by Judith Curry
I just got the reviews on my reply to the rebuttal submitted regarding my uncertainty monster paper. They take exception with my criticism of transparency of the IPCC’s attribution argument.
From the review:
Curry and Webster state: “The heart of our argument is that the broader scientific and other technical communities (beyond the field of climate science) have higher expectations for understanding and characterizing uncertainty than has been portrayed thus far by the IPCC.” Curry and Webster are entitled to their opinion, but it is inappropriate to “speak for” scientists outside the IPCC process and from other technical fields as a whole without citing support for such claims. Their views should be represented accurately as the views of two individuals, rather than as the unsubstantiated collective view of diverse scientists and scientific communities.
Curry and Webster state, “Listing a large number of uncertainty locations, and then coming up with a ‘very likely’ likelihood statement using expert judgment in the context of a consensus building approach, is at the heart of our concern regarding the IPCC’s treatment of uncertainty.” This relates to the statement from the original Curry and Webster paper that was challenged by Hegerl et al., “Since no traceable account is given in the AR4 of how the likelihood assessment in the attribution statement was reached, it is not possible to determine what the qualitative judgments of the lead authors were on the methodological reliability of their claim.” On pages 18-19 of the original article, Curry and Webster quote AR4 WG1 Chapter 9 Section 9.4 and refer to this as a description of the reasoning process used in assessing likelihood in the attribution statement. This, along with discussion in section 9.4.1 and table 9.4, provides a clear traceable account of the multiple lines of evidence supporting the attribution statement and forming the basis for the likelihood assessment. Ultimately, the synthesis of multiple lines of evidence in the development of an assessment finding and the assignment of likelihood requires the expert judgment of the author team. Chapter 9 certainly could have provided further details about some aspects, such as the downweighting of the likelihood assessment to take into account remaining uncertainties, but it is incorrect to say that a traceable account was not given.
The first guidance paper on treatment of uncertainties for IPCC authors, from the Third Assessment Report cycle (2000) encourages authors to “Prepare a ‘traceable account’ of how the estimates were constructed that describes the writing team’s reasons for adopting a particular probability distribution, including important lines of evidence used, standards of evidence applied, approaches to combining/reconciling multiple lines of evidence, explicit explanations of methods for aggregation, and critical uncertainties.” The uncertainties guidance for the Fourth Assessment Report cycle (2004) states, “Be prepared to make expert judgments and explain those by providing a traceable account of the steps used to arrive at estimates of uncertainty or confidence for key findings – e.g. an agreed hierarchy of information, standards of evidence applied, approaches to combining or reconciling multiple lines of evidence, and explanation of critical factors.” As further background (noting that this was not available at the time of the development of the AR4), the latest uncertainties guidance released last year for the Fifth Assessment Report cycle states, “Be prepared to make expert judgments in developing key findings, and to explain those judgments by providing a traceable account: a description in the chapter text of your evaluation of the type, amount, quality, and consistency of evidence and the degree of agreement, which together form the basis for a given key finding. Such a description may include standards of evidence applied, approaches to combining or reconciling multiple lines of evidence, conditional assumptions, and explanation of critical factors. When appropriate, consider using formal elicitation methods to organize and quantify these judgments.”
So, give me your comments. How should traceable account” be interpreted? Did the IPCC give a traceable account? Has uncertainty been adequately characterized by the IPCC? My statement about the broader scientific community refers to YOU (the climate etc denizens).
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