which best simulate the El Niño Southern Oscillation (ENSO), and that these were also the models which best matched the data in his regression analysis, and thus what SB11 were really testing was climate models' ability to replicate ENSO.  Trenberth et al. arrive at the same conclusion:

"Our results suggest instead that it is merely an indicator of a model’s ability to replicate the global-scale TOA response to ENSO. Since ENSO represents the main variations during a ten-year period, this is of course not surprising...what is driving all of the changes are the associations with ENSO."

Trenberth et al. performed a similar analysis to SB11, but rather than treat the model result as a single 100 year run as in SB11, they divided it into ten decade long samples of the same length as the observational record.  Trenberth et al. show their results for a model which doesn't replicate ENSO well (Figure 1), a model which does (Figure 2), and for all model runs (Figure 3).

bad ENSO model

Figure 1: Slope of regression coefficients between monthly temperature anomalies and climate models using a model which does not accurately reproduce ENSO.  This model has an equilibrium climate sensitivity of 2.4°C for doubled CO2 (relatively low sensitivity).  The black line is from observations, the red line is model results averaged by decade, and the red dashed line indicates the range of model results.

good ENSO model

Figure 2: Slope of regression coefficients between monthly temperature anomalies and climate models using a model which does accurately reproduce ENSO.  This model has an equilibrium climate sensitivity of 3.4°C for doubled CO2 (relatively high sensitivity).  The black line is from observations, the red line is model results averaged by decade, and the red dashed line indicates the range of model results.

all models

Figure 3: Slope of regression coefficients between monthly temperature anomalies and all CMIP3 climate models.  The black line is from observations, the red line is model results averaged by decade, and the red dashed line indicates the range of model results.

Contrary to SB11's conclusion, Trenberth et al. find that models with higher equilibrium climate sensitivities do a better job of replicating the observed relationship, but the correlation between model sensitivity and regression strength is of marginal statistical significance.  Thus they conclude that SB11 fundamentally take the wrong approach:

"Consequently, bounding the response of models by selection of those with large and small sensitivities is inappropriate for these model-observation comparisons."

Trenberth et al. also repeat a common criticism of Roy Spencer's research, that the climate model he uses is too simple and does not accurately represent a number of important climatic factors:

"Because the exchange of heat between the ocean and atmosphere is a key part of the ENSO cycle, SB11’s simple model, which has no realistic ocean, no El Niño, and no hydrological cycle, and an inappropriate observational baseline, is unsuitable. Use of a reasonable heat capacity for the ocean is also crucial. Importantly, SB11 treated non-radiative energy exchange between the ocean and atmosphere as a series of random numbers, which neglects the non-random variations of this energy flow associated with the ENSO cycle...None of those processes are included in the SB11 model and its relevance to nature is thus highly suspect."

This paper has been incorporated into the Intermediate level rebuttal to Roy Spencer finds negative feedback

0 0

Bookmark and Share Printable Version  |  Link to this page

Comments

Comments 1 to 15:

  1. Spencer & Braswell's model choices were very suspicious.

    Why didn't they compare 10 year model runs with 10 year observations to get an apples-to-apples comparison. Why didn't the reviewers pick up on this obvious dodgy choice and the lack of quantified errors?

    Did they run the models and get the same results as Trenberth et al? If so, why did they choose the 6 they did? They had a reason (3 most/3 least sensitive), but if I was doing the analysis and I noticed that some of the models (e.g. ECHAM5) did quite well, then I would wonder why and publish them.

    Did SB automate the analysis without checking the fit of the models to data (so their scripts would just return 3 most/3 least sensitive), or did they see this, decide they didn't like it and hide the data?

    Lindzen & Choi was similarly suspicious. They used a subjective method to pick time periods for analysis, just HAPPENED to pick periods which gave a low sensitivity and apparently 'forgot' to test the sensitivity of their model to find out it was mostly useless.

    Pretty large blunders that, if honestly made, you'd hope the scientists would own up to and correct.
    0 0
  2. Over on WUWT, I notice how they love to exagerate the scientific position so that it's always "catastrophic" & "CAGW".

    "Spencer and Braswell plus Lindzen and Choi, it throws a huge monkey wrench in climate model machinery that predict catastrophic levels of positive feedback enhanced global warming due to increased CO2."

    http://wattsupwiththat.com/2011/09/20/new-peer-reviewed-paper-clouds-have-large-negative-feedback-cooling-effect-on-earths-radiation-budget/


    If you start at that point, anything less than catastrophic or apocalyptic means the conned can declare it was all overhyped.Classic strawman.
    0 0
  3. @Phil M

    The abstract for Richard P Allan's paper says, "The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system..." .

    Isn't that what we had always thought, as it's the basis of the long-standing proposal -- about to be tested -- that geo-engineered clouds will help cool the atmosphere. I'm struggling to understand why this should lead to anyone making exaggerated claims about 'nails in the coffin of AGW' and other such comments floating around the denialosphere.
    0 0
  4. @Phil M: WUWT's problem there is that they just didn't understand the paper and got it completely wrong.

    Allan's paper doesn't say anything about modern day feedbacks. It doesn't support Spencer & Lindzen's assertions in the slightest and it looks like a decent paper. There are no errors found in it yet, unlike LC09 and SB11.
    0 0
  5. I conduct a study of a new cancer causing medicine. I have twelve subjects. I limit my report to the 3 least afflicted and the 3 most afflicted.

    The three least afflicted got better, but they were expected to do so anyway through normal treatment.

    The three worst afflicted all died, but they were so far gone that no drug would have saved them.

    The six middle patients were all greatly improved by the drug, but I don't report that. My analysis, limited to the three best and worst cases, clearly shows that the drug is ineffective and further research into it should be halted.

    That's good science for you.
    0 0
  6. @2,3,4

    I think commenter Bart Verheggen was quick to point out that Watts has misunderstood the paper, and none other than Roy Spencer confirmed it. Another commentator ('Fredb' - ??) referred to some of Watts’ language in the post:

    "... can be persuaded to commit professional suicide and resign?"
    "... all the wailing and gnashing of teeth ..."
    "... the stunt pulled ..."
    "... machinery that predict catastrophic levels of positive feedback ..."

    So Pielke sr. now famous statement that Watts "is devoted to the highest level of scientific robustness" stands on firm ground – not.

    Now back to the Trenberth, Fasullo and Abraham?
    0 0
  7. This is just yet another in a mountain of examples of WUWT spinning and misrepresenting the science to further their own ideological agenda. But of course Pielke Sr. says it is an excellent science site and that he thinks Watts is "devoted to the highest level of scientific robustness".

    This is what these guys does, they ignore or forget that a paper has been refuted and that the science has since moved on and simply keep rehashing the same old mantra. They seem to think that if one keeps repeating an error that it becomes truth. Well it doesn't.

    What is also lost on them is that why would anthropogenic forcing be the first external forcing to not result in a net positive feedback in the climate system (paraphrasing Dr. Nielsen-Gammon)? How does one explain the medieval warm anomaly of interglacial if a strong negative cloud feedback is operating? You don't.

    They do not get it because they do not wish to--- their ideological blinkers are obscuring their objectivity and their logic.
    0 0
  8. It will be interesting to see if/how Pielke responds to our question about how low climate sensitivity can gel with the paleoclimate record.

    As for this particular paper, it's just unfortunate that Spencer keeps trying to subvert the serious peer-review process instead of learning from it and correcting his mistakes. Had he submitted to a standard climate journal, no doubt a reviewer would have caught his cherrypick and made him correct it before publication. Then we wouldn't have gotten all the misleading media stories about his paper, and Dessler and Trenberth et al. wouldn't have had to waste time writing papers correcting his errors.
    0 0
  9. All,

    There is new paper in press by Eastman et al. (2011) that looks at variations in cloud cover and type over the oceans between 1954 and 2008. This is one of their conclusions:

    "In regions of persistent MSC [marine stratus and stratocumulus clouds], time series show decreasing MSC amount. This decrease could be due to further spurious variation within the data. However, the decrease combined with observed increases in SST and the negative correlation between marine stratus and sea surface temperature suggests a positive cloud feedback to the warming sea surface."

    So yet more mounting observational evidence of a positive cloud feedback. And we also know from Screen and Simmonds (2010) that there is a weak positive cloud feedback operating with Arctic amplification.
    0 0
  10. Albatross,

    The study also found a strong correlation between cloud cover and ENSO.
    0 0
  11. Jonathon @10,

    Of course they did, on interannual timescale in the tropics. You left that first part of the sentence out that specified "interannual" and "tropical". Nice cherry pick.

    We know that short-term oscillations in the climate system (like ENSO) cannot explain the amount of warming observed between 1954 and 2008. Oscillations modulate the underlying long-term trend, they cannot create it. Please stop trying to obfuscate. I'll remind you of what they said.

    "However, the decrease combined with observed increases in SST and the negative correlation between marine stratus and sea surface temperature suggests a positive cloud feedback to the warming sea surface."

    EOS.
    0 0
  12. Clement et al 2009 also supports positive cloud feedback to warming. They used observational and model data for the Northeast Pacific.

    "The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback."
    0 0
  13. We discussed Clement and a number of other relevant papers in the rebuttal to 'clouds provide negative feedback'.
    0 0
  14. dana1981 - Thanks, I should have searched a little more.

    The Eastman 2011 paper is particularly interesting to me - some time back, in discussion with one of the resident skeptics here on SkS, I came across the ship report data that seemed to indicate a positive feedback. However, I didn't have the time to assemble all the reports (54 million!), so I didn't do any serious analysis of it.
    0 0
  15. @Stig

    "I think commenter Bart Verheggen was quick to point out that Watts has misunderstood the paper, and none other than Roy Spencer confirmed it."

    It's doubtful that the readership at WUWT would even ask themselves the question, that if WUWT is misrepresenting someone batting for their own team. Then how much are they misrepresenting someone from the opposing team?

    When will Spencer & Braswell raise their standards bar a little & aim to publish in journals of higher repute?
    0 0

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.



The Consensus Project Website

TEXTBOOK

THE ESCALATOR

(free to republish)

THE DEBUNKING HANDBOOK

BOOK NOW AVAILABLE

The Scientific Guide to
Global Warming Skepticism

Smartphone Apps

iPhone
Android
Nokia

© Copyright 2014 John Cook
Home | Links | Translations | About Us | Contact Us