Continuing from the Last Day The Last Day (Part I)…
It is not over yet. We pick up the story again on the last day in Madrid. Yes, Al Sabban has lost the battle to base the D&A section of the Summary on the conclusions of Chapter 8. But now the approval process begins on the re-write of this section. Santer’s draft will now be debated line-by-line, word-by-word, and this debate continues through to the afternoon and into the night. Once again it is the new pattern studies giving the human ‘fingerprint’ that will be most resisted.
A shambolic Victory of the Virtuous
The Side Group’s redraft of the D&A section of the Executive Summary lists three key areas where recent results contributed to positive attribution.1 The first is the proxy data giving that the 20th century is the warmest century in the last six. The second is the statistical significance of the warming trend in the global mean temperature suggesting that it is unlikely to be entirely natural in origin [see SAR Fig.8.3]. This evidence on global mean temperature is well-known to be weak, continues to be expressed in the negative, had already been challenged by Australia, and it had previously been considered by the IPCC (in the 18Apr95 drafts and in the First Assessment) unable to provide positive support to the human attribution claim [see here]. As if to emphasise this, the third and final area of research, the CO2+ Sulphate pattern correlation studies, is introduced with the words ‘More convincing evidence:’
More convincing evidence for the attribution of a human effect on climate is emerging from pattern-based studies…1
These studies showed ‘pattern correspondences increase with time,’ as would be expected with increasing emissions, and there is a very low probability that ‘these correspondences could occur by chance as a result of natural variability.’ As we noted previously, the exclusion of ‘chance’ or ‘accidental’ variability implicitly leaves open the possibility of the standard century-old candidates for natural external forcing. Perhaps it was to allay concerns about natural forcing (previously expressed in the commentaries, and so they are likely to have re-emerged in the Side Group) that the next sentence makes a curious reference to the ‘vertical’ pattern studies—as per our ‘Mirror in the Sky’—as also ‘inconsistent with the possible effects of known solar and volcanic forcing.’2
For this claim to be proposed for such a peak summary is curious because exclusion of such natural external forcing is not a major claim of Santer’s studies, nor of the other pattern studies, and no such conclusion is drawn in the Chapter itself. On the contrary, the Chapter repeatedly makes reference to the problem that we really don’t know what the pattern of nature forcing looks like. The best it can say right at the end of the section titled ‘Progress since IPCC 1990’ is that ‘we have now started to see pattern-based studies’ (which are not the flagship ones by Santer) that ‘try to rule out various non-anthropogenic forcing mechanisms.’ Thus, once again we have a situation where a claim is introduced during the inter-governmental negotiations that is contrary to the underlying scientific report, and nor is it derived from the ‘new evidence’ introduced to those negotiations in Santer’s extraordinary presentation.