Authors: Mary-Elena Carr; Kate Brash; Robert Anderson; Madeleine Rubenstein
On September 8, 2010, Deutsche Bank Climate Change Advisors (DBCCA) and the Columbia Climate Center (CCC) published a report entitled “Climate Change: Addressing the Major Skeptic Arguments,” which responds to the major claims of climate change skeptics. On September 13, 2010, Professor Ross McKitrick of the University of Guelph issued a report entitled Response to Misinformation from Deutsche Bank, in which he offered several critiques of the DBCCA/CCC publication.
This is the second post of a two-part blog series in which we offer a response to Professor McKitrick’s comments. In the first part of the series, we addressed Professor’s McKitrick’s critique of the introductory section of the DBCCA/CCC report, which dealt with the so-called “hockey stick” controversy.
In this second blog post, we turn to Professor McKitrick’s comments on a later section of the DBCCA/CCC report, which covered the controversy over emails stolen in November 2009 from the Climatic Research Unit (CRU) of the University of East Anglia. For more information on the CRU emails, see the UK House of Commons report on their investigation of the emails.
Part II: Hiding what decline?
Below, excerpts from Professor McKitrick’s critiques are indicated in italics. His quotes from our report are in bold for clarity.
1. The DB report provides a cursory review of the problems revealed in the East Anglia Emails. Their discussion of the notorious “hide the decline” email is as follows. [...] Every sentence in this paragraph is untrue or misleading. I will take them one-by-one. “One of the emails mentioned a “trick” to plot long-term temperature records.” No, one of the emails mentioned a “trick” to hide the decline. The reference is to email 942777075.txt wherein Jones says “I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) and from 1961 for Keith’s to hide the decline.”
As Professor McKitrick states, the “hide the decline” quote comes from an email dated November 16, 1999, with the subject line “Diagram for WMO Statement:”
“I’ve just completed Mike’s Nature trick of adding in the real temps
to each series for the last 20 years (ie from 1981 onwards) amd [sic] from
1961 for Keith’s to hide the decline.”
Our report asserted that Professor Jones was referring to hiding the decline in a graphical representation (we stated on p. 10 of the DBCCA/CCC report that the ‘trick’ referred to making graphs of long-term temperature records). We stand by our interpretation. It is consistent with Jones’s own explanation, which is reproduced in part below:
“The phrase ‘hide the decline’ was shorthand for providing a composite representation of long-term temperature changes made up of recent instrumental data and earlier tree-ring based evidence, where it was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were.”
Our interpretation is also consistent with the graph shown on the cover of a 1999 report of the World Meteorological Organization.
2. “Critics have argued that this indicates an attempt to mislead the public.” It is not merely critics who have argued this, but the Muir Russell Inquiry as well, which summarized the issue as follows (p. 60, emphasis added). “In relation to “hide the decline” we find that, given its subsequent iconic significance (not least the use of a similar figure in the TAR), the figure supplied for the WMO Report was misleading in not describing that one of the series was truncated post 1960 for the figure, and in not being clear on the fact that proxy and instrumental data were spliced together. We do not find that it is misleading to curtail reconstructions at some point per se, or to splice data, but we believe that both of these procedures should have been made plain – ideally in the figure but certainly clearly described in either the caption or the text.”
We agree that the graph is misleading, but it is speculative to equate a misleading graph with a deliberate attempt to mislead the public. By doing so, Professor McKitrick is making an unsubstantiated claim about Jones’s intentions.
In addition, Professor McKitrick has presented the findings of the Muir Russell Inquiry selectively and out of context. Although the Muir Russell Inquiry states that the WMO figure was misleading, it also finds that:
“The word ‘trick’ has been widely taken to confirm the intention to deceive, but can equally well, when used by scientists, mean for example a mathematical approach brought to bear to solve a problem.” (pp 59-60)
“It is also clear from the submissions that it is possible to place different interpretations on the same phrase. In such circumstances, only the original author can really know what their intentions were.” (p 32)
“E-mails are rarely definitive evidence of what actually occurred.” (p 33)
This supports our conclusion that there is no proof of an intention to mislead. In fact, the Muir Russell report concluded that although the CRU scientists may not have displayed a desirable level of openness,
“their rigour and honesty as scientists are not in doubt…[nor is there] any evidence of behavior that might undermine the conclusions of the IPCC assessments.” (p 11)
3. “In fact, the “trick” refers to the use of the instrumental record after 1960 instead of temperatures estimated from tree ring widths.” The graph in question shows tree ring widths in two series, and temperatures estimated from tree ring widths in one series. The substitution of temperature data replaces one of the tree ring series (Briffa’s). In other words, the instrumental record is used to replace tree rings themselves, not “temperatures estimated from tree rings.”
This is incorrect. The graph does in fact show temperature reconstructions based on tree ring data; in the case of Briffa, the temperature is inferred from tree-ring density (as can be seen in Briffa 2000, Figure 5) or in the very similar Figure 2.21 of the IPCC 2001 [reproduced in section 6]). The instrumental data do not replace raw tree ring measurements, but instead temperatures reconstructed from tree rings.
4. “The two sources were then labeled accordingly.” False. The Figure that appeared on the cover of the World Meteorological Organization is: [figure visible online here] There is obviously no labeling of the data swap.
As stated above, Professor McKitrik’s critique of the WMO is valid: the labeling of the graph on the cover of the WMO report is misleading. Yet the cover of the WMO report is an exception; other similar graphs label the lines appropriately. In Briffa 2000 or IPCC TAR 2001 (see section 6), for example, the lines are labeled to clarify that different parameters are being plotted. Furthermore, while it is correct that the temperature record is neither a different color nor labeled as distinct on the cover of the WMO report, the accompanying figure caption does in fact say (emphasis added):
“Northern Hemisphere temperatures were reconstructed for the past 1000 years (up to 1999) using palaeoclimatic records (tree rings, corals, ice cores, lake sediments, etc.), along with historical and long instrumental records.”
Therefore, while the graph itself is indeed misleading, the caption acknowledges that instrumental temperature records are being shown together with temperatures inferred from proxies such as tree rings.
5. “Instrumental data were used after 1960 because some high-altitude tree ring records show declining growth after 1960 despite warming temperatures.” This is sheer speculation on the part of the DB paper authors, since no explanation was provided in the report as to the rationale for the trick.
Professor McKitrick is correct that divergence between the tree-ring record and the instrumental record is not discussed in the WMO report itself. In fact, the chart on the cover, which is the source of this controversy, is not itself discussed in the body of the report. However, the inference expressed in the DBCCA/CCC report is consistent with the discussions provided in other publications by the authors (e.g. Briffa 2000) and with the explanation that Professor Jones gave in a 2010 interview reproduced in part below:
“This “divergence” is well known in the tree-ring literature and “trick” did not refer to any intention to deceive – but rather “a convenient way of achieving something”, in this case joining the earlier valid part of the tree-ring record with the recent, more reliable instrumental record.”
Our inference is also consistent with the discussion of divergence in the IPCC Third Assessment report.
6. Likewise, in the IPCC Report that was produced 2 years later, Briffa’s divergent data was truncated at 1960 with no notice to the reader. The only explanation that appears to have been recorded at the time was in Jones’ email: to “hide the decline.”
We disagree that there was “no notice to the reader.” Figure 1 of the Summary for Policy Makers (IPCC SPM 2001, p 3) clearly indicates the data from thermometers in a different color with the appropriate label, thus giving due notice to the reader of where divergent tree ring data were truncated. In Chapter 2 of the full Working Group I report, Figure 2.20 (IPCC 2001, p 134) indicates in the caption that the instrumental data is in red. In Figure 2.21 of the same report (IPCC 2001, p 134), the instrumental data is in a distinct color, identified in the legend and in the caption. All three images are reproduced below.
Furthermore, the large degree of uncertainty in the use of individual proxies and multi proxy reconstructions is explicitly discussed in the TAR. The authors of the TAR are extremely clear about the use of proxies in the report, and the implications that proxies, and their uncertainties, have for the report’s conclusions:
“Several important caveats must be borne in mind when using tree-ring data for palaeoclimate reconstructions. Not least is the intrinsic sampling bias…Furthermore, the biological response to climate forcing may change over time. There is evidence, for example, that high latitude tree-ring density variations have changed in their response to temperature in recent decades, associated with possible non-climatic factors…For these reasons, investigators have increasingly found tree-ring data most useful when supplemented by other types of proxy information in “multi-proxy” estimates of past temperature change.” (IPCC 2001, p 132)
“All proxy information…require[s] careful calibration and verification against modern instrumental data.” (IPCC 2001, p 133)
Given the open acknowledgement of the phenomenon of divergence, there is no need to take words from stolen emails to explain why instrumental data were plotted for the period in which divergence occurred.
We feel it unwise to rely on emails, which were written casually, stolen, and taken out of context, to provide explanations and assign intention to these highly complex topics. Professor McKitrick has chosen to interpret the CRU researcher’s language in the worst possible light. While he is entitled to do so, we would emphasize that this is not the only possible interpretation. Furthermore, we urge caution when drawing conclusions from these emails, especially since what has been made public lacks context. Clearer explanations are available from more authoritative sources.
Briffa, K.R. 2000. Annual climate variability in the Holocene: interpreting the message of ancient trees. Quat. Sci. Rev. 19: 87-105.
IPCC. 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 881pp.
Russell, M., G. Boulton, P. Clarke, D. Eyton, and J. Norton. 2010.The Independent Climate Change E-mails Review. University of East Anglia. 160pp.